Imagine coming home from work and getting ready to make dinner, only to begin smelling a rotten scent that seems to be coming from somewhere near you. Several minutes go by as the scent gets stronger. You take out the trash and search your refrigerator to no avail – the smell is still there. Suddenly, the smell begins to subside as you begin experiencing a throbbing migraine episode. You have just been the victim of migraine related olfactory hallucination, or phantosmia.
What is the Smell Before a Migraine Episode and Why Does It Happen?
Scent hallucination is caused by changes to sensory perception in the brain when neurons begin to fire abnormally. For many people, sensory changes prior to a migraine present themselves in the form of visual disturbances. Some, however, experience changes to their olfactory function. In the majority of patients who experience olfactory hallucinations related to migraines episodes, the sensory changes last no more than an hour.
Many people who experience migraines with auras report experiencing a very specific scent prior to their migraine episodes. It is usually described as unpleasant – with only a minority reporting the smell to be neutral or pleasant. The most common smell reported is that of a smoky or burning scent. However, many also describe a smell of decomposition or metal.
Hallucinations of smells that are not real are reported to be rare, yet normal prior to a migraine episode. However, a question remains of how common phantosmia really is. Smell hallucinations, after all, are less noticeable when they are happening than visual hallucinations are, such as the zig-zags that often occur with migraine auras. While a patient is likely to report major visual disturbances to a healthcare provider, he or she is less likely to discuss olfactory symptoms.
Often, the smell prior to a migraine episode is reported as being linked to the aura phase, which usually occurs in the moments immediately preceding migraine pain. However, scent hallucinations are also believed to occur during the prodrome phase in some patients, which can begin up to several days prior to a migraine episode. The prodrome phase of a migraine often includes many of the same types of symptoms experienced in an aura, only more people are believed to experience the prodrome phase than the aura phase.
Little research has been done on smell hallucination, and it is not an officially recognized symptom of migraines by the International Classification of Headache Disorders. However, researchers believe that olfactory hallucinations can be a distinguishing type of migraine aura.
If you notice changes in smells prior to your migraine episode, you may be experiencing a migraine with aura without knowing it. Begin tracking your migraine symptoms, including any smell hallucinations you may be having, on a daily basis. If you notice that certain smells begin to precede your migraines, you may be able to start treating migraine pain before it starts.
Report your findings to your doctor or neurologist. Discovering that you have sensory perception changes prior to a migraine could shed light on the type of migraines you are experiencing and help your healthcare provider better decide how to treat them.
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