MRS and ECT: Systematic Literature Review
Out on PubMed, from researchers in Norway and New Mexico, is this review:
Magnetic Resonance Spectroscopy in Depressed Subjects Treated With Electroconvulsive Therapy-A Systematic Review of Literature.
Electroconvulsive therapy (ECT) is considered to be the most effective acute treatment for otherwise treatment resistant major depressive episodes, and has been used for over 80 years. Still, the underlying mechanism of action is largely unknown. Several studies suggest that ECT affects the cerebral neurotransmitters, such as gamma-aminobutyric acid (GABA) and glutamate. Magnetic resonance spectroscopy (MRS) allows investigators to study neurotransmitters in vivo, and has been used to study neurochemical changes in the brain of patients treated with ECT. Several investigations have been performed on ECT-patients; however, no systematic review has yet summarized these findings. A systematic literature search based on the Prisma guidelines was performed. PubMed (Medline) was used in order to find investigations studying patients that had been treated with ECT and had undergone an MRS examination. A search in the databases Embase, PsycInfo, and Web of Science was also performed, leading to no additional records. A total of 30 records were identified and screened which resulted in 16 original investigations for review. The total number of patients that was included in these studies, ignoring potential overlap of samples in some investigations, was 325. The metabolites reported were N-acetyl aspartate, Choline, Myoinositol, Glutamate and Glutamine, GABA and Creatine. The strongest evidence for neurochemical change related to ECT, was found for N-acetyl aspartate (reduction), which is a marker of neuronal integrity. Increased choline and glutamate following treatment was also commonly reported.
Keywords: brain; depression; electroconvulsive therapy; magnetic resonance spectroscopy [(1)H MRS]; neurotransmitters.
The pdf is here.
From the text:
For the last 3 decades hydrogen magnetic resonance spectroscopy (H-MRS) has helped explore the biochemical aspects of brain changes (11). MRS takes advantage of protons reacting slightly different to the magnetic field, depending on their chemical environment. This makes it possible to distinguish between different chemical compounds, and to quantify their concentrations, even at fairly low concentrations. The metabolite is measured in a specified volume, the voxel. The nuclear spin of certain nuclei is measured in the voxel, and will upon manipulation give a resonance at a certain frequency, characteristic for a certain metabolite. The most common nucleus used in MRS is the hydrogen proton (H1 ), but phosphorus ( 31P) is another nucleus that can be measured. Figure 1 is illustrative for a typical H1 -MRS spectrum, made with the LCModel software (12). MRS gives the opportunity to study a broad array of compounds in vivo in a non-invasive way. The two main methods for H1 -MRS are point resolved spectroscopy, PRESS and stimulated echo acquisition mode, STEAM. Challenges in MRS are overshadowing of metabolites that are present in very small amounts by other largely abundant substances. For gamma-aminobutyric acid (GABA) this is the case, and a special technique is required (13, 14). MRS of the brain is primarily used for research purposes, but is also used clinically, in newborns with asphyxia, both in evaluation of the hypoxic-ischemic injury and as a predictor of outcome (15, 16). MRS is also included in the work-up of brain tumors, in some centers as a routine exam, while in others as a supplementary tool, as it may help in grading the tumor, decide the extension of the tumor and as a guidance to biopsy (17). Current research will hopefully encourage further adaptation of the method for clinical use in fields such as psychiatry and ECT- even if current reviews so far have concluded with conflicting results (18).DISCUSSION Magnetic resonance spectroscopy gives us a unique possibility to study the biochemistry in depression and ECT. The MR scan is a gentle and non-invasive examination for the patient, demanding only that one can lay still in a noisy and cramped environment. Many investigations have been published on various substances, trying to establish a link between chemical compounds and clinical features of patients receiving ECT. Our systematic review suggests a reduction in N-acetyl aspartate following ECT, and increased choline and glutamate was also commonly reported. However, drawing firm conclusions about the effect of ECT for individual metabolites based on the MRS literature published to date is not possible based on diagnostic heterogeneity, concurrent medication use, small sample sizes, and scanner/acquisition differences.
There are also other metabolites which could be of interest, such as glutathione, which have not yet been investigated in this setting, but where both increase and decrease have been reported in depression (43). Hence, more research on already investigated and new metabolites is needed to explore the relevance and benefit of clinical use of MRS in treatment of depression. Future research focused on ECT’s mechanisms of action should also investigate brain changes associated with cognitive side effects, as these side effects could parallel with neurochemical changes.
This is a very interesting review of the application of MRS to ECT patients. The heterogeneity of results reflects the immaturity of the field, but MRS seems to hold much promise for the further non-invasive study of brain compounds in vivo.
The paper is very well written; anyone who wants to learn about this technology should read the paper in full, ~25 minutes. No need yet to commit the specific biochemical findings to memory, IMO.
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