Somatosensory Profiling of Patients With Cluster Headache: A Systematic Review and Meta-analysis

The objectives were 1) to synthesize quantitative sensory testing results in cluster headache (CH) patients and to identify somatosensory differences from healthy subjects (HS), and 2) between symptomatic and asymptomatic sides in CH patients. Two independent reviewers conducted a literature search in MEDLINE, EMBASE, Web of Science, and CINAHL databases. Studies with observational designs were included. Methodological quality and risk of bias were assessed with the Newcastle Ottawa Scale. The selected studies underwent qualitative and quantitative analyses. The qualitative analysis showed inconsistent findings among multiple studies. Meta-analysis showed lower pressure pain thresholds (PPTs) on the symptomatic side of CH patients than HS in V₂ (standardized mean difference [SMD] -1.01 [95% confidence interval (CI) -1.79, -.23], P = .01, I² = 73%, n = 114), V₃ (SMD -1 [95% CI -1.54, .45], P < .01, I² = 82%, n = 354), and cervical region (SMD -1.25 [95% CI -2.07, -.44], P < .01, I² = 84%, n = 194). Furthermore, lower PPTs than those detected in HS were found on the asymptomatic side in V₃ (SMD -.77 [95% CI -1.27, -.27], P < .01, I² = 79%, n = 354) and in the cervical region (SMD -1.13 [95% CI -1.97, -.3], P < .01, I² = 85%, n = 194). However, no differences were found in V₁ or the extratrigeminal points between these groups. No significant changes were found between symptomatic and asymptomatic sides in trigeminal and extratrigeminal regions. Mechanical hyperalgesia in the trigemino-cervical region of patients with CH could suggest the presence of central pain mechanisms. These results are of clinical relevance because their presence could be associated with a poorer prognosis, chronification, and treatment response. PERSPECTIVE: This study provides consistent findings on the somatosensory profile characterizing patients with CH. Clinicians should assess PPTs and other quantitative sensory testing variables in the trigeminal and extratrigeminal (cervical) regions.