Cauda Equina Neuritis has recently been renamed to Polyneuritis Equi (PNE). PNE is a progressive neurological disease of the peripheral nerves of the horse. Though frequently associated with hind limb deficits, the disease can strike any of the peripheral nerves. This article concerns itself with the diagnosis, treatment, and prognosis of this disorder.

While the disease does seem to show a predilection for the tail and anal sphincter it is often accompanied by cranial and other peripheral nerve dysfunction. There seems to be no breed, age, or sex predilection though it does not seem to happen to foals. Currently the cause for this problem is unknown and positive diagnosis requires microscopic examination of the affected peripheral nerves. Examination will reveal a granulomatous, mixed inflammatory cell infiltrate, and degeneration of the nerve. The pathological lesions are similar to those seen in Guillain-Barr syndrome in humans. Viral and autoimmune causes have been postulated.

Generally the disease has two forms:

1. An acute hyperesthesia of the perineal or head region, or both;
2. The chronic form in which the horse shows paralysis of the tail, anus, rectum, and bladder. This is often accompanied by urine and fecal retention. The results of the urine dribbling out is scalding. Males may have penile paralysis. There may be muscle atrophy and if hind limb motor neurons are affected gait deficits. Usually these gait deficits are symmetrical. The horse may have trouble with mastication, swallowing, and a head tilt. Other common cranial nerve deficits include ear or lip droop. Cranial nerve deficits are asymmetrical.
Colic due to fecal retention may be the presenting sign. If the horse displays the acute form this will generally revert to the chronic form. The disease is slowly progressive.