Repetitive Transcranial Magnetic Stimulation and Postoperative Neurocognitive Recovery

Mild cognitive impairment (MCI) affects 10-15% of the population over 65 years old. In patients for elective non-cardiac and emergency surgeries, the pooled prevalences of unrecognized cognitive impairment were 37.0% and 50.0%, respectively. Patients with preoperative cognitive impairment are at increased risk of delayed neurocognitive recovery (DNR) and postoperative neurocognitive disorder (POCD). Therefore, perioperative neurocognitive protection is particularly important for patients with preoperative cognitive impairment.

Repetitive transcranial magnetic stimulation (rTMS) is a neural modulation technique. By acting on the brain and altering the membrane potential of cortical neurons, the generated pulsed magnetic fields affect neural metabolism and electrical activity and trigger a series of physiological and biochemical reactions. It was found that high frequency (>5 Hz) rTMS increases cortical excitability, whereas low frequency (<1Hz) rTMS reduces corticol excitability. The mechanism by which rTMS regulates brain function is generally believed to be related to the long-term enhancement and long-term inhibition of synaptic transmission function.

The left dorsolateral prefrontal cortex (DLPFC) is an important target of rTMS intervention for improving cognitive function. A meta-analysis showed that high-frequency rTMS on the DLPFC and low-frequency rTMS on the right medial prefrontal cortex improved memory function; high frequency rTMS on the right inferior frontal gyrus enhanced executive ability in non-surgical patients with mild cognitive impairment or Alzheimer's disease. Another meta-analysis showed that high-frequency rTMS on DLPFC is an effective therapeutic option for improving cognitive function in Alzheimer patients.

This trial is designed to compare the effects of rTMS versus sham intervention on postoperative neurocognitive function in patients with preoperative cognitive impairment.

Inclusion criteria

• Aged ≥65 years;
• Patients with preoperative mild to moderate cognitive impairment, defined as 9<Montreal Cognitive Assessment (MoCA)<26;
• Scheduled for elective non-cardiac surgery under general anesthesia, with an expected surgical duration of >2 hours;
• Expected to stay in hospital for at least 5 days after surgery.

Exclusion criteria

• Left-handed;
• Primary school education level or below;
• Comorbid diseases including mental illness, intellectual disability, auditory and visual dysfunction, language impairment, severe neurological disorders, or other diseases that impede the completion of evaluation;
• Neurosurgery;
• Presence of contraindications to rTMS treatment, including epilepsy, pregnant or lactating women, or with a metal or electric implanted device (e.g., deep brain stimulator, ventriculoperitoneal shunt, aneurysm clip, pacemaker, cochlear implant, or surgical staples on the scalp);
• Other situations that are deemed unsuitable for inclusion in the study.