Synopsis
Localise impaired cerebrospinal-fluid circulation from symptoms and ventricular anatomy, distinguish obstructive from communicating mechanisms, and recognise when either pattern has become an acute pressure emergency.
- Obstructive hydrocephalus is blockage within the ventricular pathways; ventricles upstream of the block enlarge while the downstream compartment may remain small.
- Communicating hydrocephalus has no intraventricular block: CSF exits the fourth ventricle but absorption, or less often flow through the subarachnoid compartment, is impaired, so all ventricles usually enlarge.
- When CT confirms acute obstructive hydrocephalus in a deteriorating patient, treat it as an intracranial-pressure emergency and obtain immediate neurosurgical input for emergent ventricular drainage.
Key red flags
A rapid fall in consciousness, new unequal or poorly reactive pupil, posturing, focal weakness or abnormal breathing suggests threatened herniation.
Acute headache and repeated vomiting after subarachnoid or intraventricular haemorrhage may mark new hydrocephalus even when the initial scan was already abnormal.
A posterior-fossa lesion can obstruct the fourth ventricle or its outlets and compress the brainstem within a small compartment; clinical decline demands immediate specialist action.
In infants, accelerating head circumference, a tense fontanelle, separated sutures, persistent vomiting, lethargy, irritability or downward eye deviation can replace the adult headache history.
Fever, meningism or recent neurosurgery with ventriculomegaly raises infection-related impaired CSF absorption or device infection and requires a cause-specific pathway.
Do not perform lumbar puncture when an obstructive lesion, pressure gradient, herniation syndrome or cardiorespiratory instability is possible.
Look for rapidly progressive headache, vomiting, drowsiness, confusion, reduced GCS, gaze or pupil change, weakness, posturing and abnormal respiration. Bradycardia with hypertension is late and need not be present.
Acute ventricular enlargement with a visible CSF-pathway block in a deteriorating patient requires emergent neurosurgical management; ENLS specifically directs emergent EVD management for imaging-confirmed acute obstructive hydrocephalus.
Reasoning priorities
Rapidly confirm ventriculomegaly, identify a visible obstructive cause and detect blood, mass effect, transependymal oedema and herniation in an acute presentation.
Compare with prior imaging and correlate ventricular change with the examination. Imaging-confirmed acute obstructive hydrocephalus in a deteriorating patient requires emergent neurosurgical management rather than further routine classification tests.
Worked reasoning
CT shows enlarged lateral and third ventricles, a normal-sized fourth ventricle and a lesion near the aqueduct.
- Recognise acute obstructive hydrocephalus from the deteriorating examination and the upstream ventricular pattern; call neurosurgery and anaesthesia immediately.
- Stabilise airway, oxygenation and circulation, elevate and align the head when safe, and document GCS components, pupils and motor responses without delaying definitive care.
- Localise the likely block to the aqueduct because lateral and third ventricles are upstream while the fourth is downstream and not enlarged.
- Arrange urgent cause- and anatomy-specific CSF diversion or lesion treatment with the neurosurgical team; do not perform lumbar puncture across a suspected pressure gradient.
- Verify response with repeated examination, ventricular imaging and device or pressure data if a drain is placed.