Tactile and Pain Thresholds in Patients with Myofascial Pain of the Jaw Muscles: A Case-Control Study

Aims: To compare the tactile detection threshold, the filament-prick pain detection threshold, the pressure pain threshold, and the pressure pain tolerance detection threshold at multiple measuring points in the orofacial region and at the thenar muscle of symptom-free subjects and patients with myofascial pain of the masticatory muscles. Methods: Twenty patients (age range: 25 to 55 years) and 20 healthy subjects (age range: 25 to 55 years) were recruited. The tactile detection threshold and the filament prick-pain detection threshold were measured at the cheek skin overlying the central part of the left and right masseter muscles, at the right thenar muscle and at the tip of the tongue, using Semmes-Weinstein monofilaments. The pressure pain threshold and the pressure pain tolerance threshold were measured at the central part of the masseter muscle and on the thenar muscle, using a pressure algometer. The intensity of pain perceived during the assessment of filament prick-pain detection threshold, pressure pain threshold, and the pressure pain tolerance threshold was scored on visual analog scales. Results: The tongue tip had the lowest filament prick-pain detection thresholds as compared to the other sites. Filament prick-pain detection thresholds of the tongue and thumb sites were significantly lower in myofascial pain patients than in controls. Pressure pain thresholds of the masseter and thenar muscles were significantly lower in patients with myofascial pain than in control subjects whereas pressure pain tolerance thresholds did not differ significantly between patients and controls. Conclusions: The findings of the present study show topographic variations in the pain responses to different stimulus modalities. Different pain responses were also found between patients with myofascial pain and control subjects and were interpreted to support theories of centrally mediated pain for temporomandibular disorders. Keywords: jaw muscles, pain thresholds, temporomandibular disorders, trigeminal sensory testing, Von Frey hairs