Embryology, anatomy, and neuroanatomy of the visual system

Development

The CNS develops from the neural tube (ectoderm, closes by ~day 28) - failure of closure produces neural tube defects (anencephaly - rostral neuropore; spina bifida - caudal neuropore)
The neural tube subdivides into prosencephalon, mesencephalon, rhombencephalon -> the five secondary vesicles (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon)
Neural tube defect incidence and prevention (folate) are covered under pregnancy counselling notes

Structure	Key clinical correlate
Circle of Willis	Anastomotic ring - explains why occlusion of one vessel can be asymptomatic, and defines vascular stroke territories
Internal capsule	Dense white matter bottleneck - small lacunar infarcts here cause disproportionately severe deficits
Brainstem	Crossed findings (ipsilateral cranial nerve + contralateral limb signs) localise a lesion here
Spinal cord tracts	Corticospinal (motor, crosses at the medulla), dorsal columns (proprioception/vibration, crosses in the medulla), spinothalamic (pain/temperature, crosses at the level of entry)

Neuroanatomical localisation is the core skill of clinical neurology - a lesion's level is inferred from which tracts/nuclei are and are not affected, before imaging confirms it
Precise localisation directs which imaging is ordered and how urgently (e.g. brainstem signs -> urgent posterior fossa imaging given the risk of rapid deterioration)

Neural tube defects, Chiari malformations, syringomyelia (central canal/spinal cord developmental anomalies)

Anatomical relationships explain why specific vascular or compressive lesions produce reproducible, localisable syndromes (e.g. Wallenberg, Weber, Brown-Sequard)

4 more sections, plus exam facts

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