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Neurology Basic Concepts

From Mediwikis

Neurology is an area in Medicine that students traditionally have a bit of a struggle with, but it just takes a bit of time to figure out!

Upper vs Lower Motor Neurone Lesion

Upper motor neurone lesions involve the brain and brainstem, lower motor neurone lesions involve the nerves actually supplying muscles. Certain features suggest a lesion affecting one or the other:

Upper

Lower

Hyperreflexia

Fasiculation

Clonus

Cerebellar dysfunction

"Higher" function disrupted

Absent Reflexes

Wasting of affected muscles




Some definitions:

  • Hyperreflexia - Reflexes are very brisk/strong
  • Fasiculation - Tiny repeated contractions and relaxations of muscle fibres that can be seen when the muscle is at rest
  • Clonus - Repeated contraction and relaxation of muscles, a sign of hyperexcitation and upper motor neurone damage if it is prolonged when tested for (more than 3 beats)
  • Cerebellar Dysfunction - The cerebellum aids in the execution of complex movements, making them smooth, when there is damage to the cerebellum certain features may be seen including:
    • Nystagmus - abnormal repeated eye movements - looks as if the eye is shaking
    • Ataxia - loss of coordination in movements as if the separate parts of the movement are performed in the wrong order
    • Tremor - classically getting more severe as the movement nears completion
    • Dysarthria - change to speech - in cerebellar damage it becomes slurred with loss of normal rhytmm and intonation
  • Higher Function - This includes things like personality and memory

Particular emphasis should be placed on the difference between facial nerve palsies caused by upper and lower motor neurone lesions, (as this is an exam favourite):

  • Upper
    • If the patient attempts to smile, the affected side of the mouth remains in the neutral position
    • If the patient attempts to raise their eyebrows, the affected side has fewer wrinkles
  • Lower
    • If the patient attempts to smile, the affected side of the mouth is drooped down
    • If the patient attempts to raise their eyebrows, the affected side has no wrinkles