BOTULINUM TOXIN-F IN THE TREATMENT OF TORTICOLLIS CLINICALLY RESISTANT TO BOTULINUM TOXIN-A

Two reports have shown a Japanese preparation of botulinum toxin type F (BTX-F) to be an effective alternative for patients with torticollis who develop clinical resistance to botulinum toxin type A (BTX-A). A group of patients with torticollis, comprising five secondary non-responders and one primary nonresponder, were treated with a preparation of BTX-F produced in the UK (Speywood Pharmaceuticals). A low dose of BTX-F (220 mouse units (MU) in total) was given into clinically affected neck muscles, followed six weeks later by an injection of a total of 520 MU. Antibodies to BTX-A (mouse protection assay) were present in all secondary non-responders but not in the primary non-responder. No patients developed atrophy after injection of Dysport BTX-A (40 MU) into the left extensor digitorum brevis muscle whereas pronounced atrophy occurred in all patients after injection of 40 MU of BTX-F into the right extensor digitorum brevis muscle. Three patients improved subjectively after treatment with 220 MU BTX-F and five (all secondary nonresponders) after the subsequent dose of 520 MU (two considerably), with reduced Tsui scores, but group scores were only significantly changed after the higher dose. The primary non-responder remained unchanged after both doses of BTX-F. One patient reported mild dysphagia with 520 MU BTX-F. Mean duration of improvement with 520 MU BTX-F was five (range 4-6)weeks. Thus BTX-F provides benefit for BTX-A non-responders with few side effects but for a shorter period than BTX-A, possibly due to relative underdosing. As with BTX-A, biological sensitivity to BTX-F does not necessarily predict a clinical response.