Cranial autonomic symptoms as a protective mechanism in patients with chronic migraine: A cross-sectional study.

AimTo identify clinical predictors of cranial autonomic symptoms (CAS) in chronic migraine (CM) and explore the role of cranial parasympathetic outflow.MethodsWe conducted a cross-sectional study using audit data from first consultation letters of 333 patients diagnosed with CM at King's College Hospital London (January 2015 to September 2019). All met the International Classification of Headache Disorders, 3rd edition (ICHD-3) criteria for CM. Predictors included sex, aura, age, pain quality and headache laterality. A generalized linear regression model with a Poisson distribution was used to analyze CAS count predictors.ResultsOf 333 cases, 85.2% were female and 54% reported aura. CAS were present in 75.1%, with 19.8% experiencing unilateral symptoms. CAS count was positively skewed (mode = 0; median = 2). Female sex (β = 0.244; p = 0.036), aura (β = 0.328; p < 0.001) and unilateral CAS (β = 0.317; p < 0.001) were significant positive predictors. Pain quality and age were not significant.ConclusionsFemale sex and aura are linked to increased CAS in CM. Enhanced trigeminal-autonomic reflex activation may represent a protective cerebrovascular mechanism. CAS may contribute to maintaining perfusion or modifying nociceptive input during attacks. Targeted therapies modulating this pathway could benefit females with aura and frequent CAS.