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JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD

New Delhi • London • Philadelphia • Panama

Editors

Francesco Dispenza MD PhD

ConsultantSection of Otology and Neurotology Department of Otorhinolaryngology

“San Giovanni di Dio” Hospital “Azienda Sanitaria Locale” of Agrigento, Sicily, Italy

Alessandro De Stefano MD PhD

ConsultantInstitute of Otolaryngology

Department of Oral and Nano-Biotechnological Sciences “G.d’Annunzio” University of Chieti-Pescara, Italy

Department of Audiology and Rehabilitation for Speech Disorders“Azienda Sanitaria Locale” of Lecce, Apulia, Italy

Foreword

Michael M Paparella

Textbook of

VERTIGODiagnosis and Management

®

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Textbook of Vertigo: Diagnosis and Management

First Edition: 2014

ISBN 978-93-5090-672-9

Printed at:

®

Dedicated to

Vittoria and Chiaramy true love

Francesco Dispenza

My sister Cristinaalways present in my life

Alessandro De Stefano

Contributors vii

ContributorsMargaretha L Casselbrant MD PhD

University of Pittsburgh School of MedicineDivision of Pediatric Otolaryngology Children’s Hospital of Pittsburgh of UPMC, Pennsylvania, USA

Marcello Cherchi MD PhD

Department of Neurology Northwestern University Feinberg School of Medicine Chicago, Illinois, USA

Alfred Cuschieri MD

Department of Anatomy University of Malta, Msida, Malta


ConsultantInstitute of Otolaryngology Department of Oral andNano-Biotechnological Sciences “G.d’Annunzio” University ofChieti-Pescara, ItalyDepartment of Audiology and Rehabilitation for Speech Disorders “Azienda Sanitaria Locale” ofLecce, Apulia, Italy


ConsultantSection of Otology and Neurotology Department of Otorhinolaryngology “San Giovanni di Dio” Hospital “Azienda Sanitaria Locale” of Agrigento, Sicily, Italy

Nicolas Perez Fernandez MD PhD

Department of Otorhinolaryngology University of Navarra, Pamplona Spain

Enrique Ferreira PhD

Department of Electrical Engineering Universidad Católica del, Uruguay Montevideo, Uruguay

Carol A Foster MD

Balance LaboratoryDepartment of OtolaryngologyUniversity of ColoradoAurora, Colorado, USA

Richard Gans AuD

American Institute of Balance Orlando, Florida, USA

Dario Geisinger MD

Laboratory of Otoneurology Biomedical Engineering Program British Hospital, MontevideoUruguay

Michael E Glasscock III MD FACS

Otology Group of Vanderbilt Department of OtolaryngologyHead and Neck SurgeryVanderbilt Bill Wilkerson Center Vanderbilt UniversityNashville, Tennessee, USA

Timothy C Hain MD

Departments of Neurology, Otolaryngology, Physical Therapy and Human Movement Sciences Northwestern UniversityFeinberg School of Medicine Chicago, Illinois, USA

Raquel Manrique Huarte MD

Department of Otorhinolaryngology University of NavarraPamplona, Spain

Fayez Bahmad Júnior MD PhD

Health Sciences FacultyUniversity of BrasíliaBrasília, DF, Brazil

R Santhosh Kumar MD

ENT DivisionPD Hinduja HospitalMahim, Mumbai, Maharashtra, India

Gauri Mankekar MD

ENT DivisionPD Hinduja HospitalMahim, Mumbai, Maharashtra, India

Vladimir Marlinski MD

Barrow Neurological Institute Phoenix, Arizona, USA

Shinji Naganawa MD

Department of RadiologyNagoya University Graduate School of Medicine, Nagoya, Japan

Tsutomu Nakashima MD

Department of Otorhinolaryngology Nagoya University Graduate School of Medicine, Nagoya, Japan

Yasuo Ogawa MD

Department of Otorhinolaryngology Tokyo Medical University Nishi-Shinjuku, Shinjuku, Japan

Carlos A Oliveira MD PhD

Department of Otolaryngology University of BrasíliaMedical SchoolBrasília, DF, Brazil

Jurek Olszewski MD PhD

Department of Otolaryngology and Laryngological OncologyMedical University of LodzVeterans’ Central HospitalLodz, Poland

Michael M Paparella MD

Paparella Ear, Head and Neck Institute, Otopathology Laboratory Department of Otolaryngology University of MinnesotaMinneapolis, Minnesota, USA

Textbook of Vertigo: Diagnosis and Managementviii

Kourosh Parham MD

Division of OtolaryngologyHead and Neck SurgeryDepartment of SurgeryUniversity of ConnecticutHealth Center, Farmington Connecticut, USA

Lorne S Parnes MD FRCSC

Department of Otolaryngology University of Western Ontario London, Ontario, Canada

Stanley Pelosi MD

Otology Group of Vanderbilt Department OtolaryngologyHead and Neck SurgeryVanderbilt Bill Wilkerson Center Vanderbilt UniversityNashville, Tennessee, USA

Anna Grazia Petrucci MD

“Azienda Sanitaria Locale” of Como Como, Italy

Piotr Pietkiewicz MD PhD


Marie Therese Camilleri Podestà MD

Department of AnatomyUniversity of MaltaMsida, Malta

Alejandro Rivas MD

Otology Group of Vanderbilt Department Otolaryngology Head and Neck SurgeryVanderbilt Bill Wilkerson Center Vanderbilt UniversityNashville, Tennessee, USA

Richard A Roberts MD

Alabama Hearing and Balance Associates, Foley, Alabama, USA

Andre Luis Lopes Sampaio MD PhD

University of Brasília Medical School Brasília, DF, Brazil

Alejo Suarez MD

Laboratory of Otoneurology Biomedical Engineering ProgramBritish Hospital, Montevideo, Uruguay

Hamlet Suarez MD

Laboratory of Otoneurology Biomedical Engineering ProgramBritish HospitalMontevideo, Uruguay

Mamoru Suzuki MD

Department of Otorhinolaryngology Tokyo Medical UniversityNishi-ShinjukuShinjuku, Japan

Jenna Theriault BSc MD

Department of Otolaryngology University of Western Ontario London, Ontario, Canada

Jessica Weiss MD

Division of Otolaryngology Head and Neck SurgeryDepartment of SurgeryUniversity of ConnecticutHealth Center, Farmington Connecticut, USA

Dario A Yacovino MD

Neuro-otology SectionNeurology Research Institute“Dr, Raúl Carrea” (FLENI)Buenos Aires, Argentina

Hanna Zielińska-Bliźniewska MD PhD


MEMORY OF PROF. ALFRED CUSCHIERI (23.7.1945–25.1.2010) GENETICIST AND ANATOMIST

Alfred Cuschieri was born in Sliema, Malta and studied at St. Aloysius College B’Kara and the Secondary Technical School. He obtained his primary medical degree from the Royal University of Malta in 1967. Whilst in Malta, he had started to work on the functional anatomy of olfactory sense organs and his first paper was published in a local journal—the St. Lukes Hospital Gazette. He subsequently proceeded to Guy’s Hospital Medical School in London, UK. His studies focused on the olfactory mucosa of the mouse and the relevant histology work was included in the 35th Edition of Gray’s Anatomy 1973, p. 1090. Whilst carrying out his studies in London, he also worked as a demonstrator at Guy’s Hospital. He completed his PhD in 1972 and returned to Malta at the Anatomy Department where he was appointed Lecturer in Anatomy at the University of Malta. Scientific papers on his further studies of the development of the olfactory mucosa in the mouse using light microscopy were published in the Journal of Anatomy (1975) 119, pp. 277-286 and other eminent scientific journals. In 1979, he proceeded to Kuwait as Associate Professor in Anatomy and Consultant Geneticist where he served till 1984. He helped to set up the Cytogenetic Center as an Annexe to Al-Sabah Hospital in Kuwait and trained several young doctors in cytogenetic analysis. During this period, his work in anatomy included:• Ultrastructurallocalizationofadenosinetriphosphataseactivityinlymphocytesactivatedinvitroby

phytohemagglutinin. Histochemical Journal. 1982;14;539-607.• CytochemicaldemonstrationofincreasedATPactivityinlymphocytesactivatedinvitrobyphyto

hemagglutinin or by mixed lymphocyte reaction. Histochemical Journal. 1982;14;139-48.• The fateofphytohemagglutininactivatedhuman lymphocytes following theirpeakproliferative

activity. Journal of Anatomy. 1985;140(1):79-92.• Surfacemorphology ofmitogenactivated human lymphocytes and their derivatives in vitro.

Journal of Anatomy. 1985;140(1):pp. 93-104. He returned to Malta in 1984 and was appointed Professor of Anatomy and Genetics at the University of Malta and served as Head of Department for various periods since 1991. He also served as Director to theInstituteofGerentologyandhelpedtosetuptheUniversityoftheThirdAgein1991. He was very active in researching various aspects of congenital malformations in Malta and published a number of related scientific papers. In 1984, he was instrumental in setting up the National Register of Congenital Anomalies. From 2008 onwards, his studies focused mainly on fetuses with anomalies. He showed particular interest in telomeric causes of mental retardation and in Li-Fraumeni syndrome. He was innovative in his approach to teaching and introduced what he called “critical thinking sessions” which were aimed at helping students to understand the relevance of the basic sciences to the clinical scenarios. Prof. Alfred Cuschieri was a Member of the Royal Society of Medicine, Anatomical Society of Great Britain and Ireland, Clinical Genetics Society, and Skeletal Dysplasia Group for Teaching and Research. He was also Vice-President of the National Bio-Ethics Committee. Prof. Alfred Cuschieri was a colleague who was held in high esteem by his peers. He was a gentleman as well as having a very gentle nature. He treated all and sundry with respect and showed care and understanding towards others. He also had a sense of humor and would drop a little joke during a lecture to stimulate students’ interest. Thoughhebecameterminallyillin2009,hecontinuedtospendtimeoncampustillhishealthfailedhim.Sadly, he passed away on the 25th of January 2010 . He left to mourn his loss, his wife Monica nee Misud, whom he married in 1969, his two daughters and five grandchildren, besides numerous friends and colleagues.

Prof. Marie Therese Camilleri Podesta MD

Professor of Anatomy, University of Malta

Contents xi

Otologicaldiseasesarecommon.Theyareunidentifiedbythepublic,butcancausedisturbingandevendisabling (incapacitating) symptoms. For example, studies by the National Institutes of Health have indicated that approximately 40 million Americans have tinnitus, about 40 million Americans have a significant hearing loss, and about 90 million Americans have dizziness sufficient enough to consult their physician, most of whom have benign positional vertigo and many of whom have vertigo that is often disabling. Of all the symptoms of otological/neurotological diseases, vertigo can be one of the most incapacitating of symptoms. Vertigo almost always arises from the pars posterior (the vestibular portion of the inner ear) and rarely from central or intracranial causes. Vertigo, often associated with nausea and vomiting, can be defined as any sensation of motion, characteristically a spinning sensation, external or internal (perceived to be within the patient’s head). It should be noted, however, that peripheral vestibular diseases such as Ménière’s disease can also produce symptoms of disequilibrium, a sensation of being off-balance, visually induced vertigo or the so-called shopping center nystagmus, motion-related or positional vertigo which can be confused with benign positional vertigo, and episodes of falling. Vertigo is usually accompanied by symptoms of the cochlea (pars inferior, anterior labyrinth) such as sensorineural hearing loss, which can fluctuate and become progressive, pressure or tinnitus or an inability to tolerate loudness (recruitment), any one of which can be the patient’s chief complaint. Often, vestibular symptoms from the posterior labyrinth appear dominant over cochlear symptoms, although less often cochlear symptoms can also be of greater difficulty to the patient. I am pleased that the editors have included articles on Epidemiology of Dizziness (Chapter 3). For many years, I have observed Ménière’s disease to be far more prevalent in the northern cities as compared to southern cities, in all the countries of the world. I hope that controlled demographic studies will assess this observation. Moreover, for decades, I have described Ménière’s disease as having a genetic basis, or that the etiology of Ménière’s disease is “multifactorial inheritance” (1985). I am also pleased that a chapter on “Atypical Ménière’s Disease” (Chapter 8) is included, since many patients suffer from atypical types of Ménière’s disease with lesser symptoms, and not every patient has to have fully manifest Ménière’s disease. Since vertigo and vestibular symptoms are such common and major problems internationally, I congratulate Dr Francesco Dispenza and Dr Alessandro De Stefano for organizing, editing, and authoring this compilation of authors to shed light on this most serious symptom of vertigo and vestibular diseases that beset mankind.

Michael M Paparella MDPaparella Ear, Head and Neck Institute

Otopathology LaboratoryDepartment of Otolaryngology

University of MinnesotaMinneapolis, Minnesota, USA

Foreword

Contents xiii

Vertigo is a human symptom that has been experienced for thousands of years. As it is well known, Jonathan Swift the famous Irish author of the Gulliver’s Travel was suffering from Ménière’s disease. Although well experienced and described by the people for many centuries, the disorder of balance remains a very complex phenomenon. We remember that when we were young students at Medical Schools, some difficult to understand vestibular disorders were present, probably due to the compartmentalization of the notions in several disciplines, never summarized in a single theme. Even today, vertigo is a common and frustrating symptom told by more than a few patients to all physicians. Effectively, vertigo may be the first expression of several diseases, including life-threatening conditions. Thedifficult to analyze vertigonot only starts froman etiologicpoint of viewbut also fromaterminological one. What is vertigo? Strictly speaking, vertigo is an “illusory perception of motion”, but patients often refer ambiguously to vertigo, dizziness, giddiness and disequilibrium or imbalance. In addition, many specialists could be consulted by a dizzy patient: Otolaryngologists, Neurologists, Family Physicians, Emergency-Care Physicians and Ophthalmologists; and this variability may lead to unnecessary diagnostic tests with delay in the diagnosis and management. For this reason, we have thought of a book in which the various features of vertigo were treated by some of the most famous scientists worldwide, specialized in treatment of balance disorders. Not only Otologists but also Neurologists, Epidemiologists, Physiologists, Anatomists and Surgeons, coming from the main Schools that gave to the scientific community some of the cornerstones that led to understand and treat vertigo, described in this book their experience in the diagnosis and management of dizzy patients. Thistextbookincludesaboutathousandreferencesandexplicativeillustrations,tablesandfiguresthathelpthereadersduringthestudyoftheargument.Thechaptersdiscussaboutthemaindiseaseandsyndrome causing vertigo, starting from the basic sciences (anatomy and physiology), coming through the diagnostic pathway available for the clinicians, and ending with the treatment section divided in medical therapy and rehabilitation. For this reason, we consider this volume a complete reference for all the students and physicians who are interested in the complex but basic world of vertigo.



Preface

Contents xv

Acknowledgments

Theeditorswanttothankalltheauthorswhocontributedtothisbook.Withtheirpreciousandexpertwork, the readers can find a lot of answers to the vertigo disease. We thank the M/s Jaypee Brothers Medical Publishers (P) Ltd. New Delhi, India, for strongly believing in our project and the editorial staff who steadily supported our work. A special thanks to Prof. Carlo Dispenza, ENT Department of University of Palermo, Italy, for his master teaching during the training period and for passing the love to the ENT discipline. We sincerely thank Prof. Carmine Di Ilio Rector Magnificus (Chancellor) of “G. d’Annunzio” University of Chieti-Pescara, Italy, without whose help many of our dreams would not have been fulfilled. ThankstoDrEttoreBenniciwhoalwayssupportedourrequeststodevelopthestudyandresearchinthe field of otology and neurotology. ThanksalsotoProf.AdelchiCroceforhiswillingnessandtoDrDaniloPatrocinioforhiskindness.

Contents xvii

Contents

1. Anatomy of the Peripheral and Central Vestibular System 1Francesco Dispenza, Alessandro De Stefano, Alfred Cuschieri

• TheVestibuleandSemicircularCanals 1

• Structure of the Peripheral Receptor Cells 2

• Molecular Structure of the Mechanoreceptors 4

• Orientation of the Receptors in the Utricle and Saccule 4

• Synaptic Contacts with Receptors 6

• The Vestibular Nerve and Ganglion 7

• The Vestibular Nuclei 7

• Functional Connections of the Central Vestibular System 8

2. Essentials of Vestibular System Physiology 11Vladimir Marlinski

• TheVestibularLabyrinth 12

• TheHairCell 13

• TheVestibularNerve 14

• TheVestibularNuclei 15

• CorticalRepresentationoftheVestibularSignals 18

• VestibularReflexes 19

• VestibularDisorders 21

3. Epidemiology of Dizziness 26Anna Grazia Petrucci, Alessandro De Stefano, Francesco Dispenza

• EpidemiologyofDizziness:DifficultyintheExactDetermination 26

• Epidemiology of the Most Common Types of Dizziness 27

• EpidemiologyofDizzinessintheElderly 32

• SomeHopeintheNearFuture 35

4. Differential Diagnosis of Vertigo 38Richard A Roberts

• ThreeKeystoDifferentialDiagnosis 38

• OtherConsiderations 41

• Putting it Together 42

Textbook of Vertigo: Diagnosis and Managementxviii

5. Clinical and Computerized Test for Vertigo Evaluation 44Hamlet Suarez, Enrique Ferreira, Alejo Suarez, Dario Geisinger

• Theory of Control System 44

• ComputerizedTesting 45

• Evaluation of Ocular Movements 46

• Otolithics End-Organs Assessment: Vestibular Evoked MyogenicPotentials 51

• PerceptualTesttoVestibularDisorders 52

• ComputerizedTestforVestibulospinalFunction 56

• FinalConsiderations 60

6. Ménière’s Disease 62Carlos A Oliveira, Fayez Bahmad Júnior, Andre Luis Lopes Sampaio

• EpidemiologyofMénière’sDisease 63

• Pathology of Ménière’s Disease 66

• DiagnosticTests 73

• MagneticResonanceImaging 79

• Treatment 79

• MigraineandMénière’sDisease 81

• FinalComments 86

7. Imaging of Endolymphatic Hydrops 94Tsutomu Nakashima, Shinji Naganawa

8. Atypical Ménière’s Disease 108Nicolas Perez Fernandez, Raquel Manrique Huarte

• Spontaneous Recurrent Vertigo with or without Hearing LossinPatientswithoutMigraine 108

• Sensorineural Hearing Loss Fluctuating or Fixed with DisequilibriumbutwithoutDefiniteEpisodes 109

• DelayedEndolymphaticHydrops 110

• FromSuddenSensorineuralHearingLosstoDefinite Ménière’sDisease 112

9. Unilateral Sudden Loss of Vestibular Function and Vestibular Neuritis 115Carol A Foster

• Pathophysiology 116

Contents xix

10. Benign Paroxysmal Positional Vertigo 128Lorne S Parnes, Jenna Theriault

• AnatomyandPhysiology 129

• Pathophysiology 130

• ClinicalPresentation 133

• Management 135

• SurgicalManagement 140

• Prognosis 142

11. Malignant Paroxysmal Positional Vertigo 145Alessandro De Stefano, Francesco Dispenza

• Suggested Clinical and Instrumental Pathway to Rule Out MalignantParoxysmalPositionalVertigo 146

• Reasons to Differentiate Benign Paroxysmal Positional VertigofromMalignantParoxysmalPositionalVertigo 146

12. Superior Canal Dehiscence Syndrome and Perilymphatic Fistula 151Alejandro Rivas, Stanley Pelosi, Michael E Glasscock III

• SuperiorCanalDehiscenceSyndrome 151

• PerilymphaticFistula 157

13. Vertebrobasilar Insufficiency and Other Forms of Cervical Vertigo: Diagnosis and Management 163Jurek Olszewski, Hanna Zielińska-Bliźniewska, Piotr Pietkiewicz

• PathomechanismofCervicalVertigo 163

• PathomechanismofVertebrobasilarInsufficiencyversusVertigo 163

• DiagnosticsofVertigo 165

• CervicalVertigoTreatment 174

• PhysicalTherapy 174

14. Drug-induced Vertigo 179Jessica Weiss, Kourosh Parham

• MedicationClasses 180

• ExperimentalModels 181

15. Migraine Associated Vertigo 184Marcello Cherchi, Timothy C Hain

• MigraineAssociatedVertigo 184

• DefinitionofMigraineAssociatedVertigo 184

Textbook of Vertigo: Diagnosis and Managementxx

• PathophysiologyofMigraineAssociatedVertigo 185

• CommonHistoricalFeaturesofMigraineAssociatedVertigo 186

• DemographicsandRiskFactorsofMigraineAssociatedVertigo 186

• PhysicalExaminationinMigraineAssociatedVertigo 186

• ParaclinicalTestingforMigraineAssociatedVertigo 187

• DifferentialDiagnosisofMigraineAssociatedVertigo 188

• TreatmentofMigraineAssociatedVertigo 189

• PrognosisofMigraineAssociatedVertigo 191

16. Balance Disorders in Children 194Margaretha L Casselbrant

• Prevalence 194

• ClassesofBalanceDisorders 195

• AcuteNonrecurringSpontaneousVertigo 195

• RecurrentVertigo 196

• ManagementofVestibularMigraineDisorders 200

• NonvertiginousDisequilibrium 201

• EvaluationofDizzyChild 204

17. Vertigo in Elderly 209

Vertigo and Aging 209Michael M Paparella

Benign Paroxysmal Positional Vertigo and Aging 214Yasuo Ogawa, Mamoru Suzuki

• EpidemiologyandPathophysiology 214

• AgingintheOtolithandVestibularOrgans 215

• ClinicalCharacteristics 215

18. Medical Management of Vertigo 219Dario A Yacovino, Timothy C Hain

• Physiology 219

• Pharmacology 220

• TreatmentofIndividualConditions 225

Contents xxi

19. Surgery of Vertigo 237Gauri Mankekar, R Santhosh Kumar

• Surgery 237

• Cochleosacculotomy 237

• EndolymphaticSacSurgery 238

• Labyrinthectomy 238

• VestibularNeurectomy 239

• Surgery for Benign Paroxysmal Positional Vertigo 242

• VestibularImplant 243

20. Vestibular Rehabilitation Therapy 245Richard Gans

• StatusoftheVestibularDysfunction 245

• CaseStudy 255

Index 259

Alejandro Rivas, Stanley Pelosi, Michael E Glasscock III

CHAPTER

12 Superior Canal Dehiscence Syndrome and Perilymphatic Fistula

ABSTRACT

Superior semicircular canal dehiscence is caused by the lack of bone covering the superior semicircular canal at the level of the middle fossa plate. Patients with SCDS usually complain of both vestibular and auditory symptoms. Among the auditory symptoms, patients may present with aural full-ness, conductive hearing loss, a decreased hearing threshold for bone conduction (suprathreshold) and auto phony. The vestibular symptoms include chronic disequilibrium, occasional oscillopsia, Valsalva or pressure-induced dizziness. When suspecting SCDS, clinicians need to realize that this is a clinical diagnosis, based on symptoms and physical examination. Other diagnostic tests help to confirm the diagnosis. The decision to proceed with surgical treatment, in many cases, is difficult. The clinician must weigh the risks and complica-tions of surgery along with the patient’s symptoms and the impact those have in their quality of life.

SUPERIOR CANAL DEHISCENCE SYNDROME

OverviewSuperior canal dehiscence syndrome (SCDS) is a pathology that was discovered by Minor et al. (1998).1 Despite its recent recognition, its patho-physiology has been elegantly described, reliable tests have been developed to diagnose the disease, and a curative surgery through two different appro-aches has been elucidated. As the name of this syndrome describes, SCDS is caused by the lack of bone covering the superior semicircular canal at the level of the middle fossa plate. Carey et al. (2000)2 looked at 1,000 temporal

bones finding that approximately 0.7% and 1.4% individuals had either a dehiscence or a very thin layer of bone over the canal, respectively. Moreover, most of the individuals with dehiscence were found to have bilateral defects. Also, when they looked at infant specimens, they found a thin layer of bone at birth that gradually thickened until 3 years of age. Taking into account the bilateral nature of this abnormality and its similarity to the appearance of infant temporal bones, evidence suggests that this syndrome is a developmental anomaly, where usu-ally a second event occurs in adulthood causing new onset of symptoms. Those events can be secondary to trauma or increased intracranial pressure, caus-ing fractures over the thin bone or destabilizing the dura over a pre-existent dehiscence.2 The developmental theory is further supported by frequent findings of associated tegmen defects or brain encephalocele. In patients with unilateral SCDS who underwent surgical repair, the incidence of a tegmen defect ranges from 50% to 74%,3,4 and that number increases up to 94% in radiologic studies of patients with bilateral dehiscences.3 These findings suggest a generalized stagnant progression of bony coverage of the entire middle fossa plate.

Signs, Symptoms and PathophysiologyPatients with SCDS usually complain of both ves-tibular and auditory symptoms. Among the auditory symptoms, patients may present with aural full-ness, conductive hearing loss, a decreased hearing threshold for bone conduction (suprathreshold) and autophony. Individuals describe this last symptom as “hearing their own voice”, “hearing their eyes move”, or even “hearing the muscles of the neck move”. Occasionally, patients may also have pulsatile

Textbook of Vertigo: Diagnosis and Management152

tinnitus, which is attributed to the pulsations of the dura over the dehiscent semicircular canal. The vestibular symptoms include chronic dis-equilibrium, occasional oscillopsia, Valsalva or pre-ssure-induced dizziness and frequent noise-induced dizziness (Tullio phenomenon). Although the most common presenting symptom in SCDS is Tullio phenomenon, present in 90% of patients,5 it has also been described in other sources of labyrinthine dehiscences. These include, perilymphatic fistulas (PLFs),6 head trauma,7 cholesteatoma eroding the lateral semicircular canal,8,9 after fenestration procedures,9 and even in patients with labyrin-thine fistulas secondary to syphilitic gummatous osteomyelitis.10 All of these processes need to be considered in the differential diagnosis. During the physical examination, several ma-neuvers can be performed to elicit the characteristic nystagmus. To understand the pathophysiology of this disorder, one has to first understand the mechanism of a third window effect into the inner ear. In the normal ear, air-conducted sound moves the tympanic membrane and ossicles setting the stapes into back-and-forth motion. The resulting pressure difference between the oval and round windows leads to motion of the cochlear partition, resulting in perception of air-conducted sound. In SCDS, when sound or positive pressure in the ear are given, a portion of the endolymphatic volume displaced by the moving stapes is shunted through the dehiscent canal away from the cochlea, result-ing in an ampullofugal deflection of the superior canal cupula, which causes an excitatory verti-cal and torsional nystagmus with the slow phase going upward and inward on central gaze5,11,12 (Fig. 1A). These evoked eye movements can be elicited with excitatory maneuvers that include per-forming Valsalva against open glottis and pinched nostrils, applying positive pressure using a pneu-matic otoscope or pressing on the tragus (Hennebert sign, fistula sign), or by presenting loud noises with a portable audiometer. This last test is performed by presenting different tones from 125 Hz to 4,000 Hz at high levels, up to 110 dB normal hearing level, and observing the eye movements with either Frenzel lenses or video goggles. An inhibitory evoked nystagmus can also be provoked with tests that increase the intracranial pressure and create a downward stimulation of the dome of the dehiscent semicircular canal. The resulting endolymphatic wave causes deflection

of the superior canal cupula in an ampullopetal manner. This produces an evoked vertical torsional nystagmus with the slow component going downward and outward on the side of the lesion on central gaze (Fig. 1B). These maneuvers include Valsalva with closed glottis, hyperventilation or jugular venous compression. A recent in-office procedure was described using vibratory stimuli to diagnose SCDS. Use of a 100 Hz vibrator, applied to the suboccipital area while the patient is seated, can elicit a vibration- induced vertical or torsional nystagmus in patients with unilateral superior semicircular canal dehiscence. In patients with bilateral dehiscences, the nystagmus tends to be purely vertical as the torsional component cancels out. This seems to be a sensitive screening test in the office setting.13 Finally, to complete the physical examination, it is important to perform a tuning fork examination, with a 512 Hz fork, to confirm the conductive hear-ing loss, which is frequently present in about 52% of cases.5 Moreover, some patients can localize the bone conduction on the affected side when placing the tuning fork against the internal malleolus of the ankle.14

Diagnostic EvaluationWhen suspecting SCDS, clinicians need to realize that this is a clinical diagnosis, based on symp-toms and physical examination. Other diagnostic tests help to confirm the diagnosis. These include audiometry, acoustic stapedial reflexes, vestibular evoked myogenic potentials (VEMP), computed tomography (CT) and recently described electro-cochleography. Audiometry is an important test in the workup of SCDS, not only preoperatively to assist in the diagnosis but also postoperatively to monitor the surgical success. Few patients present with normal hearing and only complain of aural fullness. Some other patients have only an isolated conductive hearing loss, more prominent in the low frequen-cies.12,15 Usually when present, it is accompanied with a suprathreshold bone conduction, less than 0 dB normal hearing level, previously described as “conductive hyperacusis”.5 It is crucial to recognize these two features in the audiogram so as to differ-entiate SCDS from otosclerosis.14 It is here where acoustic reflexes can be of use, as patients with SCDS have normal reflexes while patients with otosclerosis present with absent reflexes in the affected ear.

Superior Canal Dehiscence Syndrome and Perilymphatic Fistula 153

Cervical VEMP indirectly measures the vestibu-locollic reflex and is a good indicator of saccular and inferior vestibular nerve function. The VEMP path-way is thought to be activated by the transmission of sound through the stapes to the saccule, stimulating the inferior vestibular nerve, vestibular nucleus, and medial and lateral vestibulospinal tract to the ipsilateral sternocleidomastoid muscle (SCM). The VEMPs are measured using short latency electro-myograms evoked by high-acoustic stimuli at the ipsilateral ear and recorded using surface electrodes over a tonically contracted SCM.16,17 A decreased cervical VEMP threshold is indicative of SCDS and is an excellent screening tool for the diagnosis of this disorder, with a specificity and sensitivity that ranges from 80% to 93% in most series.18,19 Other conditions that can present with decreased VEMP thresholds are those where a third window effect is present, including enlarged vestibular aqueduct and some inner ear abnormalities causing a dehis-cence between the internal auditory canal and the vestibule.20 To confirm the diagnosis of SCDS, a CT of the temporal bones has to show the absence of bone covering the superior semicircular canal. Multislice computed tomography (MSCT) is currently the

ideal imaging modality to confirm SCDS. Several tomographic parameters improve the accuracy in the diagnosis of a dehiscent superior canal. These include collimation, reconstructions in the plane of the superior semicircular canal, field of view, filtering and reduction of motion artifact. Although scans with 1.0 mm collimation viewed in the axial and coronal planes have good sensitivity, the specificity and positive predictive value can significantly increase when using 0.5 mm collimation so that the reconstructions in the Stenver’s and Posch plane do not lose resolution.21 Likewise, the field of view improves resolution when the labyrinth is shown over the fixed image matrix, minimizing partial volume averaging. A bone edge-detecting filter is recommended to obtain meaningful images; however, noise reduction algorithms may filter out a thin layer of bone, decreasing the image accuracy. Several studies have documented that high-resolution MSCT overestimates the prevalence of SCDS. These studies have clearly shown a significant number of false positives using MSCT, when comparing the prevalence of a dehiscent superior canal radiographically (3–4%)22 versus looking at cadaveric histologic evaluation (0.5%)2 or comparing them to symptomatic patients (0.6%).23

Figs 1A and B: Diagrams show the stimulation pathway of the cupula of the superior canal (top panels), during pressure changes provoked by excitatory (left) and inhibitory (right) forces, in superior canal dehiscence syndrome. The bottom panels correlate the direction of the slow phase eye movement on central gaze during such stimulations. (A) Excitatory maneuvers (noise, Valsalva with pinched nostrils, positive exact audio copy pressure) producing an ampullofugal deflection, causing a torsional vertical slow phase nystagmus upward and inward on the side of the lesion. (B) Inhibitory maneuvers (valsalva with closed glottis, increased intracranial pressure) producing an ampullopetal deflection, causing a torsional vertical slow phase nystagmus downward and outward on the side of the lesion

A B


An MSCT may not only present as a false positive where a thin layer of bone over the canal is still present, but it can also overestimate the size of the dehiscence.24 For this reason, CT imaging alone can be misleading for diagnosis of SCDS and should only be weighted in the context of signs, symptoms, audiogram and vestibular testing before concluding that a patient has SCDS and that might require treatment.

Management

The decision to proceed with surgical treatment, in many cases, is difficult. The clinician must weigh the risks and complications of surgery along with the patient’s symptoms and the impact those have in their quality of life. Some patients present only with an incidental radiographic finding of dehiscence without symp-toms. In those cases, we maintain a conservative approach and follow them on a yearly or biannual basis. Some patients present with minimal symp-toms such as isolated aural fullness or isolated hear-ing loss. In those cases, most patients elect to follow a nonsurgical treatment strategy with hearing aids, particularly after counseling about the risks of mild to profound sensorineural hearing loss (SNHL), unilateral vestibular weakness, and all the other risks that a middle fossa approach might carry. Patients with symptomatic bilateral SCDS pose an interesting challenge. Symptoms and functional evaluation will dictate the surgical side to operate on first. Most patients can clearly define a side which is worse than the other. If they cannot, usually the physical examination or VEMP evaluation determines the worse side. An even more challenging decision is to perform a second sided surgery in SCDS patients with persistent or new onset of symptoms. A recent review of 5 patients showed that sound-induced and pressure-induced vertigoes were the most common symptoms prompting surgery. Although most patients developed some degree of oscillopsia after bilateral SCDS surgery, in general, they were very satisfied with second-side surgery as their other SCDS symptoms usually resolved.25 Because of the oscillopsia and previous research demonstrating that transient global vestibular hypofunction normalizes 4–6 months after surgery, waiting at least 6 months after the first surgery is advisable.26

When patients have significant disabling symptoms, surgical intervention is indicated. Two different types of techniques have been described to address the absent bone over the superior canal. Those are canal resurfacing and canal plugging. The authors prefer canal plugging as it achieves better long-term symptom control compared to canal resurfacing. This technique has been reviewed in the following paragraphs. Two major approaches to performance of canal plugging have been described. The first one is the middle fossa approach described by Minor (1998).1 The second one was described by two different groups, Agrawal and Parnes (2008) and Crovetto et al. (2008).27,28 Surgeons that advocate the transmastoid approach prefer it because they avoid performing a craniotomy, the anatomy of the mastoid cavity is more frequently visited by otologic surgeons, it can be done as an outpatient surgery, it avoids temporal bone retraction, and it does not interact with intracranial forces that may decrease the stability of a middle fossa repair.

Transmastoid Approach

The patient is placed in supine position, and dexamethasone 0.1 mg/kg is given, along with preoperative antibiotics. A “C” postauricular incision is performed and opened down to the level of the loose areolar tissue over the temporalis fascia. A small piece of temporalis fascia is harvested for later use in the canal plugging. A T-shaped mastoid periosteal incision is then made. The periosteum is then raised superiorly over the linea temporalis, posteriorly over the sigmoid and anteriorly to the edge of the external auditory canal. Using cutting and diamond burrs, a cortical mastoidectomy is then performed. The tegmen is identified superiorly, the ear canal anteriorly and the sigmoid sinus posteriorly. These three landmarks are then dissected down to the mastoid antrum, which is widely opened to visualize the lateral process of the incus. The lateral canal is used as landmark to identify the superior canal. The tegmen mastoideum is thinned paying attention not to open it, in order to prevent a potential iatrogenic encephalocele. The air cells over the superior canal are drilled, and once compact bone is identified, the superior canal is blue-lined using a 2–3 mm diamond burr, at the level of its


anterior and posterior crura. Once the bone is egg-shelled, the anterior crura of the canal is fractured inward on itself obliterating the canal anteriorly. Small pieces of fascia are then used to plug the anterior crus, followed by bone chips. The same maneuver is performed in the posterior crura. Bone pâté is then placed over the superior canal followed by a piece of fascia to promote revascularization and fibrin glue to stabilize the reconstruction. The mastoidectomy is then completed in the usual manner. The periosteum is closed using interrupted vicryl sutures. The skin is closed using interrupted vicryl sutures. The postauricular incision is then covered with ointment. The wound is then covered with a cotton ball, telfa and a mastoid dressing for 24 hours. The patient is put on a steroid taper for 2 weeks and followed in clinic 3 weeks postoperatively. This surgical technique has been effective relieving the symptoms of this pathology.29,30 However, it carries several disadvantages that include the inability to confirm the canal dehiscence during surgery, the potential inability to repair an associated tegmen defect when present, and inability to access the superior canal in patients with low laying tegmen mastoideum lateral to the superior canal. For these reasons, the authors favor the middle cranial fossa approach.

Middle Fossa Approach

The patient is placed in Park-Bench position, 0.5 mg/kg of mannitol is given, along with preop-erative antibiotics and dexamethasone 0.1 mg/kg. The intraoperative navigation system is registered against a previously obtained CT of the head. A left preauricular curvilinear incision is planned and performed (Fig. 2A). Scalp hemostasis is ob-tained using bipolar cautery or Raney clips. After identifying the temporalis fascia, a rectangular graft is harvested for later plugging of the semicircular canal and potential repair of the tegmen tympani (Fig. 2B). The temporalis muscle is then opened in a vertical fashion using monopolar cautery and dissected free from the temporal squamosa using monopolar cautery and periosteal elevators. Next, the 3 mm cutting bur on the high-speed air drill is used to fashion a rectangle-shaped craniotomy based slightly anterior to the EAC (Fig. 2C). The bone flap is elevated. The bony edges are harvested with a 1 mm Rongeur, for later use during the canal

plugging, and all the exposed air cells are obliterated with bone wax. The operating microscope is then brought into the field and the dura is dissected free from the middle fossa skull base in a posterior and anterior direction utilizing a Penfield 1 dissector (Fig. 2D). Using the Fisch middle fossa retractor, the dura is retracted from the floor of the middle fossa until the superior semicircular canal is identified using the navigation system (Fig. 2E). The dura is slowly elevated from the superior semicircular canal, preventing disruption of the membranous canal. Attention is then turned to the canal plugging. A small piece of fascia is inserted into the proximal opening of the superior semicircular canal followed by small pieces of bone chips (Fig. 2F). The same procedure is performed in the distal opening. Next, bone chips are placed over the dehiscent lumen (Fig. 2G), followed by bone cement and a large piece of fascia. When a middle fossa defect is present over the tegmen tympani or mastoideum, a second piece of fascia is placed over the bony defect followed by a split thickness calvarial bone graft. Duraseal is used to stabilize the reconstruction (Fig. 2H). The retractor is removed and the bone flap is put back in position and secured with a titanium plating system. The temporalis muscle is closed with interrupted vicryl suture and the skin is closed with running nylon. Following closure, the Mayfield-Kees head holder is removed and a mastoid compression dressing is left in place for 3 days. The patient is transferred to the neurological ICU for 24 hours and discharged to home the second or third postoperative day, with a steroid taper for 2 weeks and pain medication. The patient is followed in clinic 3 weeks postoperatively.

Results

In our experience, patients are tremendously satisfied after surgery. This improvement has been described for both types of approaches. Most patients experience significant improvement of the disequilibrium, as well as the noise-induced and pressure-induced dizziness.26 Crane et al. (2008) looked at the efficacy of surgical intervention using the dizziness handicap inventory (DHI). They found an improvement of this index from 44 ± 24 (mean ± standard deviation) to 18 ± 15 (p < 0.01).31


Figs 2A to H: Plugging of superior semicircular canal dehiscence via middle fossa approach. (A) Preauricular middle fossa incision drawn with patient in Park Bench position, and facial nerve monitor and brainstem auditory evoked response electrodes in place; (B) Temporoparietal fascia harvested; (C) Craniotomy performed; (D) Elevation of dura from the middle fossa floor; (E) Superior canal dehiscence identified (arrowhead marks the canal lumen); (F) Plugging of the ends of the superior canal with fascia followed by bone chips (arrowhead shows bone piece pushing fascia into the anterior end of the canal dehiscence); (G) Arrowhead marks bone chips placed on top; (H) Fascia graft placed on top of the repair and Duraseal used to hold reconstruction in place

A B

C D

E F

G H


A recent report by Ward et al. (2012) outlines the improvement of the low-frequency air-bone gap after surgical plugging. This is attributable to both increased bone conduction thresholds and decreased air conduction thresholds. However, a persistent mild high-frequency SNHL is encountered in 25% of the patients without change in speech discrimination, 1 month postoperatively.32 Although most patients experience improve-ment of the pulsatile tinnitus, hyperacusis and autophony, there have been a limited number of studies quantifying such benefit. Crane et al. (2010) developed an autophony handicap inventory to characterize this symptom. They found an 89% improvement after surgery. The mean autophony index decreased significantly from 42 ± 27 (mean ± SD) to 9 ± 22, (p < 0.01). Out of 18 patients evalu-ated, 13 had complete postoperative resolution, 3 had partial improvement, 1 patient had unchanged autophony, and another patient with coexisting patulous Eustachian tube had worsening autophony after SCDS plugging.33

CONCLUSION

In summary, SCDS is a disease that, despite its relatively recent description, has been extensively studied. The diagnosis is based primarily on clini-cal evaluation and special physical examination maneuvers. Both cervical VEMPs and CT scan are necessary to confirm the diagnosis. Treatment includes conservative monitoring for patients with minimal alteration of their quality of life, while sur-gical management is reserved for those patients with life disrupting symptoms. The decision to choose a middle fossa approach versus a transmastoid approach should be tailored to specific anatomic considerations and coexisting comorbidities such as tegmen defects. Most symptoms after surgery improve, including vestibular complains, pulsatile tinnitus, hyperacusis and autophony. Improvement of hearing loss is variable with significant air-bone gap improvement in the low frequencies and high frequency hearing loss in 25% of patients.

PERILYMPHATIC FISTULA

OverviewPerilymphatic fistula refers to an abnormal com-munication between the inner and the middle ear

spaces, resulting in a leakage of perilymph. The oval window is believed to be the most common site of communication, although leakage may also occur in the round window region. Because of multiple uncertainties regarding etiology, diagnosis and management, the incidence of PLF is largely unknown. One study estimated its incidence at 1/100,000.34 Another report stated that the median number of surgeries per year for PLF performed by a member of the American Otological Society was three.35

History and Theories of Pathogenesis

Perilymphatic fistulas were initially described as a complication of stapedectomy in the early 1960s.36,37 Later in the decade, Fee (1968) was the first to report the occurrence of PLF in patients without a history of prior stapes surgery, describing 2 patients with surgically confirmed fistulas following head trauma and 1 patient with spontaneous onset.38 Shortly after, Stroud and Calcaterra (1970) described 4 patients with spontaneous PLFs and postulated that increased cerebrospinal fluid pressure may account for their development.39 In 1971, Goodhill (1971) proposed mechanisms of “implosive” and “explosive” barotrauma as causes of PLF development (Fig. 3).40 Implosive etiologies introduce positive pressure into the middle ear, which is then transmitted to the inner ear via the oval or round windows. External forces leading to implosive barotrauma include nose-blowing, flying and scuba diving. Explosive barotrauma can result from forces that increase intracranial pressure, which is then transmitted to perilymph via the internal auditory canal or cochlear aqueduct. Any activity that causes a Valsalva maneuver, including cough, weight-lifting or other straining, may result in explosive barotrauma. More recent efforts have focused on identifying a potential anatomic basis for spontaneous PLF using temporal bone studies. Inner ear malformations such as Mondini deformity and enlarged vestibular aqueduct are known to be associated with perilymph or cerebrospinal fluid leakage during stapedectomy or cochlear implantation, and it has been suggested that these entities may also account for cases of spontaneous PLF.41,42 However, the relationship between PLF and abnormalities not evident on CT


Fig. 3: Mechanisms of barotrauma as proposed by Goodhill.40 Implosive forces such nose-blowing, flying and scuba diving, introduce positive pressure into the middle ear, which can then be transmitted to the inner ear via the oval or round windows. Explosive barotrauma may be caused by any activity that causes a Valsalva maneuver and increases intracranial pressure, which is then transmitted to perilymph via the internal auditory canal or cochlear aqueduct

is less clear. Microfissures have been proposed as potential conduits connecting the inner and middle ear spaces (Fig. 4). One study found microfissures to be present in the region of the oval window in 25% of temporal bone cadavers.43 Another microfissure has been described which connects the round window niche and the posterior semicircular canal ampulla.44 While some authors have suggested a causal relationship between microfissures and spontaneous PLFs,45 it is difficult to explain the high prevalence of microfissures in temporal bone specimens and the small number of patients presenting with spontaneous PLFs.46 Other anatomic abnormalities of the middle ear have been proposed as causes of PLF. In 1993, Weber et al. reported that of 80 ears found to have PLF on exploratory tympanotomy, 65 had coexisting middle ear anomalies, the most common being a deformity in the stapes superstructure.42 Other less common abnormalities in patients with PLF were an abnormally curved incus and misshapen round window.

Mechanisms of Inner Ear EffectsCurrently, the central pathophysiologic feature of all descriptions of PLF is that an increased pressure applied to the inner or middle ear causes a disruption of the membranous labyrinth with resulting effects on hearing and balance. When pressure is communicated from the middle ear or

intracranial space to an intact vestibular end-organ, this pressure is equally dispersed to all regions of the inner ear and the vestibular system is not stimulated. The presence of a fistula establishes a low-pressure region in an otherwise closed system which can preferentially vent applied pressure from the middle ear or intracranial space.34,47 This venting process results in endolymph fluid shifts and stimulation of the vestibular system, with resulting clinical symptoms. The mechanisms of hearing loss in PLF have been attributed to several factors. Amongst the more likely causes of hearing loss in PLF is pneu-molabyrinth. Several studies have demonstrated reversible cochlear dysfunction in response to artificially induced pneumolabyrinth in a guinea pig model.48,49 Other authors have used animal models to study alternate mechanisms of cochlear injury in PLF, including acute inner ear pressure changes50 or round window membrane rupture.51

Fig. 4: Proposed microfissure locations as described by Kamerer.45 It has been suggested that microfissures in the region of the round and oval windows may serve as potential sites of perilymph leakage


Causes

The potential origins of PLFs are listed in Table 1. Broadly, they may be grouped into acquired and congenital causes. Iatrogenic PLFs, usually following stapedectomy, are traditionally regarded as the most common etiology. They may develop as a consequence of prosthesis dislodgement, allowing perilymph leakage into the middle ear. Temporal bone trauma represents another possible cause of perilymphatic fistula. Blunt or penetrating trauma may cause a fracture resulting in disruption of the otic capsule and subsequent leakage of perilymph into the middle ear. Baro-trauma, as described above by Goodhill (1971),40 is another postulated mechanism of injury by which perilymphatic fistula can occur. Erosive causes of PLF include any disease process which can affect the middle ear, including cholesteatoma, syphilis or neoplasm. In cases where a precipitating traumatic event has not been identified, the etiology and diagnosis of PLF is less obvious. It is thought that some congenital abnormality may predispose to spontaneous PLF development, perhaps increasing susceptibility after minor trauma that may go unrecognized by the patient. As noted above, various middle and inner ear abnormalities have been associated with surgically confirmed spontaneous PLF.42

Clinical or Differential Diagnosis

Patients classically present with unilateral hearing loss, vertigo and tinnitus. An antecedent history of barotrauma or head trauma is suggestive of the diagnosis. Symptoms may develop suddenly or progressively, and usually both auditory and vestibular complaints are present together. In a review of 91 patients with perilymphatic fistula confirmed via middle ear exploration, nearly half of the patients presented with all three symptoms

of hearing loss, tinnitus and vertigo.52 In contrast, only 8% complained of isolated hearing loss and 13% had vertigo symptoms alone. Physical examination findings may be suggestive of the diagnosis, but neither their presence nor absence should be considered pathognomonic for PLF. Potential positive findings include Hennebert’s sign, which is marked by subjective vertigo in response to increased middle ear pressure, and Tullio’s phenomenon, where vertigo is experienced in response to loud sounds. A positive fistula test may also be suggestive, whereby nystagmus is observed in response to increased middle ear pressure. The accuracy of fistula tests in diagnosis is questionable; one study found fistula tests to be positive in 26% of surgically confirmed PLFs, and additionally in 18% of cases where no PLF was seen on exploratory tympanotomy.53 The differential diagnosis for PLF is broad and includes any condition causing inner ear dysfunction, including Ménière’s disease, viral neurolabyrinthitis, autoimmune hearing loss, superior canal dehiscence and vestibular schwannoma. Other less common erosive etiologies such as syphilis, cholesteatoma or neoplasm may also be considered depending on clinical scenario.

Diagnostic Testing

In any patient suspected of having a PLF, audi-ometry and vestibular function testing should be performed. Isolated PLFs without coexisting middle ear abnormalities classically result in SNHLs. The severity and pattern of hearing loss, however, is not consistent across patients, and frequently patients may demonstrate normal hearing. Vestibular func-tion testing may reveal a multitude of abnormalities, with a consistent finding being reduced unilateral caloric responses.54 Electronystagmography may be useful in cases where the diagnosis of PLF is suspected but unilateral SNHL is absent. Analysis of fluid suspected to be perilymph with various protein markers has been suggested, including Beta-2 transferrin, Beta-trace protein and Cochlin-tomoprotein.55-57 CT may demonstrate the presence of middle or inner ear abnormalities, although in one series of surgically confirmed PLF only 50% of preoperative CTs demonstrated anoma-lies.58 Another occasional finding on preoperative imaging is the presence of pneumolabyrinth.59

Table 1: Causes of perilymphatic fistulas

Acquired Congenital

Iatrogenic Inner ear malformation

Blunt/penetrating trauma Middle ear anomaly

Barotrauma Microfissures?

Erosive


Treatment

As is the case with diagnosis, management strategies are controversial. In the scenario where diagnosis of PLF is uncertain, exploratory tympanotomy provides an opportunity for both diagnostic confirmation and therapeutic intervention. In clinical scenarios where diagnosis is unequivocal (i.e. pneumolabyrinth), either a conservative or operative management strategy may be pursued. Conservative approaches include bed rest, head elevation, avoidance of straining and stool softeners. Surgery may be performed from the outset or in cases where progressive hearing loss and persistent vertigo develop following an initial period of observation. Most authors agree that the goal of surgery is to improve vestibular symptoms and stabilize hearing, although it has suggested that hearing can improve in some patients.50,60 Middle ear exploration via transcanal approach is the typical method of PLF repair. Intraoperative maneuvers to increase intracranial pressure and facilitate perilymph leakage may be employed, although their true utility remains uncertain. These include forced Valsalva, ossicular chain manipulation, bilateral jugular vein compression and Trendelenburg positioning. Inspection of the middle ear may show perilymph collecting around the oval or round window. However, even if no visible perilymph is evident, most authors recommend plugging of both windows with a perichondrial, fascial or fat graft.35,60 Additionally, inspection of other potential sites of perilymph leakage should be performed, including Hyrtl’s fissure or temporal bone fracture lines through the otic capsule. Postoperative care includes the same conservative strategies employed prior to surgery. Patients may be kept on bed rest for 1–2 days postoperatively, and subsequently are instructed to limit any straining for up to 3 weeks after surgery. Outcomes reported following PLF repair are variable. The Iowa series reported that 95% of patients had resolution or improvement of their vestibular symptoms, while 23% of patients had improvement of hearing to a serviceable range.52 Other reports have quoted rates of vertigo improvement of 80–89%,61-63 hearing improvement rates between 13% and 47%,61,64 and hearing

stabilization in 67%.63 Postoperative hearing loss, either sensorineural or conductive in nature, may occur in about 5% of patients as well.61 A new conductive hearing loss, when present, is generally attributed to impairment of stapes motion after oval window graft placement.

CONCLUSION

Perilymphatic fistula remains a challenging otologic disorder due to multiple uncertainties regarding diagnostic and management strategies. A high index of clinical suspicion is necessary in establishing a diagnosis due to the constellation of nonspecific signs and symptoms associated with the disorder. Moreover, the decision regarding if/when to surgically intervene in PLF patients remains controversial and, despite suggestive clinical findings, it is generally accepted that a significant percentage of patients may have negative explorations. Further efforts are necessary to improve diagnosis and therapeutic interventions for this elusive otologic condition.

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