Neuroradiology (Brain, Head and Neck, Spine)
Neuroradiology covers stroke and haemorrhage pathways, brain tumour and demyelination patterns, spinal emergencies and head and neck nodal staging.
Stroke
Non-contrast CT excludes haemorrhage; early signs include loss of the insular ribbon, lentiform nucleus obscuration and sulcal effacement. ASPECTS scores 10 regions of the middle cerebral artery territory, deducting one point per affected region; a score of 6 or less indicates a large core. CT angiography identifies large vessel occlusion, and perfusion imaging selects patients for thrombectomy beyond 6 hours.
Haemorrhage and tumours
Subarachnoid haemorrhage is hyperdense in the basal cisterns; if CT is negative after 6 hours and clinical suspicion is high, lumbar puncture for xanthochromia is considered. Ring-enhancing lesions include metastasis, abscess, glioblastoma and toxoplasmosis. Multiple sclerosis shows periventricular ovoid lesions perpendicular to the ventricles.
Spine
Cauda equina syndrome: bilateral leg symptoms, saddle anaesthesia, bladder dysfunction - urgent MRI. Spinal epidural abscess: fever, back pain, raised inflammatory markers - contrast MRI, and do not delay for lumbar puncture.
Worked example
A 70-year-old with right hemiparesis 5 hours after onset has a non-contrast CT ASPECTS of 8 and a proximal M1 occlusion on CTA. ASPECTS 8 means a small core, so the patient is a candidate for thrombectomy; perfusion imaging is not required within 6 hours if CT and CTA are concordant.
Traps
Giving thrombolysis before excluding haemorrhage; over-reading early ischaemic change; missing a posterior fossa infarct on CT; doing lumbar puncture before imaging in suspected cord compression; forgetting that MRI, not CT, is the test for cord compression.