Neuromuscular effects distant from the site of botulinum neurotoxin injection

Physiological effects of botulinum toxin in spasticity

There is considerable evidence that injection of botulinum toxin (BTX) into muscles with spastic overactivity reduces resistance to passive movement in joints supplied by the injected muscles. The demonstration of improvement in active performance of the paretic limbs has been only anecdotal to date, and represents the most difficult challenge in research on BTX therapy in spastic paralysis. Data are reviewed that indicate several neurophysiological actions of BTX, other than the blocking of acetylcholine release at the neuromuscular ending: effects on the central nervous system, including retrograde axonal transport, reduced motoneuronal excitability, action on central synapses such as decreased Renshaw inhibition and increased presynaptic inhibition; action on gamma motoneuronal endings; action on most active terminals; spread of BTX to neighboring muscles; spread of BTX effects to remote muscles. Several of these neurophysiological actions are likely to contribute to improvement in active movements, as they may antagonize the primary mechanisms of functional impairment in patients with spastic paralysis: weakness, spastic cocontraction, spastic dystonia, and muscle shortening. We review the evidence for reduction of spastic cocontraction in both the injected muscle and its antagonist, and for improvement of antagonist weakness after BTX injection. The capacity of intramuscular BTX to reduce spastic dystonia and lengthen shortened muscles is also discussed based on prior literature. When injected into the more overactive of a pair of spastic antagonists around a joint, BTX should affect all the main mechanisms impairing active function around the joint.

Movement, visceral and autonomic disorders: use of botulinum toxin

This article reviews the development of botulinum toxin treatment, how it works, the range of conditions it can treat and the benefits and side effects. It sets out how it is used in practice in specialist units.

Comparison of botulinum toxins A and B in the aesthetic treatment of facial rhytides

Botulinum toxin injections have become a popular treatment for minimizing or eliminating facial wrinkles. After injection, the toxin acts to paralyze or weaken facial mimetic muscles. Two antigenically distinct serotypes, botulinum toxin type A (BTX-A) and botulinum toxin type B (BTX-B), are currently available. BTX-A is a lyophilized powder preparation requiring reconstitution; BTX-B is a ready-to-use liquid formulation. Both agents produce the same resultant clinical effect (i.e., muscle weakening). However, in addition to differences with respect to formulation, they are pharmacologically distinct in terms of molecular size, cellular mechanism of action, and species sensitivity. BTX-A has been used for aesthetic purposes for more than 10 years. Clinical studies and observations have shown that it is an effective agent for treating hyperkinetic facial lines. BTX-B was approved for use in cervical dystonia in 2000, but it has been used off-label to treat facial wrinkles as reported in several open-label studies. These preliminary dose-ranging studies have demonstrated that BTX-B is also effective. Both agents are extremely safe nonsurgical modalities for hyperkinetic facial lines. This article reviews the pharmacology and molecular features of BTX-A and BTX-B and highlights some of the key clinical studies that have been published to date with these two agents.

Clinical impact of single-fiber electromyography

The major clinical impact of single-fiber electromyography has been from its role in confirming, or excluding, the diagnosis of myasthenia gravis (MG). Jitter measurements also have a clinical role in demonstrating changes in disease severity in patients with MG and Lambert-Eaton myasthenic syndrome, in demonstrating subtle changes in motor unit architecture and physiology in patients with nerve and muscle diseases, and in demonstrating the remote effects of locally injected botulinum toxin. In addition to these clinical roles, the ability to identify the activity from single muscle fibers makes it possible to mark the discharges of single motor units. This, along with information gained by jitter and fiber-density measurements, has uniquely increased our understanding of motor unit organization and function in normal and disease states.

Muscle strength following direct injection of doxorubicin into rabbit sternocleidomastoid muscle in situ

Direct intramuscular injection of doxorubicin results in permanent myofiber loss. A previous phase I trial demonstrated that such injections could successfully treat blepharospasm and hemifacial spasm. Our previous in vitro study demonstrated that doxorubicin resulted in a dose-dependent reduction in isometric force generation in sternocleidomastoid muscle in rabbits. This present study examined alterations in force generation in these treated muscles in situ, i.e., with the blood and nerve supply intact. Two months after a single doxorubicin injection, functional changes in peak twitch, tetanic force generation, and fatigue rate were assessed in control and doxorubicin-treated sternocleidomastoid muscles in rabbits. Peak force measurements were reduced in the treated muscles. These reductions in muscle strength were significantly greater at tetanic peak amplitudes. Fatigue rate was not altered by doxorubicin treatment of the sternocleidomastoid muscles. These findings support the potential clinical use of doxorubicin chemomyectomy for the treatment of patients with cervical dystonia.

Complications and adverse reactions with the use of botulinum toxin

Botulinum toxins are the causative agents of the severe food-borne illness botulism. With lethal doses approximating 10(-9) g/kg body weight, these neurotoxins represent some of the most toxic naturally occurring substances. Regardless, botulinum toxin is considered a safe therapy for inappropriate muscle spasms with adverse effects being typically self-limited. This article deals with some of the complications that have occurred with these treatments. The greatest concern with the use of BOTOX is probably the formation of blocking antibodies leading to nonresponse of subsequent treatment. Prevalence of resistance is less than 5%. Most complications associated with its aesthetic use are few and anecdotal. Nevertheless, the common problems and pitfalls associated with aesthetic treatment of the various areas of the face and neck with botulinum toxin are discussed. Also included are recommendations as to how to avoid these very undesirable, yet common, problems.

Botulinum toxin type B: an overview of its biochemistry and preclinical pharmacology

Produced by Clostridium botulinum, botulinum toxins are high molecular weight protein complexes consisting of the neurotoxin and additional nontoxic proteins that function to protect the toxin molecule. The neurotoxin acts to inhibit the release of acetylcholine at the neuromuscular junction, causing muscle paralysis. Purified toxin complexes have found a niche in the treatment of clinical disorders involving muscle hyperactivity. The different serotypes are structurally and functionally similar; however, specific differences in neuronal acceptor binding sites, intracellular enzymatic sites, and species sensitivities suggest that each serotype is its own unique pharmacologic entity. Recently, botulinum toxin type B has been developed as a liquid formulation to avoid the lyophilization (vacuum-drying) and reconstitution processes associated with decreasing the potency and stability of current type A toxin preparations. Biochemical tests were conducted to evaluate the quality of toxin in this formulation. In 3 consecutive manufacturing lots, the botulinum toxin type B complex was found to be highly purified, intact, uniform, and consistent from lot to lot. Also, it showed long-term stability at refrigerator and room temperatures (2 to 25 degrees C). Electrophysiologic studies in cynomolgus monkeys showed that botulinum toxin type B is effective in paralyzing injected muscle groups, with minimal spread to relatively distant noninjected muscles.

Botulinum toxin B: a review of its therapeutic potential in the management of cervical dystonia

Botulinum toxins are well known as the causative agents of human botulism food poisoning. However, in the past two decades they have become an important therapeutic mainstay in the treatment of dystonias including cervical dystonia, a neurological disorder characterised by involuntary contractions of the cervical and/or shoulder muscles. The toxins inhibit acetylcholine release from neuromuscular junctions, producing muscle weakness when injected into dystonic muscles. Data from three double-blind, randomised, placebo-controlled trials demonstrate that botulinum toxin B effectively reduces the severity, disability and pain of cervical dystonia. In two of the trials, mean Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)-Total score at week 4 (primary efficacy measure) after botulinum toxin B 10 000U was reduced by 11.7 (25%) or 11 (21%) compared with baseline. These changes were significantly greater than those obtained with placebo [4.3 (10%) or 2 (4%)] and were generally similar in patients who were responsive or resistant to botulinum toxin A. Statistically significant benefits compared with placebo were also evident for a range of other efficacy parameters including TWSTRS-Severity, -Pain and -Disability subscales, patient- assessed pain and patient-/physician-assessed global improvement ratings. In another trial, the percentage of patients with botulinum toxin A-resistant or -responsive cervical dystonia who had a > or =20% improvement in the TWSTRS-Total score between baseline and week 4 was significantly higher with botulinum toxin B 2500 to 10 000U (58 to 77%) than with placebo (27%). Overall, botulinum toxin B was generally well tolerated. The most frequently reported treatment-related adverse events were dry mouth and dysphagia. Most adverse events in patients receiving botulinum toxin B were mild or moderate; no serious adverse events or laboratory abnormalities were associated with the use of botulinum toxin B and, where reported, no patients discontinued from any of the clinical trials as a result of adverse events.

CONCLUSIONS

Botulinum toxin B has shown clinical efficacy in patients with cervical dystonia at doses up to 10 000U and is generally well tolerated. Its efficacy extends to patients who are resistant to botulinum toxin A. Although the potential for secondary resistance to botulinum toxin B remains unclear, it may occur less than with botulinum toxin A because methods for manufacturing commercially available botulinum toxin B do not include lyophilisation and the product does not require reconstitution before use. As injection with botulinum toxin is generally considered the treatment of choice for patients with cervical dystonia, botulinum toxin B should be considered a potential treatment option in this setting.

Botulinum toxin in motor disorders: practical considerations with emphasis on interventional neurophysiology

After a brief review of the pharmacological properties of the botulinum toxin (BT), its mechanism of action on the nerve endings of the neuromuscular junctions, and the general therapeutic principles and adverse side effects, we discuss the advantages of interventional neurophysiology for the treatment of focal motor disorders by means of botulinum toxin A (BTA) muscle infiltration. Electromyography (EMG) provides a valuable objective information in the diagnosis of many motor disturbances and enables the precise identification of the muscles that contribute to the abnormal movement or posture. The use of EMG guidance for BTA injection seems advisable in every muscle but it become indispensable in those difficult to access, deeply located or partially atrophied by previous toxin infiltrations. The EMG study also serves to localise the areas with the highest abnormal activity and the motor point of the muscle, where the injection of toxin exerts its maximal effect. Consequently, lower doses of BTA can be employed without decreasing the efficacy of treatment but reducing the potential risk of side effects, antibody production and the cost of treatment. Electrophysiological diagnosis and BTA treatment may be performed during the same exploration. Considerations on the particular aspects and lines of action are given referring to the main focal muscular hyperactivity motor disorders such as cervical, oromandibular and laryngeal dystonias, blepharospasm, writer's cramp, hemifacial and hemimasticatory spasms, infantile and adult forms of spasticity and some other focal disturbances such as strabismus, detrusor-sphincter dyssynergia and anismus.

Botulinum toxin type B: an overview of its biochemistry and preclinical pharmacology

Produced by Clostridium botulinum, botulinum toxins are high molecular weight protein complexes consisting of the neurotoxin and additional nontoxic proteins that function to protect the toxin molecule. The neurotoxin acts to inhibit the release of acetylcholine at the neuromuscular junction, causing muscle paralysis. Purified toxin complexes have found a niche in the treatment of clinical disorders involving muscle hyperactivity. The different serotypes are structurally and functionally similar; however, specific differences in neuronal acceptor binding sites, intracellular enzymatic sites, and species sensitivities suggest that each serotype is its own unique pharmacologic entity. Recently, botulinum toxin type B has been developed as a liquid formulation to avoid the lyophilization (vacuum-drying) and reconstitution processes associated with decreasing the potency and stability of current type A toxin preparations. Biochemical tests were conducted to evaluate the quality of toxin in this formulation. In 3 consecutive manufacturing lots, the botulinum toxin type B complex was found to be highly purified, intact, uniform, and consistent from lot to lot. Also, it showed long-term stability at refrigerator and room temperatures (2 to 25 degrees C). Electrophysiologic studies in cynomolgus monkeys showed that botulinum toxin type B is effective in paralyzing injected muscle groups, with minimal spread to relatively distant noninjected muscles.

Severe adult botulism

A case of severe adult botulism with paralysis, respiratory failure and cranial nerve palsies is presented. The pathophysiology, clinical manifestations, diagnosis and treatment options for botulism are discussed.

Complications and adverse reactions with the use of botulinum toxin

Botulinum toxins are the causative agents of the severe food-borne illness botulism. With lethal doses approximating 10(-9) g/kg body weight, these neurotoxins represent some of the most toxic naturally occurring substances. Regardless, botulinum toxin is considered a safe therapy for inappropriate muscle spasms with adverse effects being typically self-limited. This article deals with some of the complications that have occurred with these treatments. The greatest concern with the use of BOTOX is probably the formation of blocking antibodies leading to nonresponse of subsequent treatment. Prevalence of resistance is less than 5%. Most complications associated with its aesthetic use are few and anecdotal. Nevertheless, the common problems and pitfalls associated with aesthetic treatment of the various areas of the face and neck with botulinum toxin are discussed. Also included are recommendations as to how to avoid these very undesirable, yet common, problems.

Remote F-wave changes after local botulinum toxin application

OBJECTIVE

Although the therapeutic effects of botulinum toxin A can be explained by its action at the neuromuscular junction, central or more proximal effects have also been discussed.

METHODS

Eleven patients with torticollis spasmodicus and 3 patients with writer's cramp were studied before and 1 and 5 weeks after the first treatment with botulinum toxin. We measured compound muscle action potentials (CMAPs), motor conduction velocities (MCVs), the shortest (SFL) and the mean F-wave latencies (MFL) and F-wave persistence (30 trials) of untreated muscles for each side (ulnar nerve-abductor digiti minimi muscle, peroneal nerve-tibialis anterior muscle).

RESULTS

CMAPs and MCVs showed no significant changes. For both nerves, however, SFL and MFL were prolonged slightly 1 week after treatment and returned to about baseline after 5 weeks (t test). The F-wave persistence was reduced 1 week after treatment for the right ulnar and both peroneal nerves (t test).

CONCLUSIONS

These results are not likely due to an impairment of neuromuscular transmission. Instead, we propose a decreased excitability of alpha-motoneurons supplying non-treated muscles. A reduction of muscle spindle activity or changes of the recurrent inhibition are discussed as possible causes.

Botulinum A toxin: Dysport improvement of biological availability

We investigated the efficacy and potency of Dysport, a botulinum neurotoxin type A complex approved for therapy, under various conditions. Conditions for maximal expression of biological activity were explored in vitro in the phrenic nerve-hemidiaphragm preparation, while conditions for optimal distribution of the toxin were tested in vivo in a double blind trial involving volunteers, using the foot Muscles extensor digitorum brevis. In contrast to the recommendations of the manufacturer, the biological availability of Dysport could be enhanced by (1) lowering its concentration, (2) supplementing with albumin, and (3) increasing the injection volume. On the basis of these experimental findings Dysport was diluted to a final concentration of 50 U/ml for therapeutic purposes. In a blind, single crossover study patients suffering from various forms of dystonia were treated with Dysport, first diluted and dosed as suggested by the manufacturer and then with doses cut by approximately 70% in accordance with the experimental findings. The low-dose treatment was as effective as the treatment with the recommended higher doses, but side effects were considerably less apparent. The benefits to be derived from these adjustments include a low risk of antibody formation, which could preclude continued or future treatment and substantial cost savings.

Pharmacological identification of SM-21, the novel sigma(2) antagonist

SM-21 is a tropane analogue with high affinity and selectivity for sigma(2) receptor subtype. In the absence of highly selective sigma(2) antagonists, the aim of the present study was to determine whether SM-21 is endowed with antagonistic activity. The experiments were conducted in rats by inducing neck dystonia, which is reported to be subsequent to activation of sigma(2) receptors. SM-21 (10 nmol/0.5 microl) was able to prevent torsion of the neck obtained by administration of the sigma(1)-sigma(2) agonist 1,3-di-(2-tolyl)guanidine (DTG, 5 nmol/0.5 microl) in the red nucleus. These data indicate that SM-21 is a potent and selective sigma(2) antagonist.

Long-term botulinum toxin treatment of cervical dystonia--EMG changes in injected and noninjected muscles

OBJECTIVE

To evaluate changes in quantitative EMG of injected and noninjected sternocleidomastoid muscles following long-term unilateral botulinum toxin treatment of cervical dystonia.

METHODS

We investigated 27 patients with cervical dystonia, who received repeated unilateral botulinum toxin injections of the sternocleidomastoid muscle, with quantitative EMG at rest and at maximal voluntary contraction. The patients had on the average 7.1 botulinum toxin treatments and the follow-up period was on the average 31 months (SD 16).

RESULTS

After the first treatment, the injected sternocleidomastoid muscles showed a significant decrease in turns/s (mean 45%) and amplitude (mean 52%) at rest, and in amplitude at maximal flexion (mean 24%) and rotation (mean 39%). Except for a reduction in turns/s at rotation (mean 19%) no further reductions in EMG parameters were seen after long-term treatment. The contralateral noninjected sternocleidomastoid muscles showed no significant change in EMG activity after the first BT treatment, but after long-term treatment a significant reduction in turns/s and amplitude at both maximal flexion (turns: mean 28%; amplitude: mean 25%) and rotation (turns/s: mean 32%; amplitude: mean 25%) were seen as compared to pretreatment values.

CONCLUSION

The results indicate that there seems to be no cumulative chemodenervation by repeated botulinum toxin injections of sternocleidomastoid muscles measured by quantitative EMG. Contralateral noninjected sternocleidomastoid muscles however, seem to be affected following long-term treatment. The mechanism behind this finding is unknown.

Serial SFEMG studies of orbicularis oculi muscle after the first administration of botulinum toxin

Serial single fiber electromyography (SFEMG) examinations of orbicularis oculi muscle in patients with blepharospasm or hemifacial spasm treated with botulinum toxin injections were performed. The aim of the study was to evaluate the impairment of neuromuscular transmission, to follow reinnervation after botulinum toxin administration and to find out whether there was a relationship between SFEMG parameters and clinical symptoms. Examinations were performed before injection, during early and late remission of symptoms, and after recurrence of the involuntary movement. Severe impairment of neuromuscular transmission, as revealed by increased jitter and increased presence of abnormal potential pairs and pairs with blocking, was found in early remission, but fiber density remained unchanged when compared with pretreatment values. In late remission, increased fiber density was registered for the first time. The recurrence of involuntary movements was related to the further increase of fiber density and tendency to normalization of jitter parameters. The study therefore suggests that formation of new neuromuscular junctions and their functional maturation is responsible for muscle recovery after botulinum toxin administration.

Clinical spectrum of botulism

Botulism is a paralyzing disease caused by the toxin of Clostridium botulinum. The toxin produces skeletal muscle paralysis by producing a presynaptic blockade to the release of acetylcholine. Recent studies have pinpointed the site of action of the several types of botulinum neurotoxin at the nerve terminal. Since the discovery of the toxin about 100 years ago, five clinical forms of botulism have been described: 1) classic or foodborne botulism; 2) wound botulism; 3) infant botulism; 4) hidden botulism; 5) inadvertent botulism. A clinical pattern of descending weakness is characteristic of all five forms. Almost all human cases of botulism are caused by one of three serotypes (A, B, or E). Classic and wound botulism were the only two forms known until the last quarter of this century. Wound botulism was rare until the past decade. Now there are increasing numbers of cases of wound botulism in injecting drug users. Infant botulism, first described in 1976, is now the most frequently reported form. In infant botulism spores of Clostridium botulinum are ingested and germinate in the intestinal tract. Hidden botulism, the adult variant of infant botulism, occurs in adult patients who usually have an abnormality of the intestinal tract that allows colonization by Clostridium botulinum. Inadvertent botulism is the most recent form to be described. It occurs in patients who have been treated with injections of botulinum toxin for dystonic and other movement disorders. Laboratory proof of botulism is established with the detection of toxin in the patient's serum, stool, or wound. The detection of Clostridium botulinum bacteria in the stool or wound should also be considered evidence of clinical botulism. Electrophysiologic studies can provide presumptive of botulism in patients with the clinical signs of botulism. Electrophysiologic testing can be especially helpful when bioassay studies are negative. The most consistent electrophysiologic abnormality is a small evoked muscle action potential in response to a single supramaximal nerve stimulus in a clinically affected muscle. Posttetanic facilitation can be found in some affected muscles. Single-fiber EMG studies typically reveal increased jitter and blocking, which become less marked following activation. The major treatment for severe botulism is advance medical and nursing supportive care with special attention to respiratory status.

A double blind, randomised, parallel group study to investigate the dose equivalence of Dysport and Botox in the treatment of cervical dystonia

OBJECTIVE

This study was designed to establish whether a ratio of three units of Dysport is equivalent to one unit of Botox for the treatment of cervical dystonia.

METHODS

Patients with predominantly rotational cervical dystonia, and a minimum of four previous Botox treatments, were randomised to receive either the clinically indicated dose of Botox or three times that dose in Dysport units. Study botulinum toxin was administered in a double blind fashion, to one or more clinically indicated muscles, at one or more sites per muscle. Patients returned for assessment two, four, eight, and 12 weeks after treatment.

RESULTS

A total of 73 patients (Dysport, 38; Botox, 35) were entered. The Dysport group received a mean (SD) dose of 477 (131) (range 240-720) Dysport units, and the Botox group received a mean (SD) dose of 152 (45) (range 70-240) Botox units. The mean (SEM) post-treatment Tsui scores for the Dysport group (4.8 (0.3)) and the Botox group (5.0 (0.3)) were not statistically different (p=0.66). The study had 91% power to detect a clinically significant difference of two points. Both groups showed substantial improvement in Tsui score by week 2 (mean (SD); Dysport, 46 (28)%; Botox, 37 (28)%), with a peak effect at week 4 (mean (SD); Dysport, 49 (29)%; Botox, 44 (28)%). A similar response profile was seen for other assessments of efficacy. The duration of effect, assessed by time to retreatment, was also similar (mean (SD); Dysport, 83.9 (13.6) days; Botox, 80.7 (14.4) days; p=0.85). During the study 22 of 38 (58%) Dysport patients reported 39 adverse events, and 24 of 35 (69%) Botox patients reported 56 adverse events (p=0.35). A global assessment of efficacy and safety considered that 29 of 38 (76%) Dysport patients and 23 of 35 (66%) Botox patients were treatment successes (p=0.32).

CONCLUSION

Patients with predominantly rotational cervical dystonia treated with the clinically indicated dose of Botox or three times that dose in Dysport units show similar improvements and do not have significantly different safety profiles.

Sialorrhea in amyotrophic lateral sclerosis: a hypothesis of a new treatment--botulinum toxin A injections of the parotid glands

The inhibitory action of botulinum toxin is not confined to the neuromuscular junction. The toxin has long been known to block all the autonomic cholinergic fibers, including the major secretomotor parasympathetic fibers to salivary glands. The parotids are the largest of the salivary glands and their selective chemodenervation with botulinum toxin A is likely to result in substantial reduction of saliva production. Injection of the parotid glands with botulinum toxin is proposed as an new treatment for sialorrhea in patients with amyotrophic lateral sclerosis and other neurological diseases.

Botulinum-A toxin in the treatment of craniocervical muscle spasms: short- and long-term, local and systemic effects

Botulinum toxin has become the initial treatment of choice for the management of essential blepharospasm, hemifacial spasm and other craniocervical dystonias. Numerous studies have confirmed a 90% to 95% response rate. Although a number of common side effects have been reported, the occurrence and incidence of rare local complications remains poorly understood. More importantly, the acute and chronic distant effects of botulinum toxin have not been clearly elucidated. A better understanding of such effects is essential if clinicians are to appropriately advise patients on the use of this therapeutic modality. This article is based on the Duke University experience in the management of over 500 patients with craniocervical spasm disorders, combined with a review of the published literature. These disorders include essential blepharospasm, oromandibular dystonia, hemifacial spasm, and torticollis. The incidence of side effects following more than 6000 treatments with botulinum toxin is presented. Pertinent research relating to the causes of these complications is also reviewed. The most common complications of treatment with botulinum toxin are related to acute local effects resulting from chemodenervation. The most important clinical effect in this group is weakening of the levator muscle resulting in ptosis, and the corneal consequences of lagophthalmos. The latter includes exposure keratitis, dry eyes, blurred vision, and hypersecretion epiphora. Less common local effects include facial numbness, diplopia, and ectropion. Some distant effects are being observed with increasing frequency. These include pruritus, dysphagia, nausea, and a flu-like syndrome. Most significant, however, are the rare reports of generalized weakness and the documentation of EMG abnormalities distant to the site of toxin injection. This has been seen with injections for both blepharospasm and torticollis. Until further studies on the long-term distant complications of botulinum toxin are available, it is recommended that patients receive as few life-time doses of toxin as possible, consistent with adequate management of their spasms. The practice of reinjecting patients routinely every three months, or at the first return of mild spasms should be discouraged.

Botulinum-A toxin as a treatment of detrusor-sphincter dyssynergia: a prospective study in 24 spinal cord injury patients

PURPOSE

The paralytic effect of botulinum-A toxin injections on the external urethral sphincter was investigated prospectively in patients with neurogenic voiding disorders.

MATERIALS AND METHODS

Transurethral versus transperineal botulinum-A toxin injections were performed in 24 spinal cord injury male patients with detrusor-sphincter dyssynergia and the respective efficacy was compared.

RESULTS

In 21 of 24 patients detrusor-sphincter dyssynergia was significantly improved with a concomitant decrease in post-void residual volumes in most cases. Botulinum-A toxin effects lasted 3 to 9 months, making reinjections necessary.

CONCLUSIONS

Although costly, botulinum-A toxin injections, which aim at suppressing detrusor-sphincter dyssynergia but not bladder neck dyssynergia, appear to be a valid alternative for patients who do not desire surgery or are unable to perform self-catheterization.

Botulinum toxin: influence on respiratory heart rate variation

Remote adverse effects of local intramuscular botulinum toxin were investigated in a prospective follow-up study. Twenty-six patients with spasmodic torticollis were examined (18 women, eight men, 45 +/- 13 years). Respiratory heart rate variation (HRV) was investigated by a computerized method. Different parameters were recorded (beats per minute, coefficient of variation, root mean square successive difference (RMSSD), spectral analysis, difference and quotient between maximum and minimum RR intervals, mean circular resultant). After one intramuscular injection of 12.5 ng botulinum toxin (Porton Products Ltd., England), no significant influence on HRV was seen. After the second injection, a significant attenuation was seen of four parameters (coefficient of variation, Rmax - Rmin, Rmax divided by Rmin, mean circular resultant) that lasted up to several months. No clinically manifest remote side effects and no cardiac arrhythmia were seen for several months of botulinum toxin treatment. Our investigation proves an effect of local intramuscular botulinum toxin on autonomic cardiac innervation.

Serial neurophysiological studies of intramuscular botulinum-A toxin in humans

To characterize the time course of intramuscular botulinum toxin-induced paresis, we serially performed electrophysiological measurements and recorded the sonographic size of an extensor digitorum brevis (EDB) muscle in 10 human subjects before and after injecting the EDB with 10 units of botulinum-A toxin. All EDB CMAPs decreased within 48 h, with peak decline at day 21 (8.3 +/- 3.1 mV to 3.0 +/- 0.9 mV). Decline of mean rectified voltage during maximal voluntary contraction of the EDB paralleled the change in CMAP amplitude. Average decrements to 2-Hz repetitive stimulation never exceeded 6% (day 42) and exercise failed to facilitate significantly CMAP amplitude. Atrophy peaked at day 42. The F-wave to M-wave ratio increased at day 2; silent periods did not change. Our findings confirm a primary peripheral action of the toxin, but a superimposed, transient central effect of the drug cannot be excluded. Intramuscular injections into EDB provide a useful model for studying chemodenervation effects.

Electromyographic single motor unit potentials after repeated botulinum toxin treatments in cervical dystonia

Electromyographic (EMG) single motor unit potentials (MUPs) of the sternomastoid muscles (STM) were made before and after repeated treatment with botulinum type A toxin (Bx) for cervical dystonia. Post-treatment examinations were 6-25 weeks after the latest injection, when symptoms and EMG interference pattern had recurred and signs of denervation were scarce. Concentric needle EMG records of 200 motor unit potentials in 10 patients showed reduced durations and areas after treatment (P < 0.05). Increased polyphasia or satellite potentials were not observed. Macro-EMG records of 110 MUPs in 6 patients showed reduced amplitudes and areas in the injected STM when compared to the untreated side (P < 0.05). Fibre density was within the same range (1.0-1.2). The results indicate that the pattern of the terminal innervation is mainly restored even after repeated Bx treatments, but the number or size of active muscle fibres within the motor unit is reduced. The clinical relapse could be due to recovery of the original nerve terminals, or to nerve sprouts closely imitating the blocked terminal nerve twigs or both.

Botulinum toxin converts muscle acetylcholine receptors from adult to embryonic type

To assess the postsynaptic consequences of botulinum toxin injection into muscle we characterized the nicotinic acetylcholine receptor (nAChR) with the patch clamp technique, using adult mouse muscle after destruction of the nerve ending and after treatment with botulinum toxin (BoTX). In both, embryonic channels with a conductance of 30 and 34 pS could be identified, whereas on adult control muscle nAChR channels had a conductance of 48 pS. The mean open times were 1.2 ms for the channels in control, 2.5 ms in denervated and 2.4 ms in BoTX-treated muscle. The dose-response curves of the maximal acetylcholine-elicited currents showed a Km of 60 mumol/L for denervated, 70 mumol/L for BoTX-treated, and 100 mumol/L for control muscle. Destruction of the nerve ending and inhibition of acetylcholine release by BoTX has the same effect as far as the increase of sensitivity of the muscle to acetylcholine is concerned. In contrast to single-fiber EMG findings in patients treated for focal dystonia no distant changes could be found in the control muscle of the BoTX-treated animals.

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.

Botulinum Toxin Treatment of Spasmodic Torticollis

We reviewed the efficacy and adverse effects of repeated botulinum toxin injections into hyperactive neck muscles of 107 successive patients with spasmodic torticollis. They received 510 injection treatments over a median period of 15 months (range 3–42 months). One patient failed to benefit at all, but 101 (95%) patients reported considerable (moderate or excellent) benefit from at least one treatment. On a global subjective response rating, 93% of 429 treatments resulted in some improvement and 76% in moderate or excellent improvement. Pain reduction followed 89% of 190 treatments with moderate or excellent reduction after 66%. Median duration of benefit was 9 weeks. All torticollis types responded equally well and injections into two (or more) involved neck muscles were more effective than injection into a single muscle. The most frequent adverse effect was dysphagia, occurring after 44% of all treatments, but this was severe after only 2%. Antibodies to botulinum toxin were detected in the serum of three out of the five patients in whom loss of treatment efficacy occurred. We conclude that botulinum toxin treatment is the most effective available therapy for spasmodic torticollis and practical advice is provided for anyone wishing to set up the technique.

Botulinum toxin therapy: distant effects on neuromuscular transmission and autonomic nervous system

To evaluate distant effects of botulinum toxin, single fibre electromyography on the extensor digitorum communis muscle and six tests of cardiovascular reflexes were performed in five patients injected with BoTox (Oculinum(R) 20-130 units) for craniocervical dystonia and hemifacial spasm. Patients underwent two sessions of treatment and the second time the dosage was doubled. Botulinum toxin injection induced an increase of mean jitter value above normal limits in all cases. An increase of fibre density was recorded six weeks after the treatment. Cardiovascular reflexes showed mild abnormalities in four patients. The data confirm distant effects of botulinum toxin on neuromuscular transmission and on autonomic function.

Treatment of spasmodic torticollis with local injections of botulinum toxin. One-year follow-up in 37 patients

Thirty-seven patients with spasmodic torticollis (cervical dystonia) who received repeated local injections of botulinum toxin have been followed up for a mean period of 12.3 (10-29) months, during which time 138 treatment sessions were performed. Mean doses per muscle averaged 320 mouse units (mu; range 160-1000 mu botulinum toxin A prepared by CAMR, Porton Down, UK). Eighty-six per cent of patients experienced significant improvement of posture and 84% of those with pain had relief following the first injection. Muscular patterns of recurrent torticollis were relatively constant and in most patients efficacy was maintained with subsequent injections, while 15% of all follow-up sessions failed. Only 2 of 37 patients were consistent nonresponders; 22% and 10% of all sessions were complicated by transient dysphagia and weakness of neck muscles, respectively. It is concluded that local botulinum toxin injections can be a safe and efficaceous long-term treatment of spasmodic torticollis and that optimal doses should be between 200 and 400 mu/muscle.

Distant effects of locally injected botulinum toxin: a double-blind study of single fiber EMG changes

We used single fiber electromyography (SFEMG) to study 42 patients who had enrolled in a double-blind, placebo-controlled trial undertaken to assess the efficacy of botulinum toxin (BTX) injection of neck muscles to treat torticollis. SFEMG in a limb muscle was performed before treatment, 2, and 12 weeks after injection of placebo or BTX. Before treatment, the mean jitter was 26.8 microsec in patients who were to receive BTX, and 25.7 microsec in the placebo group. Two weeks after injection, mean jitter in the group receiving BTX was 43.6 microsec. In the placebo group, it was 26.5 microsec (P = less than .05). Twelve weeks after injection, mean jitter in the BTX group was 35.5; for the placebo group it was 24.5. Fiber density did not change in any patient during the study. There were no remote clinical effects of BTX. Injection of BTX into muscles affected with focal dystonia is a promising and safe treatment, but there are subclinical effects on uninjected muscles.

Botulinum A toxin (Oculinum) in ophthalmology

Botulinum A toxin has been used to treat strabismus and a variety of spasmodic neuromuscular diseases. Botulinum toxin treatment of strabismus is not as definitive and stable as the traditional surgical approach, but it has been found most useful in postoperative overcorrection, small deviations, sensory deviations, and acute sixth nerve palsy. This toxin has been effective in the treatment of essential blepharospasm and hemifacial spasm, for which it produces temporary relief of symptoms. In addition, this treatment has been applied to lower lid entropion, myokymia, aberrant regeneration of the seventh nerve, lid retraction, corneal exposure, nystagmus, spasmodic torticollis, and adductor spastic dysphonia.