Neuroradiology (Brain, Spine, Head and Neck)
Core concepts
Know the vascular territories and the imaging of acute stroke: early signs (loss of insular ribbon, hyperdense MCA sign), the role of CT angiography and perfusion, and the distinction between cytotoxic and vasogenic edema. Understand intracranial hemorrhage: epidural (lens-shaped, middle meningeal artery), subdural (crescentic, bridging veins), subarachnoid (basal cisterns), and intraparenchymal. Recognize the patterns of hydrocephalus (temporal horn dilation, transependymal seepage). Master brain tumor features: glioblastoma (ring enhancement, necrotic core), metastases (gray-white junction, multiple), meningioma (dural tail, extra-axial). In the spine, know disc herniation versus bulge, spinal stenosis, and the signs of cord compression. In head and neck, understand nodal levels and the imaging of squamous cell carcinoma.
Traps
Do not confuse an epidural hematoma with a subdural based on shape alone; the dural attachment and vessel of origin matter. A ring-enhancing lesion is not always an abscess-consider tumor and demyelination. Beware the hyperdense MCA sign as an early but subtle finding. In the spine, a disc bulge is broad-based, while a herniation is focal.
Rule of thumb
Use the shape and dural attachment to classify hemorrhage: lens-shaped and dural-attached = epidural; crescentic and crossing sutures = subdural.
Worked example
A trauma patient with a brief lucid interval and a biconvex hyperdense collection at the temporal bone: epidural hematoma, likely middle meningeal artery injury, requiring urgent neurosurgical evacuation.