Transcranial magnetic stimulation for treatment-resistant depression: Naturalistic treatment outcomes for younger versus older patients

Effectiveness of Prefrontal Transcranial Magnetic Stimulation for Depression in Older US Military Veterans

OBJECTIVE

While typical aging is associated with decreased cortical volume, major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) likely exacerbates this process. Cerebral atrophy leads to increased coil-to-cortex distance and when using transcranial magnetic stimulation (TMS), potentially reducing effectiveness in older adults.

METHODS

Data from a large-scale quality improvement project was used. Included veterans eligible for TMS and completed TMS treatment. Age was assessed as a predictive factor of depression outcomes after TMS treatment among veterans. Secondary analyses examined the impact of age on 1) MDD response and remission and 2) MDD change within MDD-only verses comorbid MDD and PTSD groups.

RESULTS

The entire sample included 471 veterans. Primary analysis revealed age as a negative predictor of depression outcomes (p = 0.019). Secondary analyses found age to be a significant predictor of remission (p = 0.004), but not clinical response. Age was not a predictive factor in depression outcomes between those with MDD-only compared to MDD+PTSD.

CONCLUSIONS

Increased age predicts greater MDD symptom reduction after TMS. Although age did not predict response rates, it did predict increased rates of remission in veterans. Age did not differentially predict depression outcomes between those with or without PTSD. The sample size was sufficient to discern a difference in efficaciousness, and limitations were those inherent to registry studies in veterans. This data indicates that TMS can be an important treatment option for older individuals.

Identifying predictive biomarkers for repetitive transcranial magnetic stimulation response in depression patients with explainability

Repetitive Transcranial Magnetic Stimulation (rTMS) is an evidence-based treatment for depression. However, the patterns of response to this treatment modality are inconsistent. Whilst many people see a significant reduction in the severity of their depression following rTMS treatment, some patients do not. To support and improve patient outcomes, recent work is exploring the possibility of using Machine Learning to predict rTMS treatment outcomes. Our proposed model is the first to combine functional magnetic resonance imaging (fMRI) connectivity with deep learning techniques to predict treatment outcomes before treatment starts. Furthermore, with the use of Explainable AI (XAI) techniques, we identify potential biomarkers that may discriminate between rTMS responders and non-responders. Our experiments utilize 200 runs of repeated bootstrap sampling on two rTMS datasets. We compare performances between our proposed feedforward deep neural network against existing methods, and compare the average accuracy, balanced accuracy and F1-score on a held-out test set. The results of these experiments show that our model outperforms existing methods with an average accuracy of 0.9423, balanced accuracy of 0.9423, and F1-score of 0.9461 in a sample of 61 patients. We found that functional connectivity measures between the Subgenual Anterior Cingulate Cortex and Centeral Opercular Cortex are a key determinant of rTMS treatment response. This knowledge provides psychiatrists with further information to explore the potential mechanisms of responses to rTMS treatment. Our developed prototype is ready to be deployed across large datasets in multiple centres and different countries.

The cognitive effects of adjunctive repetitive transcranial magnetic stimulation for late-onset depression: a randomized controlled trial with 4 week follow-up

Objectives

Cognitive impairment is common and linked to poor outcomes in patients with late-onset depression (LOD). The cognitive effects of repetitive transcranial magnetic stimulation (rTMS) for LOD are not well understood. This study aimed to investigate the effects of rTMS on cognitive function in elderly patients with LOD.

Methods

In total, 58 elderly patients (aged 60 to 75 years) with depression were enrolled and randomly assigned to an active rTMS group or a sham group. The participants received active or sham rTMS over the left dorsolateral prefrontal cortex for 4 weeks, 5 days a week, at a frequency of 10 Hz rTMS and 120% of the motor threshold (MT). Cognitive function was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) at baseline, the end of the 4 week treatment period, and at the 4 week follow-up.

Results

The active rTMS group showed significant improvements in immediate memory and attention scores on the RBANS compared to the sham group. However, no significant differences were observed between the two groups in other cognitive domains assessed by the RBANS. No serious adverse events related to rTMS treatment were observed.

Conclusion

Treatment with 120% MT rTMS was associated with improvement in cognitive defects related to the active phase of LOD. These findings suggest that rTMS could provide early improvements in cognitive function in clinical settings for elderly patients with LOD.Clinical trial registration: https://www.chictr.org.cn/showproj.html?proj=40698, identifier ChiCTR1900024445.

Targeting Slow Wave Sleep Deficiency in Late-Life Depression: A Case Series With Propofol

Slow wave sleep (SWS), characterized by large electroencephalographic oscillations, facilitates crucial physiologic processes that maintain synaptic plasticity and overall brain health. Deficiency in older adults is associated with depression and cognitive dysfunction, such that enhancing sleep slow waves has emerged as a promising target for novel therapies. Enhancement of SWS has been noted after infusions of propofol, a commonly used anesthetic that induces electroencephalographic patterns resembling non-rapid eye movement sleep. This paper 1) reviews the scientific premise underlying the hypothesis that sleep slow waves are a novel therapeutic target for improving cognitive and psychiatric outcomes in older adults, and 2) presents a case series of two patients with late-life depression who each received two propofol infusions. One participant, a 71-year-old woman, had a mean of 2.8 minutes of evening SWS prior to infusions (0.7% of total sleep time). SWS increased on the night after each infusion, to 12.5 minutes (5.3% of total sleep time) and 24 minutes (10.6% of total sleep time), respectively. Her depression symptoms improved, reflected by a reduction in her Montgomery-Asberg Depression Rating Scale (MADRS) score from 26 to 7. In contrast, the other participant, a 77-year-old man, exhibited no SWS at baseline and only modest enhancement after the second infusion (3 minutes, 1.3% of total sleep time). His MADRS score increased from 13 to 19, indicating a lack of improvement in his depression. These cases provide proof-of-concept that propofol can enhance SWS and improve depression for some individuals, motivating an ongoing clinical trial (ClinicalTrials.gov NCT04680910).

Treatment-Resistant Late-Life Depression: A Review of Clinical Features, Neuropsychology, Neurobiology, and Treatment

Major depression is common in older adults (≥ 60 years of age), termed late-life depression (LLD). Up to 30% of these patients will have treatment-resistant late-life depression (TRLLD), defined as depression that persists despite two adequate antidepressant trials. TRLLD is challenging for clinicians, given several etiological factors (eg, neurocognitive conditions, medical comorbidities, anxiety, and sleep disruption). Proper assessment and management is critical, as individuals with TRLLD often present in medical settings and suffer from cognitive decline and other marks of accelerated aging. This article serves as an evidence-based guide for medical practitioners who encounter TRLLD in their practice.

Outcome of transcranial magnetic intermittent theta-burst stimulation in the treatment of depression - A Swedish register-based study

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is an established treatment of depression. The more recently introduced intermittent Theta-burst stimulation (iTBS) has shown significant superiority over sham-stimulation and equal effect sizes to a 10 Hz protocol in one clinical trial. The aim of the current study was to investigate the effectiveness and tolerability of iTBS in a naturalistic, clinical setting. Further, we explored demographical and clinical predictors of response.

METHODS

Data was collected from seventeen rTMS-sites in Sweden between January 2018 and May 2021, through the Swedish National Quality register for repetitive Transcranial Magnetic Stimulation (Q-rTMS). We included 542 iTBS-treated patients with unipolar or bipolar depression. Outcome was assessed with Clinical Global Impression Severity and Improvement scores in an intention to treat analysis.

RESULTS

The response rate was 42.1 % and 16.1 % reached remission. The response rate was significantly larger in the oldest age group compared to the youngest (odds ratio 3.46, 95 % confidence interval 1.65-7.22). Less severe level of depression (Montgomery-Åsberg depression rating scale self-assessment < 36) at baseline predicted response and remission. Only <1 % were much or very much worse after treatment. Drop-out rate was 10.9 %. No serious adverse events were reported.

LIMITATIONS

Retrospective analysis of register data. No comparison group.

CONCLUSIONS

In a clinical setting, iTBS was shown to be safe and tolerable and the response rate was similar to that reported from clinical trials. Older age-group and less severe illness predicted response.

Intravenous Ketamine for Late-Life Treatment-Resistant Depression: A Pilot Study of Tolerability, Safety, Clinical Benefits, and Effect on Cognition

OBJECTIVE

Evidence-based treatment options for late-life treatment-resistant depression (TRD) are limited. Ketamine is a promising treatment for TRD; however, there is a paucity of data on its safety and efficacy in older adults.

METHODS

In this pilot clinical trial, 25 adults aged ≥60 years with TRD received IV ketamine openly twice a week for 4 weeks; partial responders at the end of this acute phase were eligible to receive weekly infusions for 4 more weeks in a continuation phase. Acceptability, tolerability, and safety, including adverse and serious adverse events (AEs and SAEs), blood pressure changes, dissociation, craving, in addition to rates of depression response and remission were evaluated. The NIH Toolbox Cognitive Battery was used to assess specific measures of executive function (EF) and overall fluid cognition.

RESULTS

Completion rates were 88% for the acute phase and 100% for the continuation phase. No AEs resulted in participant discontinuation, and there were no SAEs. Treatment-emergent elevation of blood pressure, dissociation, and craving were transient and did not result in any participant discontinuation. Depressive symptoms improved significantly and 48% of participants responded. During the acute phase, the EF measures and the fluid cognition composite score improved (Cohen's d = 0.61), and these improvements were sustained in the continuation phase.

CONCLUSION

This pilot study suggests that repeated IV ketamine infusions are well-tolerated and are associated with improvement in depression and EF in older adults with TRD. These promising findings need to be confirmed and extended in a larger randomized controlled trial.

Efficacy and tolerability of repetitive transcranial magnetic stimulation for late-life depression: A systematic review and meta-analysis

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is a widely available treatment for major depression, but its efficacy and tolerability are uncertain for patients with late-life depression (LLD). To assess the existing evidence of rTMS for LLD treatment, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) according to PRISMA guidelines.

METHODS

We retrieved RCTs from four databases published between 1 January 2000 and 10 September 2021 comparing the effects of active and sham stimulation in LLD patients. We performed subgroup analyses to examine the impact of different parameters. The primary outcomes were the response and discontinuation rates of rTMS for LLD patients, representing for efficacy and tolerability, respectively. Secondary outcomes were remission and dropout rates. Discontinuation referred to patients who withdrew for any reason, while dropout referred to participants who withdrew early because of adverse events.

RESULTS

Nine articles describing 11 studies (two articles each contained two studies) met the eligibility criteria. All outcomes were analyzed using a random-effects model. The summary analysis of nine suitable RCTs revealed a cumulative response rate of 2.86 (95 % confidence interval (95 % CI), 1.87-4.37) and a remission rate of 4.02 (95 % CI, 1.83-8.81) in the active group compared to the sham group. The pooled odds ratios (ORs) for discontinuation and dropout rates were not significantly different between the two groups. In addition, some rTMS parameters were associated with better efficacy.

CONCLUSIONS

The meta-analysis suggested that rTMS is an effective, well-tolerated treatment for patients with LLD. Future efforts should enhance study methodologies to improve their efficacy and increase the homogeneity of rTMS parameters to promote comparability between studies.

Pre-frontal stimulation does not reliably increase reward responsiveness

Depression is the leading cause of disability worldwide and its effects can be fatal, with over 800,000 people dying by suicide each year. Neuromodulatory treatments such as transcranial magnetic stimulation (TMS) are being used to treat depression. Despite its endorsement by two regulatory bodies: NICE (2016) and the FDA (2008), there are major questions about the treatment efficacy and biological mechanisms of TMS. Ahn et al.'s (2013) justified the use of TMS in a clinical context in an important study indicating that excitatory TMS increases reward responsiveness. A pseudo-replication of this study by Duprat et al., (2016) also found a similar effect of active TMS, but only with the addition of an exploratory covariate to the analyses-trait reward responsiveness. Here we replicate Ahn et al.'s (2013) key study, and to test the reliability of the effects, and their dependency on trait reward responsiveness as described by Duprat et al., (2016). Using excitatory and sham TMS, we tested volunteers using the probabilistic learning task to measure their reward responsiveness both before and after stimulation. We also examined affect (positive, negative) following stimulation. Irrespective of TMS, the task was shown to be sensitive to reward responsiveness. However, we did not show TMS to be effective in increasing reward responsiveness and we did not replicate Ahn et al., (2013) or Duprat et al., (2016)'s key findings for TMS efficacy, where we provide evidence favouring the null. Moreover, exploratory analyses suggested following active stimulation, positive affect was reduced. Given our findings, we question the basic effects, which support the use of TMS for depression, particularly considering potential deleterious effects of reduced positive affect in patients with depression.

Adjunctive accelerated repetitive transcranial magnetic stimulation for older patients with depression: A systematic review

OBJECTIVE

We performed this systemic review to investigate the therapeutic potential and safety of adjunctive accelerated repetitive transcranial magnetic stimulation (aTMS) for older patients with depression.

METHODS

We included published randomized clinical trials (RCTs) and observational studies targeting adjunctive aTMS for older patients with depression.

RESULTS

Two open-label self-controlled studies (n = 29) fulfilled the criteria for inclusion. The included studies reported significant improvements in depressive symptoms from baseline to post-aTMS (all Ps < 0.05). One study reported a dropout rate of 10.5% (2/19). Mild headache was the most common adverse reaction.

CONCLUSION

The currently available evidence from two open-label self-controlled studies indicates that adjunctive aTMS is a safe and effective therapy for older patients with depression.

A comparative study of amplitude of low-frequence fluctuation of resting-state fMRI between the younger and older treatment-resistant depression in adults

Background

Treatment-resistant depression (TRD) may have different physiopathological neuromechanism in different age groups. This study used the amplitude of low frequency fluctuations (ALFF) to initially compare abnormalities in local functional brain activity in younger and older patients with TRD.

Materials and methods

A total of 21 older TRD patients, 19 younger TRD, 19 older healthy controls (HCs), and 19 younger HCs underwent resting-state functional MRI scans, and the images were analyzed using the ALFF and further analyzed for correlation between abnormal brain regions and clinical symptoms in TRD patients of different age groups.

Results

Compared with the older TRD, the younger TRD group had increased ALFF in the left middle frontal gyrus and decreased ALFF in the left caudate nucleus. Compared with the matched HC group, ALFF was increased in the right middle temporal gyrus and left pallidum in the older TRD group, whereas no significant differences were found in the younger TRD group. In addition, ALFF values in the left middle frontal gyrus in the younger TRD group and in the right middle temporal gyrus in the older TRD were both positively correlated with the 17-item Hamilton Rating Scale for Depression score.

Conclusion

Different neuropathological mechanisms may exist in TRD patients of different ages, especially in the left middle frontal gyrus and left caudate nucleus. This study is beneficial in providing potential key targets for the clinical management of TRD patients of different ages.

Clinical and radiomic features for predicting the treatment response of repetitive transcranial magnetic stimulation in major neurocognitive disorder: Results from a randomized controlled trial

Image-guided repetitive transcranial magnetic stimulation (rTMS) has shown clinical effectiveness in senior adults with co-occurring depression and cognitive impairment, yet the imaging markers for predicting the treatment response are less investigated. In this clinical trial, we examined the efficacy and sustainability of 10 Hz rTMS for the treatment of depression and cognitive impairment in major neurocognitive disorder (NCD) patients and tested the predictive values of imaging-informed radiomic features in response to rTMS treatment. Fifty-five major NCD patients with depression were randomly assigned to receive a 3-week rTMS treatment of either active 10 Hz rTMS (n = 27) or sham rTMS (n = 28). Left dorsolateral prefrontal cortex (DLPFC) was the predefined treatment target. Based on individual structural magnetic resonance imaging scans, surface-based analysis was conducted to quantitatively measure the baseline radiomic features of left DLPFC. Severity of depression, global cognition and the serum brain-derived neurotrophic factor (BDNF) level were evaluated at baseline, 3-, 6- and 12-week follow-ups. Logistic regression analysis revealed that advanced age, higher baseline cognition and randomized group were associated with the remission of depression. Increased cortical thickness and gyrification in left DLPFC were the significant predictors of clinical remission and cognitive enhancement. A 3-week course of 10 Hz rTMS is an effective adjuvant treatment for rapid ameliorating depressive symptoms and enhancing cognitive function. Pre-treatment radiomic features of the stimulation target can predict the response to rTMS treatment in major NCD. Cortical thickness and folding of treatment target may serve as imaging markers to detect the responders. ChiCTR-IOR-16008191, registered on March 30, 2016.

In Older Adults the Antidepressant Effect of Repetitive Transcranial Magnetic Stimulation Is Similar but Occurs Later Than in Younger Adults

Background

Treatment resistant depression is common in older adults and treatment is often complicated by medical comorbidities and polypharmacy. Repetitive transcranial magnetic stimulation (rTMS) is a treatment option for this group due to its favorable profile. However, early influential studies suggested that rTMS is less effective in older adults. This evidence remains controversial.

Methods

Here, we evaluated the rTMS treatment outcomes in a large international multicenter naturalistic cohort of >500 patients comparing older vs. younger adults.

Results

We show that older adults, while having similar antidepressant response to younger adults, respond more slowly, which may help to explain differences from earlier studies when the duration of a treatment course was shorter.

Conclusions

Such evidence helps to resolve a long-standing controversy in treating older depressed patients with rTMS. Moreover, these findings provide an important data point in the call to revise policy decisions from major insurance providers that have unfairly excluded older adults.

Proof of concept study to develop a novel connectivity-based electric-field modelling approach for individualized targeting of transcranial magnetic stimulation treatment

Resting state functional connectivity (rsFC) offers promise for individualizing stimulation targets for transcranial magnetic stimulation (TMS) treatments. However, current targeting approaches do not account for non-focal TMS effects or large-scale connectivity patterns. To overcome these limitations, we propose a novel targeting optimization approach that combines whole-brain rsFC and electric-field (e-field) modelling to identify single-subject, symptom-specific TMS targets. In this proof of concept study, we recruited 91 anxious misery (AM) patients and 25 controls. We measured depression symptoms (MADRS/HAMD) and recorded rsFC. We used a PCA regression to predict symptoms from rsFC and estimate the parameter vector, for input into our e-field augmented model. We modeled 17 left dlPFC and 7 M1 sites using 24 equally spaced coil orientations. We computed single-subject predicted ΔMADRS/HAMD scores for each site/orientation using the e-field augmented model, which comprises a linear combination of the following elementwise products (1) the estimated connectivity/symptom coefficients, (2) a vectorized e-field model for site/orientation, (3) rsFC matrix, scaled by a proportionality constant. In AM patients, our connectivity-based model predicted a significant decrease depression for sites near BA9, but not M1 for coil orientations perpendicular to the cortical gyrus. In control subjects, no site/orientation combination showed a significant predicted change. These results corroborate previous work suggesting the efficacy of left dlPFC stimulation for depression treatment, and predict better outcomes with individualized targeting. They also suggest that our novel connectivity-based e-field modelling approach may effectively identify potential TMS treatment responders and individualize TMS targeting to maximize the therapeutic impact.

Repetitive Transcranial Magnetic Stimulation for Major Depressive Disorder in Older Adults: Systematic Review and Meta-Analysis

BACKGROUND

Major Depressive Disorder (MDD) in older adults is a serious public health concern. Repetitive transcranial magnetic stimulation (rTMS) is a non-pharmacological intervention approved for Major Depressive Disorder (MDD) treatment in adults, but its value in older adults remains unknown. The present study aims to systematically review and meta-analyze evidence of rTMS efficacy in MDD treatment among older adults.

METHODS

We systematically reviewed the literature for randomized controlled trials (RCTs) and open-label studies assessing rTMS for the treatment of MDD in patients older than 50 years-old, published until June 2020. Random-effects meta-analyses using standardized mean differences (SMD) were conducted to assess change in depression severity score (primary outcome), while odds-ratios (OR) were used to assess secondary categorical outcomes (response and remission). Additionally, univariate meta-regression analyses were performed to identify potential predictors of change in depression severity scores.

RESULTS

Fourteen RCTs were included in meta-analyses and 26 studies (10 RCTs and 16 open-label studies) in meta-regression. Active rTMS was significantly superior to sham-treatment for reduction of severity (SMD=0.36; 95%CI=0.13-0.60), as well as response (OR=3.26; 95%CI=2.11-5.04) and remission (OR=4.63; 95%CI=2.24-9.55). Studies were of moderate to high quality, with funnel plots and Egger's regression test not suggestive of publication bias. In meta-regressions, higher mean age and number of sessions were significantly associated to greater improvement.

CONCLUSIONS

Our results support that rTMS is an effective, safe and well-tolerated treatment for MDD in older adults, and that it should be considered in the treatment of this vulnerable population.

Ten years' data of Transcranial Magnetic Stimulation (TMS): A naturalistic, observational study outcome in clinical practice

Transcranial Magnetic Stimulation (TMS) is used reliably as an alternative method in the treatment of a number of treatment-resistant psychiatric disorders. However, information about the daily practice is limited. In this article, we aim to report and discuss the 10-years results of a clinic that applies TMS to treatment-resistant psychiatric disorders. This naturalistic study is a retrospective review of data routinely collected from patients undergoing TMS between 2010 and 2020. A total of 284 patients with diagnoses of major depressive disorder (MDD), obsessive-compulsive disorder, generalized anxiety disorder, and post-traumatic stress disorder (PTSD) were included in the study. The mean age of the participants was 40.49±12.64 years. In general, when the responses of all patients were examined, 26.1% were evaluated as response, 29.2% as partial response, and 44.7% as inadequate response. It has been determined that MDD responds to treatment better than other disorders. Regardless of the diagnosis, a significant relationship was found between response and age. The multivariate logistic regression analysis suggested that patients with improvement from TMS were less likely to have advanced age and not to have been diagnosed with PTSD. The idea that TMS may be useful for some patients, but not every patient, is supported.

Adverse events of repetitive transcranial magnetic stimulation in older adults with depression, a systematic review of the literature

OBJECTIVE

In the last decade, repetitive transcranial magnetic stimulation (rTMS) has been introduced as a non-invasive neuromodulation therapy for depression. Little is known, however, about (serious) adverse events (AE) of rTMS in older adults with a depression. In this article, we want to study what is known about (serious) AE of rTMS in older adults (>60 years) with late-life depression (LLD).

METHODS

A systematic search has been performed according to the PRISMA guidelines in PubMed, EMBase and PsycInfo. We have screened 622 articles for eligibility. Eleven studies, evaluating 353 patients in total, were included in this review.

RESULTS

AE were reported in 12.4% of the older adults with a LLD treated with rTMS, serious AE in 1.5%. Headache (6.9%) and discomfort at the stimulation site (2.7%) are the most commonly reported AE. Serious AE reported are: psychiatric hospitalization (three times), a combination of posterior vitreous detachment and retinal tear, and increased suicide ideation (both once).

CONCLUSIONS

rTMS in older adults with LLD was concluded overall to be safe due to the low frequency of AE reported in trials and observational studies. In case-reports, however, more serious AE have been described. To tailor use of rTMS in older adults with LLD, more research is needed in larger samples to optimize tolerance.

Identifying response and predictive biomarkers for Transcranial magnetic stimulation outcomes: protocol and rationale for a mechanistic study of functional neuroimaging and behavioral biomarkers in veterans with Pharmacoresistant depression

BACKGROUND

Although repetitive transcranial magnetic stimulation ('TMS') is becoming a gold standard treatment for pharmacoresistant depression, we lack neural target biomarkers for identifying who is most likely to respond to TMS and why. To address this gap in knowledge we evaluate neural targets defined by activation and functional connectivity of the dorsolateral prefrontal cortex-anchored cognitive control circuit, regions of the default mode network and attention circuit, and interactions with the subgenual anterior cingulate. We evaluate whether these targets and interactions between them change in a dose-dependent manner, whether changes in these neural targets correspond to changes in cognitive behavioral performance, and whether baseline and early change in neural target and cognitive behavioral performance predict subsequent symptom severity, suicidality, and quality of life outcomes. This study is designed as a pragmatic, mechanistic trial partnering with the National Clinical TMS Program of the Veteran's Health Administration.

METHODS

Target enrollment consists of 100 veterans with pharmacoresistant Major Depressive Disorder (MDD). All veterans will receive a clinical course of TMS and will be assessed at 'baseline' pre-TMS commencement, 'first week' after initiation of TMS (targeting five sessions) and 'post-treatment' at the completion of TMS (targeting 30 sessions). Veterans will be assessed using functional magnetic resonance imaging (fMRI), a cognitive behavioral performance battery, and established questionnaires. Multivariate linear mixed models will be used to assess whether neural targets change with TMS as a function of dose (Aim 1), whether extent and change of neural target relates to and predicts extent of behavioral performance (Aim 3), and whether extent of neural target change predicts improvement in symptom severity, suicidality, and quality of life (Aim 3). For all three aims, we will also assess the contribution of baseline moderators such as biological sex and age.

DISCUSSION

To our knowledge, our study will be the first pragmatic, mechanistic observational trial to use fMRI imaging and cognitive-behavioral performance as biomarkers of TMS treatment response in pharmacoresistant MDD. The results of this trial will allow providers to select suitable candidates for TMS treatment and better predict treatment response by assessing circuit connectivity and cognitive-behavioral performance at baseline and during early treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04663481 , December 5th, 2020, retrospectively registered. The first veteran was enrolled October 30th, 2020.

An update on the clinical use of repetitive transcranial magnetic stimulation in the treatment of depression

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is an increasingly used treatment for patients with depression. The use of rTMS in depression is supported by over 20 years of clinical trials. There has been a significant increase in knowledge around the use of rTMS in recent years.

OBJECTIVE

The aim of this paper was to review the use of rTMS in depression to provide an update for rTMS practitioners and clinicians interested in the clinical use of this treatment.

METHODS

A targeted review of the literature around the use of rTMS treatment of depression with a specific focus on studies published in the last 3 years.

RESULTS

High-frequency rTMS applied to the left dorsolateral prefrontal cortex is an effective treatment for acute episodes of major depressive disorder. There are several additional methods of rTMS delivery that are supported by clinical trials and meta-analyses but no substantive evidence that any one approach is any more effective than any other. rTMS is effective in unipolar depression and most likely bipolar depression. rTMS courses may be repeated in the management of depressive relapse but there is less evidence for the use of rTMS in the maintenance phase.

CONCLUSIONS

The science around the use of rTMS is rapidly evolving and there is a considerable need for practitioners to remain abreast of the current state of this literature and its implications for clinical practice. rTMS is an effective antidepressant treatment but its optimal use should be continually informed by knowledge of the state of the art.

Treating major depression and comorbid disorders with transcranial magnetic stimulation

BACKGROUND

Major Depressive Disorder (MDD) is a global disorder that negatively affects mood and quality of life. Antidepressant medication and psychotherapy are the most commonly prescribed treatments, but prior research has called their clinical efficacy into question. These treatments may be less effective when the patient has a diagnosed comorbid disorder.

METHOD

A systematic review of the literature was conducted to investigate whether an alternative method of treatment, Transcranial Magnetic Stimulation (TMS), is effective for MDD with a diagnosed comorbidity. 110 articles were identified, of which 8 were included in the current review.

RESULTS

Response and remission rates vary. A range of 39.5-70% of participants experienced an antidepressant response to treatment, and 16.6-76.9% of patients achieved remission from MDD. A range of 48.6-84.6% of participants responded to treatment of their comorbid disorder, and 50-84.6% achieved remission of comorbid symptoms.

LIMITATIONS

Limitations of the current review include small sample sizes, limited statistical power, homogenous samples, and a lack of sham or placebo-controlled studies.

CONCLUSION

Preliminary results support that TMS is effective at treating symptoms of MDD and a comorbid disorder. Additional studies are needed to confirm these results.

Efficacy of Intensive Cerebellar Intermittent Theta Burst Stimulation (iCiTBS) in Treatment-Resistant Schizophrenia: a Randomized Placebo-Controlled Study

Trans-cranial magnetic stimulation (TMS) can noninvasively modulate specific brain regions to dissipate symptoms in treatment-resistant schizophrenia (TRS). Citing impaired resting state connectivity between cerebellum and prefrontal cortex in schizophrenia, we aimed to study the effect of intermittent theta burst stimulation (iTBS) targeting midline cerebellum in TRS subjects on a randomized rater blinded placebo control study design. In this study, 36 patients were randomly allocated (using block randomization method) to active and sham iTBS groups. They were scheduled to receive ten iTBS sessions, two per day (total of 1200 pulses) for 5 days in a week. The Positive and Negative Syndrome Scale (PANSS), Brief Psychiatric Rating Scale (BPRS), Schizophrenia Cognition Rating Scale (SCoRS), Simpson-Angus Extrapyramidal Side Effects Scale (SAS), and Clinical Global Impression (CGI) were assessed at baseline, after last session, and at 2 weeks post-rTMS. Thirty patients (16 and 14 in active and sham groups) completed the study. Intention to treat analysis (ITT) using mixed (growth curve) model analysis was conducted. No significant group (active vs sham) × time (pretreatment–end of 10th session–end of 2 weeks post iTBS) interaction was found for any of the variable. No major side effects were reported. Our study fails to show a significant effect of intensive cerebellar iTBS (iCiTBS) on schizophrenia psychopathology, cognitive functions, and global improvement, compared with sham stimulation, in treatment resistant cases. However, we conclude that it is safe and well tolerated. Trials using better localization technique with large sample, longer duration, and better dosing protocols are needed.

Antidepressant Effect of Adjunct Repetitive Transcranial Magnetic Stimulation in Inpatients 60 Years and Older

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is now an established, safe, and effective treatment for adults with depression. However, specific research in rTMS for use in elderly patients with acute depression is scarce.

OBJECTIVE

The aim of the present study was to investigate the efficacy of add-on rTMS in a clinical sample of older adults experiencing an acute phase of depression.

METHOD

This study examined 114 patients (54 elderly [aged ≥60] and 60 adults [aged 18-59]) with acute depression who were drug free at baseline. They were treated with at least 10 sessions of rTMS for 4 weeks along with 1 antidepressant. Symptoms of depression were measured using the Hamilton Rating Scale for Depression at baseline and after 2 and 4 weeks of treatment. Clinical improvement and rates of response and remission were compared across groups.

RESULTS

Significant improvement was noted after 2 and 4 weeks of treatment in both adult and elderly groups. Higher remission rates were found in adult patients but with no differences in response. The stimulation intensity and course of illness were significant predictors of remission after 4 weeks of rTMS treatment in the elderly.

CONCLUSIONS

The add-on rTMS treatment for elderly depression patients is promising with respect to safety and feasibility. This preliminary evidence supports the application of rTMS to this group during acute episodes.

Repetitive transcranial magnetic stimulation for major depression: A naturalistic observational study in an Australian private hospital

Repetitive transcranial magnetic stimulation (rTMS) is an effective and evidence-based treatment for major depression, which is now as a mainstream treatment in clinical practice. However, there is limited data concerning its use in Australian private psychiatric hospital settings. This retrospective study examined routinely collected data of 153 inpatients, who received 20 rTMS treatments over four weeks. Primary outcomes measures were the 17-item Hamilton Depression Rating Scale (HAMD-17) and the 21-item Depression, Anxiety and Stress Scale (DASS-21). At post-treatment, response and remission rates were 54% and 28%, respectively, for the HAMD-17; and 53% response and 16% remission rates, for the DASS-21 Depression subscale, respectively. Although no gender differences were observed, younger patients demonstrated more improvements during acute rTMS but the effect was not significant after accounting for pre-treatment symptom severity. The findings of this naturalistic study suggest that an acute course of rTMS provided in private clinical settings resulted in similar response and remission rates to longer rTMS courses. Shorter rTMS courses appear to have satisfactory efficacy in treating major depression, in clinically diverse and real-world practice.

The Efficacy and Safety of Neuromodulation Treatments in Late-Life Depression

Purpose of review

In this review, the efficacy and safety of FDA approved neuromodulation devices (electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS) and vagus nerve stimulation (VNS)), as well as emerging neuromodulation treatments currently under investigation.

Recent findings

ECT is the "gold standard" somatic therapy for treatment resistant depression (TRD). Although the clinical benefits are outweighed by potential cognitive and cardiovascular side effects in majority of cases, it remains unfairly stigmatized. TMS has few cognitive or somatic side effects but is not as effective the treatment of psychotic depression or more treatment resistant depression in elders. VNS has limited data in older patients but has been shown to be effective in chronic, treatment resistant adults. Several investigative neuromodulation treatments including magnetic seizure therapy (MST), focal electrically administered seizure therapy (FEAST), transcutaneous VNS (tVNS), transcranial direct current stimulation (tDCS), and deep brain simulation (DBS) shown promise in geriatric TRD.

Summary

ECT, TMS and VNS are effective treatment for late-life depression, and research has continued to refine the techniques. Investigative neuromodulation techniques are promising, but evidence for the safety and efficacy of these devices in the geriatric population is needed.

Theta-Burst Stimulation for Auditory-Verbal Hallucination in Very-Late-Onset Schizophrenia-Like Psychosis-A Functional Magnetic Resonance Imaging Case Study

BACKGROUND

Treating very-late-onset (>60 years) schizophrenia-like psychosis (VLOSLP) is challenging. Age-related factors in elderly individuals (e.g., metabolism, medication side effects, drug-interaction, somatic morbidity) may adversely affect treatment. Novel therapeutic approaches are needed to ensure the favorable therapeutic outcome in geriatric patients. Previously, theta-burst stimulation (TBS), a novel form of repetitive transcranial magnetic stimulation, was reported being beneficial in the treatment for auditory-verbal hallucination (AVH) in young and middle-aged schizophrenia (SZ) patients.

CASE PRESENTATION

Here we present a case of a male patient aged 73. His first psychotic episode manifested with paranoid delusions, auditory-verbal and tactile hallucinations at the age of 66, and first remitted following a second-generation antipsychotics (SGA). Years later, after a relapse the AVH did not respond to previously effective olanzapine, whereas its augmentation with an inhibitory TBS over the left temporal lobe led to a stable remission. During his second relapse, TBS was again capable of facilitating therapeutic action of SGA in the same patient. Extending to our clinical observation, a series of functional MRI scans employing a tonal activation paradigm depicted altered auditory processing during AVH as well as brain activation change during remission.

CONCLUSIONS

The current case might indicate to favorable effects of combining conventional medicament therapy and non-invasive brain stimulation techniques for elderly patients. Also, we speculate that despite obviously distinct etiologies, the present functional imaging and clinical observation may also demonstrate a possible common pathophysiological pathway underlying AVH in VLOSLP and SZ.

Identification of Clinical Features and Biomarkers that may inform a Personalized Approach to rTMS for Depression

Repetitive transcranial magnetic stimulation (rTMS), an established treatment for treatment-resistant depression, may hold promise as a personalized medicine approach for the treatment of major depressive disorder (MDD). Clinical research has begun to identify patient-specific factors that could be used to guide rTMS treatment decisions or individualized treatment approaches. This literature review describes a range of patient factors which have been evaluated as potential biomarkers of rTMS treatment response, including patient- and illness-related characteristics, genetic factors, and biomarkers derived from neuroimaging and EEG. We highlight the need for validation data for imaging and electrophysiological biomarkers associated with rTMS as well as prospective evaluation of clinical predictors. Finally, we consider implications for future efforts to move toward a personalized medicine approach in the treatment of depression with rTMS.

Antidepressant outcomes of high-frequency repetitive transcranial magnetic stimulation (rTMS) with F8-coil and deep transcranial magnetic stimulation (DTMS) with H1-coil in major depression: a systematic review and meta-analysis

BACKGROUND

The current study aims to systematically assess and compare the antidepressant outcomes of repetitive transcranial magnetic stimulation (rTMS) with the figure-of-eight (F8)-coil and deep transcranial magnetic stimulation (DTMS) with the H1-coil in studies matched on stimulation frequency in unipolar major depressive disorder (MDD).

METHODS

Electronic search of Medline and PsycInfo identified 19 studies with stimulation frequency of 18-20 Hz using F8-coil (k = 8 randomised sham-controlled trials, RCTs, k = 3 open-label; n = 168 patients) or H1-coil (k = 1 RCT, k = 7 open-label; n = 200). Depression severity (the primary outcome) and response/remission rates (the secondary outcomes) were assessed at session 10.

RESULTS

Effects pooled with random-effects meta-analysis showed a large reduction in depression severity, 29% response, and 15% remission rates after 10 sessions of active stimulation with either coil relative to baseline. Reduction in depression severity was greater in studies with younger patients using either coil. The comparison between coils showed a larger reduction in depression severity in H1-coil vs. F8-coil studies (independent of the study design or the concurrent pharmacotherapy) and a trend towards higher remission rates in F8-coil vs. H1-coils studies. These effects are based on a low volume of studies, are not controlled for placebo, and may not be clinically-relevant. The stimulation protocols differed systematically because stimulation was more focal but less intense (80-110% of the resting motor threshold, MT) in the F8-coil studies and less focal but more intense (120% MT) in the H1-coil studies. Two seizures occurred in the H1-coil studies relative to none in the F8-coil studies.

CONCLUSION

When matched on frequency, the higher-intensity and less focal stimulation with the H1-coil reduces depression more than the lower-intensity and more focal stimulation with the F8-coil. Head-to-head trials should compare the antidepressant outcomes of F8-coil and H1-coil to identify the most optimal stimulation protocols for acute and longer-lasting efficacy.

Safety and Efficacy of Accelerated Repetitive Transcranial Magnetic Stimulation Protocol in Elderly Depressed Unipolar and Bipolar Patients

OBJECTIVE

Major depressive disorder (MDD) is a prevalent condition in older adults. Although antidepressant drugs are commonly prescribed, efficacy is variable, and older patients are more prone to side effects. Repetitive transcranial magnetic stimulation (rTMS) is an alternative therapy used increasingly in the treatment of MDD. Even though recent studies have shown efficacy of rTMS in elderly depressed patients, the safety and efficacy of accelerated rTMS has not been studied in this population.

METHODS

Data were retrospectively analyzed for adults with treatment-resistant depression (N = 73, n = 19 ≥60years, n = 54 <60 years) who underwent an accelerated protocol of 30 sessions (2 sessions per day) of left dorsolateral prefrontal cortex high-frequency (20 Hz) rTMS.

RESULTS

There were statistically significant improvements in depression and anxiety symptoms from baseline to post-treatment in both age groups, but those 60years and older showed statistically greater improvement in depression and anxiety symptom scores (p = 0.01) than those less than 60. There were significantly more responders (p = 0.001) and remitters (p = 0.023) in the older group. The age groups did not differ significantly in clinical and demographic characteristics or severity of current depressive episode, although baseline anxiety was less severe in those 60years and older. Unipolar and bipolar patients had a similar clinical response, and treatment appeared to be well tolerated by all patients.

CONCLUSION

Our results suggest that accelerated rTMS protocol is a safe and effective treatment for unipolar and bipolar depressed subjects, including older adults.

Predictors of response to synchronized transcranial magnetic stimulation for major depressive disorder

BACKGROUND

Synchronized transcranial magnetic stimulation (sTMS) is a new modality to reduce symptoms of major depressive disorder (MDD). sTMS uses rotating neodymium magnets to deliver low-field stimulation matched to the individual alpha frequency (IAF). A previous multisite study showed that sTMS significantly reduced MDD symptoms in the per-protocol sample. To this end, we evaluated clinical features associated with optimal sTMS outcomes.

METHODS

Using the per-protocol sample (n = 120) from the parent sham-controlled trial, we performed univariate and stepwise linear regression to identify predictors of response after 6 weeks of sTMS. A subsample (n = 83) that entered a 4-week open/active continuation phase also was examined. Candidate variables included age, sex, comorbid anxiety, number of failed antidepressants in the current depressive episode, MDD severity (17-item Hamilton Depression Rating Scale; HAMD17), anxiety symptom severity (HAMD17 anxiety/somatization factor), and IAF.

RESULTS

We found that greater baseline depressive (p < 0.001) and anxiety (p < 0.001) symptom severity were associated with better response to active sTMS, whereas fewer failed antidepressant trials predicted superior response to sham (p < 0.001). MDD severity and antidepressant resistance predicted outcomes in open/active phase sTMS; lower IAF predicted poorer response in participants who received 10 weeks of active sTMS (p = 0.001).

CONCLUSIONS

Participants with greater severity of depression and higher anxiety had superior responses to active sTMS, whereas treatment naïve individuals exhibited a greater response to sham. These results lend support to the primary efficacy findings, and support further investigation of sTMS as a therapeutic noninvasive brain stimulation modality.

Clinical effectiveness of repetitive transcranial magnetic stimulation treatment in children and adolescents with neurodevelopmental disorders: A systematic review

Neurodevelopmental disorders, including autism spectrum disorder, are common in children and adolescents, but treatment strategies remain limited. Although repetitive transcranial magnetic stimulation has been studied for neurodevelopmental disorders, there is no clear consensus on its therapeutic effects. This systematic review examined literature on repetitive transcranial magnetic stimulation for children and adolescents with neurodevelopmental disorders published up to 2018 using the PubMed database. The search identified 264 articles and 14 articles met eligibility criteria. Twelve of these studies used conventional repetitive transcranial magnetic stimulation and two studies used theta burst stimulation. No severe adverse effects were reported in these studies. In patients with autism spectrum disorder, low-frequency repetitive transcranial magnetic stimulation and intermittent theta burst stimulation applied to the dorsolateral prefrontal cortex may have therapeutic effects on social functioning and repetitive behaviors. In patients with attention deficit/hyperactivity disorder, low-frequency repetitive transcranial magnetic stimulation applied to the left dorsolateral prefrontal cortex and high-frequency repetitive transcranial magnetic stimulation applied to the right dorsolateral prefrontal cortex may target inattention, hyperactivity, and impulsivity. In patients with tic disorders, low-frequency repetitive transcranial magnetic stimulation applied to the bilateral supplementary motor area improved tic symptom severity. This systematic review suggests that repetitive transcranial magnetic stimulation may be a promising intervention for children and adolescents with neurodevelopmental disorders. The results warrant further large randomized controlled trials of repetitive transcranial magnetic stimulation in children with neurodevelopmental disorders.

A systematic review of noninvasive brain stimulation for post-stroke depression

BACKGROUND

Post-stroke depression (PSD) is among the most frequent neuropsychiatric consequences of stroke, negatively affecting the patient's functional recovery and the quality of life. While pharmacological therapy has limited efficacy and important side effects, new appropriate treatments based on specific physiological mechanisms for PSD remain to be developed. Non-invasive brain stimulation (NIBS) techniques, modulating brain plasticity, might offer valid, alternative strategies.

METHODS

We systematically searched four databases: MEDLINE, PsycARTICLES, PsycINFO and Web of Science, up to December 2017, using definite keywords, to identify studies on TMS and tDCS treatment for PSD.

RESULTS

Seven studies met the inclusion criteria and the results indicate that both tDCS and rTMS are safe and have very low side effects. The reported positive results, suggesting that these methods can be considered effective therapeutic options, are questionable, and a general statement about their efficacy for PSD is premature due to small sample sizes, heterogeneous methodologies, lack of uniform diagnostic criteria, and divergent data.

LIMITATIONS

The selected articles suffer lack of information about quality of life and daily living performance measures; in addition, the number of randomized controlled trials is small.

CONCLUSION (S)

The aim of this review was to analyze current research in the clinical use of noninvasive brain stimulation (NIBS) in PSD treatment in order to verify whether there are alternative perspectives in the treatment of PSD. Given the present evidence, future research is needed to address methodological limitations and evaluate the long-term efficacy of these methods, alone and in combination with pharmacological treatment.

Intravenous Ketamine for Adolescents with Treatment-Resistant Depression: An Open-Label Study

BACKGROUND

Novel interventions for treatment-resistant depression (TRD) in adolescents are urgently needed. Ketamine has been studied in adults with TRD, but little information is available for adolescents. This study investigated efficacy and tolerability of intravenous ketamine in adolescents with TRD, and explored clinical response predictors.

METHODS

Adolescents, 12-18 years of age, with TRD (failure to respond to two previous antidepressant trials) were administered six ketamine (0.5 mg/kg) infusions over 2 weeks. Clinical response was defined as a 50% decrease in Children's Depression Rating Scale-Revised (CDRS-R); remission was CDRS-R score ≤28. Tolerability assessment included monitoring vital signs and dissociative symptoms using the Clinician-Administered Dissociative States Scale (CADSS).

RESULTS

Thirteen participants (mean age 16.9 years, range 14.5-18.8 years, eight biologically male) completed the protocol. Average decrease in CDRS-R was 42.5% (p = 0.0004). Five (38%) adolescents met criteria for clinical response. Three responders showed sustained remission at 6-week follow-up; relapse occurred within 2 weeks for the other two responders. Ketamine infusions were generally well tolerated; dissociative symptoms and hemodynamic symptoms were transient. Higher dose was a significant predictor of treatment response.

CONCLUSIONS

These results demonstrate the potential role for ketamine in treating adolescents with TRD. Limitations include the open-label design and small sample; future research addressing these issues are needed to confirm these results. Additionally, evidence suggested a dose-response relationship; future studies are needed to optimize dose. Finally, questions remain regarding the long-term safety of ketamine as a depression treatment; more information is needed before broader clinical use.

Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex to alleviate depression and cognitive impairment associated with Parkinson's disease: A review and clinical implications

The rapid methodological development and growing availability of neuromodulation techniques have spurred myriad studies investigating their clinical effectiveness. Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) has in many instances been proven to exert antidepressant-like effects superior to placebo and equivalent to standard psychopharmacological treatment. Due to the similar neuroanatomy and neurophysiology of executive and affective control processes, rTMS to the DLPFC may be able to address multiple issues simultaneously. This review pools available literature on the therapeutic usage of rTMS on non-motor symptoms of Parkinson's disease associated with the DLPFC (i.e. mood disturbance and cognitive impairment). To the best of the author's knowledge, it is one of the few available of its' kind, up to this date. Most studies included in the review found beneficial effects of high frequency prefrontal rTMS on PD-related depression. In regard to the usability of rTMS to alleviate cognitive impairment associated with PD, definitive claims are yet to be established.

Neuroimaging Mechanisms of Therapeutic Transcranial Magnetic Stimulation for Major Depressive Disorder

Research into therapeutic transcranial magnetic stimulation (TMS) for major depression has dramatically increased in the last decade. Understanding the mechanism of action of TMS is crucial to improve efficacy and develop the next generation of therapeutic stimulation. Early imaging research provided initial data supportive of widely held assumptions about hypothesized inhibitory or excitatory consequences of stimulation. Early work also indicated that while TMS modulated brain activity under the stimulation site, effects at deeper regions, in particular, the subgenual anterior cingulate cortex, were associated with clinical improvement. Concordant with earlier findings, functional connectivity studies also demonstrated that clinical improvements were related to changes distal, rather than proximal, to the site of stimulation. Moreover, recent work suggests that TMS modulates and potentially normalizes functional relationships between neural networks. An important observation that emerged from this review is that similar patterns of connectivity changes are observed across studies regardless of TMS parameters. Though promising, we stress that these imaging findings must be evaluated cautiously given the widespread reliance on modest sample sizes and little implementation of statistical validation. Additional limitations included use of imaging before and after a course of TMS, which provided little insight into changes that might occur during the weeks of stimulation. Furthermore, as studies to date have focused on depression, it is unclear whether our observations were related to mechanisms of action of TMS for depression or represented broader patterns of functional brain changes associated with clinical improvement.

Transcranial Magnetic Stimulation (TMS) in the Elderly

PURPOSE OF REVIEW

This article aims to review select applications of Transcranial Magnetic Stimulation (TMS) that have significant relevance in geriatric psychiatry.

RECENT FINDINGS

Small study sizes and parameter variability limit the generalizability of many TMS studies in geriatric patients. Additionally, geriatric patients have unique characteristics that can moderate the efficacy of TMS. Nonetheless, several promising experimental applications in addition to the FDA-approved indication for major depression have emerged. Cognitive impairment, neuropathic pain, and smoking cessation are experimental applications with special significance to the elderly. Cognitive impairment has been researched the most in this population and evidence thus far suggests that TMS has potential therapeutic benefit. There is also evidence to suggest benefit from TMS for neuropathic pain and smoking cessation in working age adults. TMS is consistently reported as a safe and well-tolerated treatment modality with no adverse cognitive side effects. TMS is a safe treatment modality that can be effective for certain applications in the elderly. Additional research that specifically includes older subjects is needed to replicate findings and to optimize treatment protocols for this population.

Anaesthesia, not number of sessions, influences the magnitude and duration of an aHF-rTMS in dogs

Background

Currently, the rat has been a useful animal model in brain stimulation research. Nevertheless, extrapolating results from rodent repetitive Transcranial Magnetic Stimulation (rTMS) research to humans contains several hurdles. This suggests the desperate need for a large animal model in translational rTMS research. The dog would be a valid choice, not only due to the fact that humans and dogs share a neurophysiological background, but a similar neuropathological background as well.

Hypothesis

In order to evaluate the feasibility of the canine rTMS animal model, this study aimed to evaluate the neurophysiological response in dogs on a, clinically used, accelerated high frequency (aHF) rTMS protocol. This aHF-rTMS (20 Hz) protocol was performed under anaesthesia or sedation and either 20 sessions or 5 sessions were given to each dog.

Methods

21 healthy dogs were randomly subjected to one of the four aHF-rTMS protocols (1 sham and 3 active protocols). For each dog, the perfusion indices (PI), of a [^99mTc]HMPAO scan at 4 time points, for the left frontal cortex (stimulation target) were calculated for each protocol.

Results

Concerning sham stimulation, the average PI remained at the baseline level. The main result was the presence of a direct transitory increase in rCBF at the stimulation site, both under anaesthesia and sedation. Nevertheless the measured increase in rCBF was higher but shorter duration under sedation. The magnitude of this increase was not influenced by number of sessions. No changes in rCBF were found in remote brain regions.

Conclusion

This study shows that, despite the influence of anaesthesia and sedation, comparable and clinically relevant effects on the rCBF can be obtained in dogs. Since less methodological hurdles have to be overcome and comparable results can be obtained, it would be acceptable to put the dog forward as an alternative translational rTMS animal model.