Extrapyramidal

Anatomy

• It is a part of the motor system network causing involuntary actions.
  • Pyramidal tracts (Corticospinal tract and Corticobulbar tracts) may directly innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn cells or certain cranial nerve nuclei)
  • Extrapyramidal system centers on the modulation and regulation (indirect control) of anterior (ventral) horn cells.

• Extrapyramidal tracts (EPS) are chiefly found in the reticular formation of the pons and medulla.
• EPS originate in brainstem, carrying motor fibers to the spinal cord.
• They are responsible for the unconscious, reflexive or responsive control of musculature, eg muscle tone, balance, posture and locomotion.
• EPS target lower motor neurons in the spinal cord that are involved in reflexes, locomotion, complex movements, and postural control.
• EPS are modulated by nigrostriatal pathway, Basal ganglia, Cerebellum, Vestibular nuclei, and sensory areas of cerebral cortex
• EPS modulate motor activity without directly innervating motor neurons

Function

EPS serves an essential function in maintaining posture and regulating involuntary motor functions. In particular, the EPS provides:

• Postural tone adjustment
• Preparation of predisposing tonic attitudes for involuntary movements
• Performing movements that make voluntary movements more natural and correct
• Control of automatic modifications of tone and movements
• Control of the reflexes that accompany the responses to affective and attentive situations (reactions)
• Control of the movements originally voluntary then become automatic through exercise and learning (e.g., in writing)
• Inhibition of involuntary movements (hyperkinesias), which are particularly evident in extrapyramidal diseases.

Subdivisions

Functionally, the EPTs can be subdivided into four tracts

• Vestibulospinal and Reticulospinal tracts (do not decussate, providing ipsilateral innervation).
• Rubrospinal and Tectospinal tracts (decussate, provide contralateral innervation)

Extrapyramidal symptoms

• Extrapyramidal symptoms are archetypically associated with Extrapyramidal tracts
• When such symptoms are caused by medications, they are also known as extrapyramidal side effects (EPSE).

Classification

• Acute dystonic reactions: Painful muscular spasms of neck, jaw, back, extremities, eyes, throat and tongue
  • Oculogyric crisis: An acute dystonic reaction that involves the prolonged involuntary upward deviation of eyes.

• Akathisia: A feeling of internal motor restlessness that presents as tension, nervousness, anxiety and an inability to sit still.
• Parkinsonism: Rigidity + Bradykinesia + Tremor + Tardive dyskinesia
• Pseudoparkinsonism: Rigidity, Bradykinesia, Tremor, Masked faces, Shuffling gait, Stooped posture, Sialorrhoea and Seborrhoea
  • Although Parkinson's disease is primarily a disease of the nigrostriatal pathway and not EPS, loss of dopaminergic neurons in the substantia nigra leads to dysregulation of EPS. Since this system regulates posture and skeletal muscle tone, a result is the characteristic bradykinesia of Parkinson's.
• Tardive dyskinesia: Involuntary muscle movements in the lower face and distal extremities; this can be a chronic condition associated with long-term use of antipsychotics.

Related disease

• Restless Leg Syndrome: Akathisia has very similar sensation
• Parkinson Disease
• RBD

Entities / Miasms

	JE	WNE	CJD	GSS	FFI
Ataxia	+++	+++	+++	+++	+++
Tremor	+++	+++	+++	+++	+++
Bradykinesia / Parkinsonism	+++	+++	+++	+++	+++
Rigidity	+++	+++	+++

Note

• It seems that Extrapyramydal sign / Symptoms would be another COD, named EPS COD
• RLS, RBD, Parkinson disease are belonging to this COD