Brain Anatomical Overview

• The brain has well-mapped discrete regions, each responsible for specific functions:
  • Frontal lobe: executive functions, personality, planning, voluntary movement, emotional and behavioural control, speech (Broca’s area).

• • Parietal lobe: integrates sensory information (touch, temperature, pain), perception.

• • Occipital lobe: visual processing.
  • Temporal lobe: memory, smell, hearing, comprehension of both spoken and written language (Wernicke’s area).

• • Brainstem (Midbrain, Pons, Medulla Oblongata):
    • Midbrain: visual and auditory reflexes, Reticular Activation System (RAS, reticular formation – level of consciousness)
    • Pons: respiratory rhythmicity, RAS
    • Medulla Oblongata: cardiovascular and respiratory control centers, RAS, reflexes (swallowing, coughing, vomiting)

• • Diencephalon:
    • Hypothalamus: endocrine, thermoregulatory, behavioural drives, and autonomic nervous system (ANS) control center
    • Thalamus: gateway to the cortex, directs sensory and motor pathways
    • Epithalamus: pineal gland, mediate circadian rhythm

• • Basal nuclei and Cerebellum: coordination of movement

Effects of Focal Brain Lesions

• Damage to specific brain areas causes discrete functional deficits:
  • Motor cortex damage: motor deficits, paralysis, difficulty moving limbs.
  • Sensory cortex damage: loss of sensation (touch, pain, temperature).
  • Parietal lobe damage: impaired perception.
  • Visual cortex damage: vision loss.
  • Temporal lobe damage: memory deficits, language comprehension issues.

Local Lesions – Focal Effects

• Lesion location:
  • Discrete, affecting specific functions.
  • Example: paralysis of the right arm suggests damage to the left motor cortex.
  • Sensory deficits on the right side imply issues in left parietal lobe.
• Clinical clues:
  • Loss of sensation or ability to move localized to specific regions.
  • Helps localize lesion sites.

Expanding or Diffuse Lesions

• Lesions can spread due to:
  • Inflammation.
  • Bleeding.
  • Tumor growth.
• Can cause more extensive deficits:
  • Spread of paralysis, sensory loss, and cognitive issues.
• Increased inflammation can elevate intracranial pressure (ICP).

Increased Intracranial Pressure

• The skull is a fixed, rigid compartment.
• Expansion of lesions, bleeding, or swelling leads to ICP buildup.
• Elevated ICP causes capillary pinching, reducing blood flow to neurons.
• Neurons are highly sensitive to oxygen and nutrients; prolonged ICP can cause neuronal death.
• Symptoms of increased ICP:
  • Headache.
  • Nausea and vomiting.
  • Altered consciousness.
  • Brain herniation may occur if pressure isn’t relieved.

Clinical Importance

• Minimize ICP to prevent brain ischemia.
• Surgical intervention (e.g., ventriculostomy, cyst decompression) may be necessary.
• Early detection of increasing ICP improves outcomes.

Summary

• Brain functions are localized; damage causes specific neurological deficits.
• Lesions can expand, involving more areas and worsening symptoms.
• The skull’s rigidity makes ICP management critical during injury or disease.