Clinical Neurology and Neuro-ophthalmology
What you must own
Localisation is the core skill. Build a disciplined approach: mental status, cranial nerves, motor (tone, power, reflexes), sensory, cerebellar, gait. Know the upper versus lower motor neuron pattern (spasticity, hyperreflexia, upgoing plantar versus flaccidity, wasting, fasciculation). Distinguish pyramidal from extrapyramidal (rigidity, bradykinesia, tremor) and cerebellar (dysmetria, intention tremor, ataxia) signs.
Neuro-ophthalmology is high yield. Understand the pupillary light reflex pathway (afferent: optic nerve, chiasm, optic tract, pretectal, Edinger-Westphal; efferent: oculomotor). Differentiate:
- Optic nerve lesion: ipsilateral blindness, afferent pupillary defect
- Optic tract lesion: contralateral homonymous hemianopia, no afferent defect in the tract itself but relative afferent defect may occur
- Chiasmal lesion: bitemporal hemianopia
- Post-chiasmal lesion: contralateral homonymous hemianopia, macula-sparing if occipital
Know Horner syndrome, third/fourth/sixth nerve palsies, internuclear ophthalmoplegia (MLF), and papilloedema versus optic atrophy.
Traps
Questions test whether a relative afferent pupillary defect is present (optic nerve or severe retinal disease) versus absent (cortical or tract lesions). Another trap: distinguishing a sixth nerve palsy from a gaze palsy, and recognising that a third nerve palsy with a fixed dilated pupil suggests compressive aetiology (e.g. aneurysm).
Rule of thumb
For visual field defects, follow the pathway: nerve = monocular; chiasm = bitemporal; tract/radiation/cortex = homonymous; occipital = macula-sparing.
Worked example
A patient has a left third nerve palsy with a dilated, non-reactive pupil. The pupil is parasympathetic and travels on the outside of the nerve, so a compressive lesion such as a posterior communicating artery aneurysm is likely - urgent imaging is required.