Neurology · MU Sofia

6. Extrapyramidal system: anatomy, physiology, extrapyramidal syndromes

Covers the extrapyramidal system's anatomy, starting with the basal ganglia components and their connections, then its neurotransmitters and physiological functions. It then sets out the hypokinetic-rigid (parkinsonian) syndrome, with its clinical features, causes and a TRAP mnemonic, followed by the hyperkinetic syndromes such as tremor, chorea, athetosis, dystonia, hemiballismus and tics. It closes with examination findings for these disorders, including how rigidity differs from spasticity.

Inside: 1 section · 3 labelled pictures · 15 flashcards · 2 min

Topic 6 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 273 words (2 min of reading), with 15 flashcards.

In this note

  1. Extrapyramidal system - anatomy, physiology, extrapyramidial syndromes

Extrapyramidal system - anatomy, physiology, extrapyramidial syndromes

Extrapyramidal System

The extrapyramidal system is a network of nuclei and pathways that regulates muscle tone, posture, automatic movements, balance, and coordination of voluntary movements. It does not initiate movement but modulates and smooths it.

Anatomy

  • Basal Ganglia Components

Caudate nucleus. Putamen. Globus pallidus. Subthalamic nucleus. Substantia nigra (midbrain)

  • Main Connections

The basal ganglia communicate with: Motor cortex. Thalamus. Brainstem

  • Neurotransmitters
  • Dopamine (substantia nigra) → facilitates movement
  • Acetylcholine → opposes dopamine effects
  • GABA
  • Glutamate

Physiology

Functions

  • Regulation of muscle tone
  • Maintenance of posture and balance
  • Control of automatic and associated movements
  • Coordination and smooth execution of voluntary movements
  • Suppression of unwanted movements

A balance between dopamine and acetylcholine is essential for normal motor function.

Extrapyramidal Syndromes

Extrapyramidal disorders are characterized by abnormal involuntary movements, altered muscle tone, and postural disturbances without significant weakness.

1. Hypokinetic-Rigid Syndrome (Parkinsonian Syndrome)

Caused by dopamine deficiency in the basal ganglia.

  • Clinical Features

Bradykinesia (slowness of movement). Resting tremor. Muscle rigidity ("lead-pipe" or "cogwheel"). Postural instability. Shuffling gait. Mask-like face (hypomimia). Reduced arm swing. Micrographia

  • Causes

Parkinson disease. Drug-induced parkinsonism. Vascular parkinsonism

Mnemonic: TRAP ( Tremor. Rigidity. Akinesia/Bradykinesia.Postural instability)

2. Hyperkinetic Syndrome

Characterized by excessive involuntary movements.

  • Tremor: Rhythmic oscillatory movement.
  • Chorea: Rapid, irregular, jerky movements.. Example: Huntington disease
  • Athetosis: Slow, writhing movements of distal limbs.
  • Dystonia: Sustained involuntary muscle contractions causing abnormal postures.
  • Hemiballismus: Violent flinging movements of one side of the body.
  • Usually due to lesion of the subthalamic nucleus
  • Tics: Sudden, repetitive, stereotyped movements or vocalizations.

Examination Findings in Extrapyramidal Disorders

Muscle Tone: Increased rigidity. Not velocity-dependent (unlike spasticity)

Reflexes: Usually normal

Muscle Strength: Usually preserved

Sensation: Normal

Involuntary Movements: Tremor. Chorea. Dystonia. Tics. Athetosis

Read the full note free

The whole note is free with an AceMed account, with its 15 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note