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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Granulomatous inflammatory condition involving the extradural nerve roots of the cauda equina and often cranial nerves
  • Used to be known as “cauda equina neuritis”; however, it can present with cranial nerve signs so has been renamed PNE

Signalment!!navigator!!

No age or sex predilection; not usually seen in the very young or very old.

Signs!!navigator!!

  • Clinical signs usually include retention of feces and urine, or incontinence, loss of tail and anal tone, and analgesia of the tail and perineum. Urine scalding often present in the perineal area in mares and on the distal hind limbs in males with urinary incontinence
  • Abnormalities in the pelvic limb gait and muscle wasting are seen less often
  • Analgesia of the perianal skin may be surrounded by a zone of hyperesthesia. For that reason some cases can present for tail rubbing
  • Asymmetric and fluctuating cranial nerve signs on occasion precede cauda equina signs. The cranial nerves most often affected include the trigeminal (masseter muscle paresis), facial (paresis of muscles of facial expression), vestibular (head tilt), and hypoglossal nerves (tongue paresis)
  • Clinical signs generally progress more slowly than in typical EHV-1 cases, and only rarely are horses ataxic
  • Lesions may progress to involve lumbar plexus, leading to pelvic limb paresis (initially subtle and asymmetric)

Causes and Risk Factors!!navigator!!

The cause is unknown, but it is thought to be predominantly an immune-mediated event that may be initiated by viral and/or bacterial infections.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Sacral fractures—far more common than PNE. Rule out using rectal palpation, radiography, and scintigraphy
  • EHV-1 myeloencephalopathy—tends have a more acute onset, stabilizes more rapidly, and responds well to treatment. May need CSF tap cytology and viral titers to differentiate
  • Equine protozoal myeloencephalitis
  • Rabies
  • Sorghum cystitis

CBC/Biochemistry/Urinalysis!!navigator!!

Most often normal—may be reflective of any secondary disease or complications that may have occurred, such as dehydration due to impaction colic or urinary tract infection due to urinary retention.

Other Laboratory Tests!!navigator!!

Lumbosacral CSF tap to rule out equine protozoal myeloencephalitis. CSF may be difficult to obtain from the lumbosacral area due to the space-occupying nature of the lesions and may be xanthochromic with elevated protein levels and cell counts.

Imaging!!navigator!!

  • Scintigraphy and radiography to help rule out sacral fractures
  • Rectal ultrasonography can be used to make an antemortem diagnosis based on enlarged and hypoechoic appearance of the extradural sacral nerve roots as they exit the ventral sacral foramina

Pathologic Findings!!navigator!!

  • Necropsy is the only way to reach a definitive diagnosis
  • Cauda equina and cranial nerves become thickened and covered with fibrous material
  • Granulomatous inflammation includes infiltrates of inflammatory cells, including neutrophils, lymphocytes, and macrophages. Axonal degeneration and myelin degeneration in the cauda equina and cranial nerves. Inflammation classically stops abruptly at the central nervous system/peripheral nervous system border

Treatment ⬆ ⬇

TREATMENT

  • Supportive
  • If cranial nerve signs are present and animals are having difficulty eating then they may have to be fed a complete feed as a mash. If fecal retention is a problem then feeding bran mash is appropriate
  • May have to evacuate feces manually
  • Some horses can be maintained for a long time with supportive care, but the disease is relentlessly progressive

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Antibiotics for secondary urinary tract infections
  • Anti-inflammatory drugs are ineffective in the long term

Contraindications/Possible Interactions!!navigator!!

N/A

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Follow progress of hypoalgesia in the tail region.

Patient Monitoring!!navigator!!

Monitor for choke, impaction colic, and fecal and urinary incontinence.

Expected Course and Prognosis!!navigator!!

Disease usually progresses, and long-term prognosis is poor.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

None

Age-Related Factors!!navigator!!

Adult horses.

Zoonotic Potential!!navigator!!

None

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Abbreviations!!navigator!!

  • CSF = cerebrospinal fluid
  • EHV-1 = equine herpesvirus 1
  • PNE = polyneuritis equi

Suggested Reading ⬆ ⬇

Aleman M, Katzman SA, Vaughan B, et al. Antemortem diagnosis of polyneuritis equi. J Vet Intern Med 2009;23:665–668.

Divers TJ, Mayhew IG. Neurology. Clin Tech Equine Pract 2006;5(1):1–80.

Hahn CN. Polyneuritis equi: the role of T-lymphocytes and importance of differential clinical signs. Equine Vet J 2008;40:100.

Mayhew IG. Large Animal Neurology, 2e. Ames, IA: Wiley Blackwell, 2008.

Author(s) ⬆

Author: Caroline N. Hahn

Consulting Editor: Caroline N. Hahn