Review Normal Pressure Hydrocephalus

Supattra Tribuddharat

13/10/48

Ventricular system

lateral ventricle foramen of Monro third ventricle, cerebral aqueductfourth ventricle foramina of Luschka and Magendie subarachnoid space arachnoid granulations dural sinus venous drainage.

CSF production 0.2-0.35 ml/min; total volume 120 ml

Hydrocephalus

A disturbance of formation, flow, or absorption of CSF an increase in volume in CNS

Communicating / non Communicating

(full communication between ventricles and subarachnoid space)

Cerebral atrophy and focal destructive lesions vacant space filled with CSF

(hydrocephalus ex vacuo)

Normal pressure hydrocephalus (NPH)

First described in 1965 by Hakim and Adams Clinical triad of symtoms :

- gait disturbance

- dementia

- incontinence Image: communicating hydrocephalus Potenially reversible by shunting: symptoms <2y

Etiology of NPH

• Idiopathic : ~50%,elderly > 60 y, worse response to shunting (30–50%)

• Secondary : ~50%, younger age, better response to shunting (50–70%)

- head injury - subarachnoid haemorrhage- meningitis - neurosurgery

Etiology of idiopathic NPH

Combination of mechanisms > a single cause• Decreased CSF resorption at arachnoidal villi or gra

nulations increases transmantle pressure (CSF pressure within ventricles > in subarachnoid space) ventricular enlargement

• Short-lasting CSF pulsations (B waves) periodically apply pressure to the ventricular walls and have a water-hammer effect that enlarges the ventricles

Anatomy

• Enlarged third ventricle

• Dilation of the occipital, frontal, and temporal horns of the lateral ventricles.

• Presumably, the periventricular white matter is stretched and dysfunctional as a result of inadequate perfusion, without actually being infarcted

Clinical features

Considerable variation in nature, severity, and course of progression

Gradually progressive disorder Gait disturbance : the most readily recognized

feature Cognitive disturbances : not occur in all patients Signs and symptoms of INPH are typically

bilateral

Gait disorder

• An initial manifestation of NPH• Mechanisms: enlargement of the ventricles

1. compression motor neuron fibers passing through corona radiata (an early hypothesis; pyramidal tract: not supported by recent study)

2. a disorder of subcortical motor control• with progression of extensive subcortical white

matter changes, pyramidal tract involvement may become more likely

described as “apractic,” “bradykinetic,” “glue-footed,” “magnetic,” “parkinsonian,”

“short-stepped,” and “shuffling.” Bradykinetic, broad-based, and shuffling Mimics PD: start hesitation, difficulty

turning, freezing Increased tone and with brisk tendon

reflexes in the lower limb Plantar responses may be flexor or extensor,

unilaterally or bilateral

Differentiate NPH from PD: • May occur but less commonly : rigidity, tre

mor, and slowing of rapid, alternating movements

• Does not respond significantly to carbidopa/levodopa

• No true ataxia or weakness, described as gait apraxia.

Parkinsonian symptoms in INPH : abnormal pulsatile CSF flow affecting the substantia substantia nigra and/or striatum,

Dementia

• Mental deterioration is frequently mild and subcortical

• Memory problems, poor attention, bradyphreni and slowing of information processing

• It progresses less rapidly than the dementia of Alzheimer disease

Incontinence

• Usually urinary but may be fecal.

• Increased frequency and urgency may be seen in early stages ; progression to frank urinary incontinence with disease progression.

• Results from disruption of periventricular pathways to the sacral bladder center decreased inhibition of bladder contractions and instability of bladder detrusors

• more advanced stages : indifference to the episodes of incontinence, is associated with frontal executive dysfunction.

Unexpected manifestration

• Papilledema

• Seizure

• headache

Brain Imaging

• MRI or CT must be performed to assess ventricular size and to rule out ventricular obstruction.

• Either CT or MRI can document noncommunicating ventriculomegaly sufficient to satisfy the brain imaging requirements for routine diagnosis of INPH.

• CT scan or MRI - Ventricular enlargement out of proportion to sulcal atro

phy

- Prominent periventricular hyperintensity (transependymal flow of CSF)

- Prominent flow void in the aqueduct and third ventricle, the so-called “jet sign,” (presents as a dark aqueduct and third ventricle on a T2-weighted image where remainder of CSF is bright)– Thinning and elevation of corpus callosum on sagittal i

mages– Rounding of frontal horns

• May have hyponatremia (SIADH)

a rounded frontal horn

T2-weighted MRI showing dilatation of ventricles out of proportion to sulcal atrophy

The arrow points to transependymal flow.

Measurement of CSF-OP

• Normal CSF-OP averages 122 ±34mmH2O• INPH, CSF-OP averages 150 ±45 mmH2O• (60-240 mm H2O) • Transient high pressures (“B waves”) are detectable

during prolonged intraventricular monitoring in adults with symptomatic INPH

• OP is elevated > 18 mm Hg indicate secondary or noncommunicating hydrocephalus than INPH

DIAGNOSING IDIOPATHIC NPH

Require clinical history, physical examination, and brain imaging

Diagnosis of INPH is complicated Resemble, or occur in combination with, various d

isorders that are prevalent in the elderly, such as CVD, neurodegenerative disorders (e.g., AD, PD, LBD), primary urological disorders, spinal stenosis, and other conditions.

May be useful to classify INPH into “probable,” “possible,” and “unlikely” categories,

PROGNOSTIC TESTS FORPREOPERATIVE ASSESSMENT OF INPH

1. CSF Removal via High-volume “Tap Test”• Remove large volumes of CSF (40–50 ml)• An objective improvement in gait• Complications : ± headaches• 62% sensitivity , 33% specificity• Good PPV for shunt response INPH• Specificity is low, many patients who might benefit

from shunting will be missed• Therefore, INPH candidates not be excluded on th

e basis of a negative tap test.

2. CSF Ro (outflow resistance)• A pump introduces CSF or saline 4ml at a rate

1ml/sec through a needle placed in the lumbar subarachnoid space

• Complications: headaches and meningismus• Sensitivity 46%, specificity87%• CSF Ro may be helpful in increasing prognostic acc

uracy for identifying SRINPH when tap test results are negative

3. ELD Test (external lumbar drainage)• Draining 10 ml CSF/ hour for 72 hrs (total, 720 ml)• Complications: bacterial meningitis and root irrigation• more patients who do not improve with CSF tap test

will show improvement with prolonged drainage and benefit from shunting

• The PPV is high, 80 to 100%, • However, hospital admission is required.• Reported complication rates with ELD are generally

low but may be significant in terms of added

Treatment

• Medication : No definitive evidence exists that medication can

successfully treat NPH.

• Surgical Care:

:Surgical CSF shunting remains the main treatment modality.

• No randomized prospective clinical trials were conducted comparing different measures or protocols of shunt outcome assessment.

• no validated, universally accepted scale for assessment of treated or untreated INPH outcome.

• Shunt outcome can be based on the documentation of either the clinical impairment, improvement after treatment, or both. Grading of either the functional status or the clinical criteria of gait, incontinence, and dementia

Patients with a good response to the above procedure

are candidates for ventriculoperitoneal or

ventriculoatrial shunting.– Best results :- patients who have no adverse risk factors;

-responded favorably to a large-volume LP;

-definite evidence of dementia and ataxia, - CT scan or MRI evidence of chronic hydrocephalus,

- a normal CSF at lumbar puncture.

– Some evidence indicates that patients with gait disturbance, mild or no incontinence, and mild dementia fare best among shunt surgery patients.

Thank you

– a baseline neuropsychological evaluation and a timed walking test.

– undergo a lumbar puncture with removal of approximately 50 cc of CSF. The above evaluations are repeated 3 hours later.

– A clear-cut improvement in mental status and/or gait predicts a favorable response to shunt surgery.

– Improvement in gait may be seen in the form of reduced time to walk a fixed distance, reduced gait apraxia, or reduced freezing of gait.

– Reduction in bladder hyperactivity also may be a sign of good outcome from shunting. Occasionally, improvement may be delayed and appear 1-2 days after the large-volume lumbar punctures.

– When clinical suspicion is high and the patient is a good candidate for surgery, repeated lumbar punctures are indicated over the next 1-2 days.

– Some clinicians use an indwelling CSF catheter in lieu of repeated lumbar punctures. This method carries a higher risk of meningeal infection but may allow for a more accurate prognosis.