Implantable Medical Device for Providing Chronic Condition Therapy and Acute Condition Therapy Using Vagus Nerve Stimulation

Abstract

Disclosed herein are methods, systems, and apparatus for treating a medical condition in a patient using an implantable medical device (IMD). The IMD is capable of generating a first electrical signal for treating a medical condition, for example epilepsy. The first electrical signal relates to a long term therapy during a first time period in which there is no indication that the patient's brain is in an stable state, the first electrical signal being a microburst stimulation signal. The implantable device is also capable of generating a second electrical signal for treating the medical condition. The second electrical signal relates to a short term therapy during a second time period, in response to an indication that the patient's brain is in an unstable state. The second electrical signal in one example, may be a conventional stimulation signal.

1 . A method of treating a medical condition in a patient using an implantable medical device, comprising:
 applying to a cranial nerve a first electrical signal characterized by having at least one microburst of a plurality of pulses during a first time period to treat the medical condition, the first time period characterized by a time period during which there is no indication that an acute condition has occurred; and   applying a second electrical signal to the cranial nerve to treat the medical condition in response to an indication of an acute event associated with the medical condition for treating the acute event, the second electrical signal characterized by at least one burst of a plurality of pulses during a second time period that is greater than a microburst duration.   
     
     
         2 . The method of  claim 1 , wherein applying a second electrical signal in response to an indication that an acute condition has occurred comprises applying the second electrical signal in response to at least one of an indication that an epileptic seizure has occurred, an indication that a seizure is substantially imminent, or than an imminent occurrence of an epileptic seizure is highly probable, and wherein applying a first electrical signal comprises applying a first electrical signal to provide a chronic treatment for the epilepsy condition. 
     
     
         3 . The method of  claim 1 , further comprising applying a seizure detection algorithm to at least one sensed body parameter selected from the group consisting of a heart rate parameter, a temperature, an EEG signal, a breathing rate, and an eye parameter, wherein the first time period is characterized by the seizure detection algorithm providing no indication that the patient has entered an unstable brain state. 
     
     
         4 . The method of  claim 1 , further comprising applying a seizure detection algorithm to at least one sensed body parameter selected from the group consisting of a heart rate parameter, a temperature, an EEG signal, a breathing rate, and an eye parameter, wherein applying the second electrical signal comprises occurs in response to the seizure detection algorithm indicating that the patient has entered into an unstable brain state. 
     
     
         5 . The method of  claim 1 , wherein applying the first electrical signal comprises at least one of applying the microburst signal in a predetermined timing pattern or applying the microburst signal substantially synchronous to the patient's heartbeat. 
     
     
         6 . The method of  claim 5 , wherein applying the microburst signal substantially synchronous to the patient's heartbeat comprises the microburst being delivered in one of a predetermined time period or a derived time period following the R-wave of the patient's heartbeat. 
     
     
         7 . The method of  claim 1 , wherein applying the first electrical signal comprises applying the first electrical signal characterized by the number of pulses per microburst being from 2 pulses to about 10 pulses and the microburst duration being less than about 100 msec. 
     
     
         8 . The method of  claim 7 , wherein applying the first electrical signal comprises applying the first electrical signal characterized by the number of pulses per microburst being from 2 to about 6 or the microburst duration being from about 20 msec to about 80 msec. 
     
     
         9 . The method of  claim 1 , further comprising providing an electrode, coupling said electrode to the cranial nerve, providing a programmable electrical signal generator coupled to the electrode, and wherein applying the first and second electrical signals to the cranial nerve comprises generating an electrical signal with the electrical signal generator and applying the electrical signal to the electrode. 
     
     
         10 . The method of  claim 1 , wherein applying the second electrical signal is characterized by at least about 100 pulses per burst and a burst duration of at least about 2 sec. 
     
     
         11 . The method of  claim 1  wherein applying said electrical signal to a cranial nerve comprises applying said electrical signal to at least one of a left vagus nerve or the right vagus nerve of the patient. 
     
     
         12 . A method of treating an epilepsy condition of a patient, comprising:
 coupling at least one electrode to at least one cranial nerve of the patient;   providing a programmable electrical signal generator coupled to the electrode;   generating a first electrical signal for providing a chronic stimulation therapy for treating the epilepsy condition;   applying said first electrical signal to said at least one cranial nerve for a first time period in which there is no indication that the patient has entered into an unstable brain state, said first electrical signal being a microburst stimulation signal;   generating a second electrical signal for providing an acute stimulation therapy for treating the epilepsy condition; and   applying said second electrical signal for a second time period in response to an indication that the patient has entered into an unstable brain state, wherein said second electrical signal is not a microburst signal.   
     
     
         13 . The method of  claim 12 , wherein generating the first electrical signal comprises generating a microburst stimulation signal that comprises at least one burst, wherein each burst comprises a plurality of pulses in the range of about 2 pulses to about 4 pulses, wherein each pulse subsequent to the first pulse is separated from the preceding pulse by an interpulse interval in the range of about 3 msec to about 10 msec. 
     
     
         14 . The method of  claim 12 , wherein generating the first electrical signal comprises providing a stimulation signal capable of reducing the probability of the occurrence of a seizure. 
     
     
         15 . The method of  claim 12 , wherein generating the second electrical signal comprises generating a stimulation signal that comprises at least one pulse burst, wherein each pulse burst is in the range of about 7 to about 60 seconds, and wherein the pulse bursts are further characterized by a frequency of from about 20 to about 30 Hz. 
     
     
         16 . The method of  claim 12 , further comprising applying a seizure detection algorithm to at least one sensed body parameter selected from the group consisting of a heart rate parameter, a temperature, an EEG signal, a breathing rate, and an eye parameter, and wherein said second electrical signal is applied in response to the seizure detection algorithm indicating that the patient has entered into an unstable brain state 
     
     
         17 . The method of  claim 12 , wherein said first electrical signal is characterized by having a number of pulses per microburst, an interpulse interval, an interburst period, and a microburst duration, and wherein at least one of the number of pulses per microburst, the interpulse interval, the microburst duration, or the interburst period is selected to enhance cranial nerve evoked potentials. 
     
     
         18 . A system for treating a medical condition, comprising:
 at least one electrode coupled to at least one cranial nerve of a patient, and   an implantable medical device operatively coupled to the electrode and comprising a programmable electrical signal generator capable of generating a first electrical signal for providing a chronic stimulation therapy for treating the medical condition, wherein said first electrical signal is applied for a first time period in which there is no indication of an acute event associated with the medical condition, said first electrical signal being a microburst stimulation signal; the implantable medical device also being capable of generating a second electrical signal for providing an acute stimulation therapy for treating the medical condition, wherein said second electrical signal is applied for a second time period in response to an indication of an acute event associated with the medical condition, wherein said second electrical signal is not a microburst signal.   
     
     
         19 . The system for treating a medical condition of  claim 18 , wherein:
 said first electrical signal is a microburst stimulation signal that comprises at least one burst, wherein each burst comprises a plurality of pulses in the range of 2 pulses to about 6 pulses, wherein each pulse subsequent to the first pulse is separated from the preceding pulse by an interpulse interval in the range of about 3 msec to about 10 msec; and   said second electrical signal is a non-microburst stimulation signal that comprises at least one pulse burst, wherein each pulse burst comprises at least about 100 pulses, wherein the burst is further characterized by a pulse frequency of from about 20 to about 30 Hz.   
     
     
         20 . A computer readable program storage device encoded with instructions that, when executed by a computer, perform a method of treating an epilepsy condition in a patient using an implantable medical device, comprising:
 applying a first electrical signal to a vagus nerve for a first time period in which there is no indication that an epileptic seizure has occurred or is imminent, wherein said first electrical signal is a microburst signal; and   applying a second electrical signal to the vagus nerve in response to an indication that an epileptic seizure has occurred or is imminent, wherein said second electrical signal is not a microburst signal.   
     
     
         21 . The computer readable program storage device encoded with instructions that, when executed by a computer, perform the method of  claim 20 , wherein applying the first electrical signal comprises at least one of applying the microburst signal in a predetermined timing pattern or applying the microburst signal substantially synchronous to the patient's heartbeat. 
     
     
         22 . The computer readable program storage device encoded with instructions that, when executed by a computer, perform the method of  claim 20 , wherein the first electrical signal is characterized by the number of pulses per microburst being from 2 pulses to about 10 pulses and the microburst duration being less than 1 sec, and the second electrical signal being characterized by a burst duration of at least 2 seconds and at least about 100 pulses per burst, wherein each burst is further characterized by a pulse frequency of from about 20 to about 30 Hz.