expanding use of botulinum toxin

9
Review Expanding use of botulinum toxin Roongroj Bhidayasiri a,b,c , Daniel D. Truong c, * a Department of Neurology, UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA b Movement Disorders Group, Division of Neurology, Chulalongkorn University Hospital, Bangkok, Thailand c The Parkinson’s and Movement Disorder Institute, 9940 Talbert Ave, Fountain Valley, CA 92708, USA Received 26 July 2004; received in revised form 14 April 2005; accepted 18 April 2005 Available online 28 June 2005 Abstract Botulinum toxin type A (BTX-A) is best known to neurologists as a treatment for neuromuscular conditions such as dystonias and spasticity and has recently been publicized for the management of facial wrinkles. The property that makes botulinum toxin type A useful for these various conditions is the inhibition of acetylcholine release at the neuromuscular junction. Although botulinum toxin types A and B (BTX-A and BTX-B) continue to find new uses in neuromuscular conditions involving the somatic nervous system, it has also been recognized that the effects of these medications are not confined to cholinergic neurons at the neuromuscular junction. Acceptors for BTX-A and BTX-B are also found on autonomic nerve terminals, where they inhibit acetylcholine release at glands and smooth muscle. This observation led to trials of botulinum neurotoxins in various conditions involving autonomic innervation. The article reviews the emerging use of botulinum neurotoxins in these and selected other conditions, including sialorrhea, primary focal hyperhidrosis, pathological pain and primary headache disorders that may be of interest to neurologists and related specialists. D 2005 Elsevier B.V. All rights reserved. Keywords: Botulinum toxin; Sialorrhea; Drooling; Hyperhidrosis; Pathological pain; Headache Contents 1. Introduction ............................................................ 1 2. Sialorrhea ............................................................. 2 3. Primary focal hyperhidrosis .................................................... 3 4. Conditions of pathological pain.................................................. 5 4.1. Headache disorders .................................................... 5 4.2. Musculoskeletal pain ................................................... 6 5. Conclusion ............................................................ 6 Acknowledgments ........................................................... 6 References ............................................................... 6 1. Introduction Botulinum toxin type A (BTX-A) is best known to neurologists as a treatment for neuromuscular conditions such as dystonias and spasticity and has recently been publicized for the management of facial wrinkles. The property that makes botulinum toxin type A useful for these various conditions is the inhibition of acetylcholine release at the neuromuscular junction [1]. The efficacy of BTX-A without systemic side effects has led to the rapid develop- ment of its application in various conditions in addition to 0022-510X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jns.2005.04.017 * Corresponding author. Tel.: +1 714 378 5062; fax: +1 714 378 5061. E-mail address: [email protected] (D.D. Truong). Journal of the Neurological Sciences 235 (2005) 1 – 9 www.elsevier.com/locate/jns

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www.elsevier.com/locate/jns

Journal of the Neurological S

Review

Expanding use of botulinum toxin

Roongroj Bhidayasiri a,b,c, Daniel D. Truong c,*

aDepartment of Neurology, UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USAbMovement Disorders Group, Division of Neurology, Chulalongkorn University Hospital, Bangkok, Thailand

cThe Parkinson’s and Movement Disorder Institute, 9940 Talbert Ave, Fountain Valley, CA 92708, USA

Received 26 July 2004; received in revised form 14 April 2005; accepted 18 April 2005

Available online 28 June 2005

Abstract

Botulinum toxin type A (BTX-A) is best known to neurologists as a treatment for neuromuscular conditions such as dystonias and

spasticity and has recently been publicized for the management of facial wrinkles. The property that makes botulinum toxin type A useful for

these various conditions is the inhibition of acetylcholine release at the neuromuscular junction. Although botulinum toxin types A and B

(BTX-A and BTX-B) continue to find new uses in neuromuscular conditions involving the somatic nervous system, it has also been

recognized that the effects of these medications are not confined to cholinergic neurons at the neuromuscular junction. Acceptors for BTX-A

and BTX-B are also found on autonomic nerve terminals, where they inhibit acetylcholine release at glands and smooth muscle. This

observation led to trials of botulinum neurotoxins in various conditions involving autonomic innervation. The article reviews the emerging

use of botulinum neurotoxins in these and selected other conditions, including sialorrhea, primary focal hyperhidrosis, pathological pain and

primary headache disorders that may be of interest to neurologists and related specialists.

D 2005 Elsevier B.V. All rights reserved.

Keywords: Botulinum toxin; Sialorrhea; Drooling; Hyperhidrosis; Pathological pain; Headache

Contents

. . . . . . . 1

. . . . . . . 2

. . . . . . . 3

. . . . . . . 5

. . . . . . . 5

. . . . . . . 6

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Sialorrhea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. Primary focal hyperhidrosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. Conditions of pathological pain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1. Headache disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.2. Musculoskeletal pain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . 6

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1. Introduction

Botulinum toxin type A (BTX-A) is best known to

neurologists as a treatment for neuromuscular conditions

0022-510X/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.jns.2005.04.017

* Corresponding author. Tel.: +1 714 378 5062; fax: +1 714 378 5061.

E-mail address: [email protected] (D.D. Truong).

such as dystonias and spasticity and has recently been

publicized for the management of facial wrinkles. The

property that makes botulinum toxin type A useful for these

various conditions is the inhibition of acetylcholine release

at the neuromuscular junction [1]. The efficacy of BTX-A

without systemic side effects has led to the rapid develop-

ment of its application in various conditions in addition to

ciences 235 (2005) 1 – 9

R. Bhidayasiri, D.D. Truong / Journal of the Neurological Sciences 235 (2005) 1–92

dystonia and spasticity, including hypersecretory disorders,

tics, tremor, stuttering, different pain syndromes, detrusor

sphincter dyssynergia or overactivity and gastrointestinal

smooth muscle/sphincter spasms [2–5]. Following local

injection into muscles, the toxin enters the nerve terminal

via endocytosis, interacts with intracellular proteins

(SNARE proteins) and inhibits the vesicular release of the

acetylcholine (Ach) neurotransmitter at the neuromuscular

junction [1,6]. Inhibition of Ach produces chemical dener-

vation and paralysis of the striated muscles. Paralysis

usually peaks 2 weeks after the injection. Because of the

Table 1

Current evidence of botulinum toxin in various disorders with the least

reasonable trial of evidence shown to be at least moderately effective by

BTX-A

(1) Focal dystonias

Blepharospasma

Cervical dystoniaa

Spasmodic dysphonia

Meige syndrome

Writer’s cramp

Foot dystonia

Oromandibular dystonia

Axial dystonia

Occupational cramps

(2) Tremor

Dystonia head tremor

Essential head tremor

Essential hand tremor

Palatal tremor

(3) Hemifacial spasma

(4) Focal spasticity in adults

Lower limb

Upper limb

(5) Focal spasticity in children

Upper limb

Lower limb

(6) Ophthalmic conditions

Strabismusa

Ptosis

(7) Autonomic disorders

Focal hyperhidrosis

Gustatory sweating

Hyperlacrimation

Sialorrhea

(8) Urological disorders

Detrusor sphincter dyssynergia

Hyperreflexive bladder

Vaginismus

(9) Gastrointestinal disorders

Anal fissure

Achalasia

Upper esophageal sphincter

Anismus

(10) Pain

Tension-type headache

Migraine

Low back pain

Chronic daily headache

Myofascial pain

(11) Wrinkles (Glabellar wrinklesa)

a Indicates conditions that have been approved by the United States Food

and Drug Administration; modified from Moore [105].

molecular turnover within the neuromuscular junction and

neuronal sprouting, neuronal activity begins to return at 3

months, with restoration of complete function at approx-

imately 6 months [7].

BTX-A is 1 of 7 botulinum neurotoxin serotypes known

alphabetically as types A to G [8]. Although these toxins

have different intracellular targets, their biological activity at

the neuromuscular junction is similar. Of these serotypes,

only A and B are currently available as commercial

preparations [9]. Types C and F have also been used in

humans, but only on an experimental basis [10,11]. The first

commercial preparation of botulinum neurotoxin to be used

clinically was based on the A serotype (Botox\), and this

product continues to be used in many countries throughout

the world. Another preparation based on the A serotype

(Dysport\) was later introduced in several countries and

may become available in the United States within several

years. In the year 2000, a product based on the B serotype

(Myobloc\/Neurobloc\) became commercially available.

Although all of these formulations inhibit acetylcholine

release, they do so at different doses [7,9,12]. Thus, all of

these products are used clinically at different unit doses that

may vary up to several orders of magnitude [9].

Although botulinum toxin types A and B (BTX-A and

BTX-B) continue to find new uses in neuromuscular

conditions involving the somatic nervous system, it has

also been recognized that the effects of these medications

are not confined to cholinergic neurons at the neuro-

muscular junction [13,14]. Acceptors for BTX-A and

BTX-B are also found on autonomic nerve terminals, where

they inhibit acetylcholine release at glands and smooth

muscle [15]. This observation led to trials of botulinum

neurotoxins in various conditions involving autonomic

innervation [16–18]. The rest of this article considers the

emerging use of botulinum neurotoxins in these and selected

other conditions that may be of interest to neurologists and

related specialists (Table 1).

2. Sialorrhea

Excessive drooling, which occurs in many different

neurological conditions, may pose significant risks of

choking with aspirations and pneumonia and may affect

patients’ social activities and self-image. Up to 20% of

patients with bulbar amyotrophic lateral sclerosis (ALS) and

78% of patients with Parkinson’s disease (PD) manifest this

problem [19]. It is usually caused by swallowing dysfunc-

tion, although primary sialorrhea rarely occurs. The

mechanism of action by which botulinum toxins reduce

saliva production may relate to the inhibition of cholinergic

autonomic parasympathetic and postganglionic sympathetic

acetylcholine release, which innervates the salivary glands.

Over the past few years, BTX-A has been studied for the

treatment of sialorrhea associated with parkinsonism,

cerebral palsy, head and neck carcinoma, neurodegenerative

R. Bhidayasiri, D.D. Truong / Journal of the Neurological Sciences 235 (2005) 1–9 3

diseases, stroke and ALS [20–33]. Although most of the

published literature describes open pilot studies with

relatively small groups of patients, up to two-thirds of the

patients experienced a marked or moderate improvement of

drooling after treatment of both parotid glands or the parotid

and submandibular glands combined, as determined by

patient ratings of drooling severity, objective measurement

of salivary flow by sialometry and weight of dental rolls

(Table 2). More recently, larger scale clinical trials have

been conducted and confirmed with favorable results

[34,35]. Encouraging results of BTX-B in sialorrhea have

recently been reported in two studies involving 25 patients

with parkinsonism [36,37]. Indeed, BTX-B may prove to be

a particularly effective treatment for sialorrhea due to an

apparent predilection for autonomic neurons. Dysphagia and

dry mouth occur more frequently from BTX-B than BTX-A,

probably reflecting preferential blockade of autonomic

neurons [38–40].

Generally, results have been encouraging with the

reported duration of the beneficial response varying from

7 weeks to 7 months. Most of these studies did not report

any significant adverse events with botulinum toxin

injections in the treatment of sialorrhea, except for local

pain, infection, dry mouth, transient dysphagia and weak-

ness of mouth opening and closure [20–24,36,37]. How-

ever, BTX-A was associated with recurrent jaw dislocation

in one patient with ALS [41]. Another study reported

marked deterioration of dysphagia and local infection of the

gland when the toxin was injected transductally in ALS

patients [26]. Most other studies have used ultrasound

guidance to direct injections into the parotid and/or

submandibular glands.

The results of these studies suggest that botulinum

neurotoxin therapy may be useful for the treatment of

sialorrhea, with a low risk of side effects. The highest safe

Table 2

Summary of selected studies on botulinum toxin in sialorrhea (n >5)

Authors Design Technique Number (n), Diagnosis

Botox\

Ellies et al. [21] Open U/S 13, carcinoma, neurodege

Bothwell et al. [32] Open Blind 9, CP

Pal et al. [24] Open Blind 9, PD

Giess et al. [31] Open U/S 5, ALS

Porta et al. [25] Open U/S 10, ALS, PD, CP, SSPE,

Suskind and Tilton [23] Open U/S 22, CP

Jongerius et al. [34] Controlled U/S 45, CP

Dogu et al. [33] Open U/S, Blind 15, PD

Dysport\

Mancini et al. [20] Controlled U/S 20, PD, MSA

Lipp et al. [35] Controlled Blind 32, ALS, PD, CBD, MSA

Myobloc\

Racette et al. [36] Open Blind 9, Parkinsonism

Ondo et al. [37] Controlled Blind 16, PD

U/S: ultrasound; CP: cerebral palsy; PD: Parkinson’s disease; ALS: amyotrophic

atrophy; SSPE: subacute sclerosing panencephalitis.

individual dose is not known and may be very low in some

patients, particularly in patients suffering from ALS, who

may be unusually sensitive to botulinum toxin. The risk can

be minimized by cautiously increasing the dose and the

number of glands treated in subsequent cycle. The positive

results of the open-labeled studies are supported by those of

small, placebo-controlled trials; further larger scale con-

trolled studies would add significantly to the literature.

3. Primary focal hyperhidrosis

Hyperhidrosis refers to excessive sweating and may be

focal or generalized. Focal hyperhidrosis usually affects

palms or soles of the feet (60%), axillae (40%) and the face

(10%) [42]. Rarely, other areas are involved. The majority

of hyperhidrosis studies have been published in dermato-

logic journals, and it is possible that this indication is not

widely recognized in the neurology community. Further-

more, patients with hyperhidrosis may seek treatment from

their general practitioners or dermatologists instead of

neurologists. Focal hyperhidrosis is most often essential or

idiopathic. A positive family history is present in 30–50%

of cases suggesting a genetic component [43]. However, the

scant literature available on the etiology of primary focal

hyperhidrosis suggests that it may be caused by neurogenic

overactivity of the sweat glands in the affected area [44].

Ross syndrome is a rare form of focal hyperhidrosis of

unknown etiology, characterized by progressive anhidrosis

due to degeneration of sudomotor fibers, associated with

compensatory hyperhidrosis in areas in which sudomotor

fibers remain intact [45].

For patients with mild hyperhidrosis, topical antiper-

spirants containing aluminum chloride hexahydrate may be

effective [46]. Anticholinergic agents, such as glycopyrro-

Region Dose per side (U) Duration (months)

nerative, stroke Parotid, SM 50–65 (total) 3

Parotid 5 2

Parotid 7.5–15 2 (approximately)

Parotid 6–20 >3

encephalopathy Parotid, SM 15–40 4–7

Parotid, SM 20–40 N/A

SM 20–25 Up to 6

Parotid 15 2–6

Parotid, SM 450–500 (total) 1

Parotid 18.75–75 3

Parotid 1000 3.5

Parotid, SM 250–1000 >1

lateral sclerosis; CBD: corticobasal degeneration; MSA: multiple system

Fig. 2. Axillary hyperhidrosis before (A) and 2 weeks after (B) botulinum

toxin type A injection in the right axilla.

R. Bhidayasiri, D.D. Truong / Journal of the Neurological Sciences 235 (2005) 1–94

nium bromide or propantheline bromide or beta blockers

can be effective, although their side effects limit the use.

Iontophoresis, or the introduction of an ionized substance

through the skin using direct current, may be effective for

some cases of plantar and palmar hyperhidrosis, but is

less useful in the axillary regions. In addition, it is a time-

consuming procedure in which the hands are soaked in

tap water with an electric current for up to 30 min.

Transthoracic endoscopic sympathectomy can be consid-

ered in severe cases of palmar hyperhidrosis [44] but

wound infection, hemorrhage, pneumothorax, Horner’s

syndrome, brachial plexus injuries, post-sympathetic neu-

ralgia, gustatory sweating and phrenic nerve damage are

among the possible complications. Intradermal injection of

BTX-A has recently been shown to be effective in

patients with gustatory sweating (Frey’s syndrome),

axillary sweating, palmoplantar sweating, or compensatory

sweating [47–49].

The development of botulinum toxin as a treatment of

hyperhidrosis came from the initial observation of hypo- or

anhidrosis in patients with botulism. Although the mech-

anism of action of botulinum toxin in focal hyperhidrosis is

unknown, it is probably different from that in dystonic

disorders. Swartling et al. [50] demonstrated that the sweat

glands were structurally normal before the botulinum toxin

therapy but that the lumen diminished after subsequent

injections, suggesting the mechanism of denervation. In

addition to several small controlled studies, the benefits of

BTX-A on patient quality of life and objective sweating in

primary axillary and palmar hyperhidrosis have been

documented in large-scale, randomized, controlled trials

[47,48,51–64]. These studies mainly involved patients with

moderate to severe hyperhidrosis. Results showed that up

to 94% of patients in the BTX-A group were responders, in

contrast to 36% of patients in the placebo group [51].

Ninety-eight percent of patients with axillary hyperhidrosis

in one multicenter study said that they would recommend

this therapy to others [62]. The duration of action of

botulinum toxin varied between 4 and 12 months with a

mean duration of 7 months after a single treatment session

(Figs. 1 and 2). Frontal hyperhidrosis also responded well

Fig. 1. Palmar hyperhidrosis before (A) and 2 weeks after (B

to the treatment with BTX-A with a reduction in sweating

of 75% for a period of at least 5 months [65]. Long-term

effects were reported, especially in gustatory sweating, and

satisfaction with treatment remained consistently high with

no diminution of effect with repeated treatments [66].

Twenty-eight percent of patients did not require more than

one injection, indicating a long-lasting benefit of more than

16 months in a substantial proportion of patients. The

adverse event that was different between the BTX-A and

placebo groups was infection, which surprisingly had a

higher incidence in the placebo group [51]. Other side

effects, which were minimal, included painful injections

and small local hematomas. Although several studies have

reported beneficial effects of BTX-B in the treatment of

hyperhidrosis, systemic side effects such as visual accom-

modation difficulties and dry mouth, as well as pain at the

injection site, limit its widespread use [40,67–69]. Table 3

provides detailed information from the literature on the

sites of injection, the doses used and the duration of action

after injections of BTX-A for both axillary and palmar

hyperhidrosis.

Overall, the efficacy and safety of BTX-A is established

in the treatment of primary, focal hyperhidrosis based on the

published controlled and open trials, as well as the

regulatory approval of at least one of the type A products

) botulinum toxin type A injection in the right hand.

Table 3

Selection of controlled and large open studies of botulinum toxin injection of focal axillary or palmar hyperhidrosis (n >20)

Authors Design Number (n) Region Dose per

side (U)

Duration

(months)

Botox\

Naver et al. [60] Open 55 Axilla 32–100 3–14

Naver et al. [60] Open 94 Palmar 120–220 3–14

Naumann and Lowe [51] Controlled 320 Axilla 50 >4

Naumann et al. [106] Follow-up,

Open

207 Axilla 50 7

Wollina et al. [107] Open 47 Axilla 200 >19

Naumann et al. [49] Open 45 Gustatory 21 >6

Laccourreye et al. [66] Open 33 Gustatory 25–175 12–36

Dysport\

Heckmann et al. [62] Controlled 145 Axilla 100–200 >6

R. Bhidayasiri, D.D. Truong / Journal of the Neurological Sciences 235 (2005) 1–9 5

for this indication in Canada, Australia, United Kingdom,

United States and a number of other countries.

4. Conditions of pathological pain

The effect of pain relief with the use of botulinum toxin

was originally observed in the treatment of hyperfunctional

facial lines in which Binder et al. [70] noted a correlation

between pericranial BTX-A injections and alleviation of

migraine headache symptoms. In addition, total relief of

pain was reported in 76% of patients in the cervical

dystonia study accompanying the improvement in motor

function [71]. Since then, the use of BTX-A has been

increasingly reported in many conditions of pathological

pain, including migraine and other headache disorders

[72,73], musculoskeletal pain, such as myofascial pain,

low back pain and other chronic pain syndromes [74–76].

These conditions represent a diverse group and the results

with BTX-A have not been universally positive. Never-

theless, many studies, including some controlled trials

[72,77], have reported benefits of this treatment on pain.

Indeed, the effects of botulinum neurotoxins on pain relief

can equal or outweigh the motor benefits in patients with

dystonia [78–82].

Although inhibition of neuromuscular activity may

alleviate pain associated with headache disorders, it does

not fully explain the pain-relief mechanism mediated by

botulinum toxin. Recent evidence suggested that the toxin

may interact with several other neuronal-signaling path-

ways, for example, blockade of substance P, glutamate and

calcitonin gene-related peptide resulting in analgesic effect

[13,83]. BTX-A has also been demonstrated to block

intrafusal fibers in the sensory feedback loop resulting in

decreased activation of muscle spindles [84]. This effec-

tively alters the sensory afferent system by reducing the

traffic along Ia spindle afferent fibers. A reduction in

afferent sensory activity coming from peripheral and cranial

muscles, and inhibition of peripheral and central trigeminal

sensitization may be the potential mechanisms by which

botulinum toxin exerts its therapeutic effect in different

headache syndromes.

4.1. Headache disorders

Primary headache disorders represent a heterogeneous

group of conditions, and the use of botulinum toxin as a

preventive headache treatment is increasing but remains

controversial [85,86]. The most important question is the

evidence of its efficacy in headache prevention. Furthermore,

the data often cannot differentiate a genuine treatment effect

from a placebo response, further confounded by the lack of

good control treatments, short follow-up, injection techni-

ques (fixed site approach vs. follow-the-pain approach) and

small number of patients. Apart from one study [87], all the

studies in tension-type headache did not show evidence for

an efficacy of botulinum toxin in reduction of headache

frequency [88–95]. Furthermore, no statistical comparison

was performed in the study that reported a significant

reduction of headache days in the treatment group but not

in the placebo group [87]. Currently, there are several large-

scale randomized placebo-controlled clinical trials in pro-

gress evaluating the efficacy, optimal dosing, and side effect

profile in migraine and other types of headache.

Although most of open studies on migraine prophylaxis

with botulinum toxin showed positive results, the data from

randomized, double-blind, placebo-controlled studies have

been conflicting and difficult to interpret [72,96–102].

While three studies did not show any significant reduction

of migraine frequency by botulinum toxin, one study

showed a significant reduction of pain intensity by

botulinum toxin [72,96,97,103]. Silberstein et al. reported

that the low-dose (25 U) group of botulinum toxin was

superior to placebo in reducing migraine attacks after 3

months [72]. However, the higher dose (75 U) did not result

in a significant improvement of migraine.

One recent retrospective study examined the effects of

botulinum toxin type A on various different types of

headache disorders [104]. In this study, patients were injected

into either fixed sites or the sites of pain and outcomes were

R. Bhidayasiri, D.D. Truong / Journal of the Neurological Sciences 235 (2005) 1–96

measured as the number of headache days per month,

headache intensity (0–3 scale), or both. Of the 271 patients

in this study series, 29 had episodic migraine, 17 had episodic

tension-type headache, 71 had mixed headache and 154 had

chronic daily headache. BTX-A treatment significantly re-

duced the number of headache days per month from appro-

ximately 19 to 8. BTX-A injections also decreased headache

intensity from amean of 2.4 points to 1.8 points. Both of these

differences were statistically significant. Of 263 patients

surveyed, 225 (85.6%) reported improvement in headache

frequency and intensity. The effectiveness of injections was

not related to the reason for treatment or injection technique,

or a variety of other variables. These results suggested that the

outcome of botulinum neurotoxin therapy was quite good for

the treatment of a variety of different headache disorders and

injection procedures. However, the reason that some patients

failed to respond and some studies failed to detect benefits of

botulinum toxin injections remains unknown [91]. Given the

large placebo effect noted in many headache studies,

psychological variables may play a role.

4.2. Musculoskeletal pain

An example of one study that examined the effects of

BTX-A on pain is a report of 31 consecutive patients with

chronic low back pain who were randomly assigned to active

treatment or placebo control [77]. Pain was measured on a

visual analog scale and disability was assessed using the

Oswestry Low Back Pain Questionnaire (OLBPQ). Results

showed that 73% of patients treated with BTX-A reported

more than 50% improvement in pain, in contrast to 25% in

the placebo group at 3 weeks post-injection. Improvements

on the OLBPQ were observed in 67% of patients treated with

BTX-A in contrast to 19% of those treated with placebo.

Both of these effects were statistically significant. No side

effects were reported by patients in this study.

In the treatment of musculoskeletal pain, BTX-A is

typically used as part of a multimodal therapeutic program

[74]. It has been suggested that botulinum neurotoxin

therapy may improve pain by reducing muscle tone and

overactivity, perhaps enabling greater benefit from physical

therapy designed to restore normal muscle length and

biomechanical balance [74]. Given this conception of the

role of botulinum neurotoxins in musculoskeletal pain,

studies that include a multimodal regimen may be more

likely to find positive results with botulinum toxin therapy.

Thus, one of the challenges of future research is to design

studies that would test this and other hypotheses in order to

determine the appropriate patients and conditions under

which botulinum toxin helps alleviate pain.

5. Conclusion

The disorders discussed here for which botulinum

neurotoxin therapies are emerging represent only a portion

of the novel applications of these treatments that have been

reported in the literature. BTX-A has been found to improve

sialorrhea, hyperhidrosis and pain with few side effects.

Although BTX-B has been less studied due to its more

recent introduction into clinical use, it also appears

promising for many of these disorders. Ultimately, these

compounds are useful because they inhibit acetylcholine

release following local injections, a property that may be

capitalized upon in the treatment of many different focal

disorders in which reduced cholinergic tone is desired. This

basic property sets the stage for additional novel uses in the

future.

Acknowledgments

Roongroj Bhidayasiri, MD, MRCP(UK) is supported by

Lilian Schorr Postdoctoral Fellowship of Parkinson’s Dis-

ease Foundation (PDF) and Parkinson’s Disease Research,

Education and Clinical Center (PADRECC) of West Los

Angeles Veterans Affairs Medical Center.

Daniel D. Truong, MD, is supported by the Parkinson’s

and Movement Disorder Foundation and the Long Beach

Memorial Foundation.

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