Magnetic seizure therapy (MST) is a proposed form of electrotherapy and electrical brain stimulation. It is currently being investigated for the treatment of major depressive disorder, treatment-resistant depression (TRD), bipolar depression, schizophrenia and obsessive-compulsive disorder.[1][2] MST is stated to work by inducing seizures via magnetic fields, in contrast to ECT which does so using alternating electric currents. Additionally, MST works in a more concentrated fashion than ECT, thus able to create a seizure with less of a total electric charge.[3] In contrast to (r)TMS, the stimulation rates are higher (e.g. 100 Hz at 2 T) resulting in more energy transfer.[4] Currently it is thought that MST works in patients with major depressive disorder by activating the connection between the subgenual anterior cingulate cortex and the parietal cortex.[5]
Magnetic seizure therapy is a new treatment modality that is being studied for the treatment of multiple psychiatric conditions, including major depressive disorder, treatment-resistant depression (TRD), bipolar depression, schizophrenia and obsessive-compulsive disorder.[1][2]
MST is currently being studied to as a potential treatment option versus ECT based on the need for a procedure with a different safety and side effect profile. Current limitations to a more widespread implementation of MST for these diseases are the variable dosages, number of treatments, and efficacy versus other treatment modalities.[3] A Cochrane review (2021) with three studies (65 participants) found insufficient evidence of a difference between MST and ECT.[6]
MST is performed with the use of a modified rTMS device that delivers a higher output.[7] Similar to ECT, because MST induces seizures, general anesthesia is used to relax the muscles.[8] However, because there is not an electric current that may stimulate the jaw muscles, a bite block is not necessary.[8] Coils are placed over the frontal cortex (usually bilaterally) and the treatment dosage is usually determined via titration with a preset dosing schedule.[3] The treatment dosage is determined once the seizure threshold has been met and a sufficient seizure is produced.[3] Various coil designs have been tested, such as the figure 8 coil, double cone coil, and cap coil.[7] The latter two are the ones that have been most reliable in seizure induction.[7]
The mechanism of action of MST is not yet clearly understood.[9] One hypothesis focuses on the neuroplasticity of the affected areas of the brain, mostly including the hippocampus and amygdala.[9] Further recent imaging with fMRI has shown an effect on the connection between the subgenual anterior cingulate cortex and the parietal cortex.[5]
Adverse effects include disorientation, emergence of mania, and superficial burns due to coil malfunctions.[10] While one study did note a decline in autobiographical memory after MST, many studies have noted no anterograde memory loss nor retrograde memory loss, both of which are more commonly seen side effects of ECT.[3][8] Other adverse effects include generalized seizures as well as side effects typically seen with general anesthesia.[11] Hearing loss is a possible adverse effect from the clicking noise of the magnetic coils if earplugs are not used.[11]