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      Difficulties with differentiating botulinum toxin treatment effects in essential blepharospasm

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          Abstract

          Blepharospasm is a focal dystonia in which the extraocular muscles contract repetitively, leading to excessive blinking and forced eyelid closure. Botulinum toxin type A (BoNTA) is the primary symptomatic treatment for blepharospasm and its effects have been evaluated using numerous rating scales. The main scales in use today were initially used to determine whether BoNTA treatment was superior to placebo, and most controlled trials have confirmed this. More recently, these scales have been used to determine whether there are efficacy differences between different BoNTs in blepharospasm. However, although the scales used in these trials are able to differentiate the effects of BoNT from placebo, they may not be sensitive enough to differentiate between BoNTs. Most of the scales include only four possible points for each item, which would necessitate a 25% greater improvement in one group than the other to detect any differences. Current scales are also relatively insensitive to patients with mild disability who may experience mainly psychosocial problems related to their blepharospasm. Clinical trials comparing BoNTs that include substantial numbers of mildly affected patients may be unlikely to find differences because the scales do not adequately measure mild symptoms. Additional challenges with evaluating blepharospasm include the lack of precision and objectivity of current measures, symptom variability, the need to evaluate aspects of the disorder that are most important to patients, and the different types of blepharospasm. Although no single scale may be able to capture all relevant aspects of blepharospasm, more sensitive and patient-centered scales are needed.

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          Most cited references 34

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          Intramuscular injection of botulinum toxin for the treatment of wrist and finger spasticity after a stroke.

          Spasticity is a disabling complication of stroke, and it is uncertain whether intramuscular injections of botulinum toxin type A reduce disability in persons with spasticity of the wrist and fingers after a stroke. We performed a randomized, double-blind, placebo-controlled, multicenter trial to assess the efficacy and safety of one-time injections of botulinum toxin A (200 to 240 units) in 126 subjects with increased flexor tone in the wrist and fingers after a stroke. The primary outcome measure was self-reported disability in four areas: personal hygiene, dressing, pain, and limb position (on a four-point scale ranging from no disability to severe disability) at six weeks; at base line, each subject selected one of these areas in which there was moderate-to-severe disability as the principal target of treatment. Subjects who received botulinum toxin A had greater improvement in flexor tone in the wrist and fingers at all follow-up visits through 12 weeks than did subjects who received placebo (P<0.001 for all comparisons). Subjects treated with botulinum toxin A had greater improvement in the principal target of treatment at weeks 4, 6, 8, and 12 (P<0.001, P<0.001, P=0.03, and P=0.02, respectively); at week 6, 40 of the 64 subjects in the botulinum-toxin group (62 percent), as compared with 17 of the 62 in the placebo group (27 percent), reported improvement of at least one point on the Disability Assessment Scale in the principal target of treatment (P<0.001). There were no major adverse events associated with injection of botulinum toxin A. Intramuscular injections of botulinum toxin A reduce spasticity of the wrist and finger muscles and associated disability in patients who have had a stroke. Copyright 2002 Massachusetts Medical Society
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            Botulinum A toxin for cranial-cervical dystonia: a double-blind, placebo-controlled study.

             J. Jankovic,  J Orman (1987)
            We studied the effects of botulinum A toxin in 12 patients with blepharospasm and 10 patients with oromandibular-cervical dystonia received in a double-blind manner. All blepharospasm patients improved, 71.6% on a clinical rating score, 60.7% by self-assessment, and 38.9% by video-rating; there was no improvement with placebo. The beneficial effects lasted a mean of 12.5 weeks (range, 5 to 28). Only 37.5% of the patients with oromandibular-cervical dystonia improved. Patients with pharyngeal dystonia and spasmodic dysphonia also improved.
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              Efficacy and safety of a new Botulinum Toxin Type A free of complexing proteins in the treatment of blepharospasm.

               W Jost,  K Bihari,  G Comes (2006)
              NT 201 is a new development of Botulinum Toxin Type A free of complexing proteins. In this double-blind Phase III trial, we compared the efficacy and safety of NT 201 and BOTOX in patients suffering from blepharospasm. Of 304 enrolled patients, 300 patients received study medication (intent-to-treat population), and 256 patients completed the study as planned (per-protocol population). At baseline, patients received a single injection of NT 201 or BOTOX (
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                Author and article information

                Contributors
                +-49-228-28715612 , +-49-228-28714692 , bettina.wabbels@ukb.uni-bonn.de
                Journal
                J Neural Transm
                Journal of Neural Transmission
                Springer Vienna (Vienna )
                0300-9564
                1435-1463
                9 January 2011
                9 January 2011
                June 2011
                : 118
                : 6
                : 925-943
                Affiliations
                [1 ]Department of Ophthalmology, University of Bonn, Abbestr. 2, 53127 Bonn, Germany
                [2 ]Department of Neurology, Deutsche Klinik für Diagnostik, Wiesbaden, Germany
                Article
                546
                10.1007/s00702-010-0546-9
                3104001
                21221669
                © The Author(s) 2011
                Categories
                Movement Disorders - Review Article
                Custom metadata
                © Springer-Verlag 2011

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