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. MST is stated to work by inducing seizures via

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

s, in contrast to

ECT ECT may refer to: Educational institutions * École Canadienne de Tunis, a school in Tunis, Tunisia * Emirates College of Technology, in Abu Dhabi Government and politics * Catalan Workers' Left ( ca, Esquerra Catalana dels Treballadors, li ...

which does so using alternating

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

s. Additionally, MST works in a more concentrated fashion than

, thus able to create a seizure with less of a total electric charge. In contrast to (r)TMS, the stimulation rates are higher (e.g. 100 Hz at 2 T) resulting in more energy transfer. 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 The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...

Medical uses

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.

Major depressive disorder and treatment-resistant depression

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.

Procedure

MST is performed with the use of a modified rTMS device that delivers a higher output. Similar to ECT, because MST induces seizures, general anesthesia is used to relax the muscles. However, because there is not an electric current that may stimulate the jaw muscles, a bite block is not necessary. Coils are placed over the frontal cortex (usually bilaterally) and the treatment dosage is usually determined via titration with a preset dosing schedule. The treatment dosage is determined once the

seizure threshold The term seizure threshold is used to describe the balance between excitatory (glutaminergic) and inhibitory ( GABA-ergic) forces in the brain which affect how susceptible a person is to seizures. Those diagnosed with epilepsy or certain other neur ...

has been met and a sufficient seizure is produced. Various coil designs have been tested, such as the figure 8 coil, double cone coil, and cap coil. The latter two are the ones that have been most reliable in seizure induction.

Mechanism of action

The mechanism of action of MST is not yet clearly understood. One hypothesis focuses on the neuroplasticity of the affected areas of the brain, mostly including the hippocampus and amygdala. Further recent imaging with fMRI has shown an effect on the connection between the subgenual anterior cingulate cortex and the

Adverse effects

Adverse effects include

disorientation Orientation is a function of the mind involving awareness of three dimensions: time, Location (geography), place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to Substance int ...

, emergence of

mania Mania, also known as manic syndrome, is a mental and behavioral disorder defined as a state of abnormally elevated arousal, affect, and energy level, or "a state of heightened overall activation with enhanced affective expression together wit ...

, and superficial burns due to coil malfunctions. 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

. Other adverse effects include generalized seizures as well as side effects typically seen with general anesthesia. Hearing loss is a possible adverse effect from the clicking noise of the magnetic coils if earplugs are not used.

References