With Migraine disease, there are many possible symptoms, including olfactory hallucinations. Olfactory hallucinations are a potential symptom of the aura phase and headache phase of a Migraine attack.
Olfactory hallucinations, also called phantosmias are events of smelling odors that aren't actually present. This symptom is reported relatively rarely in Migraine, but when it's mentioned, so many Migraineurs say, "Me too," that I wonder if it's rarely reported because it's rarely asked about.
It's also known to occur in some other headache disorders such as cluster headaches, hemicrania continua, and new daily persistent headache as well as other disorders such as temporal lobe epilepsy and schizophrenia.
Researchers at the Montefiore Headache Center reviewed the charts of 14 of their patients who reported olfactory hallucinations and 24 published cases in Migraine and headache patients to study the data from these 38 patients. Of the 38 patients:
- 84% had a diagnosis of Migraine,
- 8% had a diagnosis of cluster headache,
- 3% had a diagnosis of hemicrania continua,
- 3% had a diagnosis of new daily persistent headache, and
- 3% had an unspecified chronic daily headache diagnosis.
- 34% of those who had Migraine had Migraine with typical aura other than the olfactory hallucinations.
Among the patients with Migraine, olfactory hallucinations occurred:
- shortly before the headache phase began for 49% of the patients (during aura).
- during the headache phase for 32% of the patients.
- more than two hours before the headache phase for 11% of the patients.
The olfactory hallucinations lasted:
- between five and 60 minute in 82% of the patients in at least the majority of their attacks,
- always lasted more than an hour in 14% of the patients, and
- lasted less than one minute for one patient.
What did people smell?
- Eighty-one percent of the patients could identify the smells.
- The other 19% could describe the smells, but not identify them.
- Types of smells:
- 76% unpleasant
- 11% pleasant
- 5% neutral
- One patient described the smell evolving from pleasant to unpleasant.
- Commonly experienced odor categories:
- 21% burning
- 15% fecal/decay
- 13% food
- 10% chemical
Effect of preventive treatment: Eighty-two percent of the patients who were using preventive treatments reported a significant decrease or cessation of olfactory hallucinations.
Summary and comments
Although there's little research or medical literature on olfactory hallucinations, and it's said to be a rather rare symptom, anecdotal evidence leads me to wonder if it's really rare or if patients don't realize it's part of their Migraine, and doctors don't think to ask about it.
Is this something you experience curing a Migraine? If so what do you smell?
Coleman, E.R.; Grosberg, B.M.; Robbins, M.S. "Reappraising the Olfactory Aura in Primary Headache Disorders." Research Poster Presentation. 53rd Annual Scientific Meeting of the American Headache Society. Washington, DC. June, 2011.