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CANINE CHIARI-LIKE MALFORMATION AND SYRINGOMYELIA CM/SM

CM/SM – surgery

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There are no clear guidelines as to when surgery is indicated over medical management because robust outcome studies have not been performed.
Some authors have suggested that early surgical intervention may improve prognosis but this hypothesis has not been vigorously tested . The author is most likely to recommend surgery for painful dogs with Chiari-like malformation but without marked syringomyelia and/or dogs with syringomyelia where medical management does not give adequate pain relief. The reason why surgery has not been recommended universally is that no technique reported thus far has resulted in long term syrinx resolution . In addition surgery does not necessarily improve long-term prognosis as 25-47% of the operated dogs have recurrence or deterioration of the clinical signs within 0.2-3 years after surgery . However, it should be remembered that it is probable that previous reports of surgically managed cases include dogs with more severe clinical signs so a valid comparison between medical and surgical management cannot be made at this time.
The most common surgical management is craniocervical decompression, establishing a CSF pathway via the removal of part of the supraoccipital bone and dorsal arch of C1.

Depending on the surgeon this may be combined with a durotomy, with or without patching with a suitable graft material and with or without a cranioplasty, using titanium mesh or other prosthesis . Craniocervical decompression surgery is successful in reducing pain and improving neurological deficits in approximately 80% of cases and approximately 45% of cases may have a satisfactory quality of life two years postoperatively. The clinical improvement is probably attributable to improvement in CSF flow through the foramen magnum.

A syringosubarachnoid shunting procedure using a five French equine ocular lavage catheter has also been described. Clinical improvement in approximately 80% of cases was reported but like other reported surgeries there was no evidence of long-term syrinx resolution on post-operative MRI and dogs still expressed signs of neuropathic pain post-operatively

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