The Clinical Use of Botulinum Toxin

Botulinum toxin type A inhibits rat pyloric myoelectrical activity and substance P release in vivo

The effect of botulinum toxin type A (BTX-A) on rat pyloric myoelectrical activity in vivo and the content and distribution of substance P (SP) in pylorus were investigated, respectively, with electromyography, radioimmunoassay, and immunohistochemistry. A pair of electrodes for recording pyloric myoelectrical activity and a guide cannula for drug injection were implanted into the pylorus. The changes of pyloric myoelectrical activity were recorded followed vehicle, 10, 20, and 40 U/kg body mass of BTX-A injection. Pyloric tissues were dissected for radioimmunoassay and immunohistochemistry after recording. The 3 dosages of BTX-A injections caused the reduction of slow wave of pyloric myoelectrical activity in amplitude but not in frequency and the diminishment of spike activity in amplitude and spike burst. The inhibitory effect of 20 U/kg BTX-A was significantly different from that of 10 U/kg (p<0.05), but not from the effect of 40 U/kg administration (p>0.05). After BTX-A intrasphincteric injection, SP content was reduced in the pylorus, and cell number of SP-immunoreactivity was decreased more in myenteric nerve plexus of circular muscle and in mucosa of pylori. In conclusion, BTX-A inhibits pyloric myoelectrical slow activity in amplitude and spike activity and weakens pyloric smooth muscle contractility depending on threshold of dose or concentration. BTX-A-induced inhibition of pyloric myoelectrical activity implies a mechanism of inhibiting SP release from the autonomic and enteric nervous terminals in the pylorus.

Dysport

Since the commercial launch of Dysport in 1991, after 10 years of clinical studies on its predecessor formulations, this BTX-A product has shown great therapeutic promise with a good safety profile and low incidence of treatment failures. As with all BTX products, Dysport should not be seen as a generic equivalent but as a specific product with individual unit dosing requirements and side effect profiles. Its role as an important BTX-A molecule looks set to expand as new indications for botulinum toxin arise, and as the cosmetic usage of Dysport is approved in countries outside of South America.

Psychiatric disorders in patients with blepharospasm - a reactive pattern?

OBJECTIVE

The purpose of this study was to assess the life-time prevalence of all major psychiatric disorders in patients suffering from blepharospasm.

METHOD

A total of 31 consecutive patients with blepharospasm attending the Department of Neurology were interviewed at the Department of Psychiatry at the University of Vienna. Patients had been submitted to standard neurological diagnostic procedures, psychiatric diagnoses were made with the help of the SCID, functional impairment was assessed by the General Assessment of Functioning Scale (GAF).

RESULTS

A current or life-time psychiatric diagnosis was made for 22 patients (71%). The most frequent disorders were depressive disorders, mainly major depression (five patients, 16.1%), secondary dysthymia (six patients, 19.3%), and recurrent major depression (five patients, 16.1%). A diagnosis of simple phobia was made for seven patients (22.5%), for obsessive-compulsive disorder in three patients (9.6%). The mean GAF score of our sample was 63.1%.

CONCLUSION

In contrast to previously published results, we did not find a high rate of a single specific disorder or patterns in our study sample, though by the inclusion of life-time diagnostic criteria, the majority of patients fulfilled criteria for at least one diagnosis. This might indicate the considerable negative impact of blepharospasm on the patients' lives.

Early experience with intrasphincteric botulinum toxin in the treatment of achalasia

BACKGROUND

Recent reports have suggested that intrasphincteric injection of botulinum toxin is effective and long-lasting in the treatment of achalasia.

AIM

To report our experience of botulinum toxin injection in a prospective series of consecutive patients with achalasia.

METHODS

Eleven consecutive patients with achalasia (eight male, mean age 55 years, range 20-87) were treated with 60 units of botulinum toxin (Dysport; Speywood Pharmaceuticals Ltd, UK) into each of four quadrants at the lower oesophageal sphincter. Patients were assessed pre-treatment and 1 month after treatment using a symptom score and oesophageal manometry. Median follow-up was 12 months (range 6-28).

RESULTS

The injection procedure was simple to perform and free of adverse effects. Although treatment had a beneficial effect on dysphagia (median pre-treatment score 3 [interquartile range 3-3]; post-treatment score 2 [0-3]: P=0.03) 1 month following therapy, there was no significant improvement in chest pain or regurgitation scores. Similarly, no significant reduction in median lower oesophageal sphincter pressure was observed (29.5 mmHg [21-42] pre-treatment, 28.5 [17.5-55.5] post-treatment P=0.67). Four patients (36%) required further therapy within 3 months and the overall relapse rate was 73% (eight of 11) within 2 years.

CONCLUSION

Although botulinum toxin injection was well tolerated, these results using Dysport at a dose of 240 mouse units question its efficacy as a treatment for achalasia.

Botulinum toxin A improves muscle spasms and rigidity in stiff-person syndrome

We studied the effect of botulinum toxin A (BTA) on painful muscular spasms and rigidity in two bedridden patients with clinical, electrophysiologic, and immunologic evidence of stiff-person syndrome. We injected BTA or saline solution into several limb muscles with both the rater and patient blinded to the order of the injections. A physician, unaware of the treatment order, used an objective rating scale for rigidity and spasm frequency scale and independently assessed the treatment results. BTA administration significantly reduced rigidity and stopped the spasms in all limbs. Following BTA injection on one side, the spasm frequency decreased bilaterally possibly because of the spread of hematogenous toxin.

Diplopia following subcutaneous injections of botulinum A toxin for facial spasms

PURPOSE

To study the incidence, cause, recovery time, and prevention of diplopia following subcutaneous injection of botulinum A toxin for the treatment of facial spasms.

METHODS

Patients who experienced diplopia after botulinum A toxin injections had their deviations examined in detail. When the muscle that caused diplopia was identifiable, the injection closest to that muscle was omitted in the next treatment in an attempt to prevent diplopia.

RESULTS

Of 250 patients receiving about 1500 sets of injections, 25 (1.7%) incidents of diplopia occurred in 10 patients. Excluding two patients who declined further treatment after having diplopia on their first botulinum A toxin treatment, seven of the remaining eight patients had multiple incidents of diplopia. The most common pattern of diplopia was "uncertain diagnosis." The most common identifiable cause of diplopia was paresis of the inferior oblique muscle. Omission of the injection into the central portion of the lower eyelids in the next treatment prevented recurrence of diplopia in only one of the four patients. No significant correlation between botulinum A toxin doses injected and times to recovery was noted.

CONCLUSIONS

Diplopia following botulinum A toxin treatment is uncommon. Seven patients (3% of patients studied) had 22 episodes of diplopia (88% of episodes). When diplopia occurs, it tends to recur on reinjection, sometimes with a prolonged recovery time. This response may not be dose dependent. The extraocular muscles of some patients may be more susceptible to chemodenervation than others, or botulinum A toxin may diffuse to extraocular muscles more easily in some patients than in others.

Unilateral injection of botulinum toxin in blepharospasm: single fiber electromyography and blink reflex study

We studied six patients affected with blepharospasm (BSP). We injected botulinum toxin (BTX) around only one eye and saline solution around the other. Clinical rating of BSP was performed. Single fiber electromyography (SFEMG), compound motor action potential (cMAP) at the orbicularis oculi muscle by stimulation of the facial nerve, blink reflex, and blink reflex recovery curve were recorded. All clinical and electrophysiological investigations were carried out before, and 1, 2, and 4 weeks after treatment. Evidence of bilateral clinical benefit was provided. Following therapy, facial cMAP decreased bilaterally and SFEMG revealed statistically significant changes on both sides while the excitability curve of blink reflex remained unmodified. The results confirm that BTX affects merely the neuromuscular junctions. The clinical and neurophysiological effects are present on both sides also for unilateral injection probably because of toxin spreading.

The use of botulinum toxin in the treatment of adductor spasmodic dysphonia

Botulinum toxin injections have been used to treat 31 patients with adductor spasmodic dysphonia. Injections of 3.00-3.75 units of botulinum toxin were performed bilaterally into the thyroarytenoid muscle. This treatment significantly decreased the standard deviation of the fundamental frequency of the speech sample, indicating a reduction in the variability of pitch amongst patients. A total of 96% of patients' subjective diary reports showed an improvement with a median of 7 days to peak effect and a 5 week duration of peak effect.

Time course of distant effects of local injections of botulinum toxin

Botulinum toxin A (btx) is used to treat focal dystonias. From accidental intoxications it is known that btx can cause generalized pathologic single-fiber electromyography (SFEMG) findings. We monitored the onset and course of these disturbances in eight patients who received a small dose of btx (2-22 ng) for therapy of focal dystonias in the head/neck region for the first time via repeated SFEMG investigations at days 0, 3, 6, 9, 12, 28, and 56. Recordings were performed in the extensor digitorum brevis muscle, and in two patients additionally in the tibialis anterior muscle. In six of these patients we found an increase of jitter and blocking. The onset of these changes was in the range of 3-13 days after injection. Fiber density showed a tendency to increase. There was no correlation between SFEMG findings and the dose of injected btx. Possible mechanisms for these observations may be either a very efficient local uptake and retrograde axonal transport via the spinal motor neurons or a systemic distribution via the blood circulation.

Treatment of idiopathic hemifacial spasm with botulinum toxin

Twelve patients with idiopathic hemifacial spasm received treatment with botulinum toxin A over a period of 18 months. Of 76 treatments given, most (94.7%) led to successful relief of eyelid spasms and all treatments were successful for perioral and lower facial muscle spasms. An average dose of 9.3 units of toxin per session was given to produce a mean interval of relief of 10.8 weeks. Blepharoptosis was the only ocular side effect; it was mild, reversible and occurred in 2 patients. However, lower facial palsy was frequent (9 patients); it was mild to moderate in severity but only partially reversible in 8 patients. Dosage for lower facial muscles should therefore be reduced.