DBS for epilepsy: the brain responds within 18 minutes

Researchers at the Mayo Clinic in the US have discovered that deep brain stimulation (DBS) in people with difficult-to-treat epilepsy causes measurable changes in brain activity within just 18 minutes. These findings may eventually contribute to more personalised treatment. At present, it often takes months before it becomes clear whether the chosen settings of a DBS system are having a sufficient effect on epileptic seizures.

Deep brain stimulation is used to treat various neurological conditions, including certain forms of epilepsy and Parkinson’s disease. In DBS, electrodes are implanted in specific areas of the brain to deliver electrical impulses. This allows the activity of brain networks to be modulated.

In patients with drug-resistant epilepsy, DBS can help to reduce the number of seizures. However, determining the optimal stimulation settings remains complex. Because epileptic seizures occur irregularly and treatment outcomes may develop gradually, it can take months or even years to find the correct settings.

Changes in brain connections

Researchers at the Mayo Clinic studied nine adults with drug-resistant focal epilepsy. These patients were already undergoing intracranial EEG monitoring as part of their regular treatment. Using these measurements, the scientists analysed how communication between the thalamus and other brain regions changed following short periods of electrical stimulation.

Two stimulation patterns were compared. In conventional DBS, electrical impulses are delivered at a regular, predictable rhythm. The researchers compared this with non-periodic stimulation, in which the intervals between impulses vary.

Both patterns were found to influence communication between brain regions in different ways. Changes were particularly evident in the connections between the thalamus and the frontal lobe. According to neurosurgeon Jonathon Parker, senior author of the study, the results show that different stimulation patterns can elicit different responses in brain networks. The research team aims to determine whether such responses can predict which stimulation settings will ultimately lead to fewer epileptic seizures.

Determining whether treatment is effective

A key finding is that changes in brain connectivity were measurable within just 18 minutes. This does not mean that the treatment demonstrably reduces epileptic seizures within that time. So far, the researchers have only identified changes in communication between brain regions. If these signals are found to be linked to a long-term reduction in epileptic seizures, doctors might in future be able to assess more quickly whether certain settings are suitable for an individual patient.

Further research is needed to confirm this. The Mayo Clinic has since expanded the study to include more participants and is investigating whether similar information can be gathered using less invasive measurement methods. The team is also exploring the potential of machine learning and artificial intelligence to analyse brain signals and assist doctors in adjusting DBS systems. According to the researchers, before such algorithms can be applied clinically, they must be prospectively validated.

DBS for decoding inner speech

The findings are consistent with other studies in which scientists are attempting to apply deep brain stimulation in a more targeted manner. For example, recently we reported on a brain-computer interface (BCI) capable of decoding inner speech, words and sentences spoken silently in the mind, into text in real time. In a study involving four participants with complete paralysis, the AI system decoded imagined sentences from a vocabulary of 125,000 words with 74 percent accuracy.

The technology uses implanted microelectrodes to record brain signals. Unlike existing systems, this approach does not require users to attempt physical speech. This could represent an important advance for people with ALS or severe brain injuries who have lost their ability to communicate.

Personalised brain stimulation

The new study by the Mayo Clinic shows that the response of brain networks to electrical stimulation can be measured relatively quickly and objectively. The key follow-up question is whether these early changes are also reliable predictors of the ultimate treatment outcome. If this link is demonstrated, the calibration of DBS systems could potentially shift from a process of prolonged trial and error to an approach guided in part by measurable brain signals.

For the time being, however, this application remains a long way off. The study involved only nine patients and has not yet demonstrated a link between the measured brain responses and a long-term reduction in epileptic seizures.