Brain Injuries and Disorders

Brain Injuries and Disorders

  • Traumatic Brain Injuries (TBI)
    • Concussion: Temporary alteration in brain function; symptoms may include confusion and dizziness.
    • Contusion: Permanent damage to brain tissue, often observed with bruising.
    • Subdural/Subarachnoid Hemorrhage: Accumulation of blood leads to increased pressure, potentially pushing the brain stem through the foramen magnum, which can be fatal.
    • Cerebral Edema: Swelling of the brain that often accompanies traumatic head injury.

Cerebrovascular Accidents (CVAs - Strokes)

  • Definition: A disruption in blood supply to the brain, leading to tissue damage.
  • Ischemia: Condition where tissue is deprived of adequate blood flow, resulting in potential neural death. Main causes include:
    • Blood clots blocking cerebral arteries.
    • Glutamate Toxicity: Excess glutamate from dying cells can exacerbate damage, acting as an excitotoxin.
  • Symptoms: Hemiplegia (paralysis on one side of the body) and various sensory and speech deficits may arise.
  • Transient Ischemic Attacks (TIAs): Brief episodes of reversible ischemia; considered a warning sign for future strokes.
  • Treatment: Tissue plasminogen activator (TPA) is the only approved medication for treating acute strokes.

Degenerative Brain Disorders

  • Alzheimer’s Disease (AD)

    • A progressive brain disease leading to dementia characterized by:
    • Misfolded proteins
    • Memory loss, disorientation, and personality changes.
    • Pathological Features:
    • Formation of beta-amyloid plaques and neurofibrillary tangles within neurons, leading to neuron death and brain atrophy.

  • Parkinson’s Disease

    • Characterized by degeneration of dopamine-producing neurons in the substantia nigra, leading to:
    • Overactivity of basal nuclei and tremors at rest.
    • Possible Causes: Undefined; theories suggest mitochondrial dysfunction or abnormal protein degradation.
    • Treatments: Include L-dopa (dopamine precursor) and advanced methods like deep brain stimulation or gene therapy.

  • Huntington’s Disease

    • A hereditary, fatal condition marked by the accumulation of huntingtin protein in the brain:
    • Initial symptoms include jerky movements and later symptoms involve cognitive decline.
    • Progression leads to death within 15 years, with treatment focused on medications that mitigate dopamine's effects.

Seizures

  • Definition: Episodes of uncontrolled electrical disturbances in the brain that hinder normal function.
  • Types:
    • Absence Seizures: Characterized by brief lapses in consciousness, most common in children.
    • Tonic-Clonic Seizures: Severe seizures lasting several minutes, involving loss of consciousness, intense convulsions, potential injury, and loss of bladder control.

Diagnostic Procedures for CNS Dysfunction

  • Common tests include:
    • Knee-Jerk Reflex: Abnormal responses can indicate various neurological disorders.
    • Imaging Techniques: CT, MRI, and PET scans provide insights into tumors and other brain abnormalities.
    • Cerebral Angiography: Utilizes X-ray imaging with dye to visualize blood flow and identify blockages causing strokes.
    • Ultrasound: Can assess blood flow in cerebral arteries.

Spinal Cord Trauma and Disorders

  • Spinal Cord Injury: Damage may lead to functional losses in sensory and motor capabilities:

    • Damage to sensory pathways results in paresthesias (abnormal sensations).
    • Motor function losses arise from damage to ventral roots, resulting in paralysis.
    • Types of paralysis include:
    • Flaccid Paralysis: Results from severe ventral root damage; no muscle control, leading to muscle atrophy.
    • Spastic Paralysis: Involves upper motor neuron damage, leading to involuntary muscle contractions while preserving some reflex actions.

  • Transection Effects:

    • Paraplegia: Caused by damage between T1 and L1, affecting both lower limbs.
    • Quadriplegia: Results from cervical spine injuries affecting all four limbs.

  • Poliomyelitis: A viral infection causing loss of motor neurons, which can lead to muscle atrophy and potentially fatal respiratory failure. Survivors may later experience post-polio syndrome.

  • Amyotrophic Lateral Sclerosis (ALS): Characterized by the degeneration of motor neurons leading to impaired ability to move, talk, and breathe; typically fatal within five years.

Developmental Aspects of the CNS

  • Prenatal Factors Affecting CNS:
    • Maternal exposure to harmful substances like drugs or infections can disrupt brain development (e.g., alcohol, opiates).
  • Aging Effects:
    • Cognitive decline may begin at older ages, with significant brain shrinkage occurring as age increases.
    • Lifestyle factors (e.g., excessive drinking, high-impact sports) can cause aging-like symptoms unrelated to actual age.

Clinical Considerations in CNS Development

  • Cerebral Palsy: Neuromuscular condition due to brain damage, leading to muscle control issues, often due to oxygen deprivation at birth.
  • Anencephaly: Failure of cerebral and brainstem development.
  • Spina Bifida: Incomplete closure of vertebral arches, often linked to folic acid deficiency during pregnancy.