BEDSIDE CLINICS 9TH EDITION

Hydrocephalus 391
Aetiology of hydrocephalus :
1. Meningitis (bacterial or tuberculous). 6. Cerebral haemorrhage.
2 Head injury. 7. Congenital e.g.. Arnold-Chiari malformation.
3. Subarachnoid haemorrhage. 8. 'Normal pressure hydrocephalus.
4. Sagittal sinus thrombosis. 9- Cerebellar abscess or haemorrhage.
5. Brain tumours (posterior fossa). 10. 3rd ventricle colloid cyst.
* Obstructive 5, 6, 7. 9 and 10: non-obstructive—1, 2, 3, 4 and 8; 1, 2 and 3 are responsible for
majority of cases.
Causes and features of acute hydrocephalus :
Causes are :
1. Head injury with its complications.
2. Subarachnoid haemorrhage.
3. Acute exudative meningitis.
Features are :
1. Severe headache and vomiting. 4. 6th cranial nerve palsy (false localising sign).
2. Drowsiness, convulsions or coma. 5. Jerks— Brisk (may be lost).
3. Papilloedema may be evident. 6. Plantar response Extensor.
What is ‘normal pressure' hydrocephalus ?
It is a misnomer. Initially there is increased pressure but ultimately CSF haemodynamics compromise
(ventricles dilate) and it becomes normal or low pressure hydrocephalus. Actually, it is a
variety of communicating hydrocephalus. This rare condition is predominantly seen in old age with the
triad of symptoms such as dementia, ataxia and urinary incontinence. Though it may result from
head injury, subarachnoid haemorrhage or meningitis, many a time no cause is identiiied.
How to diagnose hydrocephalus very early ?
By serial recording of head circumference of the child. An increase in the head circumference by
more than 1 cm in every 2 weeks for the first 3 months of life, makes the pediatrician suspicious.
What is normal intracranial pressure (ICP) ?:
It is 5-10 mm of Hg when measured indirectly. Now-a-days, devices measure ICP directly by
implanting into the lateral ventricles. When ICP is > 15 mm of Hg, it is known as raised intracranial
pressure.
What is benign intracranial hypertension (BIH) ?
Previously the term BIH was used synonymously with pseudotumour cerebrei, meningeal hydrops
or otitic hydrocephalus. It is a benign or idiopathic raised ICP developed as a result of diffuse swelling
of brain with dilated ventricular system. The patient characteristically presents with headache, vomiting
and papilloedema. BIH commonly develops from corticosteroid withdrawal, tetracycline or nalidixic
acid therapy, hypervitamlnosis A, Addison’s disease, hypoparathyroidism, or COPD with type II
respiratory failure. The CSF is under increased pressure but its analysis remains normal. CT scan is
within normal limit except the dilated ventricles. Aeetazolamide or repeated lumbar puncture may be
of some help.
Diagnosis of hydrocephalus by investigations :
1. X-ray of skull-
(i) Enlargement of calvariurn.
(ii) Sutural diastasis (separation).
(iii) Thinning of bone.
(iv) Erosion of clinoid process.
(v) Deepened sella turcica.
2. Ventriculography or cisternography by a suitable contrast medium (to see the site of
obstruction).
3. Pneumoencephalography may be tried to localise the site oi obstruction not done now-a
days.
4. CT or MRI scan (to show enlarged ventricles and cortical atrophy).
5. CSF flow studies may be done (CSF analysis is not informative).
6. Measurement of ICP—diagnostic.