Abstract

An adult female Northern fur seal (Callorhinus ursinus) was found stranded on the California coast in 2013 with significant neurologic dysfunction and apparent visual deficits. Magnetic resonance imaging (MRI) was suggestive of demyelination of the cerebrum and mild bilateral ventricular dilation. Cerebral spinal fluid (CSF) analysis revealed mild mixed inflammation with no etiologic agent identified. The fur seal was deemed non-releasable and placed at Mystic Aquarium for ongoing care. Two years later, cluster seizures began, warranting additional advanced imaging. Repeat MRI revealed generalized distension of the ventricular system and brain atrophy, suggestive of degenerative disease and non-hypertensive hydrocephalus. Electroencephalogram (EEG) showed apparently normal brain function. A medical management plan was established to stabilize the seizure activity and reduce the volume of ventricular CSF until surgical intervention could be explored. Eight weeks later, the animal underwent ventriculoperitoneal shunt placement to allow drainage of the accumulated CSF and relieve pressure on the cerebral white matter. The stent was surgically placed in the right lateral ventricle of the brain with a shunt to the right peritoneal cavity. Post-operative computed tomography (CT) confirmed correct placement of the stent. One year post-operative the fur seal remains seizure-free and maintains a good quality of life with the ability to swim and interact with conspecifics as well as participate in training. This therapeutic intervention represents the first of its kind in a Northern fur seal, and emphasizes that surgical intervention may be a viable option for management of hydrocephalus in marine mammals.

Acknowledgements

The authors would like to thank the staff and volunteers at The Marine Mammal Center (TMMC) for their initial care and stabilization of this fur seal. The authors are also grateful to the staff and students at the Henry and Lois Foster Hospital for Small Animals at Cummings Veterinary Medical Center for their assistance. The ongoing success of this case would not be possible without the unwavering dedication of Mystic Aquarium’s marine mammal husbandry staff.

* Presenting author