The central nervous system in canine giant axonal neuropathy.

The pathology of the central nervous system (CNS) in a dog with giant axonal neuropathy (GAN) is presented. Swollen axons containing excessive and disorganised neurofilaments were present in the spinal cord, mainly at the distal portions of long tracts. The fasiculus gracilis and dorsal spinocerebellar tracts were affected only in the rostral cervical cord while the lateral cortico spinal tract was principally involved in the lower thoracic and lumbar cord. Occasional swellings were also found in the central dorsal columns of the rostral lumbar segments and in the dorsal and intermediate grey matter. The nuclei gracilis and cuneatus, restiform body and ventral spinocerebellar tracts were all involved in the brain stem. Spheroids were seen in the white matter of the rostral cerebellar vermis and in the granule cell layer. The brachium of the superior colliculus contained swollen axons and the cortex was diffusely involved with spheroids. The distribution was of a distal axonopathy and the cortical changes provided an explanation for the abnormal EEG and mental retardation found in some human patients.