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.

Cauda Equina Traction - in small animals

Tail pull injury

Esp. cats after RTA

Lesion via longitudinal traction

Sacrocaudal dislocation/fracture

Limp tail

Incontinence

Hindlimb Paresis

Diagnosis on Clinical signs and history

+/- Radiographs to show dislocation/fracture

Prognosis difficult to predict

Poor prognosis if tail limp & no anal tone

Supportive treatment

Persist for >3 months if possible

Cauda Equina Neuritis - large animals

Equine version of Idiopathic polyradiculoneuritis

Extradural nerve roots of cauda equina thickened and discoloured

Inflammatory infiltrate (lymphocytes, plasma cells, macrophages)

Extensive axonal damage and demyelination

Cranial nerve involvement often occurs

Aetiology unknown:

Antecedent infection?

Antibodies to PNS myelin?

Paralysis & anaesthesia of tail

Urinary incontinence

Loss of anal reflex

Failure to defaecate

Pain/hypersensitivity in gluteal/tail-head area

Clinical signs

Recovery unlikely - most animals are destroyed.