INITIAL RESISTANCE TO BOTOX TREATMENT IN CERVICAL DYSTONIA

Drake D. Duane, M.D.

Arizona Dystonia Institute/Arizona State University

Scottsdale/Tempe, Arizona

Perhaps 10% of patients with cervical dystonia (CD) do not improve following botulinum toxin A treatment (Botox Tx) (Jankovic and Brin, NEJM, 1991). Such resistance within two exposures is not likely due to toxin antibody formation. Of 61 CD patients evaluated per protocol receiving two or more Botox Tx under multi-channel EMG monitoring, 7 (11.5%) showed no benefit following the first and second Tx, despite mild neck weakness on static muscle testing and, in some instances, EMG signs of denervation.

The 54 responders (38F\16M) had younger age onset CD (Mean 45Yr versus 60Yr), but similar duration (Mean l0Yr versus 9Yr) compared to the 6F\lM nonresponders (in contrast to Jankovic and Schwartz, Arch Neurol, 1991). Both groups had similar degrees of severity and Tx dose ( Mean 200 IU, range 112.5 - 300).

Although disparate group size prohibits statistical analysis, some interesting comparisons include: nonresponders were more apt to have extranuchal dystonic sites (72% versus 33%), antecollis (29% versus 4%), dark eyes (57% versus 19%), women with elevated ANA titre (67% versus 24%), history of intracranial surgery (29% versus 0%), significant for age focal MRI abnormality (5 of 6 versus 3 of 19). History of cervical surgery (6 patients) did not limit responsiveness. Rates of prior remission, perinatal stress, antecedent trauma, lefthandedness and family history of movement disorder were similar for both groups.

Antecollis presents problems for optimizing Tx to affected muscles, but central mechanisms may play a role in why some patients with focal dystonia do not improve with Botox Tx from the outset.

Poster presentation, 117th Annual Meeting of the American Neurological Association, October 19-21, 1992, Toronto, Ontario, Canada.

Duane, D.D. Initial resistance to Botox treatment in cervical dystonia. Annals of Neurology, 1992;32:249.

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