Extrapyramidal Symptoms

Overview

Degenerative extrapyramidal disorders (e.g. Parkinson’s disease) and drugs (such as drugs that antagonise dopamine D2 receptors including antipsychotics and antiemetics such as metoclopramide) can lead to extrapyramidal symptoms (EPS). These are characterised by:

• Acute dystonic reactions – painful muscular spasms of the jaw, neck, back, limbs, eyes etc.
  • Oculogyric crisis is a type of acute dystonic reaction where there is a prolonged involuntary upward deviation of the eyes
  • May be treated with procyclidine (an anticholinergic drug)
• Akathisia – severe restlessness:
  • May manifest as an inability to sit still, pacing, or anxiety
• Parkinsonism – features of Parkinson’s disease, which can be remembered with TRAP:
  • Tremors
  • Rigidity
  • Akinesia/bradykinesia – slowing of movements which may progress as movement goes on 
  • Postural instability
• Tardive dyskinesia – involuntary movements of the muscles of the lower face and distal extremities:
  • Examples are chewing and pouting of the jaw
  • Tardive – presents later, either due to a chronic condition or long-term drug use
  • May be treated with tetrabenazine

Extrapyramidal Tracts

Overview

The extrapyramidal tracts convey UMNs from the brainstem to the spinal cord and are involved in the involuntary control of the muscles, including their tone, balance, posture, and locomotion.

The extrapyramidal tracts include:

• The vestibulospinal tracts – from the vestibular nuclei to the spinal cord:
  • Control balance and posture
  • Subdivided into medial and lateral vestibulospinal pathways
  • Do not decussate – provide ipsilateral innervation
• The reticulospinal tracts – from the reticular formation in the brainstem to the spinal cord:
  • Subdivided into:
    • The medial reticulospinal tract – arises from the pons and facilitates voluntary movement and increases muscle tone
    • The lateral reticulospinal tract – arises from the medulla and inhibits voluntary movement and decreases muscle tone
  • Do not decussate – provide ipsilateral innervation
• The rubrospinal tracts – from the red nucleus in the midbrain to the spinal cord:
  • Exact function unclear, thought to be involved in the control of fine hand movements
  • They do decussate – provide contralateral innervation
• The tectospinal tracts – from the superior colliculus in the midbrain to the spinal cord:
  • The superior colliculus receives signals from the optic nerve
  • Involved in coordinating head movements in response to vision
  • They do decussate – provide contralateral innervation