Neurology: Extrapyramidal System Diseases

Diseases of the Extrapyramidal System

• Voluntary movement regulation involves the pyramidal, cerebellar, and extrapyramidal systems, interconnected nodes critical for motor coordination.
• The extrapyramidal system consists of several nuclei, primarily the basal ganglia, which include:
  • Caudate nucleus
  • Lentiform nucleus (globus and putamen)
  • Substantia nigra
  • Subthalamic nucleus
• The thalamus is essential for relaying information between basal ganglia and the motor cortex.
• Common extrapyramidal syndromes include Parkinson’s disease, rheumatic or Sydenham’s chorea, and dystonia with athetosis.

Parkinson’s Disease

• First described as "shaking palsy" by James Parkinson in 1817.
• Affects about 1% of people over 60 years; incidence peaks in mid-70s.
• Symptoms include tremors, rigidity, and hypokinesis, all responsive to levodopa treatment.
• Etiology:
  • Associated with genetic mutations (Synuclein, Parkin, LRRK2) in familial cases.
  • Characterized by depletion of dopamine in the substantia nigra, leading to predominance of acetylcholine's excitatory action.
• Pathologic features:
  • Loss of pigmented neurons in substantia nigra.
  • Presence of Lewy bodies, eosinophilic inclusions in neurons.
• Clinical features include:
  • Tremors: Begin in fingers, may spread; visible at rest, decrease with movement.
  • Rigidity: Increase in muscle resistance; can be lead-pipe or cogwheel type.
  • Hypokinesis (Bradykinesia): Delay in movement initiation, characteristic shuffling gait.
  • Postural Instability: Difficulty maintaining balance, can be severely disabling.
• Diagnosis often requires functional imaging (PET, SPECT) for accuracy.
• Differential diagnoses include essential tremor, hypothyroidism, cerebellar tremors, and metabolic issues.
• Treatment options:
  • Anticholinergic drugs: Limited effects on hypokinesis, significant side effects.
  • Levodopa: Effective for hypokinesia; combined with Carbidopa to enhance efficacy and reduce side effects.
  • Dopamine receptor agonists: Stimulate dopamine receptors and reduce levodopa dosage requirement.
  • Amantadine: Mild effects on symptoms; may cause confusion or seizures.
  • Surgical treatment: Reserved for severe, resistant cases.

Rheumatic or Sydenham’s Chorea

• Sydenham’s chorea linked to rheumatic fever; first described by Dr. Thomas Sydenham in the 17th century.
• Defined by rapid, irregular movements affecting extremities and face; movements may appear purposeful.
• Common in children and adolescents, especially females; usually follows a streptococcal infection.
• Etiology involves an autoimmune response triggered by group A beta-hemolytic streptococci, leading to increased dopamine activity in basal ganglia.
• Clinical features include:
  • Hypotonia, muscular weakness, emotional disturbances, behavioral changes, and jerky involuntary movements.
  • Diagnostic signs: hyperpronation of the arm (pronator sign) and difficulty holding the tongue out (tongue sign).
• Generally self-limiting, yet can relapse following streptococcal infections.
• Treatment involves managing movements with:
  • Haloperidol: Decreases dopamine activity; gradually adjusted for control.
  • Diazepam: For severe cases, may require hospitalization.
  • Penicillin: Antibiotic for throat infections; steroids may be necessary in resistant cases.

Dystonia and Athetosis

• Dystonia: Characterized by sustained muscle contractions causing twisting movements and abnormal postures; involves simultaneous contraction of agonist and antagonist muscles.
• Movements are repetitive and can significantly impair mobility and coordination.

This quiz explores the diseases related to the extrapyramidal system in neurology. It covers the interactions between pyramidal, cerebellar, and extrapyramidal systems that influence voluntary movement. Test your knowledge on the basal ganglia and their neural connections.