LETTER TO EDITOR
|Year : 2020 | Volume
| Issue : 3 | Page : 347-348
Auditory- and visual-evoked responses in children and adolescents with epilepsy
Prateek K Panda, Indar K Sharawat
Pediatric Neurology Division, Department of Pediatrics, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
|Date of Submission||15-May-2020|
|Date of Decision||18-May-2020|
|Date of Acceptance||18-May-2020|
|Date of Web Publication||06-Nov-2020|
Dr. Indar K Sharawat
Department of Pediatrics, All India Institute of Medical Sciences, Rishikesh, Uttarakhand.
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Panda PK, Sharawat IK. Auditory- and visual-evoked responses in children and adolescents with epilepsy. J Pediatr Neurosci 2020;15:347-8
We read with great interest the recently published article entitled “Auditory and visual P300 responses in early cognitive assessment of children and adolescents with epilepsy” by Gupta et al. The authors have shown in this study that visual and auditory P300 latencies were more delayed, with reduced amplitudes in children with epilepsy as compared to controls. In focal epilepsy, only auditory P300 was significantly delayed, whereas both visual and auditory P300 were delayed in generalized epilepsy. However, these abnormalities did not correlate with any risk factors, even with or without the presence of antiepileptic treatment. However, we wish to add some points to this recently published article.
The authors have attributed these abnormalities to subtle cognitive dysfunction and abnormalities in the hippocampus, mesencephalic reticular formation, and other cortical and subcortical structures. However, we consider the P300 abnormalities noted in the study could be multifactorial, involving neural transmission, processing, and delayed reaction time. If the authors would have mentioned the latency and amplitude of N75 and P100 response in participants, it would have provided more information regarding these underlying processes. However, the authors have mentioned only the latency and amplitude of the P300 response. The P300 wave component of event-related potential (ERP) is an endogenous potential, independent of the physical attributes of the stimulus and elicited during the process of stimulus evaluation and categorization. Thus, P300 is considered to be generated due to the processing of sensory stimuli, reacting to some behavioral responses, and provides an assessment of cognitive functions. On the contrary, the P100 response of visual evoked response (VER) indicates the integrity of the stimulus transmission process from the neural elements of the retina to the occipital cortex.
Genç et al. have detected a shortened N75 latency and higher than normal P100 amplitudes in patients with photosensitive epilepsy. In patients without photosensitivity in electroencephalogram (EEG), P100 latency was prolonged, but the amplitude was normal. They attributed such variable response in children with/without photo-paroxysmal response to subtle morphologic abnormalities in cerebral parenchyma such as microdysgenesis or abnormalities in one of the neurotransmitters.
In the current study, the authors have only mentioned that the participants did not have a specific focal neurological deficit or laterality. But they did not mention the neuroimaging or EEG abnormalities in participants, including the result of activation maneuvers such as hyperventilation or photic stimulation and evoked response parameters in each of these subgroups. Moreover, the authors did not mention the exact electroclinical syndrome to which the participants belonged and just subdivided them into generalized and focal epilepsy. Even within focal epilepsy, they did not mention, how many participants had structural epilepsy such as mesial temporal sclerosis, focal cortical dysplasia, or childhood-onset self-limited focal epilepsy syndromes such as benign childhood epilepsy with centrotemporal spikes and childhood-onset occipital epilepsy (Panayiotopoulos or Gastaut type). Juvenile myoclonic epilepsy and occipital epilepsy often show photosensitivity and VER, which is predominantly controlled by the visual cortex, and the visual pathway might be relatively more aberrant in these children.
Similarly, although the auditory-evoked potential is predominantly brain stem in origin, it is also modulated by the auditory cortex in the lateral temporal lobe and thus likely to be more affected in temporal lobe epilepsy. Lastly, the authors have mentioned no significant difference between P300 latency and amplitude between those with or without antiepileptic drug treatment. Certain antiepileptic drugs (such as phenobarbitone, benzodiazepine, carbamazepine, and topiramate) are more likely to affect cognitive function and sensory processing speed more than other drugs (such as levetiracetam). So some information on the effect of specific antiepileptic drugs on evoked potential would have been more beneficial in educating readers about the impairment of cognition and executive function caused by these drugs.
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Conflicts of interest
There are no conflicts of interest.
| References|| |
Gupta S, Prasad A, Singh R, Gupta G Auditory and visual P300 responses in early cognitive assessment of children and adolescents with epilepsy. J Pediatr Neurosci 2020;15:9-14.
Kothari R, Bokariya P, Singh S, Singh R A comprehensive review on methodologies employed for visual evoked potentials. Scientifica (Cairo) 2016;2016:9852194.
Genç BO, Genç E, Güney F, Ilhan N Pattern-reversal visual evoked potentials in patients with newly diagnosed epilepsy. Epilepsia 2005;46:1219-23.
Lu Y, Waltz S, Stenzel K, Muhle H, Stephani U Photosensitivity in epileptic syndromes of childhood and adolescence. Epileptic Disord 2008;10:136-43.
Spitzer E, White-Schwoch T, Carr KW, Skoe E, Kraus N Continued maturation of the click-evoked auditory brainstem response in preschoolers. J Am Acad Audiol 2015;26:30-5.
Park SP, Kwon SH Cognitive effects of antiepileptic drugs. J Clin Neurol 2008;4:99-106.