CLEVELAND -- If patients experience different types of auras during a seizure, their epilepsy may arise from a single region of the brain, making them good candidates for surgery, researchers here said.
CLEVELAND, Aug. 21 -- If patients experience different types of auras during a seizure, their epilepsy may arise from a single region of the brain, making them good candidates for surgery, researchers here said.
In a retrospective study, 90% of patients who reported more than one type of aura and all of those with at least three aura types had epilepsy localized in the nondominant hemisphere of their brain, reported Prakash Kotagal, M.D., of the Cleveland Clinic, and colleagues in the Aug. 21 issue of Neurology.
Although getting patients to explain their auras precisely can be difficult and time consuming, the importance of the symptoms should not be underestimated, the researchers said.
"From clinical experience, the patient may report the feeling of a rising epigastric sensation with a simultaneous unpleasant olfactory odor or may have the same epigastric sensation followed later in the seizure by a visual hemifield distortion," they wrote.
Such multiple auras "should be recognized as a significant finding during history-taking and video-EEG [electroencephalogram] recordings," they said.
Studies have been done linking single auras to the lateralization or the localization of seizures in the brain. But, multiple auras have received little attention, Dr. Kotagal and colleagues said.
They searched the Cleveland Clinic's epilepsy database for patients with more than one aura type -- abdominal, auditory, autonomic, gustatory, olfactory, psychic (such as fear or dj vu), somatosensory, or visual -- occurring from 1989 through 2005.
They found only 31 patients (0.4% of 7,618 evaluations) who had experienced multiple auras during a seizure monitored using video-EEG evaluation. The median age of those with multiple auras was 34.6; 41% were women.
The low prevalence of multiple auras in the study compared with older studies (22% to 48%) may have been because of different definitions of aura, restriction of analyses to auras recorded in the monitoring unit, and other factors, the researchers said.
The patients reported 223 auras in total, of which 72 were followed by clinical seizures. Most of the patients (21) had sequential rather than simultaneous auras.
Monitoring unit reports together with bedside patient interviews identified the auras as being abdominal (61%), psychic (61%), somatosensory (35%), autonomic (26%), visual (23%), olfactory (19%), auditory (13%), and gustatory (13%).
All patients had epilepsy localized to the temporal or posterior brain regions, although most patients did not have a specific correlation between aura types and lobar localization.
Overall, 90% of the patients with more than one type of aura and 100% of those with at least three aura types had seizures originating in the nondominant right hemisphere of their brain.
The same was true for cases in which multiple auras were reported but did not develop into a clinical seizure. EEG monitoring of epileptic brain activity showed that these electrical discharges, when present, did not spread beyond the hemisphere of origin.
The patients had just one region that generated seizures rather than multiple onset zones, the investigators noted.
Of six patients who had subdural EEG recordings, five showed sequential auras. One had multiple onset zones that gave rise to separate isolated auras.
"The lack of spread to the contralateral limbic or language areas may permit the experience, expression, and memory of the seizures' march through symptomatogenic zones in the temporal and posterior brain regions," the researchers wrote.
Indeed, EEG monitoring showed that discharges did not spread beyond the lobe where clinical seizures originated for six of 11 patients who remained aware during their seizure, whereas they did spread in all seven patients who lost awareness.
Single photon emission computed tomography (SPECT) imaging in six patients during typical right-sided seizures with multiple auras showed no activation of brainstem structures involved with maintenance of consciousness.
"A common mechanism for multiple auras may be a spreading but restricted EEG seizure activating sequential symptomatogenic zones, but without the ictal activation of deeper structures or contralateral spread to cause loss of awareness and amnesia for the auras," the researchers suggested.
Among the 31 patients with multiple auras, 19 had resective epilepsy surgery, 10 of whom stopped having clinical seizures (53%). Three patients had complex partial or secondarily generalized seizures after surgery.
"Patients with multiple auras are good candidates for epilepsy surgery," the researchers concluded.
However, they noted that the retrospective study may have been limited by the patients' ability to report auras, which depends on their awareness during seizures, their age, and their intellectual level, and by the skill of the interviewer eliciting aura symptoms.