Polyneuropathy of Finnish horses characterised by inflammatory demyelination and intracisternal Schwann cell inclusions.

The study investigates a neurological disorder, dubbed ‘Scandinavian Knuckling Syndrome’, observed in various horses in Finland. The research outlines the pathological and epidemiological features of this condition, which is manifested as limb extensor paresis and causes horses to be euthanized.

Research Objective and Methods

• The goal of this research was to formally explore and report on the outbreak of ‘Scandinavian knuckling syndrome’ in southern Finland’s riding stables. This condition had been noted over the past decade but lacked detailed reports and examination of the neurological signs or neuropathological lesions.
• The team used a sample of four cases for their clinical neurological exam and evaluated the tissue of one for neuropathological analysis.

Findings

• Of the 17 horses collectively fed on ryegrass from a single source, 11 developed progressive symptoms of extensor paresis in the metatarsophalangeal (a joint in the foot), leading to the euthanasia of seven horses.
• The research team detected nervous system lesions in one horse, which were identified as a novel demyelinating, mildly inflammatory peripheral neuropathy. This type of lesion has not been previously reported in any form of equine polyneuropathy.
• The lesions were marked by Schwann cell inclusions that were positive for BiP/GRP, proteins associated with the endoplasmic reticulum, which suggests that the primary lesion is in the Schwann cells, the peripheral nerve cells in the nervous system.

Conclusions

• The clinical signs and lesions documented in the study differ from previously described types of equine polyneuropathy, which underlines the possibility of a primary Schwann cell lesion.
• The researchers proposed that this disorder should be classified as a novel demyelinating polyneuropathy, which could facilitate more targeted epidemiological investigations in the future.