Increased Botulinum Toxin Type A Dosage Is More Effective in Patients With Frey's Syndrome

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Abstract
Objective To compare the duration of effect of two dosage regimes of botulinum toxin A to treat patients with Frey's syndrome. Study Design Prospective study of two unselected cohorts of 20 patients each. Methods The dimension of the affected skin area was determined with Minor's iodine–starch test. The skin was infiltrated with botulinum toxin type A (Dysport, Ipsen Pharma, Ettlingen, Germany) using an interinjection distance of 1 cm. In the first group, a concentration of 10 mount units (MU)/0.1 mL and in the second group a concentration of 20 MU/0.1 mL was used. At each injection site, 0.1 mL of the respective solution was injected. The outcome measures were the time of reappearance of gustatory sweating, and the results of an iodine–starch test 10 and 20 months after treatment. Results Using the lower concentration, the mean duration of effectiveness was 8.3 ± 2 months (mean ± standard deviation). Using the higher concentration, the effect was much longer at 16.5 ± 6 months. Eighty‐five percent of the first group but only 5% of the second had a positive Minor's iodine–starch test 10 months after treatment. After 20 months four patients in the second group still had a negative iodine–starch test. In both groups, the amount of required botulinum toxin for the second treatment after recurrence of Frey's syndrome was the same as for the first treatment. Conclusions Using a higher concentration of botulinum toxin type A (20 MU Dysport/0.1 mL) is more effective than a lower concentration (10 MU Dysport/0.1 mL) in the treatment of Frey's syndrome.