Theta burst stimulation (TBS) is a non-invasive brain stimulation technique that uses magnetic fields to influence brain activity. It is a form of neuromodulation, which alters nerve activity through targeted stimulus delivery. This approach addresses various neurological and psychiatric conditions by adjusting brain function without surgical intervention.
Understanding Theta Burst Stimulation
Theta burst stimulation is a specific form of repetitive transcranial magnetic stimulation (rTMS). It delivers magnetic pulses in a unique pattern designed to mimic natural brain rhythms. This pattern involves short “bursts” of three magnetic pulses delivered at a high frequency, such as 50 Hz, repeated at a slower theta frequency, around 5 Hz.
This bursting pattern allows for more efficient brain stimulation compared to traditional rTMS protocols. Conventional rTMS sessions might last between 20 to 40 minutes, while an intermittent theta burst stimulation (iTBS) session can be completed in approximately 3 to 10 minutes. This reduced treatment time makes TBS a more convenient option.
How Theta Burst Stimulation Interacts with the Brain
Magnetic pulses generated by a TBS device pass through the scalp and induce electrical currents in targeted brain regions. These induced currents influence neuron excitability, changing how brain cells communicate. The effects involve mechanisms similar to long-term potentiation (LTP) and long-term depression (LTD), processes underlying brain plasticity.
LTP-like effects involve strengthening synaptic connections, enhancing brain activity in a stimulated area. Conversely, LTD-like effects involve weakening these connections, which can suppress brain activity. The specific pattern of TBS, whether continuous (cTBS) or intermittent (iTBS), determines the direction of these changes, allowing for an increase or decrease in neural activity in the targeted brain region.
Conditions Treated with Theta Burst Stimulation
Theta burst stimulation treats or is being investigated for a range of medical and neurological conditions. Major depressive disorder (MDD) is a primary application, with iTBS approved by the U.S. Food and Drug Administration (FDA) for treatment-resistant depression. For MDD, TBS often targets the left dorsolateral prefrontal cortex, a brain region implicated in mood regulation, aiming to enhance impaired long-term potentiation-like activity.
Obsessive-compulsive disorder (OCD) is another condition for which TBS, particularly deep TMS protocols, has received FDA approval. TBS is also being explored for chronic pain and in stroke rehabilitation to improve motor function. For stroke patients, iTBS may promote neuroplasticity in cortical areas.
What to Expect During a Session
During a theta burst stimulation session, individuals sit comfortably in a chair. A healthcare professional places a magnetic coil against the scalp, precisely positioned over the target brain area. Earplugs are provided to dampen the sound of the machine, which produces rapid tapping or clicking noises during pulse delivery.
As the device delivers magnetic pulses, patients report a tapping sensation, a buzzing, or a feeling akin to static electricity on their scalp. While some scalp discomfort or mild pain might occur during the tapping, it subsides during pauses in the stimulation. An iTBS session is brief, lasting around 3 to 3.5 minutes, allowing individuals to resume their normal daily activities immediately afterward.
Safety Profile and Potential Side Effects
Theta burst stimulation is considered safe, with side effects being mild and temporary. Side effects include scalp discomfort or tenderness at the site of stimulation, a mild headache, or facial muscle twitching. These effects improve shortly after a session and do not require medication.
Serious risks, such as seizures, are rare, with a risk as low as 0.02% across thousands of sessions. Seizures are self-limiting and attributed to factors like sleep deprivation, alcohol intake, or exceeding safety guidelines. Healthcare providers conduct thorough screenings to identify any contraindications, such as metal implants or pacemakers, to minimize risks before starting treatment.