Abstracts

Patients monitored with subdural elctrodes may require up to 128 electrode contacts in order to establish the origin of their epileptic seizures. In the existing system of monitoring, each line of contacts are connected via individual wires to a remote data acquisition system consisting of amplifiers, multiplexors, and computers. Therefore, patients carry a complicated system of connectors and cables that directly connect into the implanted recording electrodes. The set-up is cumbersome because of the mass of wires, cables and connectors which greatly imped their mobility and compliance. Miniaturization technology with small and light surface-mounted components and low power circuitry can significantly reduce the size of the components so that they all can be mounted directly on the patients[apos] heads.
Small, surface-mounted amplifiers with high gain (1000X) coupled with analog multiplexors and 200 Hz sampling rate per channel can be formed into 7/8-channel modular units to connect to a 16:1 analog switch to create a small head-mounted 128-channel multiplexed analog system. Therefore, only a long (e.g. 30+ m) single 6-conductor cable is attached to the patients in order to deliver the critical signals to a remote recording device.
Switching from the traditional point-to-point cable connector system to our current system led to a significant improvement at all levels of patient care. The patients gained more freedom in and around their beds. The administration of nursing care became easier because the wires and cables were no longer directly connected to the subdural electrodes to hinder their access to the patients. Only one 6-conductor cable needed to be disconnected to allow patients to leave the monitoring unit instead of mass connectors of the existing system. Patient reconnection was quick and trouble-shooting of the system was easy to do. A bad channel could only be the subdural contact or the amplifier which is easily exchanged than the multiple other locations such as cables, wires or connectors in the traditional system. EEG was less contaminated with artifacts becauseof the proximity of the amplifiers to the generators of the brain potentials. As the amplifiers were on the head, head and body movement had less contribution to artifacts than remote amplifiers. The postoperative course was improved because the patients were more mobile with increased level of physical activities.
Patients with subdural electrodes no longer need to be confined, restricted, and connected by masive cables and connectors to remote data acquisition systems. Modern electronics can provide up to 128-channels of amplification and multiplexing directly over the scalp. Therefore, the patient that is being monitored with subdural electrodes can be as mobile as patients who are being monitored with head-mounted surface EEG recordings.