Acute Obstructive Hydrocephalus

Acute obstructive hydrocephalus is rapid ventricular enlargement from blockage of CSF flow within or just beyond the ventricular system, raising intracranial pressure. It is a neurosurgical emergency that can cause herniation and death within hours.

Epidemiology. It is a common complication of intraventricular and subarachnoid haemorrhage, posterior fossa tumours and haemorrhage, colloid cysts and meningitis. Shunt malfunction is a frequent cause of acute deterioration in patients with existing shunts.

Causes.

• Tumour: posterior fossa, pineal, third ventricle (colloid cyst) and brainstem tumours.
• Haemorrhage: intraventricular, subarachnoid, cerebellar, thalamic.
• Infection: meningitis, ventriculitis, abscess and neurocysticercosis.
• Aqueduct stenosis, Chiari malformation, and shunt blockage or infection.

Pathophysiology. CSF production (about 500 mL daily) continues, so ventricles enlarge upstream of the obstruction, and pressure compresses the periventricular white matter, impairs cerebral perfusion and may cause herniation.

Presentation is headache (worse in the morning or lying down), vomiting, drowsiness, upward gaze palsy (Parinaud syndrome, setting sun sign in infants), papilloedema, sixth nerve palsy, ataxia, gait disturbance, bradycardia with hypertension (Cushing response), and coma. In infants, there is a bulging fontanelle, enlarging head and irritability.

Red flags.

• Falling consciousness, bradycardia or irregular breathing.
• Sudden onset with intraventricular haemorrhage or shunt malfunction.
• Bilateral papilloedema or upward gaze palsy.

CT head (ventricular enlargement, temporal horn dilation, transependymal oedema, obstructing lesion, haemorrhage), MRI with CSF flow sequences for the level and cause, and shunt series for shunt malfunction. Do not perform lumbar puncture in obstructive hydrocephalus (risk of herniation). Check glucose, sodium, coagulation, gas and infection markers.

Differential diagnosis. Communicating hydrocephalus (subarachnoid haemorrhage, meningitis), cerebral atrophy, normal pressure hydrocephalus, idiopathic intracranial hypertension and mass lesion without hydrocephalus.

Stabilise. Head up 30 degrees, airway protection for reduced consciousness, normoxia, normocapnia, normal sodium (135 to 145 mmol/L), and avoidance of hypotension and hypotonic fluid.

Temporising measures.

• Hyperosmolar therapy for acute deterioration: 3% sodium chloride 250 mL IV over 15 to 20 minutes (2 to 5 mL/kg), or mannitol 20% 0.5 to 1 g/kg IV over 15 to 20 minutes, with osmolality under 320 mOsm/kg.
• Dexamethasone 10 mg IV then 4 mg every 6 hours for tumour oedema, as a bridge to surgery.
• Brief hyperventilation to PaCO2 of 4.0 to 4.5 kPa (30 to 35 mmHg) only for active herniation.
• Seizures: levetiracetam 60 mg/kg IV (maximum 4500 mg).

Definitive CSF diversion.

• External ventricular drain through the Kocher point (right frontal) as the first measure, set at a level of 10 to 20 cmH2O over the level of the external auditory meatus, draining slowly. Avoid over drainage, which risks upward herniation, subdural haematoma and haemorrhage from the tumour. Monitor intracranial pressure.
• Endoscopic third ventriculostomy for obstruction at aqueduct or posterior fossa level.
• Removal of the obstructing lesion (colloid cyst, posterior fossa tumour, haematoma).
• Ventriculoperitoneal shunt for persistent hydrocephalus.

Infection. For ventriculitis or shunt infection: vancomycin 15 to 20 mg/kg IV every 8 to 12 hours (levels) with meropenem 2 g IV every 8 hours or ceftazidime 2 g IV every 8 hours, with removal of infected hardware, and intraventricular antibiotics by specialists.

Intraventricular haemorrhage. External ventricular drain and consider intraventricular thrombolysis as a specialist option. Reverse anticoagulants (prothrombin complex concentrate 25 to 50 units/kg with vitamin K 10 mg IV for warfarin).

Shunt malfunction. Urgent neurosurgical revision, with shunt tap by neurosurgeons.

Monitoring. Neurological observations hourly, intracranial pressure and drain output, sodium, infection markers and repeat CT.

Referral and escalation. Neurosurgery at once. Transfer without delay if neurosurgery is not on site.

Special groups. In infants and children, specialist paediatric neurosurgery and weight based osmotherapy. In pregnancy, left lateral tilt and obstetric input.