Polymicrogyria in Four Standard Poodles: A Case Series with Histopathologic, Electroencephalographic and Magnetic Resonance Imaging Findings
This case series describes four standard poodles with polymicrogyria, including a 5-year-old spayed female, a 3-month-old intact male, a 3.5-month-old intact male and a 4-month-old intact male. Previously this disorder has been reported in only four dogs (all Standard Poodles) and in cattle. Polymicrogyria is a disorder of cortical migration resulting in abnormal, small, disorganized gyri. Further disruption is present histologically at the cortex, with loss of normal layering. Clinical signs in all dogs included cortical blindness and behavioral abnormalities. Subjects also had other neurologic abnormalities including gait changes, decreased pupillary light responses and partial seizures. Magnetic resonance imaging (MRI) of the 5-year-old patient allowed for visualization of multiple disorganized gyri in the occipital lobes, which were especially apparent on T2 weighted coronal plane images. Electroencephalogram (EEG) of this patient revealed epileptiform discharges, including both spike and spike and wave discharges with voltage maximum potentials over the parietal/occipital region. The EEG supported that a repetitive behavior displayed by the dog was a complex partial motor seizure. MRI on the 4 month old male showed asymmetric hydrocephalus. At necropsy, only one of the four animals had hydrocephalus. All dogs had occipital lobe involvement; two dogs had involvement of other lobes as well. The cases presented here demonstrate a significantly longer survival time than previous reports; as well providing an antemortem diagnosis via Magnetic Resonance Imaging and Electroencephalogram.