Distal polyneuropathy in birmans

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A degenerative polyneuropathy has recently been reported in several litters of Birman cats bred from the same parents. A recessive mode of inheritance is suspected. Pathologically, the central nervous system (CNS) lesions were most prominent in the lateral pyramidal tracts of the lumbar spinal cord, the fasciculi gracili of the dorsal column in the cervical spinal cord, and the cerebellar vermian white matter. Lesions were characterized by diffuse loss of myelinated fibres and fibrillary astrocytosis. Inflammatory changes were not seen. Neurons of the cerebral cortex, cerebellum, and brainstem were normal. In the PNS, numerous degenerating nerve fibres were observed in the sciatic nerves but not in the spinal nerve roots. No changes were found in the cauda equina, dorsal root ganglia, or ventral horn cells. Ultrastructurally, degenerating ovoids consisting of myelin debris and disrupted axons were frequently observed. Selective involvement of distal portions of the CNS and PNS suggested that this disorder is a distal central-peripheral axonopathy (dying-back disease). Clinical signs were first noted in cats 8 to 10 weeks of age. Affected cats fell frequently and had a tendency to stand and walk on their hocks which were held in an adducted fashion. The gait was characterized by slight hypermetria in all limbs and there was progressive pelvic limb ataxia. Analysis of blood and CSF was normal. Nerve conduction velocity studies were normal; however, EMG revealed presence of fibrillation potentials and positive sharp waves in pelvic limbs. Prognosis is poor. Presently, there is no treatment. Future breeding trials should confirm that this condition is caused by a genetic defect and help characterize the exact mode of inheritance.