OBJECTIVES

To evaluate the long-term outcome of ventriculoperitoneal shunt placement in a series of dogs with acquired hydrocephalus.

MATERIALS

Five adult dogs were presented to the University of Glasgow Veterinary School Hospital between April 2000 and January 2001 with a history of progressive forebrain signs and diagnosed with acquired hydrocephalus; based on adult onset of clinical signs, presence of enlarged ventricular system on CT images, unremarkable CSF analysis, initial response to prednisolone therapy and sustained improvement after shunt placement. Patient age ranged from 12 months to 11 years. Initial therapy with prednisolone 0.25-2 mg/kg BID resulted in marked improvement of clinical signs within 2 weeks of presentation. Ventriculoperitoneal shunting was performed 4-8 weeks after diagnosis. Commercial medium-pressure (15cm H20) shunt systems (Unishunt, Radionics Corp.) were used. Surgical approach consisted of paramedian rostro-tentorial burr hole craniectomy. The tip of the shunt was introduced into the lateral ventricle using a stylette, provided by the manufacturer. The rest of the procedure has been described elsewhere . Postoperative recovery was uneventful and all patients were discharged 3-6 days after surgery on broad spectrum antibiotics. Prednisolone therapy was continued, progressively reduced from 2 weeks post-operatively and ultimately withdrawn.

RESULTS

Outcome was considered excellent in two dogs, good to excellent in one and poor in two patients. Outcome was considered excellent when medical therapy could be discontinued after shunt placement and no recurrence of clinical signs was detected. Outcome was excellent to good in one dog due to unilateral collapse of the cerebral cortex but without clinical significance. Poor outcome was associated with persistence or recrudescence of clinical signs. In one patient an initial improvement for 8 months was followed by deterioration due to blockage of the intra-cranial catheter, probably as a result of poor placement. Revision was unsuccessful and medical therapy with low dose prednisolone and frusemide was successfully reinstituted. In another patient signs such as head pressing, poor vision and compulsive progression were controlled but associated seizure activity was not. Normal neurological function was sustained after shunt placement in the remaining three cases, with no chronic medication necessary.

CONCLUSION

This case series describes a surgical alternative to long-term steroid therapy for cases of suspected acquired hydrocephalus. Several studies have demonstrated variability in ventricular size in neurologically normal dogs. In this review, the presence of clinically significant hydrocephalus was confirmed by sustained improvement of neurological signs after shunt placement. CSF pressure measurement is not currently available in this hospital. We describe an alternative approach to the lateral ventricles to the one described in the literature.¹ The two most common complications reported in the literature are infection and undershunting. Overshunting and seizures are seen less commonly.¹ In one case described here, overshunting was suspected, with collapse of the ipsilateral hemisphere. However, subdural haemorrhage was not encountered. Undershunting and blockage was seen in one case. In general, complications deleteriously influenced both outcome and long-term management. Post-operative infection has been reported in the literature, but was not encountered in this series. The author's feel that overall this is a successful technique if complications can be avoided.

References

1.  Harrington M L et al. "Hydrocephalus" Veterinary Clinics of North America: Small Animal Practice. Vol 26. July 1996.