Paradoxical Alteration in Cortical Excitability Following 10 Hz rTMS in Patients with Untreated Obstructive Sleep Apnea Syndrome (OSAS) (P05.007)

Abstract

Objective: To investigate changes in cortical excitability in patients with obstructive sleep apnea syndrome (OSAS) undergoing 10Hz repetitive transcranial magnetic stimulation (rTMS) during wakefulness. Background OSAS is a syndrome characterized by repetitive upper airway collapse or narrowing during sleep with sequelae include adverse cardiovascular and metabolic outcomes, decline in quality of life, and neurocognitive impairment. Although altered cortical excitability in OSAS is well documented, the effect of rTMS on the excitability changes in OSAS patients has not previously been studied. This is important as rTMS can potentially be used as an adjunct therapy in OSAS. Design/Methods: We recruited 13 untreated severe OSAS (10 males, mean apnea-hypopnea index=54.6±13.01h) patients and 12 age-matched healthy volunteers. The TMS parameters measured were resting motor threshold (RMT), motor evoked potential (MEP) amplitude, central motor conduction time (CMCT), cortical silent period (CSP) and short-interval intracortical inhibition (SICI). These parameters were measured in the morning more than 2h after arising. After the baseline TMS studies, the patients and healthy volunteers were subjected to 10 Hz rTMS over left dorsolateral prefrontal cortex. The TMS parameters (RMT, MEP, CMCT, CSP and SICI) were repeated thereafter. Results: OSAS patients had a significantly higher RMT and a longer CSP duration (t-test, p 0.05). The rTMS showed an prolongation of CSP in OSAS subjects (ANOVA, p Conclusions: This TMS-based study suggests that untreated severe OSAS patients have imbalanced cortical excitabilities that enhanced inhibition or decreased brain excitability when awake during the day. The paradoxical response of rTMS in OSAS patients highlights the complex interplay of excitatory and inhibitory cortical circuits in OSAS. This intriguing result needs further replication. Disclosure: Dr. Das has nothing to disclose. Dr. Vijayakumari has nothing to disclose. Dr. Radhakrishnan has nothing to disclose.