Brain PET metabolic substrate of TMS response in pharmaco-resistant depression

Advancements in Transcranial Magnetic Stimulation Research and the Path to Precision

Transcranial magnetic stimulation (TMS) has become increasingly popular in clinical practice in recent years, and there have been significant advances in the principles and stimulation modes of TMS. With the development of multi-mode and precise stimulation technology, it is crucial to have a comprehensive understanding of TMS. The neuroregulatory effects of TMS can vary depending on the specific mode of stimulation, highlighting the importance of exploring these effects through multimodal application. Additionally, the use of precise TMS therapy can help enhance our understanding of the neural mechanisms underlying these effects, providing us with a more comprehensive perspective. This article aims to review the mechanism of action, stimulation mode, multimodal application, and precision of TMS.

Transcranial Magnetic Stimulation and its Imaging Features in Patients With Depression, Post-traumatic Stress Disorder, and Traumatic Brain Injury

Transcranial magnetic stimulation (TMS) is a type of noninvasive neurostimulation used increasingly often in clinical medicine. While most studies to date have focused on TMS's ability to treat major depressive disorder, it has shown promise in several other conditions including post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI). As different treatment protocols are often used across studies, the ability to predict patient outcomes and evaluate immediate and long-term changes using imaging becomes increasingly important. Several imaging features, such as thickness, connectedness, and baseline activity of a variety of cortical and subcortical areas, have been found to be correlated with a greater response to TMS therapy. Intrastimulation imaging can reveal in real time how TMS applied to superficial areas activates or inhibits activity in deeper brain regions. Functional imaging performed weeks to months after treatment can offer an understanding of how long-term effects on brain activity relate to clinical improvement. Further work should be done to expand our knowledge of imaging features relevant to TMS therapy and how they vary across patients with different neurological and psychiatric conditions.

Changing Cerebral Blood Flow, Glucose Metabolism, and Dopamine Binding Through Transcranial Magnetic Stimulation: A Systematic Review of Transcranial Magnetic Stimulation-Positron Emission Tomography Literature

Transcranial magnetic stimulation (TMS) is a noninvasive neuromodulation tool currently used as a treatment in multiple psychiatric and neurologic disorders. Despite its widespread use, we have an incomplete understanding of the way in which acute and chronic sessions of TMS affect various neural and vascular systems. This systematic review summarizes the state of our knowledge regarding the effects TMS may be having on cerebral blood flow, glucose metabolism, and neurotransmitter release. Forty-five studies were identified. Several key themes emerged: 1) TMS transiently increases cerebral blood flow in the area under the coil; 2) TMS to the prefrontal cortex increases glucose metabolism in the anterior cingulate cortex of patients with depression; and 3) TMS to the motor cortex and prefrontal cortex decreases dopamine receptor availability in the ipsilateral putamen and caudate respectively. There is, however, a paucity of literature regarding the effects TMS may have on other neurotransmitter and neuropeptide systems of interest, all of which may shed vital light on existing biologic mechanisms and future therapeutic development. SIGNIFICANCE STATEMENT: Transcranial magnetic stimulation (TMS) is a noninvasive neuromodulation tool currently used as a treatment in multiple psychiatric and neurologic disorders. This systematic review summarizes the state of our knowledge regarding the effects TMS on cerebral blood flow, glucose metabolism, and neurotransmitter release.

Brain SPECT perfusion and PET metabolism as discordant biomarkers in major depressive disorder

Background

Brain SPECT perfusion and PET metabolism have been, most often interchangeably, proposed to study the underlying pathological process in major depressive disorder (MDD). The objective of this study was to specify similarities and inconsistencies between these two biomarkers according to global characteristics of the disease. We conducted a retrospective study in 16 patients suffering from treatment-resistant MDD who underwent, during the same current episode, a cerebral perfusion SPECT with ^99mTc-HMPAO and a metabolic PET with ¹⁸F-FDG. Whole-brain voxel-based SPM(T) maps were generated in correlation with the number of depressive episodes and in correlation with the depression duration, separately for the two exams (p-voxel < 0.001 uncorrected, k > 20).

Results

No significant correlations were found between brain metabolism and either the number of depressive episodes or the duration of the disease, even at an uncorrected p-voxel < 0.005. On the other hand, the increased number of depressive episodes was correlated with decreased perfusion of the right middle frontal cortex, the right anterior cingulum cortex, the right insula, the right medial temporal cortex and the left precuneus. The increased depression duration was correlated with decreased perfusion of the right anterior cingulum cortex.

Conclusions

This preliminary study demonstrates more significant results with brain perfusion compared with glucose metabolism in treatment-resistant MDD, highlighting the value of brain SPECT despite less favourable instrumentation detection compared to PET.