Lateralizing Value of the Auditory Aura in Partial Seizures

Abstract

Summary: Purpose: To describe the semiological features of auditory aura and to assess their possible lateralizing value in partial epilepsy.Methods: Out of a series of 8,000 patients with epilepsy, we investigated 121 cases with partial seizures in whom auditory features were the first ictal symptom. According to the dominant type of aura, patients were divided into four subgroups-1A (67 cases), 1B (22 cases), 2A (14 cases), and 2B (18 cases)-corresponding to the presence of simple or complex hallucinations and positive or negative illusions, respectively. The side of the epileptic zone (EZ) was defined based on available data: surgical/presurgical study or presence of a neuroradiological lesion, corresponding interictal epileptiform EEG and ictal semiology (level 1); a left EZ was also hypothesized in right-handed patients with ictal aphasia plus a left neuroradiological lesion or a left interictal EEG focus (level 2).Results: Forty-five patients (37%) described the aura as unilateral. The side of epileptogenic zone (EZ) was definable in 36 patients (level 1: 24; level 2: 12). Overall, a unilateral auditory aura was contralateral to the EZ in half of the cases (8/16), but always contralateral in patients studied for presurgical evaluation (4/4). Simple hallucinations lateralized seizure onset on the right side in nine cases, on the left in 12. Among 1B patients (either musical and verbal contents), the EZ was on the left side in all cases (5/5). Positive illusions were associated with right foci in two cases, and left foci in two. Negative illusions always lateralized seizure onset to the dominant hemisphere (6/6).Conclusions: Auditory aura is a rare symptom in partial epilepsy. The perception of the auditory sensation referred to one ear is not a unique lateralizing sign for the contralateral temporal neocortex. Complex hallucinations with verbal content and negative illusion may lateralize seizure onset in the dominant hemisphere. The role of laterality for musical hallucinations remains unclear as it depends on individual musical ability and hemispheric dominance for music.

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“…Auditory aura is considered a symptom of temporal lobe epilepsy and is rare in a general population of patients with epilepsy (1.9%) (16). In our case, auditory hallucinations may have resulted from left temporoparietal AVM involvement in the cortical and subcortical areas that are connected to auditory centers.…”

Voices behind the left shoulder: Two patients with right-sided temporal lobe epilepsy

“…In contrast, no pathological activity was recorded over the left hemisphere in both patients, making it very likely that the focal seizures also originated in the right temporal lobe [3]. Second, the auditory phenomena were perceptually lateralized to the left in both patients, providing independent support for a functional relationship with the contra-lateral, right temporal lobe [1,2]. Such perceptual lateralization of auditory hallucinations is not a typical feature of hallucinations in endogenous psychosis, supporting the clinical differentiation of the two phenomena.…”

“…Auditory phenomena in epileptic seizures may be basic tonal or ringing sensation, as well as more complex hallucinations comprising auditory objects, melodies, and also human voices. The foci of auditory seizures are generally found close to the auditory cortex and are often contra-lateral to the side of the perception [1,2]. However, auditory vocal hallucinations were reported almost exclusively in left-sided temporal lobe epilepsy [1], possibly indicating a relationship with language lateralization.…”

“…The foci of auditory seizures are generally found close to the auditory cortex and are often contra-lateral to the side of the perception [1,2]. However, auditory vocal hallucinations were reported almost exclusively in left-sided temporal lobe epilepsy [1], possibly indicating a relationship with language lateralization. Here we report two patients with right-sided temporal-lobe epilepsy, who repeatedly reported left-lateralized auditory vocal hallucinations.…”

Musical hallucinations following insular glioma resection

“…In the series of 8000 patients of Florindo et al 10 the auditory aura was present in only 121 cases. The role of laterality in epilepsy, where aura musical hallucinations occur, is a mechanism that must still be elucidated.…”