Referred pain from the trochlear region in tension-type headache:: A myofascial trigger point from the superior oblique muscle

Background.-Tension-type headache (TTH) is a prototypical headache in which myofascial trigger points (MTrPs) can play an important role. To our knowledge, MTrPs in the muscle tissues of the trochlear region, ie, the superior oblique muscle (SOM), have not been previously mentioned, and a referred pain pattern from this region has never been reported. Objective.-To describe the referred pain from the trochlear area based on the examination of MTrPs in the SOM in patients with episodic and chronic TTH (CTTH). Design.-A blinded, controlled study. Methods.-The trochlear region was examined in 15 patients with CTTH, 15 patients with episodic TTH (ETTH), and 15 control subjects. Referred pain elicited by different maneuvers performed during manual palpation, ie, maintained pressure, active muscle contraction, and stretching of the muscle, was assessed with a visual analogue scale. Patients with ETTH were examined on days when they were headache-free, whereas CTTH patients were examined on days in which headache intensity was less than 4 points on a 10-cm horizontal visual analogue scale. Results.-Eighty-six percent of patients with CTTH and 60% with ETTH had referred pain that originated from MTrPs in the SOM, while only 27% of the controls reported referred pain. This pain was perceived as a deep ache located at the retro-orbital region, sometimes extending to the supra-orbital region or the homo-lateral forehead. Pain intensity was greater in CTTH patients than in ETTH patients or control subjects (P < .001). Conclusions.-MTrPs in the SOM may evoke a typical referred pain pattern in patients with TTH. The presence of a myofascial disorder in the trochlear region might contribute to the pathogenesis of TTH.