CMAJ Review CME Neuromodulation for treatment-refractory major depressive disorder Nir Lipsman MD, Tejas Sankar MD, Jonathan Downar MD PhD, Sidney H. Kennedy MD, Andres M. Lozano MD PhD, Peter Giacobbe MD MSc ajor depressive disorder is among the cranial direct current stimulation.6 Invasive Competing interests: See most prevalent psychiatric disorders options include vagal nerve stimulation7 and deep end of article. and is a leading cause of morbidity brain stimulation. Here we focus on the 3 modali- This article has been peer M 1 and lost productivity. The 1-year prevalence of ties for which the most evidence is currently reviewed. major depressive disorder in the Canadian popu- available: electroconvulsive therapy, transcranial Correspondence to: lation is 3.2%–4.6%.2 A large, multisite prospec- magnetic stimulation and deep brain stimulation. Peter Giacobbe, tive trial showed that only 28% of patients ex - [email protected] peri ence remission following monotherapy with Electroconvulsive therapy CMAJ 2014. DOI:10.1503 /cmaj.121317 a serotonin reuptake inhibitor.3 Further, remis- Electroconvulsive therapy is the oldest neuro- sion rates following antidepressant use decrease modulatory modality still used to treat major with each successive treatment failure, such that depressive disorder. It arguably remains the after 12 months of follow-up and up to 4 gold-standard to which other antidepressant attempts at symptom control with different med- treatments are compared, yet it is underused.8 ications, only 60% of patients experience remis- Electroconvulsive therapy involves the adminis- sion.4,5 The remaining patients can be classified tration of an electrical current to the brain via the as having treatment-refractory depression. scalp to induce a seizure while the patient is in a The failure of monoamine-modulating medi - state of general anesthesia. Although its mech an - cat ions to successfully treat a significant percent- isms are unknown,9 the superiority of real elec- age of cases of major depressive disorder chal- troconvulsive therapy over sham electroconvul- lenges the traditional conception of this sive therapy (anesthesia, with or without a condition as a monoamine deficiency state.5 subconvulsive dose of electrical current) sug- Accordingly, and in light of neurocircuitry mod- gests that the induction of the seizure plays a role els of the brain (Appendix 1, available at www in the antidepressant effects of this treatment.10,11 .cmaj .ca /lookup /suppl /doi :10 .1503 /cmaj .121317 / Meta-analyses comparing electroconvulsive -/DC1) and advances in technology allowing var- therapy to antidepressant medication (Table 1) ious means of modulating activity in key struc- have found that electroconvulsive therapy is sup - tures of the brain, interest in the therapeutic er ior to medication in reducing depressive symp- potential of neuromodulation for difficult-to-treat toms (effect size 0.80, 95% confidence interval mood disorders has increased in recent years. In [CI] 0.29–1.29)10 and in achieving an antidepres- this review, we outline the mechanisms, safety sant response, defined as a 50% or greater reduc- and clinical evidence for neuromodulation in tion in patients’ scores on the Hamilton Rating treatment-refractory major depression. The qual- scale for Depression compared with baseline ity of evidence for the different neuromodulation (odds ratio [OR] 3.72, 95% CI 2.60–5.32).11 Tra- strategies varies substantially, ranging from ditionally, it has been thought that the melan- small, open-label case series to blinded, random- ized controlled trials and meta-analyses (Box 1). Key points • Major depressive disorder is often refractory to standard What are the neuromodulation pharmacologic treatment but may respond well to neuromodulation. options for major depression? • Transcranial magnetic stimulation is least invasive but is less effective than electroconvulsive therapy or deep brain stimulation for treatment of major depression. Neuromodulation is either noninvasive or inva- • The acceptability and tolerability of electroconvulsive therapy is hampered sive, based on the extent to which the technology by adverse effects on episodic memory and other forms of cognition. interacts directly with the brain (Figure 1). Non- • Neuromodulation can lead to major long-term improvements in invasive options include electroconvulsive ther- depression ratings and quality of life. apy, transcranial magnetic stimulation and trans - © 2014 Canadian Medical Association or its licensors CMAJ, January 7, 2014, 186(1) 33 Review cholic subtype of major depressive disorder was convulsive Therapy suggest that the median num- the most responsive to electroconvulsive therapy, ber of electroconvulsive therapy treatments although recent studies have suggested that elec- required to produce an antidepressant response is troconvulsive therapy can produce an antidepres- 3, the number for resolution of suicidal thoughts sant response across multiple subtypes of major is 4, and the number for remission is 7.14 Given depressive episodes.17–19 Data from the multicentre that electroconvulsive therapy is typically admin- study by the Consortium for Research in Electro- istered 2 or 3 times per week during an acute course, achieving a clinically significant response Box 1: Evidence used in this review in 1–3 weeks with electroconvulsive therapy compares favourably with the 4–6 weeks typic al - We searched PubMed for articles about neuromodulation in major depression. We used the following search terms alone or in combination: ly required with antidepressant medications. “electroconvulsive therapy,” “transcranial magnetic stimulation,” “deep brain Routine use of general anesthesia, muscle stimulation,” “vagal nerve stimulation,” “direct current stimulation,” “major relaxants, continuous oxygenation, vital sign depression” and “treatment resistant depression;” we also searched using the monitoring and brief electrical stimuli have mini - acronyms “DBS,” “ECT” and “TMS.” We did not limit our searches by date. There were no meta-analyses of deep brain stimulation in depression, but we mized the risks associated with electroconvulsive found 21 meta-analyses on electroconvulsive therapy and 17 on transcranial therapy. The mortality rate has been estimated to magnetic stimulation. We found no published randomized controlled trials of be less than 1 death per 73 440 treatments.20 The deep brain stimulation for the treatment of depression. We identified most common adverse effects (myalgia [1 in 5 134 arti cles on transcranial magnetic stimulation for depression, as well as patients], headache [1 in 3 pa tients]) are transient, 230 arti cles on electroconvulsive therapy. All results were manually searched. We included only those that were relevant and enhanced our discussion and lasting minutes to hours, and can be treated with those with clearly defined patient populations and outcome measures. analgesics.21 Electroconvulsive therapy is associ- ated with immediate posttreatment disorientation B. Deep brain stimulation 24 32 25 14c A. Transcranial magnetic stimulation Glutamate C. Electroconvulsive therapy AMPAR NMDAR 2+ Ca 2 1 CaM CaMKII Figure 1: (A) Transcranial magnetic stimulation is thought to produce durable changes in synaptic strength via the NMDA-receptor– dependent mechanisms of long-term potentiation and long-term depression. Simultaneous stimulation of presynaptic and postsynap- tic neurons strengthens or weakens the synaptic connection, depending on the frequency and pattern of stimulation. When applied to areas of prefrontal cortex that are hypoactive in depression, repetitive transcranial magnetic stimulation gradually increases their activity, thereby relieving the illness. (B) With deep brain stimulation, electrodes are inserted under stereotactic guidance into regions of the brain believed to drive maladaptive thoughts and behaviours. Constant electricity, provided by an implanted pulse generator, disrupts neural activity both at local sites (i.e., at the target) and at remote, yet connected, structures, comprising a “mood circuit.” (C) Electroconvulsive therapy induces ictal activity, as shown by the electroencephalographic recording. 34 CMAJ, January 7, 2014, 186(1) Review and retrograde amnesia. Although these effects can produce long-lasting changes in neural are generally short lived, a 6-month longitudinal excitability. The frequency of stimulation deter- follow-up study found that retrograde amnesia mines the effects of transcranial magnetic stimula- persisted in about 1 in 8 patients (12.4%).22 The tion. Low-frequency (< 5 Hz) stimulation inhibits amnestic effects of electroconvulsive therapy are neuronal firing, and high-frequency (> 5 Hz) stim- greater for recent events (i.e., within 3 mo of first ulation increases neuronal firing rates.26 treatment) than for remote events (i.e., greater Transcranial magnetic stimulation typically than 3 yr).23 Factors associated with greater cog- involves 10–30 treatment sessions of 15–45 min- nitive impairment following electroconvulsive utes duration, administered once daily, 5 days a therapy include pre-existing cognitive impair- week on an outpatient basis. High-frequency ment, older age and the use of bilateral electro- stimulation to the dorsolateral prefrontal cortex convulsive therapy.24 There are no absolute con- is the typical protocol for patients with major traindications to electroconvulsive therapy, and it depressive disorder, based on neuroimaging evi- can be used safely