Hydrocephalus
- ‘Water on the brain’ – mismatch between CSF production and absorption
- Not always pathological, if there has been a loss of brain substance due to an infarction etc then there is an increase in CSF to occupy the space – ‘hydrocephalous ex vacuo’
- We make 400-500ml of CSF per day
- 90% is produced in the lateral ventrical
- CSF production is an active process so can be stopped by ischaemia or major metabolic abnormalities
- Carbonic anhydrase inhibitors such as acetozolamide can decrease CSF production
- Classified into;
- Communicating
- Non-communicating
Causes
Congenital
- Spina bifida
- Chiari malformation (non communicating) – cerebellar tonsils pushed through foramen magnum
- Dandy walker malformation
- Aqueduct stenosis
- Neonatal infections (communicating)
Trauma
- Oedema and haemorrhage can cause and obstruction leading to non-communicating
- Subarachnoid space bleeding can lead to;
- Clotting of the ventricular system
- RBC block of the arachnoid granulations
- Fibrin in the subarachnoid spce
- Depressed fracture of the sagittal sinus can cause a venous thrombosis
Infection
- Meningitis
- TB in the basal cisterns
- Ventriculitis
- Encephalitis
- Brain abscess (lots of swelling)
- Subdural emphysema – veins in the subdural space can clot resulting in thrombosis
Metabolic
- Hypercoagulative state
Vascular
- Bleeding
Tumour
- Choroid plexus papillomas
- Obstruction
Presentation
In babies;
- Symptoms
- Often very few as the fontenelles haven’t fused
- Drowsy
- Irritable
- Stop feeding
- Vomiting
- Signs
- Large head
- Tense fontanelle, particularly when baby is at rest and sitting up
- Suture diastasis (always pathological)
- Venous engorgement – dilation of the scalp veins
- ‘Sunsetting’ – conjugate downward eye displacement due to pressure on the tectal plate
- Child investigations difficult as they often don’t want to lie still for MRI. DO ultrasound through the fontenelle
In young-middle aged people;
- Symptoms
- Generalised headache which is worse in the morning and when they put their head down
- Depressed consciousness
- Vomiting
- Visual disturbance
- Balance disorders
- In chronic hydrocephalus symptoms may present over weeks to months
- Signs
- Papilloedema (not seen if acute)
- Paranaud’s syndrome – due to pressure on tectal plate
- Conjugate eye deviation
- Failure of upward gaze
- Absence of pupillary constriction on vergence
- Diplopia due to IV and VI nerve palsies
- Neck stiffness which is a sign of impending coning
Elderly people;
- Symptoms
- If it is acute symptoms are as above, if chronic – normal pressure hydrocephalus (NPH)
- Gait abnormality
- Dementia
- Incontinence
- Communicating hydrocephalous is difficult to diagnose as big ventricles could be due to atrophic change
- Do CSF infusion studies for diagnosis
CT/MRI Scan – signs of hydrocephalus
- Look for size of ventricles
- Look at sulci – are they flattened or big which would suggest atrophy
- Enlargement of the temporal horns
- Rounding of the 3rd ventricle
- Look at the size of all the ventricles to see if it is communicating or non-communicating
- Periventricular lucency – if young people it is a sign that CSF is being pushed out through the ependyma. In older people it is a sign of ischaemia and multi infarct dementia
Colloid cyst
- Benign tumour in the roof of the 3rd ventricle
- V acute presentation of hydrocephalus
Treatment
- Questions to ask,
- Is it communicating or not?
- Is it reversible or not?
Communicating hydrocephalus
- Lumbar puncture can be used to treat
- *this is contraindicated in non-communicating hydrocephalus*
Non-communicating hydrocephalus
- Shunts
- Risk you will make the patient irreversibly dependant on the shunt – problem if something goes wrong
- If hydrocephalus is due to bleeding, shunt will block
- If there is infection, a shunt will exacerbate infection
- Endoscopic 3rd ventriculostomy
- Treat cause e.g. remove tumour
- Prior to removing tumour, give steroids (dexamethasone) to reduce swelling
- If you shunt there is a danger you can seed the peritoneal cavity with malignant cells
External ventricular drain
- Can be done before blockage is removed
- Put a catheter in the ventricle
- End of the catheter must not be lower than the ear (ventricle)
- If not, all the CSF can be siphoned off resulting in coning
- The brain collapses down to where the ventricular space used to be, this results in the brain coming away from the meninges and a tearing of the bridging veins. This results in an acute SAH
- The dependency on the drain can be checked by raising the catheter outlet and seeing if patient becomes drowsy etc
Shunts
- 3 components;
- Inlet into CSF pathway
- Valve to regulate pressure (2 types, fixed pressure or variable pressure)
- Tube draining the CSF somewhere else – generally the peritoneum. Used to be the atrium, still is in premature babies with gut abnormalities e.g. NEC
- Shunt goes into non dominant side of brain
- 1 in 20 become infected due to bacteria seeding at the time of operation. Therefore afterwards patients don’t require prophylactic antibiotics for dentistry etc
- If infected patient presents either with a shunt obstruction or peritonitis
- Average life a shunt is 10 years
- A normal CT scan cannot exclude a shunt malformation
- Don’t sedate patients who are restless due to raised intracranial pressure. The reduced respiration results in an increase in CO2, which dilates cerebral vessels resulting in a further increase in ICP