AN63.1-3 | Ventricular System & Special sensory pathways — Glossary

C-shaped cavity in each cerebral hemisphere with anterior, body, posterior, and inferior horns; main site of CSF production by choroid plexus

Interventricular foramen connecting each lateral ventricle to the 3rd ventricle; blockage causes unilateral hydrocephalus

Aqueduct of Sylvius — narrowest part of the ventricular system through the midbrain; most common site of congenital obstructive hydrocephalus

Most common cause of congenital obstructive hydrocephalus; lateral and 3rd ventricles dilate, 4th ventricle remains normal

Failure of the foramina of Magendie and Luschka to open; cystic 4th ventricle, cerebellar vermis agenesis, all ventricles dilated

Endoscopic third ventriculostomy — fenestration in the floor of the 3rd ventricle bypassing the aqueduct; preferred for aqueductal stenosis

Structure where nasal retinal fibres (carrying temporal visual field) cross to the opposite optic tract; compression causes bitemporal hemianopia

Loss of both temporal visual fields from optic chiasm compression; classic sign of pituitary tumour

Loss of the same half of the visual field in both eyes; from lesion of the optic tract, radiation, or visual cortex contralateral to the field loss

Lower fibres of the optic radiation looping through the temporal lobe; carries upper visual field information; damage causes 'pie in the sky' defect

Preservation of central vision in occipital cortex lesions; due to dual blood supply (MCA and PCA) to the macular cortex at the occipital pole

LGN — thalamic relay for the visual pathway; receives optic tract input and projects to the primary visual cortex via the optic radiation

MGN — thalamic relay for the auditory pathway; receives from the inferior colliculus and projects to the primary auditory cortex

Area 17 on the banks of the calcarine sulcus; also called striate cortex due to the line of Gennari

Sudden haemorrhage into a pituitary tumour causing acute visual loss, severe headache, and hypopituitarism — neurosurgical emergency

Only sensory pathway that does NOT relay through the thalamus; projects from olfactory bulb directly to the primary olfactory cortex

Pupils do not constrict to light but do constrict on accommodation; seen in dorsal midbrain lesions (Parinaud) and Argyll Robertson pupils (neurosyphilis)

Deep sulcus on the medial surface of the occipital lobe; the primary visual cortex (area 17) lies on its upper and lower banks

Geniculocalcarine tract from the LGN to the primary visual cortex; upper fibres through parietal lobe, lower fibres as Meyer's loop through temporal lobe

Most common pituitary adenoma; secretes prolactin causing galactorrhoea and amenorrhoea; treated medically with cabergoline (dopamine agonist)

Downward deviation of the eyes in neonatal hydrocephalus; raised ICP pushes on the superior colliculi affecting vertical gaze