Hydrocephalus and shunt emergencies: SAQ

This boy has an obstructed ventriculoperitoneal shunt with preterminal features. The early-morning headache and vomiting, the increasing drowsiness, and the shunt pump that does not refill point to a shunt malfunction, and the bradycardia, the hypertension, and the irregular respirations are the Cushing triad, which means the brainstem is herniating now. His glucose is normal, so hypoglycaemia is excluded, and the priority is to bridge him to theatre at once while the workup runs in parallel. [1]

Question 1 (10 marks)

Outline the immediate resuscitation, the investigations, and the operative pathway for this boy, including any drugs and doses you would give and the time frame for each step. [3]

I would treat this as a neurosurgical emergency with impending herniation. My first move is to call for senior paediatric and anaesthetic help and to alert the neurosurgical team at once, because the definitive treatment is operative. I would elevate the head of the bed to thirty degrees, secure the airway, and give high-flow oxygen, and I would apply continuous monitoring of the heart rate, the blood pressure, the respiratory rate, and the oxygen saturation. [3]

Because the boy has the Cushing triad, I would give a hyperosmolar bridge now, without waiting for the scan. I would give mannitol at 0.5 grams per kilogram intravenously, which is 13.5 grams for a 27 kilogram child, or three percent hypertonic saline at 2 to 5 millilitres per kilogram intravenously, which is 54 to 135 millilitres. The bridge lowers the intracranial pressure within minutes and keeps the brain perfused while the team is assembled and the theatre is prepared. [1]

The investigations would run in parallel. I would order a shunt series, which is anteroposterior and lateral skull, chest, and abdomen radiographs that trace the shunt from the ventricle to the peritoneum, looking for a disconnection, a fracture, or a migrated distal tip. I would order a computed tomography of the head, or a rapid magnetic resonance imaging where available, and I would compare the ventricular size to his baseline scan from the last clinic visit, because an increase confirms the obstruction. [11]

I would perform a shunt tap, by sterile puncture of the reservoir, to measure the opening pressure, to test whether the shunt flows when the reservoir is depressed, and to send 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]

The operative pathway is shunt revision in theatre, where the blocked component is cleared or replaced and the system is tested for flow. If the boy is unstable or the infection is suspected, the shunt is externalised and an external ventricular drain is placed. The definitive care is operative, and the hyperosmolar bridge and the shunt tap are the temporising steps that keep him alive until he reaches theatre. [3]

Question 2 (10 marks)

Discuss how you would distinguish shunt obstruction from overdrainage and from shunt infection in this presentation, and outline the family counselling and the discharge safety-net. [6]

The distinction rests on the clinical pattern, the imaging, and the shunt tap. Obstruction presents with the raised-pressure triad of early-morning headache, vomiting, and drowsiness, and the imaging shows enlarging ventricles compared to the baseline, and the shunt tap shows a high opening pressure with poor flow. This boy's pattern, with the Cushing triad and the pump that does not refill, fits obstruction. [11]

Overdrainage and the slit ventricle syndrome present differently. The headache is positional, worse on standing and relieved by lying flat, and the imaging shows small or slit ventricles, not enlarging ones. The mechanism is overdrainage from a valve pressure set too low, and the management is the opposite of obstruction, which is to raise the valve pressure or to convert to a programmable valve. The shunt tap in overdrainage shows a low opening pressure. [10]

Shunt infection presents with fever, inflammation along the shunt track or at the wound, abdominal pain, and meningism, usually within months of surgery. The commonest organism is a coagulase-negative staphylococcus. The shunt tap shows a pleocytosis and a positive culture, and the management is the two-stage removal, external drainage, and antibiotics. This boy has no fever and no track inflammation, so infection is less likely, but I would still send the cerebrospinal fluid from the tap for culture to exclude it. [6]

I would counsel the family in honest terms at each stage. I would explain that their son's shunt, the tube that drains the fluid from his brain to his tummy, has probably blocked so the fluid is building up again, that his slow heart rate and high blood pressure mean the pressure on his brain has become dangerous, and that the team is giving the medicine that lowers the pressure while the surgeons are called. I would explain that the x-rays and the scan find the block, that the operation fixes the tube, and that he will be watched in the intensive care unit afterwards. [3]

Before discharge I would give the family a written safety-net that names the red flags, which are headache, vomiting, drowsiness, and a change in the eyes or the conscious level, and that gives the direct line to the neurosurgical service. The school and the respite carers would receive the same plan, because a shunt malfunction can recur and the family and the carers must know how to reach the service without delay. I would arrange the follow-up in the paediatric neurology and neurosurgical clinics and review the boy's neurodevelopmental and educational needs. [3]