Essential Neuroanatomy Lecture Notes

Introduction

• Focus on neuroanatomy relevant to medical exams (Step 1, Step 2, Step 3)
• More detail required for Step 1 (basic science focus)
• Step 2 & 3 focus on disease-related anatomy

External Brain Anatomy

• Lobes of the Brain
  • Frontal Lobe: Behavior and impulse control
  • Parietal Lobe: Sensory integration
  • Occipital Lobe: Vision
  • Temporal Lobe: Hearing
• Divisions
  • Lateral Sulcus: Divides frontal and temporal lobes
  • Central Sulcus: Divides frontal and parietal lobes
  • Precentral Gyrus: Responsible for motor activity
  • Postcentral Gyrus: Responsible for sensory input

Important Brain Areas

• Broca's Area: Initiates speech (Frontal lobe)
• Wernicke's Area: Understanding speech (Temporal and Parietal lobes)
• Cerebral Perfusion
  • Middle Cerebral Artery: Lateral brain, associated with upper extremity symptoms
  • Anterior Cerebral Artery: Medial brain, associated with lower extremity symptoms

Basal Ganglia and Related Disorders

• Substantia Nigra: Parkinson's disease (dopaminergic neurons)
• Subthalamic Nucleus: Hemiballismus
• Caudate and Putamen: Involved in Huntington's disease
• Hydrocephalus Ex Vacuo: Appears in Huntington's due to degeneration

Arterial Circulation of the Brain

• Circle of Willis: Connection of anterior and posterior circulations
• Anterior Circulation
  • Internal Carotid Artery
  • Middle Cerebral Artery (MCA): Lateral cerebrum
  • Anterior Cerebral Artery (ACA): Medial cerebrum
  • Ophthalmic Artery: Supplies retina
• Posterior Circulation
  • Vertebral and Anterior Spinal Arteries
  • Basilar Artery and its branches
  • Posterior Cerebral Artery: Supplies occipital lobe

Stroke Syndromes

• Importance of knowing artery blockage and symptoms
• Commonly Tested Arteries
  • MCA, ACA, PCA, ASA, Ophthalmic
• Berry Aneurysms
  • Commonly occur at the anterior cerebral artery near the anterior communicating artery

Cranial Nerves and Foramina

• Know the exit points and passageways of cranial nerves (Step 1 focus)
• Examples: Optic Canal for CN II, Superior Orbital Fissure for CN III, IV, VI

Spinal Pathways

• Sensory Pathways
  • DCML (Dorsal Column Medial Lemniscus): Fine touch, vibration, proprioception
  • Spinothalamic Tract: Pain, temperature, crude touch
  • Lesions cause distinct patterns of contralateral or ipsilateral symptoms
• Motor Pathway (Corticospinal Tract)
  • Originates in precentral gyrus, pyramidal decussation at medulla, synapses in spinal cord
  • Lesions above decussation affect contralateral side, below affect ipsilateral side