Neuroanatomy MCEM Revision

Objectives

Review the BASICS of neuroanatomyRevise the clinical presentation of stroke

diseaseUnderstand the Munro-Kelly Doctrine.Revise the effects of certain cranial nerve

defectsTouch upon spinal anatomy

Curriculum contents

Huge topicGeneral: Structural arrangement of the

brain and spinal cord. Divided into

– Lobar anatomy– Neurovascular anatomy– Cranial Nerves & Nuclei– Spinal Anatomy

Clinical Considerations

Stroke diseaseSubarachnoid HaemorrhageIntracranial Pathology Cranial Nerve defectsSpinal lesions

Considering the Neocortex

Complex visual functions are processed within the occipital lobe

The motor homunculus lies posterior to the central sulcus

Division of the cortical tracts within the corpus callosum prevents processing of speech

Infacrtion of Broca’s area will cause receptive dysphasia

Considering the Neocortex

Complex visual functions are processed within the occipital lobe

The motor homunculus lies posterior to the central sulcus

Division of the cortical tracts within the corpus callosum prevents processing of speech

Infacrtion of Broca’s area will cause receptive dysphasia

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The Neocortex - Cerebral Hemispheres Frontal lobe: anterior to central sulcus

– Motor strip, eye control, speech motor function

Parietal lobe: behind central sulcus– Sensory strip, motor and sensory

projections, interpretations of motor input

Occipital Lobe: complex visual functions

Temporal Lobe: – Auditory projection, memory,

smell(medial)

Cortical Links

The cortices are linked by the Corpus Callosum– Division leaves both cortices capable of memory and

emotional responses Cortical connections to the body

– Motor, including links to cerebellum– Sensory– Special sensory

Intra cortical connections– Integration of sensory inputs with memory areas

Motor tracts Sensory Tracts

In relation to neurovascular anatomy

The circle of Willis is an anastamosis of the vertebral and external carotid end arteries

The middle cerebral artery supplies all of the parietal lobe

Occlusion of the anterior cerebral artery causes leg weakness

10% of Berry Aneurysms arise from congenital defects

In relation to neurovascular anatomy

The circle of Willis is an anastamosis of the vertebral and external carotid end arteries

The middle cerebral artery supplies all of the parietal lobe

Occlusion of the anterior cerebral artery causes leg weakness

10% of Berry Aneurysms arise from congenital defects

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Cerebrovascular Anatomy

Neurovascular Anatomy

4 Arteries supply the brain and it’s extensions– 2 Internal Carotid Arteries– 2 Vertebral Arteries– Connect together to form the Circle of Willis.

Branches of the External Carotid Arteries supply the Meninges and Skull.

Venous drainage via dural sinuses into the IJV. – Communicate with the diplopic veins of the skull into

the facial venous circulation.

Circle of Willis

Internal Carotid Branches

Anterior Cerebral Artery

Middle Cerebral Artery– Divides at the

trifurcation to form penetrating branches to the basal ganglia

Vertebral Artery Branches

2 vertebrals merge to form Basilar– Basilar supplies

cerebellum and brain stem structures

Basilar ends in formation of Posterior Cerebral

Cortical SupplySensory Homunculus Motor Homunculus

Stroke Patterns

TACI Total Anterior circulatory infarctPACI Partial Anterior circulatory infarctPOCI Posterior circulation infarctLACI Lacunar infarct

Stroke Patterns

Anterior Cerebral Artery– Leg weakness

Middle Cerebral Artery– Upper limb and face– Perforators cause lacunar stroke (20% of all)

Posterior Cerebral Artery– Short term memory– Smell & Visual defects

Lacunar Stroke

Localised lesion within the internal capsule and basal ganglia– Pure motor (50-60%)– Pure sensory (6-7%)– Sensory-motor (20%)– Ataxic Hemiparesis

Lower limb weakness, and loss of co-ordination

Sub Arachnoid Haemorrhage

Berry Aneurysm– 1% congenital defect

Found at the branch points of arteries– Posterior Communicating– Anterior Communicating– Middle Cerebral– Basilar