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Several kittens in a family of Persian cats had a metabolic storage disease. Clinically the disorder was characterized by hepatomegaly, neurological signs and early death. The microscopic lesions consisted of widespread vacuolation of neurons and glial cells in the central nervous system and in liver cells. Electronmicroscopically the lesions consisted of intracytoplasmic accumulation of membrane-bound "empty" vacuoles. In addition to the storage disease, poor myelination of the cerebral white matter was found. The defect was reproduced in breeding trials. On biochemical analysis of brain tissue, deficient function of the enzyme alpha-mannosidase was detected. The clinical and pathological features of mannosidosis in Persian cats were compared to similar defects in other species.

Albumin and IgG were quantitated in paired cerebrospinal fluid (CSF) and serum samples from dogs with demyelinating canine distemper virus (CDV) infection by means of rocket immunoelectrophoresis. The IgG index as indicator for intrathecal immunoglobulin synthesis was normal in animals with non-inflammatory demyelinating lesions and elevated in dogs with inflammatory myelin lesions. Specific antibodies against CDV and myelin were quantitated in CSF and serum from 8 dogs with an elevated IgG index. Eight of these dogs had significant amounts of antimyelin antibody and 4 dogs had neutralizing anti-CDV antibody in the CSF. Whereas the pathogenetic significance of antimyelin antibodies remains uncertain, the intrathecal antiviral immune response provides a plausible explanation for immunopathologic destruction of myelin in distemper.

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Following unsuccessful attempts to record visual-evoked potentials (VEPs) in dogs with scalp electrodes, adoption of a new stimulation technique seems to be beneficial. Previously, flashes of white light administered after dark adaptation induced relatively high amplitude electroretinograms (ERGs) covering any VEP activity over the surface of the skull. ERG amplitude, however, can be significantly reduced using flashes of red light after light adaptation (mostly cone stimulation). Simultaneous ERG and VEP recording allows identification of VEPs composed of three significantly different negative peaks (Nl, N2, and N3) measured in dogs anesth2tized with chloralnse and halothane. No more than two of the three peaks were seen in one recording. Only the N1 and N3 waves were consistently recorded in dogs anesthetized with thiopental and thiopental combined with halothane. In 50% of all recordings, N1 was seen alone. The other VEPs consisted of N l and N2, or N l and N3 occurring concurrently. The simultaneous occurrence of N2 and N3 waves, however, was never seen. Among all recordings, N1 was most frequently recorded (85% of measurements), followed by N3 and N2 (38% and 31% of measurements, respectively).Peaks of less than 90 ms are highly reproducible. Anesthesia is necessary to eliminate frequent artifacts obtained in conscious and sedated dogs. Thiopental and/or halothane had no effect on measured latencies compared with chloralose. (Journal of Veterinary Internal Medicine 1988; 2:145-149) THE LARGE VOLUME of literature on visuel-evoked potentials (VEPs) in humans reflects the importance given to this noninvasive electrophysiological tool in the diagnosis of brain dysfunction. ' In animals, direct cortical measurement after implantation of electrodes on the cerebral cortex has been used to record potentials from the visual occipital cortex2-6 and to define the normal VEP.3,7 Recording of evoked cortical potentials (ECPs) with implanted electrodes is not applicable to clinical cases. Nearly atraumatic ECP recordings with scalp electrodes are performed routinely in humans. Until recently, however, VEP recording in animals with scalp electrodes was unsuccessful. The difficulty encountered in attempts to record VEPs in dogs has been attributed to the high amplitude far-field electroretinogram (ERG) conducted over the skull masking the localized lower amplitude VEP activity.8 High amplitude ERGs result when using flashes of white light after dark adaptation, i.e., when the photoreceptors of the retina, rods, and cones are maximally loaded with their respective photopigments. Under this circumstance, retinal stimulation with white light flashes gives rise to a response from most of the reactive cells of the retina. ' Because the retinas of dogs contain more rods than cones in an approximate proportion of 95: 1 , l o a lower amplitude ERG should be obtained by stimulation of the cones only. The lower amplitude of the ERG might allow easier recording of the VEP. The objective of the present study was to design a suita...