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.