title: Lack of effect of botulinum toxin on cortical excitability in patients with cranial dystonia.
abstract: The aim of this study was to verify whether botulinum toxin (BTX)-induced clinical improvement of cranial dystonia is associated with changes in the cortical silent period (SP), a measure of cortical excitability. By transcranial magnetic stimulation (TMS), high-intensity stimuli were delivered with a round coil centered at the vertex during a maximal muscle contraction of the orbicularis oculi. Motor evoked potentials (MEPs) and SPs were obtained from surface electrodes placed over the orbicularis oculi muscle before and 2 to 3 weeks after BTX-A injection into the affected muscles in 10 patients with cranial dystonia and 8 age-matched control subjects. BTX injection improved blepharospasm in all patients. Facial muscle SPs were significantly shorter in patients than in control subjects and did not significantly change after treatment, at the time of maximal clinical improvement. We conclude that the clinical improvement induced by BTX in patients with cranial dystonia is largely symptomatic. It does not appear to result from modulation of abnormal aspects of intracortical excitability, although these may play a role in craniofacial dystonia.
authors.affiliation: Movement Disorders Unit, Hospital de Base do Distrito Federal, Brasilia, DF, Brazil.
authors.forename: Nasser
authors.initials: N
authors.lastname: Allam
authors.forename: Paulo Mauricio de Oliva
authors.initials: PM
authors.lastname: Fonte-Boa
authors.forename: Carlos Alberto Bezerra
authors.initials: CA
authors.lastname: Tomaz
authors.forename: Joaquim Pereira
authors.initials: JP
authors.lastname: Brasil-Neto
mesh_terms: D000328:Adult; D000368:Aged; D001764:Blepharospasm / Q000188:drug therapy / Q000503:physiopathology; D001905:Botulinum Toxins / Q000008:administration & dosage*; D004421:Dystonia / Q000188:drug therapy* / Q000503:physiopathology; D004576:Electromyography / Q000706:statistics & numerical data; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000187:drug effects / Q000502:physiology; D012886:Skull / Q000187:drug effects / Q000502:physiology; D018709:Statistics, Nonparametric
chemical_list: D001905:Botulinum Toxins