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 are chiefly found in the reticular formation of the pons and medulla.
• Extrapyramidal tracts target lower motor neurons in the spinal cord that are involved in reflexes, locomotion, complex movements, and postural control.
• Extrapyramidal tracts are modulated by nigrostriatal pathway, Basal ganglia, Cerebellum, Vestibular nuclei, and different sensory areas of cerebral cortex
• Extrapyramidal tracts modulate motor activity without directly innervating motor neurons.

Parts

Extrapyramidal tracts include

• Rubrospinal tract
• Pontine reticulospinal tract
• Medullary reticulospinal tract
• Lateral vestibulospinal tract
• Tectospinal tract

Clinic

• 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
• Parkinson Disease
• RBD

Entities / Miasms

• Tremor
• Bradykinesia / Parkinsonism
• Rigidity

Extrapyramidal tracts originate in the 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.

• The reticulospinal tract is one of the most important extra-pyramidal tracts for controlling the activity of lower motor neurons.

Extrapyramidal Tracts (EPS)

The 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.

Functionally, the EPTs can be subdivided into four.

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

The EPS controls the automatic activities and influences voluntary motility through a tonic function. These regulation mechanisms involve the processing of centers located in multiple brain regions eg parts of the cerebral cortex, the cerebellum, thalamus, reticular formation, and several basal ganglia (a group of subcortical nuclei)..