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Minimally invasive monitoring systemsRelated Patent Categories: Surgery: Light, Thermal, And Electrical Application, Light, Thermal, And Electrical Application, Electrical Therapeutic Systems, Output Controlled By Sensor Responsive To Body Or Interface ConditionMinimally invasive monitoring systems description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080027515, Minimally invasive monitoring systems. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCED TO RELATED APPLICATIONS [0001] The present application claims benefit of U.S. Provisional Patent Application Ser. No. 60/805,710, filed Jun. 23, 2006, to Harris et al., entitled "Implantable Ambulatory Brain Monitoring System," the complete disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates generally to systems and methods for sampling one or more physiological signals from a patient. More specifically, the present invention relates to long term, ambulatory monitoring of one or more neurological signals from a patient using a minimally invasive system. [0003] Epilepsy is a disorder of the brain characterized by chronic, recurring seizures. Seizures are a result of uncontrolled discharges of electrical activity in the brain. A seizure typically manifests itself as sudden, involuntary, disruptive, and often destructive sensory, motor, and cognitive phenomena. Seizures are frequently associated with physical harm to the body (e.g., tongue biting, limb breakage, and burns), a complete loss of consciousness, and incontinence. A typical seizure, for example, might begin as spontaneous shaking of an arm or leg and progress over seconds or minutes to rhythmic movement of the entire body, loss of consciousness, and voiding of urine or stool. [0004] A single seizure most often does not cause significant morbidity or mortality, but severe or recurring seizures (epilepsy) results in major medical, social, and economic consequences. Epilepsy is most often diagnosed in children and young adults, making the long-term medical and societal burden severe for this population of patients. People with uncontrolled epilepsy are often significantly limited in their ability to work in many industries and usually cannot legally drive an automobile. An uncommon, but potentially lethal form of seizure is called status epilepticus, in which a seizure continues for more than 30 minutes. This continuous seizure activity may lead to permanent brain damage, and can be lethal if untreated. [0005] While the exact cause of epilepsy is often uncertain, epilepsy can result from head trauma (such as from a car accident or a fall), infection (such as meningitis), or from neoplastic, vascular or developmental abnormalities of the brain. Most epilepsy, especially most forms that are resistant to treatment (i.e., refractory), are idiopathic or of unknown causes, and is generally presumed to be an inherited genetic disorder. [0006] While there is no known cure for epilepsy, the primary treatment for these epileptic patients are a program of one or more anti-epileptic drugs or "AEDs." Chronic usage of anticonvulsant and antiepileptic medications can control seizures in most people. An estimated 70% of patients will respond favorably to their first AED monotherapy and no further medications will be required. However, for the remaining 30% of the patients, their first AED will fail to fully control their seizures and they will be prescribed a second AED--often in addition to the first--even if the first AED does not stop or change a pattern or frequency of the patient's seizures. For those that fail the second AED, a third AED will be tried, and so on. Patients who fail to gain control of their seizures through the use of AEDs are commonly referred to as "medically refractory." [0007] For those patients with infrequent seizures, the problem is further compounded by the fact that they must remain on the drug for many months before they can discern whether there is any benefit. As a result, physicians are left to prescribe AEDs to these patients without clear and timely data on the efficacy of the medication. Because these drugs are powerful neural suppressants and are associated with undesirable side-effects and sedation, it is important to minimize the use and dosage of these drugs if the patient is not experiencing benefit. [0008] A major challenge for physicians treating epileptic patients is gaining a clear view of the effect of a medication or incremental medications. Presently, the standard metric for determining efficacy of the medication is for the patient or for the patient's caregiver to keep a diary of seizure activity. However, it is well recognized that such self-reporting is often of poor quality because patients often do not realize when they have had a seizure, or fail to accurately record seizures. In addition, patients often have "sub-clinical" seizures where the brain experiences a seizure, but the seizure does not manifest itself clinically, and the patient has no way of making note of such seizures. [0009] Demographic studies have estimated the prevalence of epilepsy at approximately 1% of the population, or roughly 2.9 million individuals in the United States alone. In order to assess possible causes for the seizures and to guide treatment for these epileptic patients, epileptologists (both neurologists and neurosurgeons) typically admit the patient to an epilepsy monitoring unit ("EMU"), where the patient will undergo continuous video-EEG monitoring in an attempt to capture ictal brain activity ("seizure activity") and interictal brain activity. [0010] During their stay in the EMU, the patients may be purposefully stressed in an attempt to induce seizure activity. For example, the patients are often sleep deprived, and if the patients are on medication, the medications may be decreased or stopped. However, for patients who have infrequent seizures, even in such a stressed state, many of such patients do not have a seizure during their stay in the EMU, and such costly and time consuming in-hospital monitoring provides little or no insight into the patient's condition. [0011] While in-patient video-EEG monitoring is currently the standard of care, improvements are still needed. For example, one drawback that has not been addressed by video-EEG monitoring is the fact that the sleep deprivation and/or a decrease or complete stoppage of the AEDs may cause cluster seizures and/or induce status epilepticus--which may not be reflective of the patient's typical seizures or seizure frequency. Thus, the EEG data that is collected in the EMU may not accurately reflect the patient's condition--which can complicate attempts to diagnose and properly treat the patient. [0012] Consequently, what are needed are methods and systems that are capable of long-term, out-patient monitoring of epileptic patients. It would further be desirable if the long-term monitoring could be processed into appropriate metrics that can quantify the clinical benefit of the medication or other therapies. It would also be desirable to have system that could record seizure activity, to enable the meaningful study of patients with infrequent seizures. SUMMARY OF THE INVENTION [0013] The present invention provides methods and systems for monitoring one or more physiological signals from the patient. In preferred embodiments, the present invention provides minimally-invasive systems that provide for the long-term, ambulatory monitoring of patient's brain activity. The systems of the present invention will typically include one or more implantable devices that are capable of sampling and transmitting a signal that is indicative of the patient's brain activity to a data collection device that is external to the patient's body. [0014] Instead of requiring the patient to stay in an EMU, where the patient's are in an unnatural stressed situation, the systems and methods of the present invention allow for out of hospital monitoring and will allow the patient to go about their lives substantially unimpeded. The ambulatory systems of the present invention provide for substantially continuous sampling of brain wave electrical signals (e.g., electroencephalography or "EEG" and electrocorticogram "ECoG", which are hereinafter referred to collectively as "EEG"). The ambulatory systems of the present invention are more likely to record the occurrence of a seizure--particularly for patients who have infrequent seizures. [0015] A patient could wear their external data collection device at all times of the day (except while showering, etc.). At the physicians' office, the data from the external data collection device could be uploaded into a physician's computer, which could then automatically analyze the stored EEG data and calculate certain metrics that would provide insight into the patient's condition. For example, such metrics may allow the epileptologist to determine if the patient is epileptic, determine the type of epilepsy and seizures, localize one or more seizure focuses, assess seizure frequency, monitor for sub-clinical seizures, determine the efficacy of treatment, determine the effect of adjustments of the dosage of the AED, determine the effects of adjustments of the type of AED, adjust parameters of electrical stimulation, or the like. [0016] The systems of the present invention typically include one or more low power implantable devices for sampling the patient's EEG signal. The implantable devices are in communication with a device that is external to the patient's body. The external device is typically configured to interrogate and optionally transmit power into the implantable device and to store the EEG signal that is sampled by the implantable device. The implantable device and the external device will be in communication with each other through a wireless communication link. While any number of different wireless communication links may be used, in preferred embodiments the systems of the present invention uses a high-frequency communication link. Such a communication link enables transmission of power into the implantable device and facilitates data transfer to and from the implantable device. [0017] In one aspect, the present invention provides an implantable device for monitoring a patient's EEG. The device comprises electronic components disposed within a housing and an antenna coupled to the electronic components. The antenna is configured to receive a radiofrequency signal that interrogates and temporarily illuminates the electronic components. A plurality of electrodes are in communication with the electronic components. The illuminated electronic components are configured to facilitate sampling of a EEG signal from a patient with the plurality of electrodes. The electronic components are configured to then transmit a radiofrequency signal through the antenna that is encoded with data that is indicative of the sampled EEG signal to an external device. The sampling and transmission of the EEG signals are typically carried out at a rate between 200 Hz and 1000 Hz to facilitate substantially continuous sampling of the EEG signal from the patient. [0018] The devices may be leadless and may be implanted anywhere in the body, but are preferably implanted extracranially and in between the skull and at least one layer of the scalp. Of course, if desired, the implantable devices may be implanted intracranially (e.g., epidural, subdural, or deep in the brain). [0019] The housing of the implantable device typically comprises a first portion that houses the electronic components and a second portion that houses the antenna. If desired, the housing of the implantable device may comprise an anchoring assembly to improve positioning of the device in the patient's body. A first electrode may be disposed on one end of the second portion of the housing and a second electrode may be disposed on one end of the first portion of the housing. In some configurations, the housing may comprise an x-ray marker to facilitate monitoring of the position of the implanted devices. In other configurations, the first portion of the housing is shielded so as to shield the electronic components within the housing. The first and second portions of the housing may be composed of the same materials or different materials and the properties of the first portion and second portion may have the same or different properties. For example, the second portion of the housing around the antenna is more flexible than the first portion, so as to facilitate better wrapping around the patient's skull. [0020] Some embodiments of the implantable device may comprise an internal power source (e.g., non-rechargeable or rechargeable battery) to power some or all of the electronic components, while others may be wholly powered from an external source. For embodiments that do not comprise an internal power source, the implanted devices will be substantially free of ferromagnetic material. Consequently, the implantable devices will be MRI safe. In yet other embodiments, in addition to or as an alternative to the internal power source or externally powered assemblies, the implanted device may comprise an assembly for generating power from body movements, movement of body organs or other bodily fluids, or thermal sources in the body. [0021] The electronic components of the implantable device may comprise a processing assembly that processes the sampled EEG signals. The processing may amplify, filter, convert from analog to digital, compress, encrypt, or the like. Furthermore, some embodiments of the processing assembly may comprise portions of an analysis algorithm that is configured to estimate the patient's brain state. In such embodiments, the analysis algorithm may extract a feature (e.g., electrical biomarkers) from the EEG signal and transmit the extracted feature over the radiofrequency signal that is transmitted from the implanted device. The extracted feature may be indicative of the patient's propensity for a seizure, tremor, migraine headache, episode of depression, or the like. Continue reading about Minimally invasive monitoring systems... Full patent description for Minimally invasive monitoring systems Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Minimally invasive monitoring systems patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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