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NEUROLOGY 2009;73:218-222
© 2009 American Academy of Neurology

Why do seizures in generalized epilepsy often occur in the morning?

R.A.B. Badawy, MB, BCh, MSc, R. A.L. Macdonell, MD, FRACP, G. D. Jackson, MD, FRACP and S. F. Berkovic, MD, FRACP, FRS

From the Department of Neurology (R.A.B.B., R.A.L.M., G.D.J., S.F.B.), Austin Health, Heidelberg; Epilepsy Research Centre (R.A.B.B., R.A.L.M., G.D.J., S.F.B.), Department of Medicine, University of Melbourne; and Brain Research Institute (G.D.J.), Florey Neuroscience Institutes Heidelberg West, Victoria, Australia.

Address correspondence and reprint requests to Dr. Richard Macdonell, Department of Neurology, Austin Health, Studley Road, Heidelberg, Victoria 3084, Australia Richard.Macdonell{at}austin.org.au

Objective: We used transcranial magnetic stimulation to investigate the effect of diurnal variability on cortical excitability in patients with epilepsy.

Methods: Thirty drug-naive patients with epilepsy (20 idiopathic generalized epilepsy [IGE], including 10 juvenile myoclonic epilepsy [JME], and 10 focal epilepsy) and 10 control subjects without epilepsy were studied both early in the morning and late in the afternoon. We measured the mean motor thresholds and constructed recovery curves at short (2–15 msec) and long (50–400 msec) interstimulus intervals.

Results: An increase in cortical excitability indicated by decreased short and long intracortical inhibition was observed early in the morning compared to the afternoon in patients with JME. In other IGE syndromes, there was decreased long intracortical inhibition only. No effect was found in subjects with focal epilepsy or controls without epilepsy.

Conclusion: Cortical excitability measured by transcranial magnetic stimulation increases early in the morning in patients with idiopathic generalized epilepsy, particularly in juvenile myoclonic epilepsy, but not in subjects with focal epilepsy or controls without epilepsy. This may explain the increased seizure susceptibility in this cohort at this time of day.

Abbreviations: AED = antiepileptic drug; APB = abductor pollicis brevis; CR = conditioning response; IGE = idiopathic generalized epilepsy; ISI = interstimulus interval; JME = juvenile myoclonic epilepsy; MEP = motor evoked potential; MT = motor threshold; NREM = non-REM; TMS = transcranial magnetic stimulation; TR = test response.

Disclosure: The authors report no disclosures.

Received December 24, 2008. Accepted in final form April 6, 2009.






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