BACKGROUND

Patients afflicted with movement disorders or other neurodegenerative impairment, whether by disease or trauma, may experience muscle control and movement problems, such as rigidity, bradykinesia (i.e., slow physical movement), rhythmic hyperkinesia (e.g., tremor), nonrhythmic hyperkinesia (e.g., tics) or akinesia (i.e., a loss of physical movement). Movement disorders may be found in patients with Parkinson's disease, multiple sclerosis, and cerebral palsy, among other conditions. Delivery of electrical stimulation and/or a fluid (e.g., a pharmaceutical drug) by a medical device to one or more sites in a patient, such as a brain, spinal cord, leg muscle or arm muscle, in a patient may help alleviate, and in some cases, eliminate symptoms associated with movement or other nervous disorders.

During a programming session, which may occur during implant of the medical device, during a trial session, or during a follow-up session after the medical device is implanted in the patient, a clinician may generate one or more therapy programs that provide efficacious therapy to the patient, where each therapy program may define values for a set of therapy parameters. A medical device may deliver therapy to a patient according to one or more stored therapy programs. In the case of electrical stimulation, the therapy parameters may define characteristics of the electrical stimulation waveform to be delivered. Where electrical stimulation is delivered in the form of electrical pulses, for example, the parameters may include an electrode combination, an amplitude, which may be a current or voltage amplitude, a pulse width, a pulse shape, and a pulse rate.

The sensing and monitoring of electrical signals from the patient's nervous system can be an important aspect of therapeutic and diagnostic procedures. However, such sensing and monitoring presents challenges. Neurological bioelectrical signals have relatively small magnitudes compared to those in other areas of the body, such as cardiac signals, for example. Accordingly, these signals are typically amplified for analysis. However, the application of electrical stimulation obscures these neurological bioelectrical signals during the application of the stimulation. For example, saturation of the amplifiers results, thereby rendering the sensed signal unreliable. As a result, bioelectrical signals are not typically measured during stimulation. Instead, sensing electrodes are often blocked during stimulation and re-enabled after stimulation in an attempt to observe the effect of the stimulation pulse. However, such blocking and re-enabling practice can result in missing useful information that occurs during the stimulation itself.

SUMMARY

Aspects of the present disclosure are generally directed to systems and methods for interfacing with a patient. Methods can include receiving a sense signal from a patient. The sense signal may be processed to produce a process signal. Methods may include monitoring at least one reliability signal indicative of the reliability of the sense signal or processed signal. In some examples, in the event that the reliability signal meets at least one predetermined criterion, the method includes performing at least one action to improve the reliability of the sense signal or processed signal.

In some examples, methods can include applying a test tone signal with frequency content comprising a test frequency. Methods can include monitoring the magnitude of the test frequency in the sense signal or processed signal and comparing the magnitude of the processed signal to a threshold. In some such examples, the reliability signal may include the magnitude of the test frequency in the processed signal or sense signal.

Some methods can include applying a stimulation signal comprising a stimulation frequency. The stimulation signal may be applied simultaneously with receiving a sense signal, and in some examples, both may be performed simultaneously with applying a test tone signal. In some examples, the stimulation frequency, the test frequency, and the frequency content of signals of interest in the sense signal are distinct. For example, in some methods, the stimulation frequency may be within a first frequency band, signal of interest may include frequency content within a second band separate from the first, and the test frequency may be outside of both of the first and second frequency bands.

Systems according to embodiments of the disclosure may include a processor and a plurality of electrodes for interfacing with a patient. In some examples, the processor may be configured to provide one or both of a simulation signal and a test tone signal to the patient via one or more electrodes. The system can include at least one sense electrode configured to receive a sense signal from the patient. In some examples, the system includes an amplifier for amplifying the sense signal and a processor configured to receive an amplified signal from the amplifier. The processor can be configured to determine the magnitude of the test frequency in the amplified signal and compare the magnitude to a threshold. If the magnitude falls below the threshold, the processor may be configured to lower the gain of the at least one amplifier. In some systems, the stimulation signal and test tone signal may be applied simultaneously while receiving a sense signal. In some examples, the test tone signal may be applied during a sensing procedure without stimulation being applied. Systems may include additional or alternative components to a test tone for determining the reliability of a sensed or processed signal.

