Rechargeable Brain Implant for Parkinson's Disease Patients

Parkinson's Disease (PD) patients experience movement-related symptoms (e.g., tremors in the hands and/or fingers), due to irregularities in electrical signals in the brain that are responsible for controlling movement. These irregularities are caused by decreases in the amount of neurons that produce dopamine. Deep Brain Stimulation (DBS) reduces symptoms of PD by interrupting these irregular signals that cause movement-related symptoms.

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The system that I worked consisted of a rechargeable implantable neurostimulator and its charger. Because the neurostimulator lied flushed on the skull, the charger had a form factor similar to a pair of headphones--as long as the "puck" on the band of the headphones was centered over the area of the implant, the implant could be recharged.

This research study sought to explore two early-stage designs of the external headphone charger and the ease of aligning the "puck" over the implant area. Areas of interest were:

• Can users correctly place the external charger over the area of the implant with minimal adjustment of the headphones?

• Which design of the headphones did users prefer, and why?

• Which alignment sound did users prefer, and why?

• How comfortable were each of the headphone designs?

• Do users have any concerns about their appearance when wearing the headphones, or not?

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Parkinson's Disease patients who currently do not use DBS were recruited for this study. Additionally, because a small magnet was used to simulate the implant, participants with any other implants in the body were excluded to avoid any potential disturbance to existing implants.

Data was collected via a usability study, where participants used the think-aloud method while performing tasks. Participants were well-informed on what would happen during the usability study and were given plenty of breaks to ensure their comfort.

 

After study personnel adjusted the first set of headphones to participants' heads and placed the simulated implant on the scalp, participants were instructed to align the "puck" of the headphones over the area of the implant. Then, participants wore two sets of headphones for up to 45 minutes each and performed everyday activities, such as walking around, reading a book, or playing board games. Toward the end of the end of the session, study personnel interviewed participants using Likert Scales and free response questions to gather their feedback on the headphone designs (e.g., ease of alignment, opinions on the alignment audio feedback, comfort of the headphones). Anthropometric data, such as ear length and width, were collected from participants to help further improve the fit of the headphone cups.

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Participant comments, performance, and anthropometric measurements were analyzed and summarized in a PowerPoint report.

Prior to the study, we provided the following anthropometrics and data surrounding hearing frequencies for the client to consider when creating the headphone mockups:

• Head circumference, height, and breadth*

• Ear breadth, length, and protrusion*

• Hearing frequency capabilities of populations 60+, typical loudness of various settings in dB (per AAMI HE75), and preferred frequency levels according to research studies

*Women's 1st percentile to men's 99th percentile

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Based on observations and participant feedback, some findings included:

• Participants preferred one alignment audio feedback over the other because it was less annoying and anxiety-inducing.

• Participants would like an option to adjust the volume of the alignment audio feedback (Note: The volume was fixed for the study).

• The headphones were not entirely stable on participants' heads, which led to the "puck" moving out of alignment. Stability of the headphones should be further researched to reduce the amount of times users need to re-align the "puck."

• Participants with glasses felt uncomfortable wearing the headphones. Therefore, the final design should consider users with glasses.

• Participants found the earpads on the headphone cups comfortable, and thus they did not need to take off the headphones at any point during the study due to discomfort.

• All participants would feel comfortable wearing these headphones in front of their family, but most noted they would not wear the headphones in public. Further research can be done on the "stigma" users may feel wearing a medical device in public.