Obstructive Sleep Apnea Syndrome: A Preliminary Navigated Transcranial Magnetic Stimulation Study

Abstract

Maja Rogić Vidaković,1 Joško Šoda,2 Ana Jerković,1 Benjamin Benzon,1 Karla Bakrač,1 Silvia Dužević,1 Igor Vujović,2 Mario Mihalj,3 Renata Pecotić,1,4 Maja Valić,1,4 Angela Mastelić,5 Maximilian Vincent Hagelien,1 Marina Zmajević Schőnwald,6 Zoran Đogaš1,4 1University of Split, School of Medicine, Department of Neuroscience, Laboratory for Human and Experimental Neurophysiology (LAHEN), Split, Croatia; 2University of Split, Faculty of Maritime Studies, Signal Processing, Analysis and Advanced Diagnostics Research and Education Laboratory (SPAADREL), Split, Croatia; 3University Hospital Split, Department of Neurology, Laboratory of Electromyoneurography, Split, Croatia; 4University of Split, Split Sleep Medical Center, Split 21000, Croatia; 5University of Split, School of Medicine, Department of Medical Chemistry and Biochemistry, Split, Croatia; 6Clinical Medical Centre “Sisters Of Mercy”, Department of Neurosurgery, Clinical Unit for Intraoperative Neurophysiologic Monitoring, Zagreb, CroatiaCorrespondence: Maja Rogić VidakovićUniversity of Split, School of Medicine, Department of Neuroscience, Laboratory for Human and Experimental Neurophysiology (LAHEN), Split, CroatiaTel [phone]Fax [phone]Email [email protected]: An increase in resting motor threshold (RMT), prolonged cortical silent period duration (CSP), and reduced short-latency afferent inhibition (SAI), confirmed with previous transcranial magnetic stimulation (TMS), suggest decreased cortical excitability in obstructive sleep apnea syndrome (OSAS). The present study included MRI of OSAS patients for navigated TMS assessment of the RMT, as an index of the threshold for corticospinal activation at rest, and SAI as an index of cholinergic neurotransmission. We hypothesize to confirm findings on SAI and RMT with adding precision in the targeting of motor cortex in OSAS.Subjects and Methods: After acquiring head MRIs for 17 severe right-handed OSAS and 12 healthy subjects, the motor cortex was mapped with nTMS to assess the RMT and SAI, with motor evoked potentials (MEPs) recorded from the abductor-pollicis brevis (APB) muscle. The 120%RMT intensity was used for the SAI by a paired-pulse paradigm in which the electrical stimulation to the median nerve is followed by magnetic stimulation of the motor cortex at inter-stimulus intervals (ISIs) of 18– 28 ms (ISIs18-28). The SAI control condition included a recording of MEPs without peripheral stimulation. Latency and amplitude of MEP at RMT at 120%RMT for eleven different at ISIs18-28 were analyzed.Results: The study showed a significantly lower percentage deviation of MEP amplitude at ISIs(18-28ms) from the control condition between OSAS and healthy subjects (U=44.0, p=0.01). The intensity of stimulation at RMT was significantly higher in OSAS subjects (U=55.0, p=0.04*). Correlation analysis showed that BMI significantly negatively correlated (ρ=− 0.47) with MEP amplitude percentage deviation in OSAS patients.Conclusion: The nTMS study results in increased RMT, and reduced cortical afferent inhibition in OSAS patients for SAI at ISIs18-28, confirming previous findings of impaired cortical afferent inhibition in OSAS. Future nTMS studies are desirable to elucidate the role of RMT and SAI in diagnostics and treatment of OSAS, and to elucidate the usefulness of nTMS in OSAS research.Keywords: short-latency afferent inhibition, obstructive sleep apnea, transcranial magnetic stimulation, motor evoked potentials, primary motor cortex, transcutaneous electrical nerve stimulation

Keywords

• short-latency afferent inhibition
• obstructive sleep apnea
• transcranial magnetic stimulation
• motor evoked potentials
• primary motor cortex
• transcutaneous electrical nerve stimulation