hyporeflexia

{{short description|Reduction or absence of bodily reflexes}}

{{More citations needed|date=November 2016}}

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Hyporeflexia is the reduction or absence of normal bodily reflexes. It can be detected through the use of a reflex hammer and is the opposite of hyperreflexia.{{cn|date=October 2024}}

Hyporeflexia is generally associated with a deficit in the lower motor neurons (at the alpha motor neurons from the spinal cord to a muscle), whereas hyperreflexia is often attributed to lesions in the upper motor neurons (along the long, motor tracts from the brain). The upper motor neurons are thought to inhibit the reflex arc, which is formed by sensory neurons from intrafusal fibers of muscles, lower motor neurons (including alpha and gamma motor fibers) and appurtenant interneurons. Therefore, damage to lower motor neurons will subsequently result in hyporeflexia and/or areflexia.{{cn|date=October 2024}}

In spinal shock, which is commonly seen in the transection of the spinal cord, hyporeflexia can transiently occur below the level of the lesion and can later become hyperreflexic. Cases of severe muscle atrophy or destruction may render the muscle too weak to show any reflex and should not be confused with a neuronal cause.{{cn|date=October 2024}}

Hyporeflexia may have other causes, including hypothyroidism, electrolyte imbalance (e.g., excess magnesium), and drug use (e.g, depressants).{{Cite web|url=https://www.ncbi.nlm.nih.gov/mesh?term=Hyporeflexia|title=Reflex, Abnormal - MeSH - NCBI|website=www.ncbi.nlm.nih.gov|access-date=2019-04-03}}

Diseases associated with hyporeflexia include:

• Centronuclear myopathy{{cn|date=October 2024}}
• Guillain–Barré syndrome{{cn|date=October 2024}}
• Lambert-Eaton myasthenic syndrome{{Cite journal|last=Wirtz|first=P. W.|last2=Kuks|first2=J. B.|last3=Wintzen|first3=A. R.|last4=Verschuuren|first4=J. J.|date=2001-01-13|title=[Proximal muscle weakness, depressed tendon reflexes and autonomic dysfunction: the Lambert-Eaton myasthenic syndrome]|journal=Nederlands Tijdschrift voor Geneeskunde|volume=145|issue=2|pages=57–61|issn=0028-2162|pmid=11225256}}
• Hypothyroidism
• Polyneuropathy (achilles and plantar reflexes){{cn|date=October 2024}}
• Friedreich's Ataxia{{cn|date=October 2024}}