Neuroimaging, Neurocritical Care, and Vascular Neurology Emergencies
Core concepts
Neuroimaging must answer the clinical question. Noncontrast CT detects hemorrhage and mass effect but may be normal early in ischemia. CTA identifies large-vessel occlusion, dissection, aneurysm, and collateral status. CT perfusion and MR perfusion estimate core and penumbra. Diffusion-weighted MRI with ADC mapping detects acute infarction within minutes and helps distinguish true ischemia from seizure, migraine, and encephalopathy. Gradient echo or susceptibility-weighted imaging detects hemorrhage and microbleeds; FLAIR helps date infarcts and identify venous thrombosis. Vessel-wall imaging and catheter angiography are problem-solving tools. Neurocritical care emphasizes airway protection, oxygenation, temperature control, glucose management, seizure treatment, and avoidance of secondary injury. Elevated intracranial pressure requires head elevation, sedation, osmotic therapy, and decompressive surgery for malignant edema in selected patients. Recognize herniation syndromes, status epilepticus, and basilar occlusion. After thrombolysis or thrombectomy, monitor blood pressure, neurologic worsening, and hemorrhagic transformation.
Traps
Do not equate restricted diffusion with stroke; seizures, abscess, and migraine can mimic it. Do not ignore a normal CT in a patient with thunderclap headache and a delayed presentation. Do not use sedation alone for a declining patient with hydrocephalus. Do not delay decompressive hemicraniectomy for a young patient with malignant MCA infarction and early deterioration.
Worked example
A patient with acute basilar thrombosis and fluctuating consciousness: CT may be normal, so obtain CTA urgently; reperfusion can reverse deficits. Imaging must target the suspected vascular territory rather than follow a routine sequence.