Motor Evoked Potentials And Video-EEG Analysis During Cataplexy In Narcolepsy

PartⅠ.Cortical hypoexcitability and prolonged MEP latency during cataplectic attack in narcolepsyObjective:To assess the alteration of motor conduction pathways before and during the cataplectic attack by motor-evoked potentials(TMS-MEP).Discuss the relationships between the excitability of primary motor cortex and mechanism of cataplexy.Methods:Nineteen narcolepsy patients with cataplexy and twenty-two healthy age-and heightmatched control subjects were recruited.All patients completed standard night Polysomnography(PSG)and daytime Multiple Sleep latency Test(MSLT).MEPs were performed during quiet wakefulness and cataplexy;measures of cortical excitability included resting motor threshold(RMT),1m V motor threshold(1m V MT),cortical silent period(CSP),intracortical facilitation(ICF)and short latency intracortical inhibition(SICI).Results:1.The average SOREMPs and sleep latency during MSLT in narcolepsy with cataplexy were 3.16±0.83 and 2.28±1.91 min,respectively.All patients meet the diagnostic criteria of narcolepsy type 1.2.During quiet wakefulness,ICF decreased in narcoleptic patients compared with healthy controls(108.21±51.40% vs 182.73±68.59%,P=0.002).While 1m V MT(48.39±7.12% vs 44.86 ±4.91%,P=0.072),RMT(36.44(33.00 38.50)% vs 36.18(33.0038.25)%,P=1.000),CSP(68.00(47.50 79.50)ms vs 58.73(39.50 67.00)ms,P=0.160)and SICI(43.42% vs 18.80%,75.71% vs 178.95%)differences didn’t reach statistical significance.3.We monitored nine cataplectic attacks in six patients.In global cataplexy,when given 1m V MT and RMT stimulation,mean MEP amplitude decreased 73.45% and45.47%,total mean MEP latency prolonged 4±2ms.2 patients characterized by increased ICF(98.68% vs 124.00%,52.86% vs 110.53%),reversed change of SICI(43.42% vs18.80%,75.71% vs 178.95%)and lengthened CSP duration(78ms vs 132 ms,64ms vs104ms)in recovery stage.Conclusion:Narcolepsy patients with cataplexy showed decreased ICF in non-cataplectic state and notable decreased MEP amplitude with prolonged MEP latency in both global and segmental cataplexies.We demonstrated that the inhibition of corticospinal tracts and motor cortical hypoexcitability were involved in the mechanism of cataplexy.Part Ⅱ.Ambulatory Video-EEG-EMG-ECG Monitoring and Analysis During cataplexy in NarcolepsyObjective:To comprehensive analyze the clinical and electroneurophysiology characteristics during the occurrence and development of cataplexy,which provide assistance for the diagnosis and study of cataplexy.Methods:Five(4 males)drug-naive narcolepsy patients with typical cataplexy were enrolled.All patients’ clinical course were less than one year and three among them were dignosed with status cataplecticus.Patients stood in a protected and soundproof room subsequent to a 30 min sleep.Cataplexy was triggered by an experienced physician and the whole cataplexy process was under a video-EEG-EMG-ECG monitoring.Results:Fourteen cataplectic attacks in five patients were recorded.We observed that1.Cataplexy is a dynamic process.We proposed a modified cataplexy staging based on previous study.New staging included initial phase,resistance/falling phase,atonic phase and recovery phase.Patient was triggered by emotional stimulus(initial phase),started twitching and became postural instability(resistance/falling phase),then progressed to general weakness(atonic phase),finally,recovered from atonic phase gradually(recovery phase).2.Distinctive transient paroxysmal theta ryhthm(hypersynchronous paroxysmal theta,HSPT)was recorded while patients twitched in resistance/falling phase and low voltage mixed frequency wave was observed in atonic phase.Recovery phase was featured with alpha and beta ryhthm.3.A comparison of EEG.The amplitude of theta ryhthm in cataplexy was significantly higher than that in SOREMPs phase(119.60 vs 52.35 u V),accompanied by a faster frequency(5.23 vs 5.18Hz).The low voltage mixed frequency in atonic phase(26.25 u V,8.28Hz)was different from quiet wakefulness and night REM sleep.Conclusion:The clinical and electroneurophysiology characteristics of cataplexy phases were distinct from each other and reflexed a dynamic and inverse relationship of neurotransmitters.We considered the resistance/falling phase and typical hypersynchronous paroxysmal theta(HSPT)was a break of the blance and progressed to a cataplectic attack.