Scent of aura? Clinical features of olfactory hallucinations during a migraine attack (OHM)

Introduction Olfactory hallucination during a migraine attack (OHM) is a rare phenomenon. At present, it is not considered a manifestation of migraine aura. Material and methods The clinical features of OHM were collected in 11 patients. Results Of the 11 patients, 10 had migraine without aura and one migraine with aura associated with OHM. Mean age at onset of headache and at appearance of OHM were respectively 17.8 and 32.3 years. Migraine average frequency was 3.9 attacks/month, 19% of them being associated with OHM. The temporal pattern of OHM maintained the same characteristics in the different attacks. OHM onset was described as sudden ( n = 5), gradual ( n = 3), initially sudden and then gradual ( n = 2), or developing in a few seconds ( n = 1). In most of the cases ( n = 8) OHM lasted from 3 to 10 minutes; it persisted during the pain phase (2-24 hours) in only three patients. The type of the perceived smell was invariably constant in nine patients. Conclusion OHM features fulfilled the ICHD-III beta criteria for typical aura.