Normal CSF Circulation
- CSF is an ultrafiltrate of the plasma
- Secreted by the choroid plexuses of the third, fourth and lateral ventricles
- Total volume of CSF is approximately 150 ml
- Approximately 500 ml of CSF is produced each day
- CSF circulates from ventricles into subarachnoid space
- Absorbed by the arachnoid granulations around the superior sagital sinus
- In health rate of production equals rate of absorption
- CSF pressure is usually 10-15 cm water
Causes of hydrocephalus
- Hydrocephalus is characterised by dilated cerebral ventricles
- Intraventricular pressure can be normal or raised
- Usually arises due to interruption to the normal flow of CSF
- Two main types of hydrocephalus are recognised
- Communicating hydrocephalus
- Non-communicating hydrocephalus
Communicating hydrocephalus
- Obstruction is in the subarachnoid space
- Results in dilatation of the entire ventricular system
- Causes include:
- Meningitis
- Intraventricular haemorrhage
- Congenital absence of the arachnoid granulations
- Arnold-Chiari malformation
- Encephalocele
- Choroid plexus papilloma
Non-communicating hydrocephalus
- Obstruction is within the ventricular system
- Usually results from congenital or neoplastic lesions
- Causes include:
- Aqueduct stenosis
- Atresia of the foramina of Magendie and Luschka
- Ventriculitis
- Intraventricular tumours
- Dandy-Walker syndrome
Clinical Features
- May be diagnosed on antenatal ultrasound
- Postnatal diagnosis depends on the rate of progression of the hydrocephalus
- Acute hydrocephalus presents with features of raised ICP
- Features include headache, vomiting, drowsiness and papilloedema
- Chronic hydrocephalus presents with:
- Enlarging head circumference
- 'Sun-set' eyes
- Tense fontanelle
- Cranial nerve palsies
- Diagnosis and causes can be confirmed by CT or MRI scan
Management
- Established hydrocephalus requires CSF drainage
- Temporary CSF drainage can be achieved with an external ventricular drain
- Permanent CSF drainage is carried out by diversion of CSF into a body cavity
- Possible routes included
- Peritoneum
- Right atrium
- Pleural cavity
- Most shunts have several components including
- Proximal catheter
- One way valve
- CSF reservoir
- Distal catheter
- Complications of ventricular peritoneal shunts
- Infection
- Blockage
- Overdrainage
- Disconnection
- Intracranial haemorrhage
- Ascites
Bibliography
Li V. Methods and complications in surgical cerebrospinal fluid shunting. Neurosurg Clin North
Am 2001; 12: 685-693.
Lo P, Drake J M. Shunt malfunctions. Neurosurg Clin North Am 2001: 12:
695-701.
Meyer P G, Ducrocq S, Carli P. Pediatric neurologic emergencies. Curr Opin Crit
Care 2001; 7: 81-87.
Siddique M S, Mendelow A D. Surgical treatment of intracerebral haemorrhage. Br Med Bull
2000; 56: 444-456. |