Effects of long-lasting antiepileptic therapy on brainstem auditory evoked potentials

Music and epilepsy: a critical review

The effect of music on patients with epileptic seizures is complex and at present poorly understood. Clinical studies suggest that the processing of music within the human brain involves numerous cortical areas, extending beyond Heschl's gyrus and working within connected networks. These networks could be recruited during a seizure manifesting as musical phenomena. Similarly, if certain areas within the network are hyperexcitable, then there is a potential that particular sounds or certain music could act as epileptogenic triggers. This occurs in the case of musicogenic epilepsy, whereby seizures are triggered by music. Although it appears that this condition is rare, the exact prevalence is unknown, as often patients do not implicate music as an epileptogenic trigger and routine electroencephalography does not use sound in seizure provocation. Music therapy for refractory epilepsy remains controversial, and further research is needed to explore the potential anticonvulsant role of music. Dopaminergic system modulation and the ambivalent action of cognitive and sensory input in ictogenesis may provide possible theories for the dichotomous proconvulsant and anticonvulsant role of music in epilepsy. The effect of antiepileptic drugs and surgery on musicality should not be underestimated. Altered pitch perception in relation to carbamazepine is rare, but health care professionals should discuss this risk or consider alternative medication particularly if the patient is a professional musician or native-born Japanese. Studies observing the effect of epilepsy surgery on musicality suggest a risk with right temporal lobectomy, although the extent of this risk and correlation to size and area of resection need further delineation. This potential risk may bring into question whether tests on musical perception and memory should form part of the preoperative neuropsychological workup for patients embarking on surgery, particularly that of the right temporal lobe.

Somatosensory evoked potentials in epileptic children treated with carbamazepine or valproate in monotherapy - a preliminary study

PURPOSE

Data from the literature suggest that long-term therapy with various antiepileptic drugs can be responsible for the functional disturbances within the nervous system e.g. peripheral neuropathy and encephalopathy. Useful and non-invasive instruments for evaluation of even subclinical nerve conduction abnormalities in somatosensory tracts are somatosensory evoked potentials (SEPs). The aim of this study was to assess the potentially drug-induced abnormalities in the SEP parameters in epileptic children, treated chronically in monotherapy with one of the two most often used antiepileptic drugs: valproate (VPA) or carbamazepine (CBZ).

MATERIALS AND METHODS

SEP from left median nerve stimulation were recorded in twenty children with idiopathic/cryptogenic epilepsy treated in monotherapy with CBZ (9 patients) or VPA (11 patients). The mean age of the patients was 13.4 ± 2.9 years (range 7-17 years). The plasma concentrations of the drugs were consistently within therapeutic range. The mean duration of treatment was eight months. The control group consisted of twenty-four age-matched children with tension type headache. The latencies of the components: N9, N13, N20, P25 and the peripheral conduction time (PCT) and central conduction time (CCT) were analyzed.

RESULTS

No significant differences in all analyzed SEP parameters between the epileptic and control children were found.

CONCLUSIONS

Our results indicate that during the first 8 months from the beginning of antiepileptic treatment in children, monotherapy with VPA or CBZ does not induce nerve conduction disturbances within both the peripheral- and the central part of the somatosensory tracts, detected in SEP examination.

Comparison of acute, chronic and post-treatment effects of carbamazepine and vinpocetine on hearing loss and seizures induced by 4-aminopyridine

OBJECTIVE

To compare the acute, chronic and post-treatment effects of the classic antiepileptic drug carbamazepine (CBZ) and the potential antiepileptic vinpocetine (VPC), successfully used in the treatment of brain vascular origin disorders, on 4-aminopyridine (4-AP)-induced increase in auditory threshold, brain-auditory-evoked-potentials (BAEPs) later waves alterations and epileptiform activity.

METHODS

BAEP and EEG recordings before and following 4-AP (3mg/kg, i.p.) were obtained in guinea pigs. One week after, the animals received a daily injection (i.p.) of vehicle, 3mg/kg VPC or 17 mg/kg CBZ for 13 days. The acute and chronic effects before and following 4-AP were tested at the 1st and last days, respectively, and the post-treatment effect 1 month after the end of treatment.

RESULTS

CBZ and 4-AP increased BAEPs threshold and BAEPs P4 wave latency. Chronic CBZ inhibited 4-AP-induced increase in P3 amplitude. In the VPC-treated group, all the 4-AP-induced BAEPs changes were prevented. Seizures were prevented in 50% and 75% of the animals by chronic CBZ and VPC, respectively. After acute VPC and after the end of VPC-treatment 4-AP failed to induce seizures in 50% of the animals.

CONCLUSION

VPC inhibits 4-AP-induced seizures and hearing loss, even after post-treatment, at a concentration about 10 times lower than CBZ.

SIGNIFICANCE

The complications in hearing that can accompany epilepsy can be prevented by VPC, indicating its advantage as an alternative antiepileptic.

Acute and chronic effects of carbamazepine, phenytoin, valproate and vinpocetine on BAEP parameters and threshold in the guinea pig

OBJECTIVE

To characterize the acute and chronic effects of the antiepileptic drugs (AEDs): carbamazepine (CBZ), phenytoin (PHT), valproic acid (VPA) and vinpocetine (VPC), at doses 20, 6, 30 and 2mg/kg, respectively, on the latencies and amplitudes of the waves of brainstem auditory evoked potentials (BAEPs) elicited by a supra-threshold stimulus alongside BAEP threshold.

METHODS

BAEPs elicited by a stimulus of high (100dB nHL) intensity and BAEP thresholds were obtained at 4 and 8kHz: before, after the start of treatment, and following 28 days of a daily injection of the AEDs.

RESULTS

After the start of treatment BAEPs were unchanged. After the long term treatment, CBZ and PHT increased P3 and P4 wave peak latencies and reduced P4 amplitude. Chronic VPA did not modify BAEP waves, and chronic VPC reduced P3 and P4 latencies. P1 and P2 were unchanged. BAEP thresholds at 4 and 8kHz were increased by CBZ, PHT and VPA, and decreased by VPC.

CONCLUSIONS

The chronic administration of several AEDs modifies BAEP waves of retro-cochlear origin.

SIGNIFICANCE

Alterations in the generators of the later waves of BAEPs underlie, in most cases, the changes in hearing sensitivity produced by the long term treatment with AEDs at therapeutic relevant doses.

Elevated pitch perception owing to carbamazepine-activating effect on the peripheral auditory system: auditory brainstem response study

Auditory disturbance is an uncommon side effect of carbamazepine, the pathophysiologic mechanism of which has not been clearly elucidated. We performed an auditory brainstem response study in a 9-year-old boy with epilepsy who had suffered from falsely higher pitch perception immediately after the start of carbamazepine treatment. The auditory brainstem response results showed that both the peak latency of wave V and the interpeak latencies of waves I to V were significantly prolonged with 85 dB HL click stimulation and that the peak amplitudes of the waves were noticeably elevated, particularly with lower click stimulation intensity. Although it has been shown that carbamazepine has a suppressive effect on the central nervous system, these auditory brainstem response findings might constitute evidence of a carbamazepine-activating effect on the peripheral auditory system, which probably increased the sensitivity to low-pitched sounds, causing the development of falsely higher pitch perception in our patient.

Carbamazepine-induced abnormal pitch perception

A 7-year-old boy began to complain that his pitch perception was decreased just after oral medication with carbamazepine was initiated for the treatment of epilepsy. When he played the piano, he felt as if he had played a musical note of almost a half pitch lower than he had. His pitch perception recovered soon after the cessation of carbamazepine. A 14-year-old girl noted a lowered pitch of music sounds while she played the piano just after the administration of carbamazepine for the treatment of epilepsy. Carbamazepine was withdrawn and the auditory symptoms disappeared. Both patients were musically trained. Reversible pitch perception abnormalities are a rare adverse effect of carbamazepine, however, the clinical features of the reported cases were similar; they were musically trained, young, female and Japanese. Although the mechanism remains unclear, we have to pay attention to this subtle adverse effect when we treat epileptic patients with carbamazepine.

Visual and auditory evoked potentials during long-term vigabatrin treatment in children and adolescents with epilepsy

OBJECTIVES

The aim of the study was to estimate the effects of Vigabatrin (VGB) as add-on therapy on visual (VEP) and brain-stem (BAEP) evoked potentials.

METHOD

The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these AEDs. Combination therapy was administered using add-on VGB in the recommended dose 57.4+/-26.5 mg/kg body mass/day. VEP and BAEP evoked potentials were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age matched control group.

RESULTS

Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the interpeak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes.

CONCLUSIONS

Adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs. Our electrophysiological studies demonstrate abnormalities in EPs parameters due to subclinical toxicity induced by AEDs. Major alterations produced bitherapy of VPA-SR + VGB and minor SR formulations of CBZ or VPA.

Effects of monotherapy and polytherapy on the blink reflex in epileptic patients

We performed the blink reflex (BR) in 20 normal volunteers, 13 epileptic patients receiving antiepileptic drug (AED) monotherapy, and 13 epileptic patients receiving AED polytherapy. Comparison of R1, ipsilateral and contralateral R2 and VIIth nerve latencies in the three groups showed no statistically significant differences R1 and VIIth nerve latencies among the three groups. There were statistically significant differences between the polytherapy group and the monotherapy and control groups in comparisons of ipsilateral and contralateral R2. There were no significant differences between the monotherapy group and the control group for ipsilateral and contralateral R2. We hypothesized that AED polytherapy might interfere with synaptic transmission in the polysynaptic pathway of the blink reflex, prolonging the latency of R2. These results provide further evidence of the pathophysiologic effects associated with polytherapy in epileptic patients.

Effect of acute doses of controlled-release carbamazepine on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function

The neurotoxic effect of acute doses of carbamazepine controlled-release (CBZ-CR) divitabs (800, 1,200, and 1,600 mg) was assessed on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function in 10 healthy volunteers in a double-blind, randomised, placebo-controlled, phase I study. Significant changes compared to placebo were demonstrated for the clinical scales, ataxia (AT), convergence of the near-point (CNP), peak saccadic velocity (PSV), critical flicker fusion (CFF), spectral analysis of the EEG, and brainstem auditory evoked potential (BAEP) tests. Digit repetition, digit symbol substitution, Sternberg memory scanning time, Sternberg choice reaction time, saccadic latency, and saccadic accuracy showed important negative findings. Significant clinical tolerance to side effects developed within 20 to 33 h after CBZ-CR dosage during a period in which the mean CBZ blood levels remained virtually unchanged. CBZ-CR, 800, 1,200, and 1,600 mg yielded low, medium, and high therapeutic blood levels, respectively, for +10 to +33 h after dosage without the development of severe clinical side effects.