Medullary Lesions Lecture Notes

Overview

• Topics Covered: Medullary lesions, including medial and lateral medullary syndromes.
• Importance: Understanding the anatomy and blood flow of the medulla is essential to comprehend these syndromes.

Anatomy of the Medulla

Key Structures

• Hypoglossal Nucleus (CN XII): Motor to tongue.
• Dorsal Nucleus of Vagus (CN X): Parasympathetic fibers.
• Nucleus of Tractus Solitarius: Taste and visceral sensory.
• Vestibular Nuclei: Medial and inferior, involved in balance.
• Cochlear Nuclei: Dorsal and ventral, involved in hearing.
• Inferior Olivary Nucleus: Coordinates movement.
• Corticospinal Tracts: Descending motor pathways.
• Medial Lemniscus: Sensory pathway for touch and proprioception.
• Spinal Lemniscus: Pain and temperature sensation.
• Inferior Salivatory Nucleus: Salivation control.
• Nucleus Ambiguus: Motor to pharynx and larynx.
• Descending Sympathetic Tract: Sympathetic outflow.
• Tectospinal Tract: Head and eye movement.
• Medial Longitudinal Fasciculus: Eye movement coordination.

Blood Supply

Main Arteries

• Vertebral Arteries: Supply lateral medulla.
• Anterior Spinal Artery: Supplies medial medulla.
• Posterior Inferior Cerebellar Artery (PICA): Supplies lateral medulla.
• Posterior Spinal Artery: Supplies caudal medulla.

Medial Medullary Syndrome

Cause

• Occlusion: Anterior spinal artery.

Affected Structures

• Hypoglossal Nucleus and Nerve: Tongue motor control.
• Medial Lemniscus: Sensory pathway.
• Corticospinal Tracts: Motor pathway.

Clinical Presentation

• Ipsilateral Tongue Deviation: Due to hypoglossal nerve lesion.
• Contralateral Loss of Proprioception, Fine Touch, Vibration: Medial lemniscus damage.
• Contralateral Hemiplegia or Hemiparesis: Corticospinal tract damage.

Lateral Medullary Syndrome (Wallenberg's Syndrome)

Cause

• Occlusion: Posterior inferior cerebellar artery (PICA).

Affected Structures

• Vestibular Nuclei: Balance and equilibrium.
• Cochlear Nuclei: Hearing.
• Descending Sympathetic Tract: Sympathetic control.
• Spinal Nucleus and Tract of Trigeminal Nerve: Facial sensation.
• Nucleus Ambiguus: Speech and swallowing.
• Spinal Lemniscus: Pain and temperature.
• Inferior Cerebellar Peduncles: Coordination.

Clinical Presentation

• Vertigo, Nausea, Vomiting: Vestibular nuclei damage.
• Unilateral Sensory Neural Deafness: Cochlear nuclei damage.
• Horner's Syndrome: Ptosis, miosis, anhidrosis due to sympathetic tract damage.
• Ipsilateral Loss of Facial Sensation: Trigeminal tract damage.
• Dysphagia, Dysphonia, Dysarthria: Nucleus ambiguus damage.
• Contralateral Loss of Pain and Temperature: Spinal lemniscus damage.
• Ipsilateral Ataxia: Inferior cerebellar peduncles damage.

Summary

• Medial Medullary Syndrome: Anterior spinal artery occlusion affects medial medulla.
• Lateral Medullary Syndrome: PICA occlusion affects lateral medulla.
• Clinical Manifestations: Include ipsilateral and contralateral sensory and motor deficits based on the syndrome.