Myofascial Pain with Referral from the Anterior Digastric Muscle Mimicking
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OROFACIAL PAIN Myofascial pain with referral from the anterior digastric muscle mimicking a toothache in the mandibular anterior teeth: a case report Mythili Kalladka, BDS, MSD/Muralidhar Thondebhavi, MD, CCT, MBA/Sowmya Ananthan, BDS, DMD, MSD/ Gautam Kalladka, BDS, MDS/Junad Khan, BDS, MPH, MSD, PhD Background: Non-odontogenic toothaches often present as a Amitriptyline 10 mg once daily was prescribed for 1 month. In diagnostic dilemma to clinicians. Myofascial pain with referral addition, she was advised home care instructions to control from the trigger points in the masticatory muscles are one of the predisposing, perpetuating, and precipitating factors, and given common causes of non-odontogenic toothaches. However, there home care exercises, a hard joint stabilization splint, physiother- are limited reports of myofascial pain from the anterior digastric apy, and postural re-education. Conclusion: Non- odontogenic muscle referring pain to the mandibular anterior teeth and mim- toothaches may be multifactorial. The case presented empha- icking odontogenic pain. Case presentation: A case of non- sizes the importance of a comprehensive evaluation to differen- odontogenic toothache in the mandibular anterior teeth due tiate odontogenic pain from non-odontogenic pain. Irreversible to myofascial pain with referral from trigger points in the anterior dental procedures should be instituted after an accurate diagno- digastric muscle is presented. The patient had significant relief sis and multidisciplinary management may be required in com- with a trigger point injection of the anterior digastric muscle. plex cases. (Quintessence Int 2020;51: 56–62; doi: 10.3290/j.qi.a43615) Key words: anterior digastric muscle, myofascial pain, pain, temporomandibular disorder, trigger point Non-odontogenic toothaches often present as a diagnostic palpated when using the myofascial examination protocol. challenge to clinicians. The clinical picture is confusing and the Spreading pain may also be present.”2 Referred pain from a diagnosis is often elusive. Multiple dental procedures are often myofascial trigger point is defined as “pain arising from a attempted, presuming the pain to be odontogenic in nature. trigger point, but felt at a distance often remote from the Myogenous temporomandibular disorders (TMD) com- source.”3 The trigger points in different muscles have docu- prise a significant proportion of the cases of non-odontogenic mented reproducible patterns of referral; primarily related toothache,1 although the exact epidemiologic data are not to their site of origin.3 The pattern of referred pain from trig- available. The diagnostic criteria for TMD (DC/TMD) for clinical ger points is often distant from the site of the trigger point and research applications broadly classifies myogenous TMD and may not entirely coincide with the peripheral nerve dis- into local myalgia, myofascial pain, and myofascial pain with tribution or dermatomal segment.3 A trigger point is defined referral.2 The DC/TMD criteria describes myofascial pain with as a “hyperirritable spot in a skeletal muscle that is associated referral as “pain of muscle origin that is affected by jaw move- with a hypersensitive palpable nodule in a taut band.”2-4 The ment, function or parafunction and replication of this pain oc- patient’s complaints of pain are replicated when the muscle is curs with provocation testing of the masticatory muscles and examined using the examination protocol by DC/TMD cri- with referral of pain beyond boundary of the muscle being teria with pain referral beyond the muscle being tested. 56 QUINTESSENCE INTERNATIONAL | volume 51 • number 1 • January 2020 Kalladka et al Myofascial pain with referral is confirmed by the presence of medications were administered for a period of 3 weeks. The trigger points, pain referral to distant sites characteristic for patient did not report any side effects at the dose administered. each muscle, twitch response at the site, and reproduction of The medications did not have any effect on the pain. the patient’s pain complaint. It may also be accompanied The patient was advised to have a removable partial den- by motor dysfunction and autonomic symptoms.2-5 In many ture in the area of the missing mandibular anterior teeth. instances the pain may be referred to the maxillary and/or During the course of the dental treatment, the patient devel- mandibular teeth. The characteristic referral patterns of the var- oped tenderness in her jaw and was referred to an oral surgeon. ious masticatory and accessory muscles have been described in A soft night guard was fabricated. She had a mild reduction in detail by Simons et al.3 pain with the soft night guard. She was then referred to a pain Presented is a case of non-odontogenic toothache in the physician who in turn referred her to the Orofacial Pain Center. mandibular anterior teeth due to myofascial pain with referrals Investigations ordered by previous dental practitioners and from trigger point in the anterior digastric muscle, and the physicians included an panoramic radiograph, full-mouth management is described. radiographs, temporomandibular joint (TMJ) tomograms, com- puted tomography (CT) of the brain and face, magnetic reso- nance imaging (MRI) of the brain, complete blood count (CBC), Case presentation thyroid profile, and peripheral smear, all of which were within A 43-year-old woman presented to the Orofacial Pain Center normal limits. The CT scan showed a deviated nasal septum to with the chief complaint of pain in the mandible and mandibu- the left with bilateral inferior turbinate hypertrophy. The pan- lar teeth. oramic radiograph and full-mouth radiographs were negative Six months previously, following an episode of intense for dental pathology. yawning, the patient reported that she felt a “stretching sen- At the time of her presentation, the pain was severe (VAS sation” in her jaw and developed pain and sensitivity in the 80 mm). In the region of the mandibular anterior teeth, the mandibular anterior teeth. She consulted a general dental pain was sharp and continuous, with no known aggravating or practitioner and was prescribed multiple brands of desensi- relieving factors. The patient did not notice the pain during tizing toothpastes and medicaments, assuming her com- sleep. However, the patient reported disturbed sleep with diffi- plaints were related to dentinal hypersensitivity. At the time culty initiating and maintaining sleep. The patient had gastritis of onset of symptoms, the patient described the pain in the and a history of right sided Bell palsy a few months prior to the alveolar process of the mandibular anterior teeth as being onset of the symptoms of facial pain. She was prescribed pred- continuous, dull aching (20 mm on a visual analog scale nisolone and physiotherapy for the Bell palsy. Her medical and [VAS]) and the pain in the mandibular anterior teeth as similar family history was otherwise noncontributory. The patient’s job to a tooth being sensitive. was active and involved regular bending. The patient also Subsequently, she was referred to an endodontist who per- reported mouth breathing. Extraoral examination revealed a formed root canal treatments (RCTs) of the mandibular right moderately built and nourished, conscious, cooperative patient and left central and lateral incisors, presuming the complaints who was well-oriented with the surroundings. She had mild had an endodontic origin. She was prescribed multiple broad deficits on the right side of the face (weakness of the facial and narrow spectrum antibiotics, assuming an odontogenic muscles) due to Bell palsy. infection. The medications and RCTs failed to provide relief and TMJ and musculoskeletal evaluation revealed a range of the pain persisted. Hence, the RCTs were repeated and finally movement that was within normal limits. She had mild tender- the patient was advised to undergo extraction of the mandib- ness on the lateral and posterior pole of the right TMJ. Muscle ular right and left central and lateral incisors and both mandib- palpation revealed severe tenderness and trigger points in the ular canines 4 months after the pain complaints started. This right superficial masseter, sternocleidomastoid muscle (SCM), resulted in an aggravation and change in the quality of pain and anterior digastric muscle. Palpation of the trigger points in (from mild, continuous, dull aching pain to severe, continuous, the right anterior digastric reproduced the patient’s com- sharp pain [VAS 70 mm]). plaints. Intraoral examination revealed an edentulous area in The patient was then prescribed a trial of carbamazepine the region of the mandibular right and left central incisors, lat- 300 mg once daily, pregabalin 75 mg once daily, and vitamin eral incisors, and canines. A bony spicule was present in the B12, presuming the condition to be trigeminal neuralgia. The region of the extraction site of the mandibular right canines. QUINTESSENCE INTERNATIONAL | volume 51 • number 1 • January 2020 57 OROFACIAL PAIN GE Subcutaneous tissue Digastric Anterior Belly Digastric Anterior Belly 1 2 1 3 cm 2 Fig 1 The digastric muscle on ultrasound. Fig 2 Digastric trigger point injection. On palpation of the bony spicule, the patient reported mild tion using a Luer-Lok syringe was slowly deposited in the anter- tenderness, but it did not reproduce the patient’s chief com- ior belly of the digastric muscle with a gentle needling motion plaint. A full-mouth radiograph taken 1 month previously was to break up the trigger point (Fig 2). The patient had complete negative for dental pathology. Topical local anesthetic spray relief of pain for 1 day (VAS 0 mm) and partial relief for 1 week was used and an infiltration of 1 mL of 2% lignocaine without (VAS reduced from 80 mm to 30 mm). She was followed up epinephrine local anesthetic injection bilaterally in the region with home care instructions on controlling predisposing, per- of the mandibular anterior teeth did not resolve the pain. The petuating, and precipitating factors, home care exercises, hard clinical examination, radiographs, and local anesthesia tests joint stabilization splint, amitriptyline 10 mg once daily for ruled out odontogenic sources of pain.