Electrical activation of the orbicularis oculi muscle does not increase the effectiveness of botulinum toxin type A in patients with blepharospasm.
BACKGROUND
Our primary aim in this study was to determine whether electrically induced activation of the injected muscle increases effectiveness of botulinum type A toxin (BonT-A) in patients with blepharospasm (BPS). The second aim was to assess the safety of BonT-A by investigating whether BonT-A injection alters the excitability of blink reflex circuits in the brainstem.


METHODS
Twenty-three patients with BPS received BonT-A (Botox) injected bilaterally into the orbicularis oculi muscle at a standard dose. In 18 patients, electrically induced muscle activation of the orbicularis oculi muscle on one side was performed for 60 min (4 Hz frequency) in a single session, immediately after BonT-A injection and in five patients for 60 min once a day for five consecutive days. The severity of BPS was assessed clinically with the BPS score. Compound muscle action potential (cMAPs) from the orbicularis oculi muscles were measured bilaterally. The blink reflex recovery cycle was studied at interstimulus intervals of 250 and 500 ms. Participants underwent clinical and neurophysiological assessment before BonT-A injection (T0) and 2 weeks thereafter (T1).


RESULTS
Compound muscle action potential amplitude significantly decreased at T1 but did not differ between stimulated and non-stimulated orbicularis oculi in the two groups. BonT-A injection left the blink reflex recovery cycle tested on the stimulated and non-stimulated sides unchanged.


CONCLUSIONS
In patients with BPS, the electrically induced muscle activation neither increases the effectiveness of BonT-A nor produces larger electrophysiological peripheral effects. The lack of BonT-A-induced changes in the blink reflex recovery cycle provides evidence that BonT-A therapy is safe in patients with BPS.
Conte
A
A
Department of Neurological Sciences, Sapienza University of Rome, Rome, Italy.
Fabbrini
G
G
Belvisi
D
D
Marsili
L
L
Di Stasio
F
F
Berardelli
A
A
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000368:Aged; D000704:Analysis of Variance; D001764:Blepharospasm / Q000188:drug therapy* / Q000503:physiopathology / Q000628:therapy*; D001767:Blinking / Q000187:drug effects; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000627:therapeutic use*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004576:Electromyography; D005154:Facial Nerve / Q000187:drug effects / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009465:Neuromuscular Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D009801:Oculomotor Muscles / Q000187:drug effects* / Q000503:physiopathology; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A