Equis ISSN 2398-2977

Musculocutaneous nerve: paralysis

Contributor(s): Frank Andrews, Caroline Hahn, Graham Munroe, Vetstream Ltd

Introduction

  • Cause: this is a rare condition as an isolated paralysis and is more commonly involved with other nerve dysfunction. Brachial plexus injuries and spinal cord lesions involving the brachial intumescence may affect this nerve. External trauma directly or indirectly (via upper forelimb fractures) to this nerve individually are very uncommon.
  • Signs: no gait deficits to very mild gait deficits, unilateral unusually, an overextension of the elbow, atrophy of the biceps and brachialis muscles, hypoalgesia of the craniomedial carpus and cannon.
  • Diagnosis: clinical signs, neurological examination and electrodiagnostics.
  • Treatment: DMSO, corticosteroids, physiotherapy, rest.
  • Prognosis: good.

Pathogenesis

Etiology

  • This is a rare condition as an isolated paralysis and is more commonly involved with other nerve dysfunction.
  • Brachial plexus injuries and spinal cord lesions involving the gray matter of the brachial intumescence may affect this nerve.
  • External trauma directly or indirectly (via upper forelimb fractures) to this nerve individually are very uncommon.

Pathophysiology

  • Paralysis of any of this nerve rarely occurs as a single event.
  • Paralysis of this nerve can be associated with dynsfunction of other peripheral nerves such as the median ulnar nerves.
  • The musculocutaneous nerve supplies the muscles extending the shoulder and flexing the elbow. Section of the proximal part of the nerve experimentally results in decreased elbow flexion and subsequent toe dragging. Partial sensory loss occurred in the skin over the craniomedial carpus and cannon.

Timecourse

  • Experimental studies showed that the gait deficits may disappear within 2 or 3 months due to compensation and adaptation.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references fromPubMedandVetMedResource.
  • Hahn C (2008)Peripheral nerves in the horse.In Practice30(6), 322-329BMJ Online.
  • Alexander K & Dobso N H (2003)Ultrasonography of peripheral nerves in the normal adult horse.Vet Radiol Ultrasound44(4), 456-464PubMed.
  • Blythe L L & Kitchell R L (1982)Electrophysiologic studies of the thoracic limb of the horse.Am J Vet Res43(9), 1511-1524PubMed.

Other sources of information

  • Mayhew I G (2009)Large Animal Neurology. 2nd edn. Wiley-Blackwell, Oxford, UK. pp 309.
  • Blythe L L (1997)Peripheral Neuropathy.InCurrent Therapy in Equine Medicine. 4th edn. Ed. Robinson N E. Saunders, Philadelphia, USA. pp 314-318.


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