Patients and methods

This was a retrospective study evaluating the outcome of the first treatment of BTX intramuscular injections in consecutive patients suffering from chronic myofascial pain treated at our department during a 2-year period (from February 2014 to March 2016). The diagnosis was based on anamnestic and clinical evaluations and patients were categorized according to the DC/TMD guidelines and were divided into local myofascial pain and referring myofascial pain for analysis.

Clinically patients complained of pain in the perimandibular area that was often aggravated with jaw function, and was not associated with limited mouth opening. The pain was elicited with palpating the involved muscles, replicating the chief complaint. The diagnosis of local myofascial pain was given to patients when pain was localized to the site of palpation or the muscle palpated. Tender sites were palpated for approximately 5 seconds to ensure the pain did not refer to distant sites. A diagnosis of referring myofascial pain was given to patients experiencing pain spreading beyond the boundary of the muscle being palpated.

Patients to be treated with BTX at our department had to meet the following criteria:

• •

  Failure to achieve satisfactory response to previous conservative therapies consisting of rest, habitual modifications, self exercises, office-based physical therapy program, pharmacologic treatment (a benzodiazepine with or without a non-steroidal anti-inflammatory drug), and either a 3-month period of occlusal splint therapy or a 3-month trial with Tricyclic antidepressants.

• •

  Constant pattern of pain localization and characteristics in at least two different clinical examinations. Undefined pain patterns with poor localization were not candidates for BTX injections.

• •

  Absence of concomitant intra-articular temporomandibular joint disorders.

All conservative therapies were discontinued when the decision to undergo BTX injections was made, which was usually several weeks before the injection appointment. Botox (Allergan pharmaceuticals, Mayo, Ireland), which is a type-A BTX was used in all cases. An ampoule of 100 MU was diluted in 1 mL of normal saline. The injections were given on an individual basis into points of tenderness in painful muscles, and were individualized to each patient depending on the pain location and laterality. Only painful muscles were injected, and as close as possible to the tender points. Patients first identified the areas of pain by pointing with their fingers or hands; then the examiner palpated the tender spot and the surrounding areas, checking for additional tender points and possible referral points. The involved muscle was palpated during clenching and relaxation. BTX was injected directly into or as close as possible to the clinically identifiable tender points in the affected muscles, with two to four injections per tender muscle. In cases of myofascial pain with referral, no attempt was made to inject the distant sites to which the pain referred to, rather the injections were given to the muscle being palpated. The most common areas to which the pain referred to were the eyebrow, forehead, vertex, and occiput. All injections were performed by one surgeon (W.A.) and immediately after dilution of the toxin. Each injection point received 0.1 mL of solution containing 10 MU of BTX. A 23G 30-mm-long needle was used to inject the masseter, anterior portion of temporalis, sternocleidomastoid, and posterior digastric muscles. A 27G 15-mm-long needle was used to inject the middle and posterior areas of the temporalis muscle. A 27G 37-mm audio-amplified electromyographic (EMG) needle was used to inject the medial pterygoid muscle. The antero-inferior portion of the temporalis muscle was injected in two different depths: a superficial injection at the depth of the medial surface of the zygomatic arch, and a deep injection when the needle contacted bone at the outer surface of the lateral orbital wall ( Fig. 1 ). All injections were performed transcutaneously. Patients were asked to clench their teeth and open wide every 10 minutes in the few hours following the injections, as muscular activity facilitates more efficient incorporation of toxin into the endplates. Patients were allowed to use analgesics as required in the postoperative period. Muscle relaxants were not prescribed, and none of the patients underwent office-based physical therapy programme in the following months.

Coronal section illustrating the two different depths of injection into the antero-inferior portion of the temporalis muscle: 1, superficial injection point at the depth of the medial surface of the zygomatic arch; 2, deep injection point when the needle contacts bone at the outer surface of the lateral orbital wall.

Pain evaluations were conducted at each follow-up examination and documented in the medical records as a routine practice and not for the conduction of a clinical trial. For the purpose of this study the data was drawn from the medical records retrospectively and analysed. At each follow-up examination, patients were asked to evaluate the level of pain compared with pre-treatment on a four-level scale. The patients were asked whether there was a “Significant improvement” in pain levels, “Moderate improvement” in pain levels, “No improvement”, or “Worse” pain compared with baseline. The follow-up assessments conducted at 1 month, 2 months, and approximately 4 months postoperatively were used to evaluate response to treatment. This was considered the primary outcome variable. The secondary outcome variables were request to undergo additional BTX treatment after the effect has waned, and use of analgesics throughout the follow-up period.

Results

Twenty-five patients underwent BTX injections for the first time and attended at least two follow-up examinations at 1 and 2 months postoperatively and were included in the study. The mean age was 46.5 years (range 20–71), and 68% of the patients were female. Thirteen patients were diagnosed preoperatively as suffering from localized myofascial pain and 12 patients from myofascial pain with referral. The duration of pain ranged from 1.5 to 6 years, with an average of 4.1 years. There was no significant difference between the two groups with regard to age, gender, and duration of disease ( Table 1 ).

Patients received amounts ranging from 30 to 180 MU of BTX, injected into one to six muscles, uni- or bilaterally. The decision on the location and number of injection points depended on the pattern of each patient’s individual complaint. Fifteen of the 25 patients (60%) had bilateral complaints and received bilateral injections ( Table 1 ). The most commonly injected muscle was the masseter (injected in 22 patients, 88%), followed by the temporalis (19 patients, 76%), sternocleidomastoid (7 patients, 28%), posterior digastric (2 patients, 8%), and medial pterygoid (2 patients, 8%).

The primary outcome variable was the patients’ self-reported evaluation of pain reduction after treatment. At the 1-month follow-up evaluation, eight of the 13 patients (61.5%) with localized myofascial pain and four of the 12 patients (33.3%) with referring myofascial pain reported “Significant improvement” in pain levels. The difference was not statistically significant ( P = 0.237). At the 2-month follow-up examinations, nine patients (69.2%) with localized myofascial pain achieved “Significant improvement” whereas the proportion of “Significant improvement” in the referring myofascial pain group dropped to two (16.7%). This difference was statistically significant ( P = 0.015) ( Table 2 ). None of the patients reported worsening of symptoms after treatment. Many patients did not attend a third follow-up visit at approximately 4 months after the injections. Evaluations of only 10 of the 13 patients with localized myofascial pain and six of the 12 patients with referring myofascial pain were available; therefore as much as 36% of the study population was lost to follow-up at this time point. Of interest, all the patients previously achieving “Significant improvement” attended the 4-month follow-up examinations, whereas only few of those reporting “Moderate improvement” and “No improvement” did. A clear trend towards deterioration into baseline pain values was evident for both groups; six of the nine patients with localized myofascial pain previously reporting “Significant improvement” regressed to baseline pain values and reported the effects of the injections have waned, and similarly the two patients with referring myofascial pain previously reporting “Significant improvement” both reported to regress to baseline values at the 4-month evaluation. The average duration of BTX effects on pain was 3.21 months, with no significant difference between the two groups. Many patients reported waning of the analgesic effect over a few days.

The two secondary outcome variables were use of analgesic drugs and patient’s request for additional BTX injections ( Table 3 ). Patients were asked about use of analgesics at each visit, and if used the frequency, type, and dose. The majority of patients with localized myofascial pain (10 of 13) reported using less analgesic throughout the follow-up period, whereas only three of the 12 with referring myofascial pain reported so ( P = 0.017). At the 4-month visit, patients were asked about their willingness to undergo a second BTX treatment. Of the 10 patients with localized myofascial pain who continued to be followed up at this time, seven requested additional BTX treatment after reporting the effects of the injections had subsided. Of the six patients with referring myofascial pain attending the 4-month visit, three expressed willingness to undergo additional BTX treatment ( P = 0.51).

Table 3

Secondary outcome variables: using less analgesic and request for additional BTX injections.

	Using less analgesic			Request for additional BTX
	LMP	RMP	P	LMP	RMP	P
Yes	10/13 (77%)	3/12 (25%)	0.017	7/10 (70%)	3/6 (50%)	0.51
No	3/13 (23%)	9/12 (75%)		3/10 (30%)	3/6 (50%)
Total	13 (100%)	12 (100%)		10 (100%)	6 (100%)

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Temporomandibular joint disc perforation: a retrospective study
2. Is oestrogen associated with mandibular condylar resorption? A systematic review
3. Aesthetic and functional outcomes in patients with a nasal prosthesis
4. The application of a delayed expansion technique for horizontal alveolar ridge augmentation in dental implantation
5. Impact of highly active antiretroviral therapy on the prevalence of oral lesions in HIV-positive patients: a systematic review and meta-analysis
6. Pain-relieving effects of clonazepam and amitriptyline in burning mouth syndrome: a retrospective study

Stay updated, free dental videos. Join our Telegram channel

Join