Therapies applied to neural tissue may include, but are not limited to, electrical stimulation to enhance nerve activity, electrical stimulation to reduce or block nerve activity, and ablation of neural pathways. However, it can be difficult and time consuming to find the neural target for the therapy.
For example, it has been proposed to reduce blood pressure by electrically stimulating baroreceptor regions to induce a baroreflex response. Baroreceptors play an important role in regulating blood pressure, and are located throughout the body, but primarily in the arch of the aorta and the carotid sinuses of the left and right internal carotid arteries. Through a negative feedback baroreflex system, the central nervous system can regulate the blood pressure to maintain the blood pressure at a relatively stable level. For example, arterial pressure that causes stretch triggers the baroreflex to send nerve impulses to the brain which responds by controlling the pumping activity of the heart and blood vessel dilation to reduce the blood pressure.
The blood pressure response can fluctuate dramatically when different areas of the baroreceptor region are stimulated. For example, the blood pressure response at a first site within the baroreceptor region can be significantly different than the blood pressure response at a second site within the baroreceptor region. Animal experiments indicate responses can dramatically fluctuate spatially within 1 mm; and yet the carotid sinus area in humans is rather large (e.g. typically about 2 cm×1 cm). Thus, the implantation of a baromodulation device to stimulate a small baroreceptor region in the carotid sinus usually requires extensive mapping of the internal carotid arteries in order to find a desirable stimulation location along the carotid artery that provides an effective or that appears to provide one of the largest possible blood pressure responses if not the largest response. Currently, surgeons manually hold one or more electrode(s) at various locations near the carotid sinus to map the baroreceptor region during an implantation procedure. Mapping a tissue region to find candidate neural targets may take up to several hours. This procedure takes significant time and effort due to the difficulty of manually positioning the electrode and maintaining steady and consistent blood pressure. Longer procedure times also undesirably expose the patient to longer anesthesia times. Thus, the clinical procedure is often unable to access a full mapping area. Moreover, the manual operation may cause trauma, or introduce mechanical activation of the baroreceptors which may hinder the evaluation of the blood pressure responses to the electrical stimulation. Much of the long procedure time is spent waiting for stable baselines or return of blood pressure or heart rate values to pre-stimulation values.