Monitoring closed-loop neural stimulation therapy

An implantable device for delivering closed-loop neural stimulation therapy, the device comprising:

• a plurality of electrodes including one or more stimulus electrodes and one or more sense electrodes;
• a stimulus source configured to provide neural stimuli to be delivered via the one or more stimulus electrodes to a neural pathway of a patient in order to evoke neural responses on the neural pathway;
• measurement circuitry configured to capture signals sensed at the one or more sense electrodes subsequent to each neural stimulus;
• and
• a control unit configured to deliver closed-loop neural stimulation therapy by:
• controlling the stimulus source to provide a first neural stimulus according to a first stimulus parameter;
• measuring, in the sensed signal, an intensity of a neural response evoked by the first neural stimulus;
• computing a feedback variable from the measured intensity of the evoked neural response;
• adjusting, based on the computed feedback variable, the first stimulus parameter;
• and
• repeating the controlling, measuring, computing and adjusting to maintain the feedback variable at a target response intensity,
• wherein the control unit is further configured to:
• control the stimulus source to provide, interleaved with the first neural stimuli, a plurality of second neural stimuli according to respective second stimulus parameters, wherein the second neural stimuli are different from the first neural stimuli;
• and
• monitor the closed-loop neural stimulation therapy by analysing the sensed signals captured by the measurement circuitry subsequent to respective second neural stimuli of the plurality of second neural stimuli.