HISTORY

Two 11-months-old Italian Spinone male puppies (A and B) from a litter of 6 males were referred for evaluation of a progressive symmetric ataxia. The parents and other 2 males were clinically normal, but we lack information about the remaining 2 males. At 7-8 months both showed tripping over the forelimbs, followed by dysmetria in the hindlimbs. Afterwards, generalized ataxia-dysmetria, intention tremors and wide-based stance were observed. NE findings included reduced spinal myotatic reflexes, bilaterally reduced/absent menace response and depressed physiologic nystagmus. Further signs in dog A were a recumbent posture, bilaterally absent corneal reflex and reduced facial sensation. In dog B a wide-based stance, ataxia, hypermetria, delayed postural reactions and a pendular abnormal nystagmus were also present. CBC, serum biochemistry, urinalysis, CSF analysis and BAEP, MNCV, EMG were unremarkable in both dogs. In dog A abnormal SEP and Blink Reflex (BR) were present. In dog B, BR was normal, while SEP showed abnormal tracings. Necropsies were performed and SNC were totally removed and fixed in 10% buffered saline formalin as well as tissue specimens collected from the organs of thoracic and abdominal cavities for histological investigations. No evidences of gross pathology of SNC were recorded. Histopathological findings were recorded in cerebellum and in particular cerebellar folia of hemispheres showed Purkinje cells and internal granular cells number reduction. Purkinje cells showed tigrolysis and necrosis. White matter cerebellar folia myelination was normal.

DISCUSSION

History and clinical signs in both patients were typical of a progressive diffuse cerebellar disease, most severely affected was dog A, which started showing neurological deficits earlier. Findings not characteristic of cerebellar disease were the reduced/absent corneal reflex and facial sensation and abnormal BR in case A, and hyporeflexia in the spinal nerves and alterations in SEP recordings in both dogs. Short-latency SEP by tibial nerve stimulation were evaluated, recording lumbar (LP) and cortical potentials (CP). LP absolute latencies were bilaterally normal and LP-CP interpeak latencies were bilaterally delayed. BR test in case A detected bilaterally increased latencies of R1. Comparison between the latency of R1 and the latency of the direct facial response (D) showed a bilaterally increased R1/D ratio. Similar electrophysiologic findings have been detected in human hereditary cerebellar ataxia and in experimental lesions of cerebellar cortex in animal models, and suggest a correlation between somatosensory and Blink Reflex pathways and cerebellar function. Histopathology of the CNS were confined to the cerebellum and were consistent with cerebellar cortical abiotrophy. This disease, described in several breeds of dogs, is presumed to be a hereditary condition. Breeding history supports the hypothesis of an inherited genetic disorder and genetic investigations are in progress. An autosomal recessive pattern of inheritance is suspected. To the authors' knowledge, this the first report of cerebellar cortical abiotrophy in Italian Spinone breed.