How BeBiTT Helps Evaluate BCI Assistive Technology for People with Tetraplegia

Assistive technology is transforming how we think about rehabilitation after spinal cord injuries. Additionally, incorporating BCI assistive technology can enable users to control devices directly with their brain signals, restoring independence in daily tasks.

For people with cervical spinal cord injury (cSCI), even simple two-handed activities can be a daily struggle. Such as eating, dressing, or brushing teeth.  New innovations in the field of brain-computer interfaces (BCIs) offer exciting ways to restore independence. In this study, authors utilized such assistive technology in the form of a hand exoskeleton.

While these tools are promising, researchers still need reliable methods to measure how much they improve everyday function. To address this, scientists have developed the Berlin Bimanual Test for Tetraplegia (BeBiTT).

Developing the BeBiTT

BeBiTT is a new test designed specifically to assess two-handed (bimanual) performance in people with cSCI. The test focuses on common grasp types (like pinching or power grip). Also, on key activities of daily living, such as eating, dressing, and personal hygiene.

From an initial list of 32 tasks identified through interviews with patients and therapists, the researchers selected 9 tasks. These tasks best represent real-life challenges, while keeping the test short and practical.

The BeBiTT uses a structured scoring system to evaluate three main aspects of bimanual function:

• Grasping (active vs. passive grip strength)
• Manipulating (how easily an object can be used, and whether compensatory strategies are needed)
• Lifting (how well both arms can work together against gravity)

Each task is scored up to 10 points. So, we get a total score between 0 (no bimanual function) and 90 (fully unimpaired function).

The test is quick to administer, around 20 minutes. It requires simple materials and is designed to capture improvements from BCI assistive technology like hand exoskeletons.

Setting up the study with brain/neural hand exoskeleton (B/NHE)

Researchers recruited 14 participants with tetraplegia, but during the study 4 of them were excluded. In total, there were 5 participants with total cSCI and 5 with partial.

There were 2 conditions in the study: without and with intervention. The intervention condition included the BCI setup with EEG + exoskeleton, designed to support neurorehabilitation by promoting motor recovery through brain-driven feedback.

EEG data was collected in real-time using mbt’s portable EEG system. With the same system, they also collected EOG data. This can easily be done by configuring a few EEG channels for a separate measurement.

Authors investigated sensorimotor event-related desynchronization (SMR-ERD) in the EEG signal. SMR-ERD is associated with intended grasping motions so here, they translated it into closing motions.

Horizontal EOG was used to control opening motions of the exoskeleton.

Validating the BeBiTT test

Authors wanted to assess interrater reliability. To do so, they obtained ratings from instructors and three independent raters. Independent raters were blinded to the participants’ diagnosis and were given a short explanation of the rating system. Then, they filled it out watching the recorded sessions.

Participants rated BeBiTT as feasible, reliable, and valid. Internal consistency and interrater reliability were also excellent.

For an additional analysis, they calculated the Pearson correlation between BeBiTT and two other scoring systems.

One was the Spinal Cord Independence Measure III (SCIM III). And the other was the Quadriplegia Index of Function (QIF). Authors reported strong correlations in this case, which supports BeBiTT’s construct validity.

BCI-assistive technology improves BeBiTT score

BeBiTT captured overall improvements from brain-controlled hand exoskeleton. The difference in scores is statistically significant, shown in the boxplot below:

Taking a closer look at the scores shows grasping and lifting performance is much better with the exoskeleton:

People with tetraplegia often rely on the passive tenodesis grasp, which is too weak for many daily tasks. Using a hand exoskeleton gave them active grip strength, which improved both grasping and lifting abilities.

But manipulation didn’t significantly improve. This was likely due to technical limits of the exoskeleton and users’ lack of experience with it. Some participants struggled with fine control, while others managed better, leading to high variability in results.

Broader application of the BeBiTT in and outside neurorehabilitation

Beyond neurotechnology, the BeBiTT could also be used to evaluate other rehabilitation strategies (e.g., tendon transfer or functional electrical stimulation). Also, for comparing different therapies, or tracking recovery driven by neuroplasticity.

While developed for tetraplegia, it could be adapted for other groups such as stroke survivors. The authors emphasize that bimanual function deserves more focus in rehabilitation, given its central role in daily life.

Researchers also noted some limitations of the study:

• Some daily living categories are underrepresented to keep the test short.
• Findings need validation in larger and more diverse clinical populations.
• Results may have been influenced by fatigue, learning effects, or uneven BCI control abilities.
• The test was done with a single-hand exoskeleton; future studies should explore bilateral use.

The BeBiTT is a powerful new tool to assess bimanual function systematically and reliably. Especially for testing the impact of assistive technology such as hand exoskeletons. Further research can help understand how BeBiTT could fit into broader clinical acceptance.

You can read the original paper linked here.