[The dosage of botulinum toxin type B in adductor type spasmodic dysphonia]

Today, most patients with severe adductor type spasmodic dysphonia are treated with repeated injections of botulinum toxin type A (BTA). It is known that patients who have been treated for many years and have received a high cumulative dosage may develop antibodies against BTA, making them "resistant" to further injections. For these patients, botulinum toxin type B (BTB, NeuroBloc) is considered to be a new chance to continue the treatment. When changing to BTB, one has to find an "equivalent dosage" which is estimated for cervical dystonia to be 25-33-fold of the previous Botox dosage and the 10-13-fold for the previous Dysport dosage. We report on a 62 year old female patient with antibodies against BTA. For maximum care, the first injection of BTB was performed with the sixfold of the previous Dysport dosage, which was almost the half of the needed dosage predicted from experience with cervical dystonia. The relief only lasted 3 weeks and was therefore disappointing. For the subsequent injections, we consulted Sataloff who also had one patient with antibodies treated with BTB. Based on his personnel advice, we chose the 30-fold dosage, which was effective for 3 months, resulting in improvements to voice quality (both psychoacoustic rating and acoustic measures), voice "quantity" (voice range profiles), aerodynamics (maximum phonation time, phonation quotient), and voice handicap. As with Sataloff et al. (2002), we found that the dosage of BTB probably has to be much higher than in cervical dystonia.