Polyneuritis Equi

• A non-infectious central nervous inflammatory disease
• Polyneuritis equi (PNE) is an uncommon disease which affects mature horses
• Formerly known as 'cauda equina syndrome' or 'cauda equina neuritis'
• May occur as:
  • A disease effecting the spinal nerve roots and ganglia of the cauda equina.
  • A disease effecting the cranial nerves.
• Cauda equina disease is characterised by progressive loss of anal tone, tail paralysis, urinary and/or faecal incontinence, urine scalding of the hindlimbs, hyperaesthesia and muscle fasciculations over hindquarters.
• If the pelvic nerve roots are also involved, there may be changes in hindlimb gait.
• Cranial nerve signs may be apparent, including signs associated with facial nerve paralysis.
• Changes in the CSF are often non-specific.
  • There is usually a moderate mononucloear pleocytosis.
  • Protein is usually elveated.
• Histologically, the disease presents as a severe, chronic, destructive lymphocytic and histiocytic polyradiculoneuritis.
• Pathogenesis is not completely understood, but considered to be a T-lymphocyte mediated response to myelin, followed by destruction of myelin and axons by macrophages
• Disease appears similar to:
  • Guillain-Barré Syndrome (GBS), an autoimmune demyelinating diease in humans
  • Experimental allergic neuritis (EAN) in laboratory animals
• Important differential diagnoses for progressive neurologic signs effecting the bladder, rectum, perineum, tail, penis and hindlimbs in horses include:
  • Equine herpesvirus-1 myeloencephalopathy
  • Sacral/coccygeal trauma
  • Equine motor neuron disease
  • Abberant parasite migration (e.g. Strongylus spp.)
  • In endemic areas, Sarcocystis neurona myelitis (equine protozoal myelitis), rabies and rhodococcus equi myeloencepahlitis should also be considered.