Case 6

Case 6

1. Structure & Function of Brain

   • Lobes
     • Frontal
       • Personality & Behaviour changes
       • Problem solving, language, mood, personality
     • Occipital
       • Visual field defects
       • Primary visual cortex
     • Parietal
       • Attention defect
       • Visuospatial & language
     • Temporal
       • Recognition defects
       • Primary Auditory Cortex
   • Sulci
     • Central
     • Lateral/Sylvian
       • Insula
       • Frontal/Parietal/Temporal
     • Lunate
       • In occipital cortex
     • Parieto-occipital
       • Seen on medial side only
   • Gyri
     • Pre-central
       • Primary motor cortex
     • Post-central
       • Primary somatosensory cortex
     • Superior temporal
       • Sound
   • Corpus Callosum
     • Connects hemispheres
   • Brainstem
     • Midbrain - CNIII & CNIV
     • Pons - CNV
     • Medulla - CNIX, CNX & CNXIII
     • Pons-Medulla Junction - CNVI-VIII
   • Blood Supply
     • Anterior Cerebral
       • Anteromedial cerebral hemispheres (except occipital lobes)
     • Middle Cerebral
       • Most lateral portions of cerebrum
     • Posterior Cerebral Artery
       • Interior cerebral hemisphere & occipital lobes
     • Basilar
       • Brainstem, cerebellum & cerebrum
     • Vertebral arteries
       • Cranial meninges & cerebellum
     • Anterior communicating artery
     • Posterior communicating artery
       • Optic tract, cerebral peduncle, internal capsule & thalamus
     • Venous drainage
       • From dural venous sinuses --> IJV
       • Superior --> Superior sagittal sinus
       • Posterior & Interior --> Straight, transverse & superior petrosal sinuses
       • Great Cerebral Vein (of Galen)
         • Union of internal cerebral veins
         • Merge with inferior sagittal sinus --> straight sinus
   • CSF
     • Produced in choroid plexus of ventricular system
     • Drainage: Lateral ventricles (1 & 2) --> Via IV foramina --> 3rd ventricle --> Via cerebral aqueduct --> 4th ventricle --> Subarachnoid space
     • Reabsorbed in subarachnoid cisterns
     • SA space --> arachnoid granulations in dura mater --> dural venous sinuses

2. Memory

3. Histology of Brain

   • Cells
     • Oligodendrocytes
       • Produce myelin sheath for CNS axons
       • Myelination
         • Occurs post-natally
         • Sheaths show deterioration with age
         • Pathology: MS & oligodendroglioma
     • Astrocytes
       • Maintain electrical coupling by ensuring low Ca2+ concentration
       • Control breathing
       • Keep K+ levels low by taking up K+ in ECF & redistributing it
         • Epilepsy
       • Maintain glutamate
       • Astrocytoma
       • Astrogliosis
     • Microglia
       • 'Immune system' of brain
     • Ependyma
       • Ciliated, cuboidal epithelial cells
       • Line ventricular system
       • E.g. Choroid plexus cells
   • Substance
     • White Matter
       • Myelinated axons
       • Organised into tracts, fascicles & cortical medulla
       • Connect nuclei & hemispheres
     • Grey Matter
       • Cell bodies
       • Organised into nuclei, laminae & reticular foramen

4. Dementia

   • Alzheimer's
     • Pathophysiology
       • Build up of beta-amyloid plagues
         • Amyloid pre-cursor protein on chr. 21
       • Tau (on chromosome 21) tangles, damages & kills neurones
     • Clinical Features
       • Progressive memory loss
         • Preservation of early memories
       • Problems with language
       • Apraxia - Skilled motor function
       • Agnosia - Object recognition
       • Personality changes
       • Anosognosia - Insight
   • Staging
     • 1. Pre-dementia: Mild
     • 2. Early-stage: Forget dates, mild confusion, apathy
     • 3. Middle-stage: Short-term memory loss, speech impairment, paraphasia, unusual behaviour, urinary incontinence
     • 4. Late-stage: Agression, loss of ability to feed/walk
   • Treatment
     • AChE Inhibitor
       • Donepezil, Galantine, Rivastignine
     • Memantine: Glutanergic Receptor antagonist - Blocks toxic levels of glutamate
     • Levodopa: Movement problem relief
   • Dementia with Lewy Bodies
     • Symptoms
       • Hallucinations
       • Fluctuating cognition
       • Sleep disorders
       • Dysautonomia
     • Pathophysiology
       • Deposits of protein Lewy Bodies in nerve cells
       • Low levels of acetylcholine & dopamine
   • Vascular Dementia
     • Types
       • Stroke-Related
       • Small-vessel disease (Sub-cortical)
       • Mixed (with Alzheimer's)
     • Symptoms
       • NB: Usually constant then suddenly deteriorating
       • Speed of though, concentration & communication
       • Depression & Anxiety
       • Stroke-Like
       • Memory problems
       • Seizures
       • Hallucinations

5. Ear Structure & Function

   • Anatomy

6. Synaptic Tranmission

   • Neurotransmitters
     • Excitatory: CNS
     • Inhibitory: GABA
     • Acetyl CoA
   • Process
     • 1. Action potential arrives at pre-synaptic neuron
     • 2. Calcium ions accumulate in nerve terminal
     • 3. Neurotransmitter (stored in vesicle) released by exocytosis
     • 4. Neurotransmitter binds to receptors on post-synaptic membrane
     • 5. Depolarisation occurs
     • 6. Neurotransmitter broken down & reabsorbed