Lower Motor Neuron Lesions

Flaccid paralysis

A.P. conduction from CNS--> muscles is blocked. (as consequence of lesion).

Why do LMN lesions get rapid, severe atrophy?

Because of sever "disuse" of muscle--don't have any spasticity.

What causes the fasciculations?

In LMN lesions--> neurons degenerate-->which release inappropriate packets of Ach-->cause muscle to fasciculate.

Fasciculations

Involuntary contractions of small groups of muscle cells. Seen only for about a month or two after lesion occurs.

With hypo or areflexia is muscle atrophy fast or slow?

It is faster and a more severe "disuse" because there is no spastic activity.

Is there clonus with Lower motor n. lesions?

No clonus activity because you need intact reflexes and in LMN lesions they don't have intact reflexes.

Hypo or Areflexia

Reflexes subdued or absent. If totally wipe out the m.n. going to quads and tap tendon no sensory n. going to cord can get back to muscle.

What do lower motor neuron lesions affect?

The alpha and gamma motor neurons themselves.

Do lower motor lesions affect spinal reflexes?

Yes Because it is happening as axon enters the dorsal root-->no A.P. going out.