Side-to-side differences in pressure pain thresholds and pericranial muscle tenderness in strictly unilateral migraine C. Ferna ´ ndez-de-las-Pen ˜as a,b , M. L. Cuadrado b,c , L. Arendt-Nielsen d and J. A. Pareja b,c Department of a Physical Therapy, Occupational Therapy, Physical Medicine and Rehabilitation of Universidad Rey Juan Carlos; b Esthesiology laboratory of Universidad Rey Juan Carlos; Departments of c Neurology of Fundacio ´n Hospital Alcorco ´n and Universidad Rey Juan Carlos, Alcorco ´n, Madrid, Spain; and d Centre for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark Keywords: central sensitization, migraine, muscle tender- ness, pressure pain threshold Received 30 June 2007 Accepted 12 November 2007 Previous studies dealing with pressure pain sensitivity or muscle tenderness in migraine have shown conflicting results. Our aim was to explore the differences in mechanical pain sensitivity and pericranial muscle tenderness between patients with unilateral migraine and healthy controls, and to analyse side-to-side differences in both study groups. Pressure pain thresholds (PPT) at cephalic and neck points, plus local and total tenderness scores were blindly assessed in 25 patients with strictly unilateral migraine and 25 healthy subjects. For PPT in the neck there were significant differ- ences between groups (F = 47.029; P < 0.001) and sides (F = 6.363; P < 0.01), and a significant interaction between group and side (F = 5.201; P = 0.02), while PPT in the cephalic point showed differences between groups (F = 11.774; P < 0.001), but not sides (F = 2.838; P = 0.1). The total tenderness score showed significant differ- ences between groups (F = 6.800; P < 0.01) and sides (F = 17.699; P < 0.001), along with a significant interaction between group and side (F = 14.420; P < 0.001). Patients had lower PPT and increased pericranial tenderness on the symptomatic side as compared with the non-symptomatic side and to either side in controls (P < 0.001), whereas no significant differences were identified between the non- symptomatic side and controls (P > 0.9). In migraine patients, PPT levels and muscle tenderness scores were negatively correlated (P < 0.001). The enhancement of local tenderness scores was related to hyperesthesia of specific muscles (sternocleido- mastoid, suboccipital, and temporalis) rather than a generalized pericranial tender- ness. Future studies should investigate the neuro-physiological basis for the laterality of allodynic and hyperalgesic responses in unilateral migraine. Introduction Migraine is a common disorder with a lifetime pre- valence of 16% worldwide, and a yearly prevalence of 10% [1,2]. There have been major advances in the understanding of migraine patho-physiology within the last decade. Special attention has been devoted to central mechanisms of migraine, particularly to the activation of the trigemino-vascular system [3,4]. Increased tenderness to manual palpation of peri- cranial tissues and decreased pressure pain threshold (PPT) are generally regarded as common clinical man- ifestations of peripheral excitability [5], increased excitability of the central nervous system [6], or a reduction in inhibitory mechanisms [7]. Some studies have found an increased tenderness to muscle palpation of pericranial tissues in tension-type headache, but not in migraine sufferers [8,9]. Others have reported that patients with migraine exhibit increased tenderness to palpation during headache attacks [10] and also in headache-free periods [11]. In addition, lower PPT levels have been observed in cephalic (e.g. temporalis) and extra-cephalic (e.g. upper trapezius) muscles in tension-type headache patients when compared with controls [12–14]. However, other studies have reported no differences in PPT levels be- tween migraine, tension-type headache and healthy subjects [15,16]. As migraine is associated with sensitization of tri- geminal nociceptive pathways [4,6] muscle tenderness and mechanical pain sensitivity may be altered in this condition. It is interesting to note that previous studies have included patients with bilateral or side shifting migraine [8,10,15]. We have recently found that active muscle trigger points, which reproduced the pain fea- tures of migraine headache attacks were mostly located on the symptomatic side in patients with strictly Correspondence: Ce´sar Ferna´ndez de las Pen˜as, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Avenida de Atenas s/n, 28922 Alcorco´n, Madrid, Spain (tel.: + 34 91 488 88 84; fax: + 34 91 488 89 57; e-mail: cesar.fernandez@urjc.es). 162 Ó 2007 The Author(s) Journal compilation Ó 2007 EFNS European Journal of Neurology 2008, 15: 162–168 doi:10.1111/j.1468-1331.2007.02020.x