Late-onset recurrence of neurological deficits after surgery for spinal arachnoid diverticula.

Spinal cord dysfunction secondary to spinal arachnoid diverticula (SAD) has been widely reported in the veterinary literature and there is some suggestion that surgical treatment may provide better outcomes than medical treatment. Despite this, previous reports have mentioned cases with recurrence of clinical signs following surgical treatment but the cause for this has not been further investigated. The medical records of seven dogs and one cat which presented for investigation of recurrence of neurological deficits at least six months after surgery for SAD were retrospectively reviewed. Median time to relapse of the neurological deficits was 20.5 months after surgery. On repeated imaging, 3/8 cases showed clear regrowth of diverticulum, 2/8 cases showed dorsal compression at the previous laminectomy site (presumed to be the laminectomy membrane), and 3/8 cases showed herniation of the spinal cord through the laminectomy defect associated with a stellate appearance to the spinal cord with small multiloculated areas of dilation of the subarachnoid space. Repeat surgical intervention was most successful in the cases where SAD recurrence was identified while medical treatment resulted in either subtle improvement or stabilisation on the clinical signs, sometimes followed by slow deterioration.