Lower motor neuron lesion

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Lower motor neuron lesion
Lower motor neuron in red

A lower motor neuron lesion is a

One major characteristic used to identify a lower motor neuron lesion is

.

Signs and symptoms

• Muscle paresis or paralysis
• Fibrillations
• Fasciculations
  – caused by increased receptor concentration on muscles to compensate for lack of innervation.
• atonia
  – Tone is not velocity dependent.
• Hyporeflexia - Along with deep reflexes even cutaneous reflexes are also decreased or absent.
• Strength – weakness is limited to segmental or focal pattern, Root innervated pattern^{[clarification needed]}

The extensor

by the damaged nerves will be symptomatic.

Causes

The most common causes of lower motor neuron injuries are trauma to peripheral nerves that serve the axons, and viruses that selectively attack ventral horn cells. Disuse atrophy of the muscle occurs i.e., shrinkage of muscle fibre finally replaced by fibrous tissue (fibrous muscle) Other causes include

.

Diagnosis

Differential diagnosis

• Myasthenia gravis – synaptic transmission at motor end-plate is impaired
• Amyotrophic lateral sclerosis
  – causes death of motor neurons, although exact cause is unknown it has been suggested that abnormal build-up of proteins proves toxic for the neurons.

See also

• Lower motor neuron
• Upper motor neuron
• Upper motor neuron lesion

References

External links

• http://library.med.utah.edu/neurologicexam/html/motor_anatomy.html#06