Porta Back Pain 2004

Prévia do material em texto

J Neurol (2004) 251 [Suppl 1] : I/15–I/18
DOI 10.1007/s00415-004-1105-9
Mauro Porta
G. Maggioni
Botulinum toxin (BoNT) and back pain
Introduction
The successful management of pain, particularly
chronic back pain due to muscular involvement, re-
quires a multi-disciplinary approach, concerning spe-
cialists from a variety of medical fields, with frequent
difficulties in reaching a consensus to treatment or, even
worse, diagnosis of conditions for which the pathophys-
iology and aetiology are often controversial. Also, the
confusion of the nomenclature used to describe, on the
other hand, the very common condition of sub-acute or
chronic back pain arising from the muscles of the lower
back can explain the present difficulties of diagnosis.
The terms fibrositis, fibromyalgia, tendon myopathy,
tension myalgia and myofascial pain syndrome are com-
monly used to describe these situations but do not rep-
resent the same pathophysiology [1].
There are a number of recent reports of the successful
use of botulinum toxin (BoNT) for the treatment of my-
ofascial pain and related disorders [2–5].Authors report
here their experience in treating chronic back pain due to
myofascial pain originating in muscles as piriformis,
ileopsoas or superficial muscles as paravertebral and
quadratus lomborum, using local injections of BoNT.
For this procedure, it is important to identify the
anatomy of the muscle involved and to separate the dif-
ferent forms of muscular disease. In particular fi-
bromyalgia concerns mainly females of 40–60 yrs, with
chronic, diffuse and widespread pain; usually there are
multiple tender points (bilateral, at muscle or tendon
insertions), and there is not response to local anaes-
thetic. The aetiology is suspected to be related to the
central nervous system or to be psychological, and the
prognosis is disappointing. On the contrary, myofascial
pain syndrome, usually, involves all adults with no dif-
ferences between male and female: pain is acute or
chronic, located in local or regional zones; there are sin-
gle or multiple trigger points in tight bands in the mus-
cle, and it is mediated by endorphin (and not by
substance P, as it is in fibromyalgia). The aetiology pro-
posed is related to acute or chronic muscles stress, or
(micro)trauma.
In case of myofascial pain syndrome there is a bene-
fit from local injections of anaesthetic and the progno-
sis in generally good.
JO
N
 1105
Mauro Porta, MD (�) · Giorgio Maggioni,
MD
Pain center
Neurology Department
Policlinico San Marco (Bergamo) 
and Istituto Ortopedico Galeazzi (Milano),
Italy
14 Via Legnano
20121 Milano, Italy
Tel.: +39-035/886298
Fax: +39-035/885789
E-Mail: prof.porta@inwind.it
■ Abstract Myofascial pain syn-
drome is defined as subacute or
chronic pain with sensory, motor
and autonomic symptoms referred
from active trigger points with as-
sociated painful dysfunctions. Au-
thors present the usefulness of bot-
ulinum toxin A or B (BoNT/A or
BoNT/B) injected into target mus-
cles since the toxin is capable of
controlling not only the muscular
spasm but mostly the pain by alter-
native mechanisms of action,
which are discussed. Posology of
BoNT, technical aspects and results
are presented. BoNT represents an
interesting and useful tool for an
adequate management of patients
with myofascial pain.
■ Key words back pain ·
myofascial pain syndrome ·
botulinum toxin · injection
technique
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Botulinum toxin and pain
Neurologists have been using BoNT for the treatment of
focal muscle overactivity due to dystonia for more than
15 yrs [6], and of spasticity for more than 10 yrs [7]. Al-
though this relief seemed most dramatic in patients in
whom pain arose from muscle spasm, often the reduc-
tion in pain rating was greater than the reduction in
muscle power. This remarkable effect led many clini-
cians and investigators to examine BoNT as a specific
treatment for pain management [8].
Several mechanisms, including both action on intra-
and extrafusal muscle fibres, have been postulated to ex-
plain pain relief following BoNT injection and subse-
quent inhibition of gamma motor endings in muscle
spindles [9]. Recently, a possible direct influence on no-
ciceptors function was discussed,but not found by using
temperature and current pain threshold measurements
[10,11].The BoNT,or its degradation products,may also
play a role in pain reduction at the spinal cord level [12].
Other influences of BoNT on pain generation may be
possible through inhibition of the release of neuromod-
ulators (i. e. substance P), or direct/indirect effects on
blood vessels [13, 14].
Lang, in an open-label study of the use of BoNT/A in
the treatment of myofascial pain, reported that 60 % of
patients experienced good to excellent results 22 to 60
days after injection. The whole muscle in a grid-like pat-
tern, instead of the areas of tenderness only, was infil-
trated [15].
Ferrante et al.completed a 12-week randomised,dou-
ble-blind, placebo-controlled study of 132 patients with
myofascial pain treated with BoNT/A or saline injec-
tions. No significant differences in outcome were seen in
the groups. Patients receiving BoNT/A were treated with
50 to 250 U of toxin total divided among five injection
sites [16].
In a single-blinded study, Porta evaluated the poten-
tial difference between lidocaine and methylpred-
nisolone injections compared with BoNT/A injections
in myofascial trigger points within the psoas, piriformis
or scalenus anterior muscle. Injections of 80 to 150 U of
toxin were used. Each group received benefit, but the pa-
tients treated with toxin experienced a greater duration
of relief [17].
Opida presented 31 patients with post traumatic neck
pain who were treated with BoNT/B injection in an open
label study. Seventy-one percent of patients reported
significant reduction in pain and headache frequency
and severity [18]. Taqi et al. showed, in two separated
open label studies, that BoNT (type A or B) may be ef-
fective in the treatment of myofascial pain [19].
Foster et al. in a randomised controlled study involv-
ing 31 patients with chronic low back pain, studied the
effect of 200 U of BoNT/A (5 sites in the paravertebral
levels L1 through L5 or S1; 40 U of BoNT/A per site)
compared with placebo injections. Pain and extent of
disability were reported at baseline, as well as at 3 and 8
weeks: at 3 weeks, patients who had received BoNT in-
jections (73.3 % or 60 %) experienced 50 % or more pain
relief compared to the placebo-treated group (25 % or
12.5 %); at 8 weeks, there was less disability in the BoNT-
treated group compared to the placebo-treated group
[20].
Childers observed that there is a trend toward greater
pain relief for patients after receiving BoNT as opposed
to placebo, at the completion of a randomised, con-
trolled, crossover study of 9 patients with piriformis
muscle syndrome who were treated with BoNT/A (100
U) and placebo. EMG and fluoroscopic guidance were
used for the injections [21].
Fannucci et al. reported that 26 of 30 patients with
piriformis muscle syndrome who were injected with
BoNT/A under computed tomography guidance ob-
tained relief of their symptoms within 5 to 7 days [22].
Injection technique
Injections of BoNT/A or BoNT/B in muscles can be per-
formed following several methods, in particular, using:
direct injection (by manual palpation), echo guidance,
EMG guidance, computerised tomography (CT) guid-
ance, or fluoroscopy. The direct injections can be per-
formed only in case of fibromyalgia because the muscles
involved are superficial, but are not usually successful.
Likewise, the use of the EMG guidance can be useful, but
only if the target points are easy to approach; the EMG
guidance (as the echo guidance) is often difficult to use
in deep muscles, but EMG permits the localisation of
motor endplates. Fluoroscopy technique is not anymore
used. The easiest injection guide to use in deep muscle
is the CT scan, which allowstargeting the right point for
injection.
The authors use a well-established protocol that re-
flects their own experience of BoNT as effective treat-
ment of myofascial pain if combined with a strictly con-
trolled rehabilitation program, based on stretching
exercises of the muscle injected. Patients have a prelim-
inary clinical examination, an haematological and bio-
chemical screening and computerised tomography (CT)
or magnetic resonance imaging to exclude herniated
disc problems. Abdominal echography is also, some-
times, performed to exclude space occupying lesions.
Electromyographic screening is not mandatory.
■ Technical notes for piriformis and ileopsoas injection
The patient should be positioned on the CT scan tray,
face down. Two 10-ml syringes are prepared, one con-
taining 6 ml 0.25 % bupivacaine,the other containing be-
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tween 80 and 150 U of BoNT (Botox®; in alternative up
to 500 U Dysport® or 7500 U Neurobloc®) reconstituted
in 2–4 ml of free preservative saline solution (depending
on muscle size).The muscle anatomy is confirmed by CT
scan (see Figs. 1 and 2).
A 21-gauge epidural needle or 20-gauge blunt-ended
Lütz needle is inserted perpendicularly a few centime-
tres and, then, the track and position of the needle are
again confirmed by CT. The needle is then inserted to a
depth of 5 to 7 cm until a characteristic loss of resistance
and “pop” are noted, and the position of the tip is con-
firmed again. The majority of the local anaesthetic is
first injected and, with the same needle still in place, the
BoNT is injected, followed by the remaining volume of
anaesthetic to flush the needle volume of residual BoNT,
avoiding loss of toxin units. Postinjection radiographs
demonstrates the swelling of the muscle and fluid accu-
mulation within the muscle itself.
■ Technical notes for paravertebral muscles 
and quadratus lomborum injection
In these case,authors perform the injections under EMG
guidance, or directly, by manual palpation: the patient is
sitting on the EMG studying bed, relaxed. An EMG-in-
jecting needle is used to study the time-to-time position
of the needle by the EMG traces reproduced on the
screen during activation, and, at the same time, to inject
BoNT. The 10-ml syringes, containing a total dose of
80–150 U Botox® (or equivalent Dysport® or Neu-
robloc® dosages) diluted in preservative saline solution,
are connected to the EMG-injecting needle before per-
forming the EMG examination in order to avoid bias
that can occur if the needle-syringe connection in made
later.
Discussion
Myofascial pain syndrome has been considered as a pos-
sible cause for lower back pain ever since Steindler de-
fined the “posterior division syndrome”in relation to ar-
eas of tenderness in deep ligament injuries or in
myofascitis in 1937 [23, 24].
So far, the exact nature of the aetiology of myofascial
pain syndrome has not been fully established, and Gunn
has reported a hypothesis based on musculoskeletal
pain produced by abnormal impulses generated by su-
persensitive executables membranes in nerves and mus-
cles where there is an impaired physiological nerve
function [25].According to Gunn, the neuropathic man-
ifestations accompanying such musculoskeletal pain are
related to abnormal neurogenic/myogenic impulses in-
duced by changes in the environment adjacent to the
nerve or muscle.The piriformis muscle is adjacent to the
sciatic nerve and the ileopsoas muscle to the lumbar
plexus: these nervous structures can be involved in the
case of muscle contractions abnormalities.
Pain relief in myofascial syndrome can be obtained
through different mechanisms using BoNT: reducing
muscle spasm, and intrafusal muscle spindle discharges
which conveys non-nociceptive sensations to the spinal
cord. In fact, it is believed that in chronic pain condi-
tions, persistence of pain is often due to sensitisation of
“wide dynamic range neurons” in the cord that, then,
may perceive the non-nociceptive input as nociceptive.
Impairment of sympathetic transmission, but also re-
duction of the inhibitory effect of Renshaw cells on the
Ia inhibitory interneurons, the indirect effect on spinal
cord neurons and an analgesic effect of BoNT metabo-
lites, have to be considered.
Fig. 1 CT radiograph of ileopsoas muscle injection: after location of the injection
site, the needle is placed in the muscle; in this case the needle was withdrawn
slightly to inject optimally in the centre of the muscle
Fig. 2 CT radiograph of piriformis muscle injection: view of the lower pelvis; nee-
dle is placed in the muscle
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Conclusions
The authors believe from their experience in the useful-
ness and in the efficacy of BoNT injections in muscles
which present a myofascial syndromes causing pain,
mostly if a subsequent rehabilitation program is estab-
lished. The procedure is safe; contraindications are few,
and even the pharmacoeconomy is profitable if com-
pared to longer and more expensive alternative treat-
ments.
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