Studies have indicated that the pericranial muscles are more tender in chronic tension-type patients than in controls. It has also been reported that tension-type headache patients have harder pericranial muscles. This study examined the muscle hardness in such cases to see if it was influenced by the presence or absence of headache or if it was related to the muscle tenderness.
The researchers define and distinguish the terms hardness and tenderness as, "Tenderness is pain provoked by palpation and reflects a subjective feeling of pain. Muscle hardness is an objective parameter measured by the hardness meter defined as the degree of deformity of muscle tissue to a given pressure."
The study evaluated 20 tension-type headache patients and compared their findings to 20 healthy controls.
The scores for both hardness and tenderness were higher in patients than in the controls. Hardness did not differ on days with headache than on days without headache. The authors surmise, "This indicates that muscle hardness is permanently altered in chronic tension-type headache and that muscle hardness does not fluctuate with actual pain."
The hardness scores correlated to the tenderness scores on both the days with and without headache. But, hardness scores did not correlate to headache frequency or intensity. Furthermore, tenderness scores were higher in patients on days without headache than in healthy controls—which implies tenderness is permanently increased and not just a result of the headache episode.
This study confirms that chronic tension-type headache patients have increased pericranial muscle hardness and tenderness, as compared to a healthy population. Yet, the study concludes that tenderness and hardness in these patients is not related to the actual headache state.