Brain Funciton Disorders

Question 1

Hypoxia and Ischaemia

Answer 1

Hypoxia

• Inadequate supply O2 to tissue→ cause ATP depletion/ power failure
• Aerobic metabolism stop → less ATP produced: Na+/K+ ATPase can’t run fast enough, cell or neuron swells up with water
• Anaerobic metabolism used→ lactic acid produced: acid damages cell membranes, intracellular structure and DNA

Ischaemia

• Decreased blood supply due to constriction or obstruction of a blood vessel
• interferes with: delivery of energy stores (glucose) & damage to blood vessels (vasomotor paralysis and vasoconstriction)
• Blood flow inadequate to meet metabolic need of brain
• Changes in blood : desaturation, clotting, sludging

Question 2

Intracranial Pressure

Answer 2

• Compartment syndrome in skull (1. Brain tissue and interstitial fluid (80%), 2. Blood (10%), 3. CSF (10%))
• ICP greater than arterial blood pressure, arteries collapse; blood flow to brain cut off
• Brain swelling: vasogenic: extracellular fluid, cytotoxic: intracellular fluid
• Hydrocephalus: abnormal CSF accumulation within brain

Question 3

Hydrocephalus

Answer 3

• Overproduction or impaired drainage of CSF
• Causes: congenital malformation, tumor, inflammation, hemorrhage
• Mounting pressure squeeze brain against skull and destroy brain tissue
• More common in infant (skull fontanel not closed, cranium become enlarged), in adults cranial enlargement cannot occur, so fluid increase → increased ICD
• Treatment: creation of shunt (bypass) to drain excess CSF from the brain

Question 4

Brain Herniation

Answer 4

• Increased ICP push brain out of position
• Brain tissue compressed to center of brain (2), against bone (4), against rigid folds of dura mater (1,3), compression of oculomotor nerve is early sign:

Question 5

Traumatic Brain Injury and Haematoma

Answer 5

Traumatic Brain Injury

• Primary injuries- damage due to impact: microscopic damages ( concussion, diffuse axonal injury), contusions
• Secondary injuries- damage due to hemorrhage, ischemia, infection (meningitis, encephalitis), ICP
• Head trauma can lead to injury within skull: epidural hematoma (bleeding between dura mater and skull), subdural hematoma ( tear in wall of dural sinuses), intracerebral hematoma (bleeding into brain tissues)
• Cerebral concussion- due to blow to head or sudden movement of brain against skull as in violent shaking

Hematoma

• Epidural space: meningeal arteries
• Rapid bleeding; unconsciousness may be followed by brief→ lucid period
• Dura mater
• Subdural space (between dura and arachnoid): result of tear in small bridging veins that contact begins on cortical surface to dural sinuses. These veins readily broken in head injury
• Bleeding can occur between dura and subarachnoid (subdural hematoma) or into CSF filled subarachnoid space (subarachnoid hematoma)
• Slower bleeding; gradual development over days or weeks

Question 6

Stroke

Answer 6

“Brian attack” 2 types
Ischemic

• caused by interruption of blood flow in cerebral vessel (more common)
• Large vessel (thrombotic)- atherosclerotic disease)
• Small vessel or penetrating artery disease (lacunar infarct- small vessel stroke in deeper parts of brain ot in brain stem)
• Cardiogenic embolic (clotted blood or other elements that obstruct circulation

Hemorrhagic

•Caused by bleeding into brain tissues due to hypertension, aneurysm (outpouching or dilation in wall of blood vessel), hea dinjury, arteriovenous malformation, blood dyscrasia

Question 7

Epilepsy

Answer 7

• Partial seizures: begin in one cerebral hemisphere
• Secondarily generalised seizures: begin in hemisphere and spread to other
• Generalised seizures: involve both hemispheres

Seizure Types

• Absence (petit mal): disturbances in consciousness
• Atonic: loss of muscle tone
• Myoclonic: muscles contract
• Tonic clonic (grand mal): muscle contraction and loss of consciousness
• Generalised convulsive status epilepticus: seizures continue with recovery between them

Question 8

Dementia

Answer 8

• Cognitive decline caused by damage to association areas of cerebral hemispheres or subcortical area link to memory and learning
• Many dementias associated with abnormal inclusions in brain: Alzheimer disease (amyloid plaques), Pick disease (frontotemporal dementia- atrophy of frontal and anterior temporal lobes of brain), prion disease or Creutzfeldt- Jakob disease (caused by infective protein agent called prion, causes degeneration of pyramidal and extrapyramidal systems)

Dementia other causes

• Multi infarct dementia: brain damage from chronic ischemia (e.g those caused by series of small strokes)
• Wernicke- Korsakoff syndrome- result from chronic alcoholism. Caused by vitamin B12 (thiamin) deficiency which interferes with glucose production, brain’s main nutrient
• Inherited atrophy of brain structure (huntington’s disease): GABA, GABA receptors and ACh found to be reduced, dopamine pathway preserved = imbalance of dopamine and ACh lead to disease

Alzheimer’s

• Brain disorder due to degeneration of cerebral cortex and hippocampus
• Cause intellectual impairment, mood changes, confusion, memory loss
• Change in brain: amyloid beta protein forming plaques, neurofibrillary tangles involving protein tau prevent communication between cells and kills neurons, and brain shrink (especially hippocampus and basal forebrain involved in thinking and memory), decreased ACh production due to loss of neurons in basal forebrain

Alzheimer’s Disease Stages

• First: short term memory loss
• 2nd: confusional stage- disorientation, lack of insight, impaired hygiene and language use, sundown syndrome
• 3rd: incontinence, inability to recognise family and friends