Riverview Medical Services Inc.

rTMS is a procedure in which cerebral electrical activity is influenced by a pulsed magnetic field. The magnetic field is generated by passing brief current pulses through a figure 8 coil. This coil is encased in plastic and is held close to the scalp so that the magnetic field can be focused onto specific areas of the cortex, or surface of the brain.

The magnetic field that is generated in rTMS can penetrate the scalp and skull safely and painlessly to induce a current in specific regions of the brain. These electric currents cannot be felt and cause the neurons to become active leading to the release of neurotransmitters (the brain’s chemical messengers) locally and in areas deeper in the brain.

Many aspects of rTMS, referred to as stimulation parameters, can be changed and are determined for each individual by the psychiatrist. This means that the delivery of rTMS therapy may be customized for each patient.

The stimulation parameters include:

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• The total number of stimulus trains in each session

• The intensity of the stimulation

• The frequency of the stimulation

• The duration of the stimulation

• The length of the interval between stimulations

• The site of stimulation

rTMS may be used to elicit certain desired effects in the brain (i.e. excitatory or inhibitory effects) depending on the frequency of the stimulation applied.

Low Frequency Stimulation (1 Hz or less) has been shown to decrease cortical excitability

 

High Frequency Stimulation (up to 20 Hz) has an excitatory effect on neural activity. Over time, this form increases the activity of the targeted area of the brain and induces changes in associated neural networks.

 

Theta Burst Stimulation (TBS) is a form of patterned rTMS that involves the application of very short (e.g. 3 pulses) high frequency bursts at 50 Hz. These bursts are repeated at theta frequency (5 Hz). Continuous TBS results in a decrease in cortical excitability. Intermittent TBS (iTBS) produces an increase in cortical excitability.