“Clinical signs and mri findings of bilateral porencephaly and caudal vermian hypoplasia in a young dog”

The present report describes a 4 months-old mixbreed female dog referred to the Veterinary Teaching Hospital of Bologna University for the suspicion of atypical seizure activity. The dog was adopted 40 days before from a kennel. After ten days, the owner noticed the occurrence of sudden-onset “attacks”, described as follows: sudden tilting of the head to the right, falling towards her right side, pathologic nystagmus and opisthotonus. After approximately 30 seconds, the dog recovered completely to a normal status. Episodes occurred two to three times per day. The owner reported also episodes of tail chasing and right circling lasting 10 to 15 minutes, which tended to stop once the patient was diverted. Physical evaluation showed an abnormal right deviation of the nasal structures. The neurological examination showed a normal mental status and behaviour, a mild right head tilt, vestibular ataxia, decreased postural reactions more pronounced on the left limbs, menace response absent on the left side and reduced contralaterally, and right ventral strabismus. Neuroanatomical localization of the lesion involved the central vestibular structures and the forebrain. Major differential diagnoses included as first anomalous disorders. CBC and serum biochemistry were within the normal range. The dog underwent magnetic resonance imaging (MRI) of the brain. The dog was imaged in sternal recumbency with a 0.22-T permanent magnet using a human knee coil. Sagittal, transverse, and dorsal plane images of the brain were acquired. Image sequences included T2- and T1-weighted images, and FLAIR. An area of low signal intensity was observed on T1-weighted images in the caudal cerebellar vermian region. The same region was characterized by a high signal intensity on T2-weighted images. These characteristics were consistent with the presence of a fluid-filled cavity in the region of the cerebellum, assumed to be due to cerebrospinal fluid accumulation. A second lesion with the same characteristics, connecting the lateral ventricle with the subarachnoid space, was observed in the left parietal lobe. A third, smaller, porencephalic area was noted in the right cerebral hemisphere. The final diagnosis, based on the clinical signs and MRI findings was congenital bilateral porencephaly and caudal vermian hypoplasia. The vestibular episodes were considered as possible partial-complex epileptic seizures and anticonvulsant therapy with Phenobarbital was instituted. The rate of recurrence of the seizures did not improve at starting dose. After an adjustments in the dosage based on serum Phenobarbital level, the episodes improved in frequency and entity. The non-progressive, atypical, clinical signs in our puppy fits very well with the multiple abnormalities documented on MRI, affecting both the cranial and the caudal fossa. Caudal fossa lesions are consistent with those reported in the Dandy-Walker Syndrome (DWS). DWS is a well known human congenital brain disorder which refers to a malformation complex characterized constantly by cerebellar vermis hypoplasia and enlargement of the fourth ventricle frequently associated to different abnormalities of other areas of the central nervous system and/or the heart, face, limbs, fingers and toes. In veterinary literature, these kinds of malformation have been sporadically reported in animals, including calves, foals, lambs, cats and dogs. The malformation is often incomplete in respect to human medicine, with varying degrees of vermian hypoplasia and differences in the severity of clinical signs. Forebrain MRI abnormalities in our puppy can be defined as asymmetric bilateral porencephaly. Porencephaly refers to the occurrence of single or multiple cystic cavities in the cerebrum, usually communicating with the lateral ventricles or subarachnoid space. To the authors’ knowledge, this is the first description of CNS malformation consistent with Dandy-Walker syndrome associated to...