Equis ISSN 2398-2977

Polyneuritis equi

Synonym(s): PNE, Cauda equina neuritis (CEN), Neuritis of the cauda equinae (NCE)

Contributor(s): Frank Andrews, Ruth Morgan, Vetstream Ltd


  • A distinct pathologic syndrome characterized by chronic inflammation of the extradural roots of the cauda equina and (occasionally) cranial nerves.
  • Cause: pathologic lesions strongly suggest an immune etiology.
  • Signs: perineal analgesia; paralysis of tail, anus, perineum, rectum and bladder and/or cranial nerve signs. Rarely pelvic limb ataxia.
  • Diagnosis: clinical signs; ruling out of sacral fractures (more common).
  • Treatment: none, although supportive treatment may prolong useful life.
  • Prognosis: poor.



  • Obscure, but lesions strongly suggest an infectious/immune-mediated mechanism causing a polyneuropathy.


  • Infections with equine herpes virus 1, campylobacter and streptococcus have been implicated in the pathogenesis but have not been confirmed.


  • A granulomatous polyneuritis.
  • Although cauda equina involvement appears to lead to the major clinical signs, it is not uncommon for there to be cranial and other peripheral nerve involvement.
  • PNE has been hypothesized be the result of the chronic form of equine herpes myeloencephalitis-1 infection   CNS: myeloencephalopathy - EHV   in some cases.
  • Perineuritis of caudal nerve roots of cauda equina   →   analgesia and areflexia of perineal region   →   flaccid tail, fecal and urinary incontinence, colic and cystitis.
  • Inflammation of sacral and even lumbar nerve roots and extension of polyneuritis to lumbosacral plexus   →   pelvic limb weakness, muscle atrophy and gait abnormalities.
  • Cranial nerve involvement   →   facial paralysis (VII), masseter atrophy and weakness (motor V) and vestibular signs (head tilt, nystagmus and staggering gait (VIII)).
  • Other cranial nerves less commonly affected   →   tongue weakness (XII), difficulty in swallowing (IX, X), absent pupillary light reflex (II, III) and blindness (II).
  • There is gross and histopathologic documentation of involvement of the autonomic nervous system.


  • This disease progresses slowly over a matter of weeks.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Aleman M & Katzman S A et al (2009) Antemortem diagnosis of polyneuritis equi. J Vet Intern Med 23 (3),665-668 PubMed.
  • Hahn C (2008) Common peripheral nerve disorders in the horse. In Pract 30 (6), 322-329 VetMedResource.
  • Hahn C (2008) Polyneuritis equi: The role of T-lymphocytes and importance of differential clinical signs. Equine Vet J 40 (2), 100 PubMed.
  • van Galen G, Cassart D et al (2008) The composition of the inflammatory infiltrate in three cases of polyneuritis equi. Equine Vet J 40 (2), 185-188 PubMed.
  • Hahn C N (2006) Miscellaneous disorders of the equine nervous system: Horner's syndrome and polyneuritis equi. Clin Tech Equine Pract (1), 43-48 VetMedResource.
  • Mayhew J & Vatistas N (1995) Differential diagnosis of polyneuritis equiIn Pract 17 (1), 26-29 (A comprehensive account of polyneuritis equi and its principle differential diagnoses) VetMedResource.
  • Reed S M et al. Ataxia and paresis in horses - differential diagnosisThe Compendium (3).
  • Fordyce P S et al (1987) Use of an ELISA in the differential diagnosis of cauda equina neuritis and other equine neuropathiesEquine Vet J 19 (1), 55-59 PubMed.
  • Wright J A et al (1987) Neuritis of the cauda equina in the horse. J Comp Pathol 97 (6), 667-675 PubMed.
  • Yvovchuk-St J K (1987) Neuritis of the Cauda Equina. Vet Clin North Am Equine Pract 3 (2), 421-427 PubMed.

Other sources of information

  • Reed S M, Saville W J A & Schneider R K (2003) Neurologic Disease: Current Topics In-Depth. In: Proc 49th AAEP Convention. pp 243-258.
  • Hahn C N, Mayhew I G & MacKay R J (1999) The Nervous System. In: Equine Medicine & Surgery.Eds: Colahan P T, Mayhew I G, Merritt A M & Moore J N. Mosby, USA. ISBN-10: 0815117434; ISBN-13: 978-0815117438.