A seizure often brings to mind visible convulsions, but these neurological events can also manifest in subtle ways. Sometimes, the brain provides a warning sign, known as an aura, before a seizure begins. These auras can involve various sensory disturbances, including unusual sights, sounds, or feelings. Among these, perceiving a specific odor that is not actually present can signal an impending seizure.
Understanding Olfactory Auras
An olfactory aura is a sensory hallucination where an individual perceives a smell not present in their environment. This sensation is a focal aware seizure, originating in a specific, localized brain area. The perceived smell is subjective, experienced only by the individual, and not detectable by others nearby. Olfactory auras are brief, lasting from a few seconds to a minute, and can precede a more significant seizure. Not all seizures are preceded by an aura, and among those that are, olfactory auras are less common than visual or auditory disturbances.
Describing the Smells
The odors reported during olfactory auras are diverse, but many individuals describe them as unpleasant. Common descriptions include smells of burning substances like rubber or toast, metallic scents, or foul odors similar to rotten eggs or chemicals. Some also perceive unusual but not unpleasant smells, like a strong floral scent or food-related odors such as roast beef or baked brownies. These phantom smells are intense and sudden, distinct from any actual odors in the surroundings. The exact nature and intensity of the smell can vary between individuals, making precise description challenging.
The Brain’s Role in Olfactory Auras
Olfactory auras arise from abnormal electrical activity within specific brain regions, primarily the temporal lobe. This area contains structures involved in processing smell, such as the piriform cortex (the primary olfactory cortex) and the amygdala, which is part of the limbic system involved in emotion and memory. When neurons in these areas misfire, they can trigger the perception of smells even in the absence of an external stimulus. This localized disruption in brain activity generates the hallucinatory odor, providing insight into the seizure’s origin point within the brain.
Responding to Olfactory Auras
Individuals experiencing these unusual smells, especially if repeated, should consult a healthcare professional, ideally a neurologist. Accurately describing the perceived smell, its intensity, duration, and any accompanying symptoms is important for diagnosis. While olfactory auras can indicate a seizure disorder, similar phantom smells (a condition called phantosmia) can also be associated with other neurological conditions or migraines. A medical evaluation is necessary to determine the underlying cause and establish appropriate management. Recognizing an olfactory aura can provide a brief warning, allowing safety measures if a more widespread seizure is anticipated.