TAK-653 is a novel α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-positive allosteric modulator being developed as a potential therapeutic for major depressive disorder (MDD). Currently, there are no translational biomarkers that evaluate physiological responses to the activation of glutamatergic brain circuits available. Here, we tested whether noninvasive neurostimulation, specifically single-pulse or paired-pulse motor cortex transcranial magnetic stimulation (spTMS and ppTMS, respectively), coupled with measures of evoked motor response captures the pharmacodynamic effects of TAK-653 in rats and healthy humans. In the rat study, five escalating TAK-653 doses (0.1–50 mg/kg) or vehicle were administered to 31 adult male rats, while measures of cortical excitability were obtained by spTMS coupled with mechanomyography. Twenty additional rats were used to measure brain and plasma TAK-653 concentrations. The human study was conducted in 24 healthy volunteers (23 males, 1 female) to assess the impact on cortical excitability of 0.5 and 6 mg TAK-653 compared with placebo, measured by spTMS and ppTMS coupled with electromyography in a double-blind crossover design. Plasma TAK-653 levels were also measured. TAK-653 increased both the mechanomyographic response to spTMS in rats and the amplitude of motor-evoked potentials in humans at doses yielding similar plasma concentrations. TAK-653 did not affect resting motor threshold or paired-pulse responses in humans. This is the first report of a translational functional biomarker for AMPA receptor potentiation and indicates that TMS may be a useful translational platform to assess the pharmacodynamic profile of glutamate receptor modulators.

Traumatic brain injury (TBI) increases cerebral reactive oxygen species production, which leads to continuing secondary neuronal injury after the initial insult. Cortical parvalbumin-positive interneurons (PVIs; neurons responsible for maintaining cortical inhibitory tone) are particularly vulnerable to oxidative stress and are thus disproportionately affected by TBI. Systemic N-acetylcysteine (NAC) treatment may restore cerebral glutathione equilibrium, thus preventing post-traumatic cortical PVI loss. We therefore tested whether weeks-long post-traumatic NAC treatment mitigates cortical oxidative stress, and whether such treatment preserves PVI counts and related markers of PVI integrity and prevents pathologic electroencephalographic (EEG) changes, 3 and 6 weeks after fluid percussion injury in rats. We find that moderate TBI results in persistent oxidative stress for at least 6 weeks after injury and leads to the loss of PVIs and the perineuronal net (PNN) that surrounds them as well as of per-cell parvalbumin expression. Prolonged post-TBI NAC treatment normalizes the cortical redox state, mitigates PVI and PNN loss, and - in surviving PVIs - increases per-cell parvalbumin expression. NAC treatment also preserves normal spectral EEG measures after TBI. We cautiously conclude that weeks-long NAC treatment after TBI may be a practical and well-tolerated treatment strategy to preserve cortical inhibitory tone post-TBI.

This study updates the results of a facial nerve preservation approach to treating vestibular schwannomas at a single institution by a single surgeon using retrosigmoid craniectomy with microsurgery (MS) and gamma knife stereotactic radiosurgery (SRS) over a 25-year interval. We retrospectively reviewed 751 patients between 1998 and 2023 and grouped them by intervention: MS only (Group 1, 217 patients), SRS only (Group 2, 447 patients), MS then SRS (Group 3, 72 patients), SRS then MS (Group 4, 10 patients), and SRS then SRS (Group 5, 5 patients). The primary outcome variable was facial nerve function, defined as House-Brackmann grade ≤2 at last follow-up. Good outcomes by group were achieved in 98.2%, 99.6%, 93.1%, 90%, and 100% of patients, respectively. Upfront SRS (Group 2) resulted in significantly better facial nerve outcomes than upfront MS (Groups 1 and 3, 289 patients) (96.9% and 99.4%, P < 0.05). Mean tumor maximum linear diameters were 3.2, 1.32, 3.23, 1.98, and 1.64 cm. Subtotal resection rates in Groups 1, 3, and 4, were 68.2%, 81.9%, and 80%, respectively. The median (interquartile range) follow-up time among patients (minimum follow-up of 12 months) was 52 (26.75-88) months, with a maximum of 297 months (24.75 years). Overall, 98.1% of patients had a good facial nerve outcome with no operative mortality. For larger tumors, MS emphasizing facial nerve preservation over gross total resection followed by adjuvant SRS for any interval tumor regrowth yields excellent facial nerve outcomes and tumor control rates. For smaller tumors, upfront SRS achieves superior facial nerve preservation with MS and SRS both viable salvage options for treatment of tumor progression. This paradigm balances tumor control, facial nerve preservation, and low morbidity.

Background/Objectives: Anterior cruciate ligament (ACL) injuries frequently lead to long-term quadriceps impairments despite surgical repair. There is growing evidence that these deficits are caused in part by alterations in the central nervous system. Thus, transcranial neuromodulation (TNM) could be valuable in ACL rehabilitation. To systematically review randomized controlled trials (RCTs) assessing the effects of TNM on neurophysiological, functional, and safety outcomes in patients with ACL injury or reconstruction. Methods: We conducted searches on PubMed, Scopus, Web of Science, and Cochrane. We considered all original studies evaluating TNM, including transcranial current stimulation (tCS) and transcranial magnetic stimulation (TMS), in patients with ACL reconstruction or injury. Measures of corticospinal excitability, safety, balance, and muscle strength were assessed. We employed the Cochrane RoB 2 method to assess the risk of bias. Results: Seven studies comprising 129 participants (64 TNM, 65 controls) were included. Most studies applied transcranial direct current stimulation (tDCS) over the primary motor cortex contralateral to the ACL injury in conjunction with physical rehabilitation. Single-session protocols demonstrated minimal effects, whereas repeated sessions resulted in improvements in corticospinal excitability, quadriceps strength, and balance. No serious adverse events were reported; minor effects included transient headache or scalp tingling. The risk of bias was assessed as low to moderate across the studies. Conclusions: TNM appears to be safe and may enhance functional recovery in individuals with ACL injuries when administered in multiple sessions alongside standard rehabilitation. Further high-quality trials are necessary to determine optimal protocols and long-term outcomes.

Target engagement determines therapeutic efficacy. In spinal cord stimulation (SCS), efficacy depends on the attributes of the electrodes used to deliver stimulation, particularly their position, interelectrode distance, size, and current orientation. We tested the effects of these electrode parameters using cervical stimulation to elicit forelimb muscle responses in the rat. We implanted devices over the C6 dorsal root entry zone (DREZ) in eight rats and measured responses in six forelimb muscles. We used custom designed electrode arrays to systematically vary position, distance, and size with linear arrays, and current orientation with circular arrays. Stimulation consisted of biphasic and pseudomonophasic pulse shapes with bipolar or distant return, and a high-definition montage with four returns surrounding a central contact to increase local current density. Efficacy was calculated from the motor thresholds of recruitment curves, and parameters were compared using linear mixed models. For position, stimulation over the DREZ was most effective, reducing thresholds by 25.9% ( p = 0.0002) relative to the midline; efficacy decreased as the electrode was positioned medial or lateral to the DREZ. For distance, placing the electrodes farther apart significantly improved efficacy ( p = 0.0022). For size, large electrodes increased SCS efficacy, reducing thresholds by 21.5% ( p = 0.0026) relative to small electrodes. After accounting for position and distance, current orientation did not affect SCS efficacy. Lastly, the high-definition montage decreased efficacy, increasing thresholds by 16.7% ( p = 0.003) relative to monopolar stimulation with a distant return. In conclusion, electrode position, distance, and size had the greatest effect on SCS efficacy, with the optimal parameters combining large electrodes at the DREZ position with a distant return. These results have the potential to lower the current needed to engage cervical spinal circuitry and to inform the design of SCS systems to improve dexterity in people with neurological injury or disease.