UPPER MOTOR NEURON LESION :

UPPER MOTOR NEURON LESION

Upper motor neuron lesion

“An Upper motor neuron lesion (pyramidal insufficiency) is a lesion of the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves.”

Location of lesion and structure involved:

  • Central nervous system-cortex, brainstem, corticospinal tracts, spinal cord.

Diagnosis or pathology:

  • Stroke, traumatic brain injury, spinal cord injury.

Tone:

  • Increased: Hypertonia, velocity dependent.

Reflexes:

  • Increased: hyperreflexia, clonus, exaggerated cutaneous and autonomic reflexes, +ve Babinski.

Involuntary movements:

  • Muscle spasms: flexor or extensor.

Strength:

  • Weakness or Paralysis: ipsilateral(stroke) or bilateral(SCI) Corticospinal: contralateral if above decussation in medulla; ipsilateral if below distribution: never focal.

Muscle bulk:

  • Disuse atrophy: variable, widespread distribution, especially of antigravity muscles.

Voluntary movements:

  • Impaired or absent: dyssenergic patterns, obligatory mass synergies.

Synergies pattern in Upper motor neuron lesion:

  • Primitive abd stereotyped movement associated with spasticity.
  • They may be elicited reflexively, as associated reactions or a voluntary movement patterns.
  • There are two basic synergies of each extremity.

(1)FLEXION SYNERGY:

(a) Upper extremity:

Flexor synergy in upper limb

 

  • Scapular elevation and retraction.
  • Shoulder abduction and external rotation.
  • Elbow flexion generaly the strongest comonent.
  • Forearm supination and wrist/finger flexion.

(b) Lower extremity:

Flexor synergy in lower limb

  • Hip flexion, generaly the strongest component abduction, external rotation.
  • Knee flexion.
  • Ankle dorsiflexion and inversion.
  • Toe dorsiflexion.

(2) EXTENSOR SYNERGY:

Extensor synergy in upper and lower limb

(a) Upper extremity:

  • Scapular protraction.
  • Shoulder adduction and internal rotation.
  • Elbow extension.
  • Forearm pronation and wrist/finger flexion.

(b) Lower extremity:

  • Hip extension, adduction and internal rotation.
  • Knee extension.
  • Ankle plantar flexion and inversion.
  • Toe flexion.

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