---
module: 081-03
language: en
chapter: 81
title: "Structural Neuroanatomy and Lesion Localisation"
module_title: "Forebrain, internal capsule, ventricles, meninges, and cerebral vascular territories"
source_sha256: 97e13e57bc196777dc2a5f1f98f41aea33444f9d28d39d41a8600c061b0853c5
---
# Forebrain, ventricles, meninges, and vascular territories

## Cortical landmarks and frontal functions
### Five lobes plus medial limbic region
### Central sulcus: motor front, sensory behind
### Motor map: face and arm lateral, leg medial
### Premotor and supplementary areas sequence action
### Frontal eye field: saccades to opposite side
### Dominant inferior frontal: language production
### Prefrontal: working memory, inhibition, planning

## Parietal, temporal, occipital cortex
### Superior parietal guides spatial action
### Nondominant inferior parietal attends both sides
#### Right lesion: profound left neglect
### Dominant temporoparietal: comprehension, reading
### Auditory cortex receives bilateral input
### Medial temporal lobe consolidates memory
### Visual cortex around calcarine sulcus
#### Central vision posterior
#### Superior field below the sulcus

## Insula and limbic networks
### Insula: taste, interoception, pain salience
### Amygdala assigns emotional significance
### Hippocampus encodes contextual memory
### Hypothalamus turns motivation into output
### Distributed networks, not isolated centres

## White matter and internal capsule
### Association, commissural, projection fibres
### Corona radiata converges into capsule
### Genu: corticobulbar fibres
### Posterior limb: corticospinal and sensory
### Retrolentiform visual, sublentiform auditory
### Small deep infarct: dense deficit
#### No aphasia, neglect or seizures

## Deep nuclei and diencephalon
### Basal ganglia form cortical loops
### Putamen and pallidum form lentiform nucleus
### Capsule between thalamus or caudate and lentiform
#### Deep perforator lesions hit motor pathways
### Thalamus relays to cortex
### Hypothalamus regulates homeostasis

## Ventricles and hydrocephalus
### Lateral, third, aqueduct, fourth ventricle
### Choroid plexus secretes most fluid
### Absorbed via granulations and lymphatics
### Obstruction: noncommunicating, upstream dilation
### Poor absorption: communicating
### Raised pressure: headache, papilloedema, sixth nerve
### Distinguish from ex-vacuo enlargement
### Normal-pressure hydrocephalus triad imperfect

## Meninges and haemorrhage
### Dural layers separate to form sinuses
### Folds: falx, tentorium, diaphragma sellae
### Subarachnoid space holds fluid and vessels
### Meningeal irritation: headache, neck stiffness
### Epidural: arterial, limited by sutures
### Subdural: bridging veins, crosses sutures
### Subarachnoid blood disperses through cisterns

## Arterial territories and strokes
### Circle of Willis links carotid and vertebrobasilar
### Anterior cerebral: medial surface, leg
#### Leg-predominant weakness, abulia, bladder
### Middle cerebral: lateral hemisphere, deep
#### Face-arm deficit, aphasia or neglect
### Posterior cerebral: occipital, thalamus, midbrain
#### Contralateral homonymous hemianopia
### Deep perforators are end arteries
#### Lipohyalinosis occludes, hypertension ruptures
#### Lacunar syndromes
### Emboli lodge at branch points
### Watershed infarcts in severe hypoperfusion

## Venous drainage
### Superficial veins to superior sagittal sinus
### Deep veins to straight sinus
### Sigmoid sinuses to internal jugular veins
### Emissary veins can transmit infection
### Outflow block raises capillary pressure
#### Oedema, haemorrhage, intracranial hypertension
### Venous infarcts ignore arterial territories

## Herniation and localisation
### Fixed skull volume limits compensation
### Subfalcine: may compress anterior cerebral
### Uncal: third nerve, posterior cerebral, peduncle
### Tonsillar threatens medullary centres
### Cortical signs point to cortex
### Dense deficit without them: deep or brainstem