ABSTRACT
OBJECTIVE: There are numerous distinctive benign electroencephalographic (EEG) patterns which are morphologically epileptiform but are non-epileptic. The aim of this study was to determine the prevalence of different benign epileptiform variants (BEVs) among subjects who underwent routine EEG recordings in a large EEG laboratory over 35 years. METHODS: We retrospectively studied the prevalence of BEVs among 35,249 individuals who underwent outpatient EEG recordings at London Health Sciences Centre in London, Ontario, Canada between January 1, 1972 and December 31, 2007. The definitions of the Committee on Terminology of the International Federation of Societies for EEG and Clinical Neurophysiology (IFSECN) were used to delineate epileptiform patterns (Chatrian et al. A glossary of terms most commonly used by clinical electroencephlographers. Electroenceph Clin Neurophysiol 1974;37:538-48) and the descriptions of Klass and Westmoreland [Klass DW, Westmoreland BF. Nonepileptogenic epileptiform electroenephalographic activity. Ann Neurol 1985;18:627-35] were used to categorize the BEVs. RESULTS: BEVs were identified in 1183 out of 35,249 subjects (3.4%). The distribution of individual BEVs were as follows: benign sporadic sleep spikes 1.85%, wicket waves 0.03%, 14 and 6 Hz positive spikes 0.52%, 6 Hz spike-and-waves 1.02%, rhythmic temporal theta bursts of drowsiness 0.12%, and subclinical rhythmic electrographic discharge of adults in 0.07%. CONCLUSION: The prevalence of six types of BEVs was relatively low among the Canadian subjects when compared to the reports from other countries. SIGNIFICANCE: BEVs are relatively uncommon incidental EEG findings. Unlike focal epileptic spikes and generalized spike-and-waves, BEVs do not predict the occurrence of epilepsy. Accurate identification of the BEVs can avoid misdiagnosis and unnecessary investigations.
Subject(s)
Cerebral Cortex/physiopathology , Electroencephalography/methods , Epilepsy/diagnosis , Epilepsy/epidemiology , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Epilepsy/physiopathology , Evoked Potentials/physiology , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Ontario/epidemiology , Predictive Value of Tests , Prevalence , Retrospective Studies , Theta Rhythm , Young AdultABSTRACT
We analyzed the clinical, electrophysiologic, and genetic features of Omani Arab patients suspected of manifesting the Unverricht-Lundborg form of progressive myoclonus epilepsy. Ten patients (five boys, five girls; mean age at onset, 10.2 years) were evaluated. Unverricht-Lundborg disease was confirmed in all by detection of dodecamer repeat expansion mutations in the EPM1 gene. There was no correlation between age at onset or severity of disease with sizes of dodecamer repeats. Myoclonic seizures were the presenting symptom in 70% of patients. Myoclonus was severe in adolescence, but remained stable or improved beyond 5-6 years of disease onset. No significant cognitive decline occurred. Nearly 75% of patients exhibited mild to moderate cerebellar dysfunction, which was nonprogressive after adulthood. Slowing of background activity, generalized spike-wave discharges, and photoparoxysmal responses were evident in all patients' electroencephalograms. Spike-wave discharges and photoparoxysmal responses tended to disappear in adulthood. This cluster of progressive myoclonus epilepsy patients manifested typical Unverricht-Lundborg disease. All cases had mutations in EPM1, the known gene for this disorder, and therefore do not contribute to identifying the gene in a second Unverricht-Lundborg disease locus recently mapped in Arab patients from Israel. Although Unverricht-Lundborg disease is very severe in adolescence, its clinical signs stabilize and improve somewhat in adulthood in this so-called "progressive epilepsy."
