Hydrocephalus and shunt emergencies: Viva

Branch 1: Definition and classification

The candidate should define hydrocephalus as the active distension of the cerebral ventricular system from an imbalance between the production and the absorption of cerebrospinal fluid, and rarely from overproduction. A strong candidate gives the traditional divide into communicating, where the ventricular outflow is open and the defect lies at the arachnoid granulations, and non-communicating or obstructive, where a physical block halts the flow within the ventricular system, classically at the aqueduct of Sylvius. [2]

If the examiner presses for a more functional approach, the candidate should describe the Rekate classification by the site of the disturbance, naming obstruction at the foramina of Monro, the aqueduct, the fourth ventricle outlets, the basal cisterns, and the arachnoid granulations, with overproduction from a choroid plexus papilloma the sixth category. The candidate should explain that the value of the functional approach is that it directs the surgeon to the right operation, because an aqueductal block is bypassed by an endoscopic third ventriculostomy while an absorptive failure is drained by a shunt. [2]

Branch 2: The infant presentation and the bedside assessment

If asked how the infant with raised intracranial pressure presents, the candidate should describe the age-specific signs. The infant with open sutures accommodates the pressure by head growth, so the presentation is a rapidly enlarging head circumference crossing the centiles, a tense or bulging fontanelle, splayed cranial sutures, distended scalp veins, irritability, vomiting, poor feeding, lethargy, and the sunset sign of impaired upgaze from pressure on the tectal plate. [3]

For this infant, who has vomiting, irritability, increased sleepiness, and a head that looks bigger, the candidate should run the bedside assessment. Measure and plot the head circumference against the centiles and against the child's own trajectory, palpate the fontanelle for fullness or tension in the upright and the supine infant, examine the eyes for the sunset sign and the ocular movements, and assess the conscious level. Compress the shunt reservoir and watch whether it refills, while never trusting a normal refill to exclude malfunction. [3]

Branch 3: The shunt series, the scan, and the shunt tap

If the examiner moves to the workup, the candidate should describe the shunt series as the first imaging test. The shunt series is anteroposterior and lateral skull, chest, and abdomen radiographs that trace the shunt catheter from the ventricle to the peritoneum, looking for a disconnection, a fracture, a migration, or a pulled-back distal tip. A fracture is often found at the clavicle where the catheter has fatigued over years of neck movement. [11]

The candidate should then describe the computed tomography of the head, or the rapid magnetic resonance imaging where available, and the critical point that the ventricular size is compared to the child's own baseline from the last clinic visit, not to a population normal, because the relevant question is whether the ventricles have enlarged since the child was last well. The shunt tap, by sterile puncture of the reservoir, measures the opening pressure, tests whether the shunt flows, and sends the cerebrospinal fluid for cell count, protein, glucose, gram stain, and culture. By allowing fluid to be withdrawn, the tap may also relieve the pressure and buy time on the way to theatre. [11]

Branch 4: The management and the hyperosmolar bridge

If asked to run the management, the candidate should treat this as a neurosurgical emergency. Call for senior help and alert neurosurgery at the outset, because the definitive treatment is operative. Elevate the head of the bed to thirty degrees, secure the airway, give high-flow oxygen, and apply continuous monitoring. If the conscious level falls or the preterminal Cushing triad of hypertension, bradycardia, and irregular respirations appears, give a hyperosmolar bridge of mannitol 0.5 grams per kilogram intravenously or three percent hypertonic saline at 2 to 5 millilitres per kilogram, which buys time while the theatre is prepared. [1]

The definitive management is operative. An obstructed shunt is revised in theatre, where the blocked component is cleared or replaced and the system is tested for flow. If the child is unstable or the infection is suspected, the shunt is externalised and an external ventricular drain is placed. A strong candidate closes by naming the safety-net, the family education on the red flags, and the structured neurodevelopmental follow-up, because the shunted child is a lifelong patient and the recurrence risk is high, with about a third to a half of shunts failing in the first year. [1]