Neuroradiology
Core concepts
Master the imaging of stroke: CT signs of early infarction (loss of insular ribbon, dense MCA), the role of CT angiography and perfusion, and the concept of the penumbra. Understand intracranial hemorrhage (epidural, subdural, subarachnoid, intraparenchymal) and their CT appearances and evolution. Learn brain tumor imaging: glioblastoma (ring enhancement, necrosis), metastasis (multiple, at gray-white junction), and meningioma (dural tail, homogeneous enhancement). Understand hydrocephalus and the differentiation of communicating versus non-communicating. Know the imaging of demyelination (Dawson's fingers, periventricular lesions) and the McDonald criteria concept. Learn spine imaging: disc herniation, cord compression, and the differentiation of infectious from neoplastic processes.
Traps
A normal CT does not exclude acute ischemic stroke; MRI with DWI is more sensitive. Epidural hematoma is lens-shaped and does not cross sutures; subdural is crescentic and crosses sutures but not the midline. Do not confuse a ring-enhancing lesion's causes (tumor, abscess, metastasis). Remember that subarachnoid hemorrhage may be missed on CT after 24–48 hours - use lumbar puncture or CTA. Periventricular lesions are nonspecific; clinical context matters.
Rule of thumb
For acute stroke, "time is brain": non-contrast CT excludes hemorrhage, then CTA/perfusion guides thrombectomy. Use the ASPECTS score for MCA territory involvement.