The fan-shaped temporalis muscles located over your temples on either side of your head are two of several muscles involved in jaw movement. You can easily feel them working if you put your fingertips on your temples while clenching and unclenching your jaw. When temporalis muscles go into spasm from too much clenching, headache symptoms may result. This is not to say that headaches and migraines are always caused by TMJ problems, also known as temporomandibular disorders (TMD). But given the established link between them, it definitely bears looking into — especially if a diagnosis remains elusive in your case.