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NORMAL PRESSURE HYDROCEPHALUS

DR PRAVEEN K TRIPATHI

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NORMAL PRESSURE HYDROCEPHALUS In 1964, Colombian

neurosurgeon Salomón Hakim and colleagues described a syndrome of

Progressive cognitive decline

Gait difficulties Urinary incontinence Ventricular dilatation Normal cerebrospinal

fluid (CSF) pressure during lumbar puncture

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HISTORY 1982, CM Fisher underscored the importance of

the gait disturbance in the description of NPH. 1986, Graff-Radford and Godersky correlated

clinical symptoms and shunt responsiveness. The term idiopathic adult hydrocephalus

syndrome may be more accurate, because intracranial pressure is not always normal in NPH.

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EPIDEMIOLOGY elderly individuals (age >65 y) the prevalence of

NPH was 1.4% Incidence -1.4 per 1,00,000 No race or gender prediliction more than 60% of patients with iNPH had

cerebrovascular disease.  In another similar study, more than 75% had

Alzheimer disease pathology at the time of shunt surgery.

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ETIOLOGY IDIOPATHIC – 50 % SECONDARY CAUSES subarachnoid hemorrhage (23%), meningitis (4.5%) and traumatic brain injury (12.5%)Secondary NPH has higher response rate to

shunting than idiopathic NPH

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ETIOLOGY 50% cases idiopathic

Leading theory is impairment of CSF outflowIntraventricular pressure studies reveal waves

of increased pressure- B-wavesAdult hydrocephalus syndromeAdult symptomatic hydrocephalus

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CSF DYNAMICS

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PATHOPHYSIOLOGY Ventricle enlargement leads to periventricular

ischemia regardless of etiology Compression and stretching of arterioles and

venules Arterial hypertension and cerebral

arteriosclerosis increased in NPH

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PATHOPHYSIOLOGY Increased subarachnoid space volume does not

accompany increased ventricular volume. Symptoms result from distortion of the central

portion of the corona radiata by the distended ventricles. Interstitial edema of the white matter

The periventricular white matter anatomically includes the sacral motor -abnormal gait and incontinence.

Dementia results from distortion of the periventricular limbic system.

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Kiefer, M; Unterberg, AThe Differential Diagnosis and Treatment of Normal-Pressure HydrocephalusDtsch Arztebl Int 2012; 109(1-2): 15-26; DOI: 10.3238/arztebl.2012.0015

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CLINICAL FEATURESCLASSIC TRIAD GAIT DISTURBANCE -is typically the earliest feature

noted and considered to be the most responsive to treatment No classic gait disturbance Gait may be wide based, shuffling More severely affected patients have “magnetic gait”- feet

stuck to ground and difficult to initiate walking Difficulties with walking motions resolve with minimal

support of patient or lying patient down May resemble Parkinson’s gait Hyperreflexia Apraxia of gait – no weakness or ataxia.

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DIAGNOSTIC TRIADUrinary Incontinence True incontinence found only in severely

affected patients Urinary urgency in most patients with NPH Due to stretching of periventricular nerve

fibers and loss of detrusor inhibition Bladder sphincter muscle unaffected

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CLINICAL FEATURESDEMENTIA Usually mild Presence of dementia in NPH extremely variable Some shunt responsive patients have little or no dementia Dementia usually least responsive of symptoms to

intervention Mental status changes may resemble depression prominent memory loss and bradyphrenia. Frontal and subcortical deficits  forgetfulness, decreased attention, Aphasia /agnosia – alternate diagnosis -Alzheimer

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DIFFERENTIAL DIAGNOSES- ALZHEIMER’S (AD)

Both AD and NPH cause memory impairment

AD- “cortical” abnormalitiesAphasia, Apraxia, Agnosia Impaired recognition and encoding deficits

NPH- “subcortical” abnormalitiesMemory impairment but intact recognitionSlow information processingDifficulty with complex tasks

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COGNITIVE IMPAIRMENTS AD VERSUS NPH

AD NPH

Impaired

MemoryLearningOrientationAttention/concentrationExecutive functionWriting

Psychomotor slowingFine motor speedFine motor accuracy

Borderline Impaired

Motor and psychomotor skillsVisuospatial skillsLanguageReading

Auditory memoryAttention/concentrationExecutive functionBehavior/personality changes

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DIFFERENTIAL DIAGNOSES- ALZHEIMER’S (AD) AD and NPH can usually be distinguished with

formal neuropsychological testing Primary care office testing may not be

adequate to distinguish Mental impairment early in course of AD but

usually late in course of NPH and often minimal impairment

AD often associated with hippocampal atrophy on imaging studies

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DIFFERENTIAL DIAGNOSES- PARKINSON’S DISEASE Both NPH and Parkinson’s Disease (PD) can

have similar gait disturbancesHypokinesiaFreezingImbalanceExtrapyramidal symptoms

Trial of levadopa can help distinguish between PD and NPH

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DIFFERENTIAL DIAGNOSES- OTHER Depression Subcortical arteriosclerotic encephalopathy Multi-infarct encephalopathy Chronic alcoholism B12, Folate deficiency Electrolyte abnormalities Cervical or lumbar stenosis Peripheral neuropathy

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH History

Insidious onsetAge over 40Symptom duration 3-6 monthsNo antecedent event known to cause

secondary NPHProgressive over timeNo other medical, psychiatric or neurological

condition that could cause symptoms

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH Brain imaging

Ventricular enlargement not attributable to cerebral atrophy or congenital disorder

No macroscopic obstruction presentAt least one of the following

Enlargement of lateral horns not attributable to hippocampus atrophy

Callosal angle greater or equal to 40 degreesEvidence of altered brain water content on

imaging not attributable ischemia or demylination

An aqueductal or fourth ventricular flow void on MRI

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CALLOSAL ANGLE Angle of roof of lateral ventricles in A-P projection

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MRI FLOW VOID Loss of MRI signal due to flow of CSF

Normal aqueduct Abnormal aqueduct02-Dec-15

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MRI FLOW VOID

Normal fourth ventricle Abnormal fourth ventricle

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH Clinical

Gait/Balance- at least two of following presentDecreased step heightDecreased step lengthDecreased cadence/speedDecreased trunk swayWidened stanceToes turned outward while walkingEn bloc turning- turns take three or more steps Impaired balance- two or more corrective steps

for eight steps on tandem gait testing02-Dec-15

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH Cognition- two of following present

Psychomotor slowingDecreased fine motor speedDecreased fine motor accuracyDifficulty dividing or maintaining attentionImpaired recall especially for recent eventsImpairment of executive functions- multi-step

procedures, working memory, formulation of abstractions, insight

Behavioral or personality changes

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH Urinary Symptoms- one of following

Episodic urinary incontinence not attributable to other causes

Persistent urinary incontinenceFecal and urinary incontinence

OR One of following

Urinary urgencyUrinary frequency- 6 or more voids in 12 hour

periodNocturia- more than two voids in night

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DIAGNOSIS- PROBABLE IDIOPATHIC NPH Physiological

Opening pressure 70-240 mmH2O

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POSSIBLE INPH History- Symptoms are

Subacute or indeterminate onsetOnset any time after childhood<3 months or indeterminate durationMay follow trauma, hemorrhage or meningitisSymptoms not entirely explained by co-existing

neurological conditionsNon-progressive or not clearly progressive

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POSSIBLE INPH Brain imaging- Ventricular enlargement

associated with followingCerebral atrophy of sufficient severity to

explain ventricular enlargementStructural lesion that may increase

ventricular size

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POSSIBLE INPH Clinical

Incontinence and/or cognitive impairment in absence of gait or balance dysfunction

Gait disturbance or dementia alone

PhysiologicalOpening pressure unavailable or outside of

range for probable NPH

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UNLIKELY INPH No ventriculomegaly Signs of increased intracranial pressure

such as papilledema No component of clinical triad Symptoms explained by other causes (eg,

spinal stenosis)

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INVESTIGATIONS- Vit B12 , Thyroid profile- CSF – analysis – opening pressure – 11 +/- 3 mm hg (150 mm H2o)

slightly higher than normal - Transient high pressure B waves may be detected- (CSF) protein Lipocalin-type prostaglandin D

synthase (L-PGDS) – marker of Frontal lobe dysfunction in iNPH – decreased due to damage of arachnoid cells

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CT SCAN Ventriculomegaly that is out of proportion to sulcal

atrophy. differentiates NPH from ex vacuo

ventriculomegaly, Frontal and occipital periventricular

hypoattenuating areas, represent transependymal CSF flow -infrequent and often may represent periventricular leukoencephalopathy

corpus callosal thinning, -nonspecific

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Rounding of frontal horns clinical picture and ventriculosulcal

disproportion on either CT or MRI scans, 50-70% of patients are likely to respond to a CSF-shunting procedure.

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CT SCAN

disproportionately enlarged temporal horns of the lateral ventricles compared with the relatively normal sulcal size. 02-Dec-15

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The Evans index (EI), a linear ratio between the maximal frontal horn width and the cranium diameter,

signifies ventriculomegaly if it is 0.3

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MAGNETIC RESONANCE IMAGING Temporal horns out of proportion to hippocampal

atrophy MRI provides additional physiologic information on

NPH  T2-weighted images, regions of moving CSF

demonstrate no signal, instead of the increased signal observed in slow-moving CSF,

CSF flow studies- jet of turbulent CSF flow may be observed distal to the aqueduct 

Cine phase-contrast MRI quantifies CSF flow in terms of stroke volume

- significant corelation to shunt responsiveness02-Dec-15

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CSF TAP TEST Most prefer 45 -50 ml removal Csf pressures may be transiently elevated Improvement may be delayed and appear 1-2

days after Sensitivity of test – 62 % and 33 % specificity However it has been listed in guidelines of

prognostic evaluation of NPH

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EXTERNAL LUMBAR DRAINAGE  greater impact on brain volume expansion 300 ml drained for 5 days Complications -including headache,

radiculopathy, and bacterial meningitis  More sensitive than csf tap test sensitivity, specificity, and negative predictive

value were 95%, 64%, and 78%, respectively. PPV 80 -100 % Requires hospitalisation specialised care

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OTHER TESTS CSF infusion testing.- One drain is used for

continuous pressure monitoring while the other drain is used to continuously infuse solution into the CSF space.

Ro – impedance of flow offered by csf absorption Isotopic cisternography is no longer in frequent use Acqueductal CSF flow – not of much diagnostic use

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PRESURGICAL EVALUATION Neuropsychological evaluation (eg, Folstein test

or formal neuropsychological evaluation)- not validated

Timed walking test. Videotaping the gait evaluation before and after

the large volume lumbar puncture.- IS PREFERABLE

Reduction in bladder hyperactivity also may be a sign of good outcome from shunting.

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MANAGEMENT No prospective, double blind, randomized, controlled clinical triaL Medical management – levodopa trial to rule out

idiopthic parkinson disease No drug is known to work in NPH

Surgical Management – mainstay Benefit expected from shunt surgery in probable case

of NPH 50 %- 61 %

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MANAGEMENT OF NORMAL PRESSURE HYDROCEPHALUS

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NEWER ADVANCES Adjustable shunt valves – adjusts the opening

pressure Gravity-controlled valves - low valve opening

pressure when the patient is lying down. G valves lower the risk of overdrainage by 90%

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Endoscopic third ventriculostomy (ETV). Alternative to shunt placement for treatment of 

hydrocephalus. Effective in obstructive hydrocephalus.

Efficacy in NPH not known

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FOLLOW UP

Routine follow up 2 to 3 times per year Earlier if shunt inection/failure Bedside clinical examination follow up CTScan

within few weeks D Dimer ,CRP in case of ventriculoatrial shunts

for subclinical septicemia and thromboembolism

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WHETHER TO SHUNT OR NOT? High CSF pressure should prompt investigation

for a secondary cause of NPH Response to a 40-mL to 50-mL (high-volume)

lumbar tap suggests a potential benefit to shunting An ELD may be used to evaluate those who do

not respond to a high-volume tap There is no substantial predictive value to MRI

CSF flow studies IF multi-infarct or Alzheimer’s disease

dementia  ??

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DIAGNOSTIC STUDIES Ventricle enlargement on CT or MRI

Severity graded by ratio of maximal frontal horn width divided by transverse inner diameter of skull

0.32 minimal for NPH but 0.40 more typical Lack of hippocampus or cortical atrophy Periventricular and cortical white matter lesions

may be found in patients with NPH Large number white matter lesions may be marker

for poor response to shunting

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NORMAL VENTRICLES

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EnlargedVentricles

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EnlargedVentricles

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ARE BENEFITS OF SHUNTING LONG LASTING? Most studies show fairly significant

decline in benefits over time Initial improvement 60-75% of patientsSustained improvement only 24-42%

Results confounded due to high mortality from co-morbid conditions57% patients dead within 5 years in study

by Raftopoulos et.al.

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HOW CAN I TELL WHO WILL BENEFIT?

Good response to shuntingClinical presentation

Gait disturbance preceded mental impairmentShort duration of mild mental impairmentKnown cause of NPH- e.g. infection, bleed

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HOW CAN I TELL WHO WILL BENEFIT?

Good response to shuntingSpecial studies

Lack of white matter lesions on MRIMarked resolution of symptoms with CSF

drainageOne time removal 30-50 cc CSFMulti-day drainage of 100-150 cc CSF

B-waves greater than 50% of time with continuous intracranial pressure (ICP) monitoring

Resistance to CSF outflow greater than 18 mmHg 02-Dec-15

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HOW CAN I TELL WHO WILL BENEFIT?

Poor response to shuntingSevere dementiaDementia presenting symptomMRI abnormalities

Cerebral atrophyMultiple white matter lesions

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HOW CAN I TELL WHO WILL BENEFIT? Indeterminate significance

Patient ageDuration of symptomsLack of response to removal CSF

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HOW ACCURATE ARE PREDICTORS OF RESPONSE TO SHUNTING?

Normal pressure hydrocephalus: an update, Stein, SC, Neurosurgery Quarterly (2001)11(1):26–35

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HOW ACCURATE ARE PREDICTORS OF RESPONSE TO SHUNTING?

Normal pressure hydrocephalus: an update, Stein, SC, Neurosurgery Quarterly (2001)11(1):26–35

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WHAT KIND OF SHUNT IS USED?

Externally programmable valve allows transcutaneous adjustment CSF outflow resistance

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SHUNT VALVE ADJUSTMENTS

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NOW THAT MY PATIENT HAS HAD A SHUNT WHAT HAPPENS NEXT?

Monitoring of mental functionPatients should have neuropsychiatric testing

prior to shuntPeriodic testing post shunt to document

improvement

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NOW THAT MY PATIENT HAS HAD A SHUNT WHAT HAPPENS NEXT? Monitor for complications of shunt

InfectionShunt malfunctionExcessive CSF drainageSubdural hematoma

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OBJECTIVE ASSESSMENT OF INPH

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KEY POINTS The INPH is a syndrome, characterized by gait

impairment, cognitive decline and urinary incontinence

Associated with ventriculomegaly in the absence of elevated CSF pressure.

Pathogenesis is not understood; intermittent intracranial hypertension, decreased CSF absorption and cerebral ischemia have been blamed.

Hallmark of neuroimaging in NPH is ventriculomegaly out of proportion with sulcal atrophy 02-Dec-15

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KEY POINTS MRI is the choice of imaging; CSF flow in NPH is

hyperdynamic, with an increase in the amount and velocity of CSF passing rostrally, then caudally, through the cerebral aqueduct with each cardiac cycle.

Clinical improvement after CSF drainage implies good response to shunting.·

The best results are found in the subjects treated with low-pressure valves.·

Increased use of adjustable valve seems to be beneficial. Gait is most likely to improve. Postoperative reduction

in ventriculomegaly is not always seen or proportionate to the clinical improvement.

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THANK YOU

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