Compact, low-power pulse generator sphenoid implant for minimally invasive electrical stimulation of deep brain regions

This paper presents an implant for electrical deep brain stimulation that can fit in the sphenoid sinus, a hollow space in the skull’s sphenoid bone that is accessible transnasally. The implant consists of flexible disk electrodes attached to a circuit capable of generating voltage pulses of up to 40 V through capacitive discharge from a 3 V DC power supply. The 10 mm × 4 mm × 3 mm circuit consumes <50 µA when idle and 50 µC/pulse. Different pulse widths and pulsing frequencies can be selected with hardware changes. When operated from a 1 mAh battery, the circuit can generate over 80000 pulses. The circuit was inserted into the sphenoid sinus of a human cadaver, and electric fields generated by the circuit in the brain were measured. Injecting a peak current of 10 mA, resulting fields of up to 15 V/m were measured in the ventral diencephalon, demonstrating sufficient amplitude to activate neurons. This work is the first demonstration of an implant for minimally invasive stimulation of deep brain structures through the skull base, which opens new horizons for clinical treatments of neural disorders.