The significance of ear plugging in localization-related epilepsy

Localizing and lateralizing value of auditory phenomena in seizures

BACKGROUND

Auditory seizures (AS) are a rare type of focal seizures. AS are classically thought to involve a seizure onset zone (SOZ) in the temporal lobe, but there remain uncertainties about their localizing and lateralizing value. We conducted a narrative literature review with the aim of providing an up-to-date description of the lateralizing and localizing value of AS.

METHODS

The databases PubMed, Scopus, and Google Scholar were searched for literature on AS in December 2022. All cortical stimulation studies, case reports, and case series were analyzed to assess for auditory phenomena that were suggestive of AS and to evaluate if the lateralization and/or localization of the SOZ could be determined. We classified AS according to their semiology (e.g., simple hallucination versus complex hallucination) and the level of evidence with which the SOZ could be predicted.

RESULTS

A total of 174 cases comprising 200 AS were analyzed from 70 articles. Across all studies, the SOZ of AS were more often in the left (62%) than in the right (38%) hemisphere. AS heard bilaterally followed this trend. Unilaterally heard AS were more often due to a SOZ in the contralateral hemisphere (74%), although they could also be ipsilateral (26%). The SOZ for AS was not limited to the auditory cortex, nor to the temporal lobe. The areas more frequently involved in the temporal lobe were the superior temporal gyrus (STG) and mesiotemporal structures. Extratemporal locations included parietal, frontal, insular, and rarely occipital structures.

CONCLUSION

Our review highlighted the complexity of AS and their importance in the identification of the SOZ. Due to the limited data and heterogeneous presentation of AS in the literature, the patterns associated with different AS semiologies warrant further research.

A comprehensive review of auditory verbal hallucinations: lifetime prevalence, correlates and mechanisms in healthy and clinical individuals

Over the years, the prevalence of auditory verbal hallucinations (AVHs) have been documented across the lifespan in varied contexts, and with a range of potential long-term outcomes. Initially the emphasis focused on whether AVHs conferred risk for psychosis. However, recent research has identified significant differences in the presentation and outcomes of AVH in patients compared to those in non-clinical populations. For this reason, it has been suggested that auditory hallucinations are an entity by themselves and not necessarily indicative of transition along the psychosis continuum. This review will examine the presentation of auditory hallucinations across the life span, as well as in various clinical groups. The stages described include childhood, adolescence, adult non-clinical populations, hypnagogic/hypnopompic experiences, high schizotypal traits, schizophrenia, substance induced AVH, AVH in epilepsy, and AVH in the elderly. In children, need for care depends upon whether the child associates the voice with negative beliefs, appraisals and other symptoms of psychosis. This theme appears to carry right through to healthy voice hearers in adulthood, in which a negative impact of the voice usually only exists if the individual has negative experiences as a result of their voice(s). This includes features of the voices such as the negative content, frequency, and emotional valence as well as anxiety and depression, independently or caused by voices presence. It seems possible that the mechanisms which maintain AVH in non-clinical populations are different from those which are behind AVH presentations in psychotic illness. For example, the existence of maladaptive coping strategies in patient populations is one significant difference between clinical and non-clinical groups which is associated with a need for care. Whether or not these mechanisms start out the same and have differential trajectories is not yet evidenced. Future research needs to focus on the comparison of underlying factors and mechanisms that lead to the onset of AVH in both patient and non-clinical populations.

Temporal lobe epilepsy in children

The temporal lobe is a common focus for epilepsy. Temporal lobe epilepsy in infants and children differs from the relatively homogeneous syndrome seen in adults in several important clinical and pathological ways. Seizure semiology varies by age, and the ictal EEG pattern may be less clear cut than what is seen in adults. Additionally, the occurrence of intractable seizures in the developing brain may impact neurocognitive function remote from the temporal area. While many children will respond favorably to medical therapy, those with focal imaging abnormalities including cortical dysplasia, hippocampal sclerosis, or low-grade tumors are likely to be intractable. Expedient workup and surgical intervention in these medically intractable cases are needed to maximize long-term developmental outcome.

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

Auditory vocal hallucinations are sometimes observed in temporal-lobe epilepsy, but are a frequent sign of psychosis and may rarely be mistaken for the latter. Here we report two patients who suffered from auditory vocal hallucinations, described as unintelligible human voices perceived at their left side during epileptic seizures. MEG revealed interictal epileptic discharges within the anterior partition of the right superior temporal gyrus; signal-to-noise ratio of these discharges was overall poor in EEG. The findings suggest that auditory vocal hallucinations without verbal content can evolve in the right hemisphere and are probably independent of language lateralization. This is in accordance with evidence from functional imaging, whereas most previous reports of seizures with auditory vocal hallucinations were confined to the left hemisphere.

An unusual presentation of epilepsy

Objective:

To report a case of fluctuating hearing due to auditory aura, as an unusual presentation of temporal lobe epilepsy.

Methods:

Case report and review of English language literature on temporal lobe epilepsy and auditory aura.

Results:

A 31-year-old man presented with intermittent symptoms of bilateral fullness in the ears associated with deafness. He was subsequently diagnosed with temporal lobe epilepsy. Further enquiry revealed a family history of epilepsy.

Conclusion:

Auditory aura as a presentation of temporal lobe epilepsy is rarely encountered in otolaryngological practice. This case highlights the importance of obtaining detailed information on epilepsy, including any family history of epilepsy, as a routine part of history-taking in patients presenting with fluctuating hearing loss.

Multiple auras: not an ominous sign for epilepsy surgery

Multiple Auras: Clinical Significance and Pathophysiology. Widdess-Walsh P, Kotagal P, Jeha L, Wu G, Burgess R. Neurology 2007;69(8):755–761. Erratum in: Neurology 2007;69(19):1890.

Background

Patients with partial epilepsy may report multiple types of aura during their seizures. The significance of the occurrence of multiple auras in the same patient is not known.

Methods

The clinical and electrophysiologic characteristics of patients with more than one aura type (abdominal, auditory, autonomic, gustatory, olfactory, psychic, somatosensory, and visual auras), evaluated in the Cleveland Clinic epilepsy monitoring unit between 1989 and 2005, were studied.

Results

Thirty-one patients experienced multiple aura types during a seizure. Ninety percent of patients with at least two aura types ( n = 31) and 100% of patients with at least three aura types ( n = 12) had seizures arising from the right/nondominant hemisphere. EEG seizures remained restricted in all patients during their auras. Twenty patients had epilepsy surgery with seizure freedom in 53%. Subdural EEG recordings in six patients showed either a march of sequential auras, or in one case, several ictal onset zones resulting in separate isolated auras. Ictal SPECT in six patients with right-sided seizures showed a lack of activation in brainstem structures.

Conclusions

Most patients who report multiple aura types have localized epilepsy in the nondominant hemisphere, and are good surgical candidates. 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.

Semiology of epileptic seizures: a critical review

Epileptic seizures are characterized by a variety of symptoms. Their typical semiology served for a long time as the major tool to classify epilepsy syndromes. The signs and symptoms of epileptic seizures include the following spheres: sensorial sphere, consciousness, motor and autonomic spheres. Most seizures involve more than one sphere, however, some like for instance aura (sensorial sphere) or dialeptic seizures (consciousness) involve only one sphere. The predominant clinical features of a seizure determines the seizure classification. The following review gives an introduction into the semiological seizure classification. This approach enables us to better identify the epileptogenic zone of our patients and to choose the most effective medical or surgical treatment.

Lateralizing value of the auditory aura in partial seizures

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.

Daily rhythms of seizure activity and behavior in a model of atypical absence epilepsy

We studied daily rhythms of chronic seizure activity and behavior in adult rats and mice treated with the cholesterol biosynthesis inhibitor AY-9944 (AY) during early postnatal development. Chronic atypical absence seizures were verified in the AY-treated animals by the presence of spontaneous 5- to 6-Hz slow spike-wave discharges (SSWDs) in the neocortex. General behavioral activity, as measured by total movements (TM), movement time (MT), ambulatory movement time (AMT), time spent in center of arena (CT), jumps (JFP), and rotational behavior (TURNS), were continuously recorded under a 12-hour light:12-hour dark photocycle. The average SSWD duration in AY-treated rats varied daily, with two peaks occurring at approximately dark phase and light phase onset. Mice treated with AY exhibited significant increases in all behavioral measures during the light and dark phases, with the exception of light-phase CT, which did not differ from that of controls. Consequently, the daily rhythm of total behavioral activity (TM) exhibited a significantly higher mean oscillation (mesor) and amplitude without evidence of phase shift compared with the TM rhythm of controls. The occurrence of SSWD activity in the AY model appears to be subject to regulation by biological timing mechanisms and, furthermore, associated with motor hyperactivity that does not alter the timing of behavioral rhythmicity.

Magnetoencephalographic spike sources associated with auditory auras in paediatric localisation-related epilepsy

OBJECTIVE

To characterise magnetoencephalographic spike sources in paediatric patients with auditory auras and recurrent localisation-related epilepsy.

METHODS

Six patients (four boys and two girls (ages 7-14 years) were retrospectively studied. All patients had auditory auras as part of their initial seizure manifestation, including four patients who underwent previous brain surgery. Scalp video electroencephalography and magnetoencephalography (MEG) were carried out in six patients, intraoperative electrocorticography in three patients and extraoperative intracranial video electroencephalography in one patient. MEG auditory-evoked fields (AEFs) were studied in four patients.

RESULTS

Three patients had elementary auditory auras, one had complex auditory aura and two had both complex and elementary auras. All six patients had clustered MEG spike sources with coexisting scattered spike sources. MEG clusters were localised in the superior temporal gyrus with surrounding scatters in four patients (two left and two right); two patients had scattered spikes in the superior temporal gyrus in addition to clustered MEG spike sources in the left inferior and middle frontal gyri or parieto-occipital region. AEFs were located within an MEG cluster in one patient and within 3 cm of a cluster in two patients. Surgical resection, including the regions of MEG clusters, was carried out in four patients. Three of four patients who had previous surgeries were seizure free at 2 years after excision of the MEG cluster region.

CONCLUSIONS

MEG spike sources clustered in the superior temporal gyrus in six patients with auditory auras. These spike sources were in close proximity or seemed to engulf the magnetic AEF. Areas with MEG spike sources contained the residual or recurrent epileptogenic zone after incomplete cortical excision for lesional epilepsy.

Lateralizing signs during seizures in focal epilepsy

This article reviews lateralizing semiological signs during epileptic seizures with respect to prediction of the side of the epileptogenic zone and, therefore, presurgical diagnostic value. The lateralizing significance of semiological signs and symptoms can frequently be concluded from knowledge of the cortical representation. Visual, auditory, painful, and autonomic auras, as well as ictal motor manifestations, e.g., version, clonic and tonic activity, unilateral epileptic spasms, dystonic posturing and unilateral automatisms, automatisms with preserved responsiveness, ictal spitting and vomiting, emotional facial asymmetry, unilateral eye blinking, ictal nystagmus, and akinesia, have been shown to have lateralizing value. Furthermore, ictal language manifestations and postictal features, such as Todd's palsy, postictal aphasia, postictal nosewiping, postictal memory dysfunction, as well as peri-ictal water drinking, peri-ictal headache, and ipsilateral tongue biting, are reviewed. Knowledge and recognition of semiological lateralizing signs during seizures is an important component of the presurgical evaluation of epilepsy surgery candidates and adds further information to video/EEG monitoring, neuroimaging, functional mapping, and neuropsychological evaluation.

John Hughlings-Jackson's Writings on the Auditory Aura and Localization of the Auditory Cortex

PURPOSE

To relate John Hughlings-Jackson's findings of the auditory aura to his ideas about the "dreamy state," and localization of primary auditory cortex.

METHODS

We reviewed Hughlings-Jackson's writings on the auditory aura and his integration of the auditory aura into his description of the "dreamy state." To integrate Hughlings-Jackson's postulations about the auditory aura and David Ferrier's localization of primary auditory cortex, we also reviewed Ferrier's localization of auditory cortex in animals.

RESULTS

Hughlings-Jackson described three cases of the auditory aura, which he integrated with his concept of the "dreamy state" (now known as mesial temporal epilepsy). In doing so, he described the current concept of elementary and complex auditory auras. Hughlings-Jackson also associated the auditory aura with seizures that began in the "auditory centre of Ferrier." Whereas Ferrier showed respect and admiration for Hughlings-Jackson's work as a whole, he did not integrate Hughlings-Jackson's ideas of localization of the auditory epileptic aura with his work in localizing the primary auditory cortex in animals.

CONCLUSIONS

Hughlings-Jackson outlined the modern concept of elementary and complex auditory auras and correctly correlated it with primary auditory cortex. The history of Hughlings-Jackson's auditory aura reflects the history of his ideas of epilepsy as a whole, which closely parallel our modern concepts of focal epilepsy.