Non-invasive Measurement of Brain Oxygen Levels in People With Subthalamic Deep Brain Stimulators
Condition: Parkinson's Disease
MeSH terms: Parkinson Disease
Study type: Interventional

Summary: 
      The purpose of this study is to determine if deep brain stimulation can change brain oxygen
      levels in people with Parkinson's Disease. Measurements will be taken using a non-invasive
      device while subjects are both on and off their medications, and while their stimulator is in
      the on and off setting.
    

Detailed description: 
      The investigators will study the effects of electrical stimulation at the subthalamic nucleus
      on frontal cerebral perfusion in 10 patients with advanced PD who have already undergone
      successful STN DBS (Medtronic, Inc., Minneapolis, MN) surgery as evidenced by a 20% or
      greater improvement in their Unified Parkinson's disease rating scale (UPDRS) motor sub-score
      (UPDRS-III) with stimulation on vs off, three or more months after surgery. The UPDRS-III is
      a widely employed and validated rating scale of Parkinson's disease symptom severity that is
      based on the neurological examination. For the purposes of this study, a movement disorders
      neurologist will perform all of the neurological assessments. Patients must also be
      demonstrated to be cognitively intact as evidenced by a Montreal Cognitive Assessment (MoCA)
      Score of 24 or greater.

      This is an experimental study in which we will compare frontal cerebral perfusion (measured
      non-invasively with the NIRS device) and UPDRS-III scores (as determined by neurological
      examination) in four clinical states: medications off/stimulation off; medication
      off/stimulation on; medication on/stimulation off; and medications on/stimulation on.

      The primary question to be answered is: Can we detect significant changes in cerebral
      perfusion with the NIRS device in response to subthalamic stimulation delivered via implanted
      DBS devices?

      This pilot study will be conducted in 10 PD patients who have undergone successful DBS
      surgery in the past. The study will be completed in one day as detailed below and will take
      about 6 hours to complete.

      Patients will arrive to the movement disorders center on the morning of their scheduled study
      visit having discontinued their medications from the night before (12 hours 'off"). They will
      arrive with their stimulators on and set to the therapeutic parameters. Dr. Shih will perform
      a neurological examination and determine the UPDRS-III score in this, the off med/on stim
      state.

      In order to perform the NIRS/perfusion measurements the subject will be fitted with a
      multipart plastic helmet, which holds a number of optical fibers against the surface of the
      subject's head. This helmet will be adjusted to fit comfortably. Additional probes will be
      positioned on the fingers in order to monitor peripheral blood oxygenation (i.e. pulse
      oximetry) to ensure that any changes observed in cerebral perfusion are due to changes in
      brain physiology, not a general physiological factor. The fibers are connected to 32 low
      power infrared laser diodes. The power emitted by these lasers is far below the typical
      maximum permissible exposure (MPE) level for skin exposure to a laser beam, as indicated by
      the American National Standards Institute, and subjects will not feel any effect from them.
      The laser light will be pointed at the top of their head, and there will be no risk to their
      eyes. The initial cerebral perfusion measurement will be made.

      The patient's DBS devices will then be turned off and 60 min will be allowed to pass,
      allowing for washout of both the clinical and CBF effects of DBS. During this time, cerebral
      oxygenation will be monitored and documented every five minutes. At the end of this period
      the UPDRS-III score will be determined (off meds/off stim) and recorded, confirming a washout
      of the clinical effects. The DBS will then be turned on employing the settings employed for
      therapy except that the stimulation frequency will be set to 20Hz, a low frequency that is
      known not to be therapeutically effective in PD. All other settings will be maintained
      constant. Again, the cerebral oxygenation will be recorded every 5 min for 60 min after which
      the UPDRS-III score will be recorded The DBS will then be reprogrammed to the patient's
      steady state therapeutic settings, the cerebral oxygenation will be recorded every 5 min for
      60 min, and at the end of the 60 min period the UPDRS-III score will be recorded again,
      completing the on stimulation/off medication evaluation. The patient will then be instructed
      to take his/her usual dose of medications, and will be sent for lunch for one hour. After
      lunch, the patient will return in the on medication/on stimulation state, the NIRS and pulse
      oximetry probes will be reapplied, and the process described for the off medication state
      will be repeated in the on medication state. After the on medication assessments are
      completed the patient will be sent home with his/her devices on and set to their therapeutic
      parameters.
    

Intervention name(s): Deep brain stimulator
Intervention type(s): Other
Intervention description(s): We will measure brain oxygen levels with a non-invasive near infrared spectroscopy device.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Parkinson's Disease; Deep brain stimulator; dbs