VI nerve palsy (abducens palsy)Paralisia do VI nervo (abducente)
Renato Luiz Nahoum Curi, Ian Curi Bonotto de Oliveira Costa, Tbatta Graciolli Moreira Barroso3
1Fluminense Federal University UFF Rio de Janeiro (RJ), Brazil. Niteri Institute of Ophthalmology ION Rio de Janeiro (RJ), Brazil.2Medical Student; Intern at the Ophthalmology Service, Antnio Pedro University Hospital (HUAP), Fluminense Federal University UFF Rio deJaneiro (RJ), Brazil.
Study conducted at the Ophthalmology Department, Fluminense Federal University Medical School UFF - Rio de Janeiro (RJ), and the ION Niteri Institute of Ophthalmology - Rio de Janeiro (RJ), Brazil
The authors review the basic aspects, etiology, clinical signs, diagnosis and treatment of the VI nerve palsy. Review the possible causesof abducent paralysis and location of determinant lesions. The clinical signs and clinical follow up are also observed in order to guide theetiology and therapeutic. The authors describe the clinical, pharmacological and surgical treatment. The authors emphasizes theirproposal of VI nerve palsy correction using the isolated Carlson-Jampolsky transposition.
Keywords: Abducens nerve; Abducens nerve diseases/etiology; Abducens nerve diseases/surgery; Palsy/surgery; Paresis;Ophthalmologic surgery procedures/methods
Neste trabalho foi realizada uma reviso da literatura com o objetivo de integrar e compilar artigos disponveis sobre a paralisia doVI nervo (abducente) para rever suas caractersticas clnicas, etiologias possveis e os procedimentos clnicos, farmacolgicos ecirrgicos para seu tratamento. Primeiramente, descreve-se sua ao, localizao, trajeto e possveis leses, depois seus principaisfatores etiolgicos para em seguida abordar-se o diagnstico e o tratamento. Proposta de transposio de Carlson-Jampolsky isoladano tratamento cirrgico da paralisia do VI nervo tambm apresentada.
Descritores: Nervo abducente; Doenas do nervo abducente/etiologia; Doenas do nervo abducente/cirurgia; Paralisia/cirur-gia; Paresia; Transposies musculares; Procedimentos cirrgicos oftalmolgicos/mtodos
Rev Bras Oftalmol. 2013; 72 (1): 59-69
The authors declare no conflicts of interest
Received for publication: 26/10/2011 - Accepted for publication: 18/5/2012
Figure 1: Left VI nerve (abducens) paresis or paralysis. Left esotropiawith major limitation of abduction, increasing on left gaze
Figure 2: Bilateral Duane syndrome, pre- and postoperatively
Rev Bras Oftalmol. 2013; 72 (1): 59-69
Curi RLN, Costa ICBO, Barroso TGM
Cranial nerve VI (abducens) innervates only oneextraocular muscle, the ipsilateral lateral rectus (LR), whose basicaction is abduction of the eye. Impairment leads to a limitation inabduction of varying intensity and an imbalance of horizontalforces, with a predominance of the intact medial rectus (MR),resulting in esotropia and homonymous diplopia (Figure 1). Smallesotropias can be masked or compensated by torticollis with thehead turned toward the action of the impaired muscle, as well asincreased horizontal fusional amplitude. With near fixation,equilibrium in convergence can occur without diplopia, thusimproving symptoms. Greater and older deviations, withsecondary muscle disorders, are not generally compensated andpermanent diplopia occurs both on distant or near fixation(1-5).
Older statistics cite VI nerve palsy as the most frequentextraocular muscle palsy. With the increasing frequency oftraumatic brain injury, largely due to traffic accidents among otherfactors, IV nerve (trochlear) paresis became the most frequentpalsy in all statistical surveys, followed by VI nerve palsy.
Isolated VI nerve paresis or paralysis is easy to observeclinically, but aetiological diagnosis is often difficult and alwaysrequires a complete neurological and medical examination(1,3,5,6).
It is important to rule out congenital or acquired abductiondeficiencies not related to abducens palsy, such as Mbiussyndrome, Duane syndrome, and mechanical restrictions as inGraves disease and in fractures of the medial wall of theorbit(1,3,4,6) (Figures 2 and 3).
The length of the VI nerve, which starts in the brain stem,runs along the base of the skull, rises through the petrous part ofthe temporal bone to the cavernous sinus, crossing it before enteringthe orbit and then innervating the LR, makes it prone to the actionof several aetiologic factors in peripheral lesions(1,3,5-7).
Central nuclear lesions produce gaze palsy to the affectedside. Fascicular (intrapontine) lesions are associated with otherlesions to cranial nerves V (trigeminal), VII (facial), and the motorpathways of the limbs, causing contralateral hemiparesis andpontine syndromes. In the clivus region nerve VI can be affectedby pre-pontine tumours, compressions caused by brain
displacements due to tumour masses in the middle and posteriorfossae, and meningitis, among other conditions. Intracranialhypertension often causes bilateral VI nerve palsy due tocompression(5-7,9) (Figure 4).
Before entering the cavernous sinus, the VI nerve ascendsalong the petrous portion of the temporal bone. Infection of themiddle ear with bone involvement, often with osteomyelitis ofthe petrous portion of the temporal (petrositis) can lead toparalysis of nerves VI and VII, with intense pain due to trigeminalinvolvement. The general condition depends on the severity ofthe infection and can lead to meningitis, which constitutesGradenigos Syndrome(5-7,9).
Trauma with fracture of the petrous part of the temporalbone can lead to similar oculomotor involvement withextravasation of blood or cerebrospinal fluid through the ear(Battles sign) (6,7,9).
Intracranial hypertension Pontine syndromes (vascular, demyelination, tumour)Trauma Injury to the cerebellar-pontine angle (acoustic neuroma, meningioma)Lumbar puncture or spinal anaesthesia Lesions of the clivus (carcinoma, chordoma)Hypertension Lesions of the middle fossa (tumour, petrositis)Diabetes Lesions of the cavernous sinus (tumour, inflammation, aneurysm, fistula)Parainfectious causes (post-viral, middleear infections in children)Basal meningitis
VI nerve paralysis and paresis: Aetiology
Figure 3 A patient with high myopia and large esotropia, withouteye movement either for abduction, elevation or depression in botheyes. Fixed strabismus due to bilateral VI nerve palsy with smallmovements of convergence. On attempted corrective surgery, noneof the 12 extraocular muscles were found, but only very thin fibrousadhesions replacing the medial recti, hence the static position
Figure 4. Bilateral VI nerve paresis caused by intracranial hypertensiondue to a pituitary tumour. Note the enlarged sella and the tumoursappearance on necropsy
Rev Bras Oftalmol. 2013; 72 (1): 59-69
VI nerve palsy (abducens palsy)
Inside the cavernous sinus, nerve VI along with nerves III,IV, the ophthalmic division of nerve V, and sympathetic fibrescan be affected by thrombosis, thrombophlebitis, aneurysm, andcarotid-cavernous fistula, leading to characteristic syndromes.Total ophthalmoplegia, trigeminal pain in the affected territory,often Horners syndrome, and vascular signs due to venous stasisor fistula (proptosis, redness, chemosis, vascular dilatation [caputmedusae], murmurs, and secondary glaucoma) are characteristicof lesions to the cavernous sinus(3,5-7). Multiple previous episodesof oculomotor paresis with proptosis and pain suggestinflammation or a tumour of the orbital apex or the superiororbital fissure. Painful ophthalmoplegia due to inflammation ofthe superior orbital fissure is known as the Tolosa-Huntsyndrome(5-7). Expansive processes in the orbital apex may leadto a similar presentation, either with normal visual acuity(Rochon-Duvignaud syndrome)(5-7) or with compression of theoptic nerve and visual loss (Rollet syndrome)(5-7).
Glaser and Bachynski(5) summarise the causes of VI nervepalsies in Table 1.
The associated clinical pictures require in-depthneurological and clinical examination in order to find thecausative factor. However, many cases are due to VI nerve palsyalone without any associated conditions. In these cases a medicaland neurological examination should be performed, but theaetiology often remains obscure. Neuroimaging rarely shows anyresults and should only be performed in worsening cases or whenother cranial nerves are affected.(3,5-8)
The intensity of LR impairment by the causative agentdetermines the presentation. Mild or early impairment can leadto homonymous diplopia and/or nystagmus toward the affectedmuscle, with esotropia proportional to the loss of function and nodeviations in other positions of the gaze(1). The tonic imbalanceof horizontal muscles of the affected eye causes hyperactivity ofthe MR, which tends to increase the esotropia in the primaryposition, with diplopia and compensating torticollis, with the headturned toward the action of the affected muscle, maintainingbifixation on contralateral gaze, where there is no deviation andbinocular vision is preserved(1). MR contracture is alsoproportional to the intensity of LR impairment, creating amechanical factor that restricts the already weak abduction. Atthis stage the angle of deviation increases in the primary positionand esotropia also occurs on contralateral gaze, causing diplopiain all eye positions(1,5, 9,10).
Spontaneous recovery of the LR occurs in a large numberof cases, depending on the aetiology and the effectiveness of
treatment. Functional recovery of the LR can lead to completecure(5,7,9). Established MR contracture prevents clinicalimprovement despite the improved function of the LR; in these