Saccadic oscillations in 4 dogs and 1 cat.

Disorders affecting the control of saccadic eye movements result in involuntary saccadic oscillations and are widely reported in human medicine. Information regarding the occurrence and potential importance of saccadic oscillations in veterinary medicine is currently limited. The clinical histories of three dogs and one cat displaying involuntary eye movements consistent with opsoclonus are presented, with final diagnoses including idiopathic generalized tremor syndrome and neuronal ceroid lipofuscinosis (NCL). A dog with eye movements closely resembling macrosaccadic oscillations is also presented, for which a final diagnosis of NCL was made. All animals had clinical signs of cerebellar disease. As in human medicine, recognition of these forms of involuntary eye movement might suggest a cerebellar neuroanatomic localization. Opsoclonus and macrosaccadic oscillations are forms of involuntary saccadic eye movement that are both unrecognized and under-reported in veterinary medicine.

Presumptive subdural empyema in a dog.

A 13 mo old mixed-breed dog was referred for acute lateralized forebrain signs. MRI of the brain demonstrated abnormalities consistent with severe meningitis and subdural empyema secondary to a retrobulbar abscess. The dog's clinical signs improved with antibiotic therapy, and repeat imaging showed resolution of subdural fluid accumulation presumed to be empyema with mild residual meningeal enhancement. Subdural empyema is an infrequent cause of encephalopathy in small animals and usually develops through direct extension of a pericranial infection. This report presents a case of presumptive subdural empyema in a dog that was successfully treated without surgical intervention. MRI is the preferred imaging modality for diagnosis of subdural empyema, and the characteristic imaging features are described.

Magnetic resonance imaging of intracranial malformations in dogs and cats.

Intracranial malformations may occur because of an inherent developmental defect or secondary to in utero injury to the brain with subsequent hypoplasia and atrophy. They can cause neurologic deficits in growing animals, although some anomalies may not produce clinical signs until adulthood. Malformations of the brain include hydrocephalus, hydranencephaly/porencephaly, holoprosencephaly, corpus callosum agenesis/dysgenesis, lissencephaly, polymicrogyria, meningoencephalocele, intracranial cysts, cerebellar malformations, and hamartomas. These conditions are defined and reviewed with an emphasis on their features in magnetic resonance images.

Imaging diagnosis--Neuronal ceroid lipofuscinosis with a chronic subdural hematoma.

A subdural hematoma was found to accompany neuronal ceroid lipofuscinosis in an 11-month-old Dachshund. Results from clinical, magnetic resonance (MR) imaging, histopathologic, ultrastructural, and molecular assessments are described. The dog had a 3-month history of progressive neurologic signs. In MR images, there was severe asymmetric cerebral atrophy with a subdural hematoma. Histopathologically, there was autofluorescent, periodic acid-Schiff-positive lipopigment in neurons and transmission electron microscopy confirmed a typical curvilinear profile of the storage bodies. We hypothesize that rapid brain atrophy contributed to the subdural hematoma formation, a complication not described previously in dogs with neuronal lipofuscinosis.

Clinical anatomy of the canine brain using magnetic resonance imaging.

The purpose of this study was to produce an magnetic resonsnce (MR) image atlas of clinically relevant brain anatomy and to relate this neuroanatomy to clinical signs. The brain of a large mixed breed dog was imaged in transverse, sagittal, and dorsal planes using a 1.5 T MR unit and the following pulse sequences: Turbo (fast) spin echo (TSE) T2, T1, and T2- weighted spatial and chemical shift-encoded excitation sequence. Relevant neuroanatomic structures were identified using anatomic texts, sectioned cadaver heads, and previously published atlases. Major subdivisions of the brain were mapped and the neurologic signs of lesions in these divisions were described. TSE T2-weighted images were found to be the most useful for identifying clinically relevant neuroanatomy. Relating clinical signs to morphology as seen on MR will assist veterinarians to better understand clinically relevant neuroanatomy in MR images.

Intracranial epidermoid cyst and syringohydromyelia in a dog.

A 5-year-old female Cocker Spaniel dog had a sudden onset of vestibular disease that localized to the caudal fossa. Upon computed tomography of the brain, a large, hypoattenuating mass with a slight peripheral ring enhancement pattern was detected ventral to the cerebellum. A hypoattenuating region was also identified in the center of the C2 spinal cord segment, consistent with syringohydromyelia. Postmortem examination of the brain revealed a fluid filled, cystic mass located dorsal to medulla oblongata that caused severe compression of the overlying cerebellum. The histopathologic diagnosis was an epidermoid cyst. Extensive syringohydromyelia and obstructive hydrocephalus were identified, both thought to be secondary to overcrowding of the caudal fossa.