The analysis of allodynia in patients with idiopathic intracranial hypertension

Objectives: Allodynia is frequently associated with migraine and other primary headaches. Our aim was to investigate the presence of allodynia and related features in idiopathic intracranial hypertension (IIH), which is a disabling secondary headache disorder. Methods: We included 46 IIH patients and analyzed their clinical and laboratory findings retrospectively. Allodynia was assessed using the validated 12-item allodynia symptom checklist (ASC-12), in addition to examining pressure (with von Frey filaments) and brush allodynia. Results: Allodynia was detected in 23 (50%) of IIH patients with ASC-12 and/or instrumental testing. The most commonly reported location was unilateral V1 distribution. The allodynic symptom profile was similar but milder when compared to 143 migraineurs with ASC-12. Only the aggravation of headache with physical activity emerged as a significant variable associated with allodynia in IIH. Among allodynic patients, only eight had previous migraine diagnosis. After onset of IIH, 20 patients reported migraine-like headache, while only three reported non-migrainous headache. In contrast, 13 of 23 non-allodynic IIH patients had non-migrainous headache features (p = 0.0045). Conclusion: Half of the IIH patients reported allodynia, and these allodynic patients had mostly migraine-like headache profiles. Our study suggested that IIH may trigger some common mechanisms with migraine in pain pathways causing allodynia.