Neurology and Stroke Quiz

Brain Damage and Neuroplasticity

• The presentation covers key topics of brain injury, neurological diseases, and neuroplastic responses to nervous system damage.

Brain Injury

• Types of brain injury include brain tumors, cerebrovascular disorders, closed-head injuries, infections of the brain, neurotoxins, and genetic factors.

Brain Tumors (Neoplasms)

• A brain tumor is a mass of cells that grows independently of the rest of the body, considered cancerous.
• Types of brain tumors include meningiomas, infiltrating tumors, and metastatic tumors.
• Meningiomas account for ~20% of neoplasms, are encapsulated within the meninges, and are typically benign and removable.
• Infiltrating tumors are the majority of cases, grow diffusely through surrounding tissue, and are often malignant, making removal or destruction challenging. Examples include gliomas.
• Metastatic tumors account for ~10% of neoplasms and originate elsewhere, often the lungs.

Cerebrovascular Disorders: Stroke

• Stroke is a sudden-onset cerebrovascular event causing brain damage.
• An infarct is dead or dying tissue.
• The penumbra is damaged tissue surrounding the infarct, potentially salvageable with early intervention.
• Causes of stroke include Cerebral hemorrhage (13% of strokes) and Cerebral ischemia (87% of strokes)
• Cerebral hemorrhage involves blood vessel ruptures, including aneurysms (weakened blood vessel points). The breakdown of blood components forms free radicals leading to damaged lipid membranes, blood-brain barrier, and DNA damage causing cell death
• Cerebral ischemia involves disruption in blood supply to the brain, including conditions like thrombosis (blood clot) and embolism (blood clot traveling to smaller vessels), and arteriosclerosis (thickening of artery walls due to fat deposits).
• Damage from ischemic strokes involves blood-deprived neurons becoming overactive, releasing glutamate, and activating NMDA receptors causing Na+ and Ca2+ influx, killing neurons and potentially releasing more glutamate before cell death.

Closed-Head Injuries

• Closed-head injuries are brain injuries caused by blows that do not penetrate the skull, resulting in the brain colliding with the skull.
• Types include direct and contrecoup injuries.
• Contusions involve hematomas (bruises).
• Concussions cause a disturbance in consciousness without structural brain damage.

Infections of the Brain

• Encephalitis is brain inflammation caused by microorganisms like bacteria, viruses, fungi, and parasites.
• Abscesses are pockets of pus.
• Meningitis is an inflammation of the meninges (membranes surrounding the brain and spinal cord). Bacterial meningitis is treated with antibiotics. Syphilis is an example of a bacterial infection.
• Viruses can also cause encephalitis, and some viruses like rabies can have a preference for neural tissue, affecting behavior, while other viruses have no preference for CNS tissue. These are often treated with vaccines and anti-viral drugs.

Neurotoxins

• Neurotoxins are substances that cause harm to the nervous system.
• Exogenous neurotoxins enter the general circulation and cross the blood-brain barrier. Examples include heavy metals (like mercury and lead, causing toxic psychosis) and toxins from certain animals (venom from spiders, snakes, and bacterial toxins).
• Endogenous neurotoxins are produced within the body, such as antibodies in autoimmune disorders and excess excitatory neurotransmitters (e.g., glutamate during strokes).

Genetic Factors

• Genetic factors can cause brain damage/disease
• Some genetic disorders, like phenylketonuria (PKU) and Becker's/Duschenne's muscular dystrophy, are caused by recessive genes.
• Most disorders, and Down syndrome in particular, are often caused by multiple genes/mutations.
• Down syndrome results in an extra chromosome 21 (trisomy 21), with a higher prevalence in mothers of advanced age.

Neurological Diseases

• Epilepsy is characterized by recurrent seizures of endogenous origin, affecting about 4% of the population. Causes include brain damage and inflammatory processes, among others. Diagnosis uses electroencephalograms (EEGs) measuring brain activity.
• Parkinson's Disease affects approximately 1% of the population, typically in middle and old age. Symptoms include slow movements, tremors, difficulty in initiating movements, muscle rigidity, reduced facial expression, pain, and dementia. Causes include degeneration of dopaminergic neurons in the substantia nigra (loss of dopamine in the basal ganglia). Diagnoses include PET scans monitoring dopamine levels within basal ganglia.
• Huntington's Disease is a progressive motor disorder, rare (1:10,000) but with a genetic basis. Symptoms involve fidgetiness progressing into jerky movements of limbs and dementia. Caused by a dominant gene, huntingtin, that produces huntingtin protein accumulation, clumps of proteins in the brain. The disease is fatal within approximately 15 years. Diagnosis generally occurs in patients in their 40s.
• Multiple Sclerosis is a progressive disease characterized by multiple hard areas (sclerosis) in the CNS, causing a loss of myelin and progressive loss of neurological function. Causes include genetic predisposition and several environmental factors, such as climate and viral/bacterial infections. Treatments include corticosteroids (to reduce inflammation) and disease-modifying immunomodulators.
• Alzheimer's disease occurs in the majority of individuals over age 65 and is caused by significant neural degeneration, loss of neurons, formation of amyloid plaques, and tau tangles, often resulting in dementia.

Neuroplastic Responses to Nervous System Damage

• Describes the process of neural degeneration, reorganisation and eventual recovery from damage. Axotomy models, showing rapid degeneration of the distal segment and slow degeneration of the proximal segment, illustrate the process. Neural regeneration is different in mammals, with regeneration being common in invertebrates and frogs, but uncommon in higher vertebrates.
• The presentation covers cell replacement therapies, both in embryonic cells and non-embryonic cells, such as neural transplantations, for the treatment of damage from Parkinson's Disease or spinal cord damage.
• Neuroprotective treatments aim to prevent neurodegeneration by addressing factors like apoptosis (cell death) inhibitors, neurotrophic factors (promoting neural growth and survival), and estrogens (which might slow neuronal death).
• Rehabilitative training through methods such as constraint-induced therapy and facilitated walking (harness on treadmill) are often beneficial in recovery from spinal injury or stroke.
• Benefits of cognitive and physical exercise, and the idea of neuroplasticity during this recovery process. The concept of reorganization (a release from inhibition or the development of collateral sprouting) is presented. A two-steps model of reorganization (inhibition and collateral sprouting) is identified.