Robert Alavi, MD

Differentiating between Cortex, Subcortical, and Cerebellar lesions is the most crucial skill in early neurology. It turns “this patient can’t move their right arm” into a precise diagnosis. 🕵️‍♂️ Is the problem global (Cortex)? Is it deep-brain connectivity (Subcortical)? Or coordination (Cerebellum)?

Save these simple differentiators for your next clinical rotation:

🧠 CORTEX = Weakness + Cortical Signs (like Aphasia or Neglect).

Deep Brain = Mixed sensory/motor or Pure Weakness or Pure Sensory (no cortical signs!).

CEREBELLUM = The “Same Side” Rule (ipsilateral coordination issues).

Localizing isn’t just about anatomy—it’s the fastest way to dictate the right treatment plan.

also, you’re probably using the Romberg test wrong.

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This video provides a high-yield medical review of neurology localization, focusing on how to clinically differentiate between lesions in the cerebral cortex, subcortical brain regions, and the cerebellum. Understanding these neuroanatomy pathways is essential for medical students preparing for the neurology shelf exam, USMLE Step 1, and USMLE Step 2. We break down the clinical signs of a cortical lesion—such as aphasia, hemispatial neglect, and gaze deviation—and compare them to the pure motor or pure sensory deficits typically seen in subcortical strokes. Additionally, we review the ipsilateral clinical findings associated with cerebellar lesions. Use this clinical neurology study guide to master the neurological physical exam, easily identify upper motor neuron signs, and improve your diagnostic skills for your internal medicine and neurology clinical rotations.