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CT-GUIDED INJECTIONS OF BOTULINUM TOXIN TYPE A IN THE TREATMENT OF MYOFASCIAL AND PSEUDORADICULAR PAIN

Matthias A.Lutze

Arzt für Neurochirurgie

Interdisziplinäre Praxisgemeinschaft

Schlüterstr. 38 D-10629 Berlin

Bundesrepublik Deutschland

Introduction:

Though the chronic musculoskeletal pain is still controversial as  a clinical entity (2), image-guided chemical or mechanical denervation of the zygapophyseal joints (pseudoradicular ‚facet syndrome‘) and various ‚trigger-point‘ infiltration techniques (myofascial pain syndrome,MPS), have been part of standard pain therapy for decades. On the other hand, the two clinical presentations are often not treated satisfactorily. It has been hypothesized that a long-acting muscle relaxant like botulinum toxin (BTX) might offer an advantage over invasive and conservative treatments because its remarkable effect is reduction of muscle spasm  a n d  - sometimes even to a greater extent -  pain (1, 4, 5).

Aim of investigation:

The present prospective study aims at determining whether CT-guided (3) intramuscular injections of botulinum toxin type A (BTX-A) enable safe and efficient relief from myofascial and spinal pseudoradicular pain.

Methods:

BTX-A is a neurotoxin that blocks the release of acetylcholine from presynaptic cholinergic nerve endings. The paralyzing effect typically lasts for 3 to 4 months after the injection.

Following a successfull diagnostic block of the affected muscle with anesthetic agents written informed consent has to be obtained from the candidates before treatment.

The target parameters are stereotactically determined and coaxial needles (22-G)  are advanced under local anesthesia and CT-monitoring. CT-visualization during  outpatient injection procedure permits the quick placement of the 22-G-needle tip precisely in the center of the involved muscle belly by avoiding the risk of intravascular, intrapleural or perineural application. Correct instrument positioning is checked by applying contrast medium (Fig. 1, 2). The patient is carefully monitored for severe inconveniences including injection induced pain and adverse reactions.

Material:

A total of 21 patients (age range: 31-83 years, mean age: 48; 10 female, 11 male)  were studied from Aug. 1999 to Sept. 2000. All patients received a total of  35 injections into affected muscle groups, e.g. longissimus thoracis and iliocostalis lumborum muscles, piriformis muscle, iliopsoas muscle, quadratus lumborum muscle, trapezius, splenius capitis and levator scapulae muscle. The standard trigger point dose was BTX-A (BOTOXâ, Merz) 50-100 U in 2 mL pysiological saline with 4 mL 0.5% bupivacaine per site, maximum 3 sites.

Patient selection criteria included:

·         Regional pain reference zones

·         Single or multiple trigger points in tight muscle-bands

·         Local twitch in response to pressure

·         Positive surface EMG study

·         Therapy resistant pain syndrome including conservative and physical treatment

·         Relief of pain and improvement of mobility by means of local anesthetic blocks.

Exclusion criteria included:

·         Progressing neurological deficits involving the painful area

·         Widespread and diffuse pain distribution

·         Possible causal surgical/medical therapy

·         Pregnancy, litigation, psychogenic aggravation

·         Other drugs, that interfere with neuromuscular transmission

Patient diagnosis:                                                  n (patients)

·         Cervicogenic headache:                                           2

·         MPS+ Cervical herniated disc:                                        4

·         MPS+ Cervical failed surgery (laminectomy, fusion):            1

·         MPS+ Failed back surgery syndrom:                          4

·         Low back pain with facet syndrome:                              6                           

·         Priformis syndrome:                                                4

Duration of pain:                                                         n (patients)

·         Less than 1 year:                                                       4

·         1 – 2 years:                                                        9

·         2-3 years:                                                             6

·         Greater than 3 years:                                                  2

Intervention per treatment:                                         n (patients)

·         1  intervention:                                                                            15

·         2  interventions:                                                                         4 (one site)

·         3  or more interventions:                                                                 2 (diff.sites)

Number of injections ( n ), dose ( u per site ) and total amount  ( tu per intervention ) in specific muscles:

·         Longissimus thoracis:           1 (100 u, 200 tu)        4 (50 u,100 tu)

·         Iliocostalis lumborum:          5 (100 u, 200 tu)         2 (50 u,100 tu)

·         Piriformis:                               1 (100 u, 100 tu)         3 (50 u, 50 tu)                  

·         Iliopsoas:                                 4 (100 u, 100 tu)                        

·         Quadratus lumborum:          1 (100 u, 100 tu)                        

·         Trapezius:                               2 (100 u, 200 tu)     4 (50 u,100 tu)               

·         Splenius capitis:                        8 ( 50 u, 100 tu)                        

Postinterventional physiotherapy program includes  early passive stretching regimen and a subsequent active exercise period. The aim is trunk stabilization (lumbosacral region)  and regaining symmetrical balance of the agonist/antagonist muscles (cervical region) by elongating and strengthening these muscle groups.

Results:

Clinical follow-up after 1, 2, 4 and 6  months post-treatment revealed lasting and marked (> 70% improvement at visual analogue scale, VAS) pain relief and improved range of motion in 72% of the patients. Twelve of the 21 patients underwent pre- and post-procedure surface EMG in order to evaluate and quantify muscular dysbalances of the involved muscle groups. In 9 patients the pathology was gone or had changed significantly.The quality of life was subjectively assessed as ‚good‘ to ‚excellent‘ by 67% of all patients on the basis of a multimodal (61 items) modified ‚measurement of patient outcome scale‘ (MOPO) before and 6 months after the intervention. Twelve months outcome data will be utilized for planning a randomised control trial. No severe side effects were noted. Two patients in the piriformis group reported a moderate local pressure feeling at the site of injection for 5 hours, and one patient in the trapezius group complained of transient weakness of the neck muscles which in the sequel increased the cervicogenic headache for two weeks. Of those patients who reported no or poor response, 65% failed to complete their schedule of physical therapy. There were no complications, such as nerve injuries, hematoma or infections. 

EXAM – score (VAS, EMG,MOPO) at 3 and 6 months after BTX-A injection in 21 patients

Discussion:

BTX-A has been used successfully in a variety of  neurological diseases, it is now considered a safe and effective treatment in many conditions associated with increased muscle contraction (1, 5). The difficulty lies in selecting the appropriate candidate, i.e. finding the patient with painful muscle dysfunctions as the primary source of pain. Successfull trial of anesthetic/corticoide agents could be recommended prior to BTX-A application.

Furthermore, few information is available at present how to calculate the dose range per muscle and number of target muscles to be treating simultaneously. We  have obtained few satisfactory responses using less than 100 U BTX-A or less than 2 ml dilute solution in large paraspinal muscle bellies.

If pain is secondary to sustained muscle contraction, directly or indirectly, lasting relaxation of affected muscle groups is the aim of the multidisciplinary approach. Postinterventional physical therapy, exercise, and posture correction (education) is therefore the key in reducing cervigogenic headache, cervicalgia, low back pain and joint dysfunctions (4).

Computerized tomography visualization  may be superior to other injection guidance measures like electromyography, electrical stimulation or ultrasound because it allows a comfortable and quick access to otherwise inaccessible muscles (3, 4).

Conclusions:

With strict indicational criteria, CT-assisted injection of BTX-A enables highly selective and safe reduction of refractory myofascial pain with considerable cost savings regarding medication and conventional infiltration treatment. Preliminary clinical results have been promising thus far. Prospective controlled studies are planned to further evaluate its effect with greater amounts of applied solution fluid and in combination with injected triamcinolone. CT- guidance allows a anatomy-directed and pathology-targeted access.

Fig.1. CT-radiographs of splenius capitis and trapezius injection on the right side

A Axial CT showing stereotactic determination of the target muscles

B Location of the coaxial needles after applying contrast agent. The right needle was slightly withdrawn

 for optimal injection into the center of the trapezius muscle.

Fig. 2. CT radiographs of iliopsoas and piriformis injection on the right side in one patient

A Sagittal CT for planning the appropriate injection level

B Axial CT showing measurement for exact needle guidance

C Axial CT showing correct needle placement in the right iliopsoas at L 4 level

D Needle in place in piriformis

References:

1.       Cheshire WP, Abashian SW, Mann JD: Botulinum toxin in the treatment of myofascial pain syndrome. Pain 1994; 59: 65 - 69

2.       Childers M, Wilson D, Galate J et al: Treatment of painful muscle syndromes with botulinum toxin: A review. J Back Musculoskel Rehabil 1998;10: 89 – 96

3.       Lutze,M., Stendel,R., Vesper,J., Brock,M.: Periradicular Therapy in Lumbar Radicular Syndromes: Methodology and Results.  Acta Neurochir (Wien) (1997) 139: 719-724

4.       Porta M, Perretti A, Gamba M et al: The rationale and results of treating muscle spasm and myofascial syndromes with botulinum toxin type A. Pain Digest 1998; 8: 346 – 352

5.       Racz GB: Botulinum toxin as a new approach for refractory pain syndromes. Pain Digest 1998; 8: 353 – 356