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NEUROIMAGES
Year : 2019  |  Volume : 67  |  Issue : 3  |  Page : 936-937

14- and 6-Hz positive bursts and N waves: Lesser known benign EEG variants in adolescents


Epilepsy Program, Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada

Date of Web Publication23-Jul-2019

Correspondence Address:
Dr. Robyn Whitney
Epilepsy Program, Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario
Canada
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.263233

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How to cite this article:
Jain P, Borlot F, Morrison-Levy N, Ochi A, Whitney R. 14- and 6-Hz positive bursts and N waves: Lesser known benign EEG variants in adolescents. Neurol India 2019;67:936-7

How to cite this URL:
Jain P, Borlot F, Morrison-Levy N, Ochi A, Whitney R. 14- and 6-Hz positive bursts and N waves: Lesser known benign EEG variants in adolescents. Neurol India [serial online] 2019 [cited 2019 Dec 7];67:936-7. Available from: http://www.neurologyindia.com/text.asp?2019/67/3/936/263233




A 9-year old, right-handed, developmentally normal boy presented with frequent brief paroxysmal events for the last 6 months. These happened only while sleeping and were characterized by multifocal jerking of bilateral arms and legs independently. In the past, he had experienced one generalized tonic–clonic seizure while sleeping 2 years ago. His magnetic resonance imaging of the brain was normal. His previous two routine electroencephalograms (EEGs) were normal. A prolonged video-EEG was requested to characterize the ongoing events. This EEG diagnosed these events to be sleep myoclonus. It did not show any interictal epileptiform abnormalities but showed interesting benign EEG variants: 14- and 6-Hz positive bursts and “N” waves [Figure 1].
Figure 1: EEG epochs from the EEG of the reported patient. (a and b) show typical 14- and 6-Hz positive bursts and N waves' morphology in bipolar (a) and referential (Pz) montages (b). N-shaped wave configuration is formed by the apposition of 14- and 6-Hz positive bursts and sleep features like vertex waves. The morphology may resemble a spike wave discharge (c). (d) shows a more complex morphology of the N wave. These discharges were seen in drowsiness, N1, and REM sleep states

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Fourteen- and 6-Hz positive bursts are predominantly seen during drowsiness, light and rapid eye movement (REM) sleep, and have maximal amplitude over the posterior temporal head region.[1] They have been shown to be of hippocampal origin on simultaneous stereotactic EEG and scalp EEG recordings.[2]

Blume et al.,[3] described “N” waves as a normal variant occurring in association with 14- and 6-Hz positive bursts. This EEG feature can sometimes be mistakenly reported as epileptiform. However, the typical 14- and 6-Hz morphology preceding the complex and its disappearance during deeper sleep stages might differentiate N waves from the epileptiform abnormalities. However, Oletsky et al.,[4] reported 14- and 6-Hz positive bursts to be consistently preceding the generalized paroxysms in an adolescent girl with childhood absence epilepsy. Thus, the morphology of N waves should be kept in mind and both under- and overreporting of EEGs should be avoided.

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  References Top

1.
Gibbs EL, Gibbs FA. Electroencephalographic evidence of thalamic and hypothalamic epilepsy. Neurology 1951;1:136-44.  Back to cited text no. 1
    
2.
Jain P, Shafi S, Ochi A, Donner E, Sharma R, Ibrahim G, et al. High voltage 14 Hz hippocampal discharges on stereotactic EEG underlying 14 and 6 Hz positive bursts on scalp EEG. Clin Neurophysiol 2018;129:1626-7.  Back to cited text no. 2
    
3.
Blume WT, Holloway GM, Kaibara M, Young GB, editors. Blume's Atlas of Pediatric and Adult Electroencephalography. Baltimore, MD: Lippincott Williams & Wilkins; 2011. p. 197.  Back to cited text no. 3
    
4.
Oletsky H, Greenfield J, Sato S. 14 and 6 Hz positive spikes preceding 3 Hz generalized spike and wave in a 15 year old patient with absence: A case report. Electroencephalogr Clin Neurophysiol 1998;106:262-4.  Back to cited text no. 4
    


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