Transcranial Magnetic Stimulation and Sleep Deprivation as Experimental Tools: When Sleep Deprivation is Too Exciting

Abstract

Sleep Deprivation Increases Cortical Excitability in Epilepsy: Syndrome-Specific Effects. Badawy RA, Curatolo JM, Newton M, Berkovic SF, Macdonell RA. Neurology 2006;67(6):1018–1022. OBJECTIVE: To use transcranial magnetic stimulation (TMS) to investigate the hypothesis that sleep deprivation increases cortical excitability in people with epilepsy. METHODS: We performed paired pulse TMS stimulation, using a number of interstimulus intervals (ISIs) on each hemisphere of 30 patients with untreated newly diagnosed epilepsy (15 idiopathic generalized epilepsy [IGE] and 15 focal epilepsy) and on the dominant hemisphere of 13 healthy control subjects, before and after sleep deprivation. RESULTS: Both hemispheres in patients with IGE and the hemisphere ipsilateral to the EEG seizure focus in those with focal epilepsy showed an increase in cortical excitability following sleep deprivation at a number of ISIs. This change in excitability was most prominent in the patients with IGE. Although there were minor changes after sleep deprivation in control subjects and the contralateral hemisphere in the focal epilepsy group seen at the 250-millisecond ISI, it was less than that in the other groups. CONCLUSIONS: Sleep deprivation increases cortical excitability in epilepsy; the pattern of change is syndrome dependent. Effects of Sleep Deprivation on Cortical Excitability in Patients Affected by Juvenile Myoclonic Epilepsy: A Combined Transcranial Magnetic Stimulation and EEG Study. Manganotti P, Bongiovanni LG, Fuggetta G, Zanette G, Fiaschi A. J Neurol Neurosurg Psychiatry 2006;77(1):56–60. OBJECTIVE: To investigate the effect of sleep deprivation on corticospinal excitability in patients affected by juvenile myoclonic epilepsy (JME) using different transcranial magnetic stimulation (TMS) parameters. METHODS: Ten patients with JME and 10 normal subjects underwent partial sleep deprivation. Motor threshold (MT), motor evoked potential amplitude (MEP), and silent period (SP) were recorded from the thenar eminence (TE) muscles. Short latency intracortical inhibition (SICI) and short latency intracortical facilitation (SICF) were studied using paired magnetic stimulation. TMS was performed before and after sleep deprivation; EEG and TMS were performed simultaneously. RESULTS: In patients with JME, sleep deprivation induced a significant decrease in SICI and an increase in SICF, which was associated with increased paroxysmal activity. A significant decrease in the MT was observed. No significant changes in any TMS parameters were noted in normal subjects after sleep deprivation. The F wave was unchanged by sleep deprivation in both control subjects and in patients with JME. CONCLUSIONS: In patients with JME, sleep deprivation produces increases in corticospinal excitability in motor areas as measured by different TMS parameters.