Characterization of stimulus response curves obtained with transcranial magnetic stimulation from bilateral anterior digastric muscles in healthy subjects

PURPOSE

The purpose of the study was to describe measurements of stimulus-response curves in the anterior digastric muscle (ADM) bilaterally following transcranial magnetic stimulation (TMS) to the right and left hemispheres. The first dorsal interosseous muscle (FDI) was the control muscle.

MATERIALS AND METHODS

The subjects were 20 healthy young adults. Test sessions determined motor thresholds (MT) and stimulus-response curves (1.0, 1.2, 1.4, 1.6 × MT) from either the FDI or ADM following TMS to left and right hemispheres using the double cone coil. Bilateral recordings of MEPs in the left and right ADM allowed us to generate stimulus response curves following ipsilateral and contralateral TMS.

RESULTS

Intraclass correlation coefficients (ICC) for MEP amplitudes from ipsilateral and contralateral ADMs were >0.60 at motor threshold (MT) and >0.90 at stimulus intensities above MT. There was a linear increase in MEP amplitudes across stimulus intensities for the FDI following contralateral TMS, while MEP amplitudes from the ADM following contralateral and ipsilateral TMS increased linearly across stimulus intensities [F_{(3, 57) [Muscle × Recording Site × Stim Intensity]} = 33.57; p < 0.05]; (ηp2 = 0.64). The slopes of the stimulus-response curve of the contralateral FDI was greater than the slopes of the stimulus response curves of the ipsilateral and contralateral ADM (p < 0.05).

CONCLUSIONS

The current study provided insights on the methodology for recording stimulus response curves in the ADM with TMS. These findings may translate into a valid, reliable, and relevant clinical outcome to study the pathophysiology of the corticobulbar motor system.

Myofascial pain with referral from the anterior digastric muscle mimicking a toothache in the mandibular anterior teeth: a case report

BACKGROUND

Non-odontogenic toothaches often present as a diagnostic dilemma to clinicians. Myofascial pain with referral from the trigger points in the masticatory muscles are one of the common causes of non-odontogenic toothaches. However, there are limited reports of myofascial pain from the anterior digastric muscle referring pain to the mandibular anterior teeth and mimicking odontogenic pain.

CASE PRESENTATION

A case of non-odontogenic toothache in the mandibular anterior teeth due to myofascial pain with referral from trigger points in the anterior digastric muscle is presented. The patient had significant relief with a trigger point injection of the anterior digastric muscle. Amitriptyline 10 mg once daily was prescribed for 1 month. In addition, she was advised home care instructions to control predisposing, perpetuating, and precipitating factors, and given home care exercises, a hard joint stabilization splint, physiotherapy, and postural re-education.

CONCLUSION

Non-odontogenic toothaches may be multifactorial. The case presented emphasizes the importance of a comprehensive evaluation to differentiate odontogenic pain from non-odontogenic pain. Irreversible dental procedures should be instituted after an accurate diagnosis and multidisciplinary management may be required in complex cases.