Extrapyramidal Motor System

Extrapyramidal System

• The human motor system governs both voluntary and involuntary movements.
• The pyramidal motor system facilitates voluntary movement via the premotor and motor cortices, sending commands through the corticospinal tract.
• Voluntary actions are aided by the extrapyramidal system, bypassing the pyramids to enforce desired movements and suppress unwanted ones.
• The extrapyramidal motor system regulates involuntary movement.
• It plays a crucial part in posture maintenance through postural tone adjustments.
• Contributing to movements to make them more natural and correct, by automatically modifying tone.
• Responsible for the regulation of involuntary motor functions.
• This system is composed of interconnected centers at various levels, forming specific tracts.
• The system's components include the cerebellum, basal ganglia, brain stem and various tracts.
• Motor Tracts include: Rubrospinal, Tectospinal, Reticulospinal (medial & lateral), Vestibulospinal (medial & lateral), Olivospinal.

Extrapyramidal Disorders

• These disorders manifest as excessive or abnormal movements in conscious patients.
• Etiology involves dysfunction within the basal ganglia, brainstem, and cerebellar connections.
• The abnormal movements can be the primary disease manifestation or part of a broader deficit pattern.
• Movement disorders are classified as either excessive (hyperkinetic) or reduced (hypokinetic) in activity.

Parkinson’s Disease

• Cardinal signs are represented by the acronym TRAP: Tremor (resting), Rigidity, Akinesia/bradykinesia, and Postural instability with altered gait.
• Often presents with a stooped posture and a shuffling gait, noticeable from a distance.
• Caused by an imbalance between dopamine and acetylcholine.
• Degeneration of basal ganglia and substantia nigra, vascular issues like atherosclerosis, inflammatory conditions like encephalitis, toxic exposure to carbon monoxide, and repeated head trauma can cause Parkinson's Disease.
• Tremors are rhythmic and frequent at a rate of 4-8 per second.
• Tremors start unilaterally in the upper limbs but may extend to all four limbs.
• "Pill rolling" posture is typical in tremors.
• Tremors intensify with stress and fatigue but diminish during sleep and voluntary movement.
• Rigidity affects proximal muscles more than distal ones.
• Rigidity of flexors is more so than extensors, creating a gorilla-like posture.
• Characterized by lead pipe rigidity and cog wheel rigidity.
• Initiation of movement is difficult, leading to a short steppage gait.
• Mask-like face due to a loss of emotional expression. Speech is monotonous.
• Arm swinging during walking is diminished.
• Other manifestations include Hyposmia and anosmia.
• Autonomic disturbances like orthostatic hypotension and urinary retention or constipation may occur.
• Sleep may be disturbed.
• Can be diagnosed through physical and neurological exams.
• Blood and lab tests are useful to exclude other conditions.
• While MRI, brain ultrasound, and PET scans can exclude other conditions, they are not very useful to diagnose Parkinson's Disease.
• Genetic testing can identify gene changes if there are known family history.
• Carbidopa-levodopa is a natural chemical that converts to dopamine in the brain.
• Combining levodopa with carbidopa aids levodopa's entry into the brain and reduces side effects like nausea.
• Dopamine agonists mimic dopamine effects in the brain.
• Anticholinergics are another treatment option.
• Deep brain stimulation (DBS), a surgical intervention involves placing electrodes within the brain.

Wilson Disease

• This autosomal recessive disorder disrupts copper metabolism due to a deficiency in ceruloplasmin, which usually binds 98% of copper.
• This causes copper deposition in all organs.
• Copper accumulation in the basal ganglia leads to extrapyramidal symptoms like chorea, dystonia, tremors, and bradykinesia.
• A diagnostic indicator is the presence of Kayser-Fleischer rings in the cornea.

Chorea

• Presents as involuntary, static, irregular, sudden, jerky, pseudopurposive movements in any part of the body.
• It occurs due to lesion in the caudate nucleus.
• Huntington's chorea is a herido-familial cause.
• Symptomatic causes include autoimmune reasons like Rheumatic chorea; and infective causes like post encephalitic chorea.
• Symptomatic causes also include Vascular and Toxic reaons.

Huntington’s Chorea

• An autosomal dominant condition.
• It predominantly affects middle-aged individuals.
• Develops gradually with coarse and progressive symptoms.
• Degeneration of basal ganglia, especially the caudate nucleus, leads to choreic movements.
• Frontal lobe degeneration results in marked mentality and behavior changes.

Dystonia

• Involuntary, slow, torsional, or twisting movements characterize dystonia.
• It affects the neck, trunk, and proximal muscles.
• Hypertonia is present during movement, with normal tone in between movements.
• Generalized dystonia is a familial disorder starting in childhood.
• Partial dystonias include Spasmodic Torticollis, Oromandibular dystonia and Writer's cramp
  • Spasmodic Torticollis is a dystonia in sternocleidomastoid especially during walking.
  • Oromandibular is a dystonia of jaw and mouth with or without dystonia of eyelid (blepharospasm).
  • Writer’s cramp is a painful spam of hand and forearm muscles on attempt to write.