lower motor neurone lesions

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lower motor neurone lesions

; LMN lesions lesions of LMN or LMN axon; causes include infection (e.g. poliomyelitis), trauma (e.g. limb fracture), autoimmune disease (e.g. multiple sclerosis), dietary deficiency (e.g. beriberi); demyelination (e.g. late-stage diabetes); characterized by loss of tendon reflexes and muscle atrophy (see Table 1)
Table 1: Effects of damage to upper and lower motor neurones
Upper motor neurone lesionLower motor neurone lesion
ParalysisSpastic-type contractureFlaccid-type contractures may develop
Tendon reflexesExaggerated; hyperreflexiaReduced/absent; hyporeflexia
Plantar responseExtensor (Babinski's sign positive)Flexor (= normal; Babinski's sign negative)
Extraneous muscle activityNo fasciculations/fibrillationsFasciculations and fibrillations