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HYDROCEPHALUS
Hydrocephalus Is an abnormal accumulation of cerebrospinal fluid (CSF) within the
ventricles and subarachnoid spaces. with dilatation of the ventricular system and
increased intracranial pressure (ICP).
Physiology and circulation of CSF:
The normal volume of circulating CSF in an adult is about 150 ml.
CSF is produced by an active process independent of intracranial pressure (ICP).80%
of CSF is produced by the choroid plexus of the ventricles, and the rest is by
tependymal cells. The daily production of the CSF about 450cc
CSF flows from the lateral ventricles down through the foramen of Monro into the
third ventricle and subsequently the aqueduct of Sylvius into the fourth ventricle,
passing laterally out of two foramina of Luschka, and inferiorly out of the foramen of
Magendie, to pass to the subarachnoid space around the brain and spinal cord. Most of
the fluid absorption occurs along the superior sagittal sinus.
CSF absorption is a pressure-dependent passive process.
Classification of Hydrocephalus:
A. Non-communicating hydrocephalus (Obstructive): results from lesions that obstruct
the CSF pathways from the lateral ventricles to the fourth ventricle.
B. Communicating hydrocephalus: characterized by patent CSF pathwaysbut there is
impaired CSF absorption.
Epidemiology of Hydrocephalus:
The incidence of infantile hydrocephalus is about 4 per 1000 live birth.
Aetiologty:
A. Non-communicating hydrocephalus (Obstructive):
1. Lateral ventricle obstruction by tumours, e.g. basal ganglia glioma,
2. Third ventricular obstruction, e.g. colloid cyst of the 3rd ventricle
3. Occlusion of the aqueduct of Sylvius (primary stenosis or secondary to a tumour)
4. Forth ventricular obstruction due to posterior fossa tumour, e.g. medulloblastoma,
ependymoma, acoustic neuroma.
5. Obstruction to flow of CSF through the basal cisterns (i.e. basal foramina of
Luschka and Magendie).
B. Communicating hydrocephalus:
A. Failure of absorption of CSF through the arachnoid granulations. scarring of
the arachnoid granulations can occur after meningitis (bacterial or
tuberculous) or subarachnoid haemorrhage
B. Oversecretion of CSF (choroid plexus papilloma).
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Clinical Features of Hydrocephalus:
age dependant.
A
. Neonatal Hydrocephalus (Infantile):
1. Failure to thrive and feeding problems.
2. Enlargement of the head with increasing head circumference.
3. Craniofacial disproportion
4. The scalp is thin and glistening.
5. The veins of the scalp are distended.
6. The anterior fontanelle is enlarged, tense, and bulging.
7. Weakness of upward gaze (the setting-sun sign)(3
rd
ventricular pressure on midbrain ).
8. Diastases of the cranial sutures.
9. Transillumination of the head is usually positive (if cortical mantle is less than 1cm
and the patient is under 9 months age)
B.
Hydrocephalus in older children and adults:
hydrocephalus will present with symptoms of raised intracranial pressure. So:
1. Headache, nausea and vomiting.
2. Deterioration in the level of consciousness.
3. May be associated ataxia.
4. Visual disturbance.
Investigations of Hydrocephalus:
A. Skull x-ray: can show 1)Separation of sutures. 2)Features of increased ICP
B. Ultrasound of the brain: can be done through opened anterior frontanelle .
C. CT scan of the Brain:1) Ventricular dilatation.2)Can show the cause of obstruction.
D. MRI of the brain: same as CT but no radiation
Management of Hydrocephalus:
1.
Removal of obstructing lesion e.g. removal of tumor will resolve hydrocephalus.
2.
Bypassing obstruction: either by:
a.
Endoscopic third ventriculostomy: by creating an opening in the floor of the third
ventricle.
b.
Internal diversion (Shunting): this is the most common form of surgical
management. The most common shunt used is ventriculo-peritoneal shunt. It consist of
three parts; ventricular catheter, a valve permitting CSF flow in one direction, and a
distal peritoneal tube. Other methods of CSF diversion include ventriculo-atrial and
ventriculo-pleural shunts.
The commonest complications of shunting include:
1. Shunt obstruction: may be due to either ventricular catheter
obstruction, valve malfunction or distal obstruction of the peritoneal catheter.
2. Shunt infection.
3. Intracranial haemorrhage
:Intracerebral haemorrhage, or Subdural haematoma.
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