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

Area of Science:

• Neuroscience
• Sleep Medicine
• Neurology

Background:

• Obstructive sleep apnea syndrome (OSAS) is associated with decreased cortical excitability, indicated by elevated resting motor threshold (RMT) and reduced short-latency afferent inhibition (SAI).
• Previous transcranial magnetic stimulation (TMS) studies suggest these changes, but precise targeting of the motor cortex is crucial for accurate assessment.

Purpose of the Study:

• To confirm reduced cortical excitability in OSAS patients using navigated TMS (nTMS) for precise motor cortex targeting.
• To assess RMT as an index of corticospinal activation and SAI as an index of cholinergic neurotransmission in OSAS.

Main Methods:

• 17 severe OSAS patients and 12 healthy controls underwent nTMS after head MRI for motor cortex mapping.
• RMT and SAI were assessed by recording motor evoked potentials (MEPs) from the abductor-pollicis brevis (APB) muscle.
• SAI was measured using a paired-pulse paradigm with electrical stimulation of the median nerve and magnetic stimulation of the motor cortex at specific inter-stimulus intervals (ISIs).

Main Results:

• OSAS patients exhibited a significantly higher RMT (stimulation intensity) compared to controls.
• A significantly lower percentage deviation of MEP amplitude from the control condition was observed in OSAS patients at ISIs of 18-28 ms.
• Body Mass Index (BMI) negatively correlated with MEP amplitude percentage deviation in OSAS patients.

Conclusions:

• nTMS confirms increased RMT and reduced cortical afferent inhibition (SAI) in OSAS patients.
• These findings reinforce previous evidence of impaired cortical excitability in OSAS.
• Further nTMS research is warranted to explore its diagnostic and therapeutic potential in OSAS.