Should a Patient With an Olfactory Aura and Epileptogenic EEG But No Clinical Seizures Receive Antiepileptic Drugs?

Gregory L. Krauss, MD


December 27, 2000


Does an individual with an epileptogenic EEG and only an olfactory aura but without clinical seizure activity require anticonvulsant therapy? Secondarily, should the patient be advised not to operate a motor vehicle if no change in symptomatology is evident for over 2 years?

Response from Gregory L. Krauss, MD

One should be cautious in diagnosing epilepsy in a patient with only olfactory symptoms. Sensory seizures with olfactory symptoms are actually quite rare. Wilder Penfield[1] reported that fewer than 1% of patients with partial-onset seizures experienced olfactory symptoms. The majority of patients with epilepsy and olfactory auras will have clear complex partial or secondary generalized seizures in addition to their sensory symptoms, although these episodes may occur at separate times.[2] Many patients with epilepsy and olfactory auras have tumors in the medial temporal lobe, and careful coronal MRI imaging should be done.

The public frequently believes that unusual smells are a common sign of epilepsy. Consequently, many patients complaining of unusual odors who have undiagnosed spells are eventually found to have nonepileptic events. The patient's epileptiform findings on EEG should be reviewed to confirm that they are not artifact or normal variant patterns such as wicket rhythms or temporal lobe slowing during drowsiness.

If the symptoms are brief, stereotyped, and occur out of the context of the environment (not only in certain settings and mental states), the episodes are likely to be olfactory seizures. If olfactory symptoms are associated with complex partial or secondary generalized seizures and if the patient has temporal or frontal lobe lesions on MRI, the episodes are likely to be sensory seizures.

Anticonvulsant treatment could be considered if olfactory seizures are troublesome for the patient (eg, they are frequent, unpleasant, or distracting). The patient can reasonably consider driving if the olfactory symptoms are not distracting and if he or she has a stable pattern of symptoms over several years without loss of consciousness. I would not suggest the patient drive if there is a progressive lesion on MRI, because the clinical seizure pattern may change. For patients with simple partial seizures who wish to drive, I ask observers to test them during a number of their episodes to confirm that they are fully responsive during the seizures and do not, in fact, have brief lapses of consciousness, which might cause crashes. Video-EEG may be helpful in unclear cases. The patient should also discuss with their motor vehicle board the possibility of driving.