Neurophysiology and Intracranial Pressure Dynamics — WACS Viva & Clinical Scenarios (Basic Neurosciences and Neurosurgical Critical Care)
Exam-style neurophysiology and intracranial pressure dynamics viva scenarios with examiner probes and model answers for Neurosurgery candidates.
Scenarios covered
- SCENARIO 1: A 28-year-old male presents with severe traumatic brain injury following a motor vehicle collision. An intracranial pressure monitor demonstrates an ICP of 28 mmHg with arterial blood pressure of 110/60 mmHg. Explain the physiological determinants of intracranial compliance according to the Monro-Kellie hypothesis, outline the calculation of cerebral perfusion pressure, and detail the physiological thresholds for cerebral ischemia.
- SCENARIO 2: Detail the physiological mechanisms governing cerebral blood flow autoregulation across mean arterial pressures of 50 to 150 mmHg. Describe the biochemical and myogenic mediators involved, and discuss how arterial carbon dioxide and oxygen tensions alter cerebral vascular resistance.
- SCENARIO 3: A patient undergoing clipping of a complex middle cerebral artery aneurysm experiences intraoperative signal degradation during somatosensory evoked potential and motor evoked potential monitoring. Detail the neural pathways interrogated by these modalities, the physiological criteria defining a critical alarm threshold, and the immediate systemic and surgical interventions required.
- SCENARIO 4: Differentiate the pathophysiology, cellular mechanisms, blood-brain barrier integrity, and fluid distribution between vasogenic, cytotoxic, interstitial, and osmotic brain edema. Explain the physiological basis of osmotic therapy using hypertonic saline versus mannitol.
- SCENARIO 5: Describe the physiological mechanisms of cerebrospinal fluid formation, circulation, and absorption. Outline the physiological alterations that lead to normal pressure hydrocephalus versus non-communicating hydrocephalus, including the concept of intracranial elastance and pulse wave amplitude.