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Case Report: Sensory Neuropathy in a Border Collie

 

A five-month-old male, entire Border Collie presented with a history of ataxia of a few days duration. He had also recently had diarrhoea which had resolved, and was mildly inappetent. The owners reported that he was generally bright, with good exercise tolerance and no collapsing episodes.

Investigations

On physical examination, the dog was very bright and was ambulatory but showed a marked reduction in muscle mass. He had a lick granuloma on his left lateral hock. He was ataxic, and proprioception was markedly depressed in all four limbs, which demonstrated lower motor neurone signs. No cranial nerve deficits were noted. Spinal reflexes at this stage were relatively normal. Biochemistry, haematology, electrolytes, PT, PTT, T4/TSH, CK and AST, Toxoplasma/Neospora serology and faecal analysis were normal. MRI of the brain and cervical spine were normal, and CSF analysis for cytology, culture, microprotein, Toxoplasma/Neospora titres and Distemper titres were negative. Faecal analysis for lungworm was negative.

Although the spinal reflexes were normal at initial examination, there was a high index of suspicion for a polyneuropathy because of the lower motor neurone signs in all four limbs. Also, the lick granuloma could be taken as evidence for a sensory neuropathy, which can induce an abnormal tingling sensation in the limbs known as paraesthesia.

Follow up investigations

The dog was re-examined three weeks later. There was still a profound ataxia, although the dog remained bright and ambulatory. Spinal nerve reflexes were now depressed and interestingly, the dog had lost consicous pain perception in all four limbs. The lick granuloma had healed, and one could speculate that a previous paraesthesia had progressed to total anaesthesia of the limbs. Nerve and muscle biopsies were taken and submitted for histopathology. The muscle was found to be relatively normal, but the nerve biopsy was showing signs of Wallerian degeneration consistent with an axonopathy. The clinical appearance of normal motor function, with reduced proprioception and pain sensation, together with the nerve biopsy findings, confirmed the diagnosis of a sensory neuropathy.

Discussion

Lower motor neurone signs in all four limbs are suggestive of multifocal disease or a peripheral neuropathy. Imaging and CSF findings did not show evidence for a central nervous system disease, and the progression to reduced spinal reflexes gave more weight to a peripheral neuropathy. The unusual features of this case however, were that the motor function appeared normal; the dog was not weak, but had instead maintained good exercise tolerance. The lick granuloma also raised the possibility of altered sensation in the limbs. However, the progression of the condition to a complete  absence of pain sensation while remaining ambulatory was strongly suggestive of a sensory neuropathy.  Histopathology of the nerves was also consistent with this. Sensory neuropathy of the border collie has been reported infrequently in the literature (e.g. Vermeersch et al 2005). It is suspected to be an inherited disorder. Unfortunately, there is no treatment for this condition currently, and the long term prognosis is poor.

Reference

K Vermeersch, L Van Ham, K G Braund, S Bhatti, M Tshamala, K Chiers, E Schrauwen) Sensory neuropathy in two Border collie puppies. JSAP 46:295-9,2005