Loss of TREM2 function impairs phagocytosis and correlates with decreased soluble TREM2 in biological fluids of patients with neurodegenerative disorders.

Objective: To review novel techniques of noninvasive brain stimulation (NBS), which may have value in assessment and treatment of traumatic brain injury (TBI). Methods: Review of the following techniques: transcranial magnetic stimulation, transcranial direct current stimulation, low-level laser therapy, and transcranial Doppler sonography. Furthermore, we provide a brief overview of TMS studies to date. Main findings: We describe the rationale for the use of these techniques in TBI, discuss their possible mechanisms of action, and raise a number of considerations relevant to translation of these methods to clinical use. Depending on the stimulation parameters, NBS may enable suppression of the acute glutamatergic hyperexcitability following TBI and/or counter the excessive GABAergic effects in the subacute stage. In the chronic stage, brain stimulation coupled to rehabilitation may enhance behavioral recovery, learning of new skills, and cortical plasticity. Correlative animal models and comprehensive safety trials seem critical to establish the use of these modalities in TBI. Conclusions: Different forms of NBS techniques harbor the promise of diagnostic and therapeutic utility, particularly to guide processes of cortical reorganization and enable functional restoration in TBI. Future lines of safety research and well-designed clinical trials in TBI are warranted to determine the capability of NBS to promote recovery and minimize disability.

Background and Purpose— Electromagnetic brain stimulation might have value to reduce motor deficits after stroke. Safety and behavioral effects of higher frequencies of repetitive transcranial magnetic stimulation (rTMS) require detailed assessment. Methods— Using an active treatment-only, unblinded, 2-center study design, patients with chronic stroke received 20 minutes of 20 Hz rTMS to the ipsilesional primary motor cortex hand area. Patients were assessed before, during the hour after, and 1 week after rTMS. Results— The 12 patients were 4.7±4.9 years poststroke (mean±SD) with moderate–severe arm motor deficits. In terms of safety, rTMS was well tolerated and did not cause new symptoms; systolic blood pressure increased from pre- to immediately post-rTMS by 7 mm Hg ( P =0.043); and none of the behavioral measures showed a decrement. In terms of behavioral effects, modest improvements were seen, for example, in grip strength, range of motion, and pegboard performance, up to 1 week after rTMS. The strongest predictor of these motor gains was lower patient age. Conclusions— A single session of high-frequency rTMS to the motor cortex was safe. These results require verification with addition of a placebo group and thus blinded assessments across a wide spectrum of poststroke deficits and with larger doses of 20 Hz rTMS.

Read the full review for this F1000Prime recommended article: An open-label, prospective study of repetitive transcranial magnetic stimulation (rTMS) in the long-term treatment of refractory depression: reproducibility and duration of the antidepressant effect in medication-free patients.