Abstracts

Rationale: Approximately 15% patients with partial epilepsy are neither drug responsive nor good candidate for surgery. There has been growing interest in neuro-responsive intracerebral local treatment of seizures such as focal cooling, electrical stimulation, or drug delivery. The latter requires an effective seizure-detection system and a drug delivery device. We present here a low-power implantable device for responsive drug delivery.Methods: The proposed implantable responsive drug delivery system was validated in a feedback-controlled hybrid platform including icEEG recordings from patients with refractory epilepsy. The device delivers focal drug to suppress the seizure following the detection of a seizure onset by a dedicated microelectronic interface. Three types of detectors (i.e. synchronous, asynchronous and hybrid detector) were used to validate the performance of the proposed drug delivery device. In order to release the drug, two prototypes of micropump were used (i.e. electromagnetic and piezoelectric based micropumps). Their performances including power consumption of dedicated driving circuits were compared for a final selection of better technology.Results: The seizure detection algorithms were validated through various modeling and simulations steps within MATLAB. The three different detectors were prototyped using off the shelf components on printed circuit broads (PCBs) and dimensions are ranged from 30 mm to 60 mm diameter. Mixed-mode (analog/digital) tuning circuitry was used to adjust seizure detection parameters to the patients specific seizure onset pattern. Furthermore, the detectors are less sensitive to instrumentation noises, external noises and unwanted brief electrical seizures. The detection performances of various dedicated circuits were validated using measurement from seven patients with refractory epilepsy. Detection performance of the asynchronous detector was as accurate as that obtained with synchronous detector, but reduced power consumption by 15%. The hybrid detector increased power consumption by 5% but increased flexibilities and reliabilities. The micropumps were miniaturized and controlled corresponding flow rates with expected accuracy. The feedback controller and micropumps were activated upon seizure detection but remained in sleep mode the rest of the time. The piezoelectric-based micropump with its controller consumed a current of 0.2 nA (sleep mode) and 69.4 mA (active mode). However the electromagnetic-based micropump consumed 0.2 nA (sleep mode) and 4.5 mA (active mode).Conclusions: Preliminary experimental results of our implantable responsive drug delivery systems indicate detection accuracy and low-power dissipation. However, the hybrid seizure detector with electromagnetic-based micropump provides better performance than others responsive drug delivery systems.