Epidural Motor Cortex Stimulation
Chronic epidural motor cortex stimulation (MCS) has been shown to have promise in the treatment of patients with refractory deafferentation pain. Precise placement of the electrode over the motor cortex region corresponding to the area of pain is essential for the success of this procedure. Whereas standard anatomical landmarks have been used in the past in conjunction with image guidance, the use of functional brain imaging can be beneficial in the precise surgical planning. The authors report the use of functional imaging-guided frameless stereotactic surgery for epidural MCS. Five patients underwent MCS in which functional imaging guidance was used. Prior to surgery, patients under-went magnetic resonance (MR) imaging with skin fiducial markers placed on standard anatomical reference prints, followed by magnetoencephalography (MEG) mapping of the sensory and motor cortices. In two patients, functional MR imaging was also performed using a motor task paradigm. The functional imaging data were integrated into a frameless stereotactic database by using a three-dimensional coregistration algorithm. Subsequently, a frameless stereotactic craniotomy was performed using the integrated anatomical and functional imaging data for surgical planning. Intraoperative somatosensory evoked potentials (SSEPs) and direct stimulation were used to confirm the target and final placement of the electrode.
Direct stimulation and SSEPs performed intraoperatively confirmed the accuracy of the functional imaging data. Trial periods of stimulation successfully reduced pain in three of the five patients who then underwent permanent internal placement of the system. At a mean 6-month follow up, these patients reported an average reduction in pain of 55% on a visual analog scale. The integration of functional and anatomical imaging data allows for precise and efficient surgical planning and may reduce the time necessary for intraoperative physiological verification.
The use of epidural MCS for the treatment of refractory deafferentation pain was first described by Tsubokawa and colleagues in 1991. Since their initial reports, other groups have reported procedure-related success in treating deafferentation pain syndromes of varying causes, with success rates ranging from 50 to 80% for both central and trigeminal neuropathic pain. This procedure, in which minimal rates of morbidity have been demonstrated, is gaining increasing acceptance.
Precise intraoperative placement of the stimulating electrode over the motor cortex region corresponding to the painful body part is essential to successful outcome. Although most groups have reported intraoperative electrophysiological confirmation of motor cortex by using SSEP and/or EMG monitoring, initial localization techniques vary. The use of surface anatomical landmarks, scalp SSEPs, and computerized tomography and MR imaging-guided systems have all been reported.
Functional imaging information, such as that obtained using MEG, fMR imaging, and optical imaging, is now routinely integrated into many neurosurgical procedures, including tumor/arteriovenous malformation resection and epilepsy surgery. Sole reliance on anatomical criteria for determination of eloquent cortex has been shown to have limitations, and the integration of such functional imaging data is a useful adjunct in preoperative planning and risk assessment as well as for intraoperative guidance. We report our experience using functional imaging guidance with MEG as well as fMR imaging in patients undergoing MCS for the treatment of refractory pain.
Chronic epidural motor cortex stimulation (MCS) has been shown to have promise in the treatment of patients with refractory deafferentation pain. Precise placement of the electrode over the motor cortex region corresponding to the area of pain is essential for the success of this procedure. Whereas standard anatomical landmarks have been used in the past in conjunction with image guidance, the use of functional brain imaging can be beneficial in the precise surgical planning. The authors report the use of functional imaging-guided frameless stereotactic surgery for epidural MCS. Five patients underwent MCS in which functional imaging guidance was used. Prior to surgery, patients under-went magnetic resonance (MR) imaging with skin fiducial markers placed on standard anatomical reference prints, followed by magnetoencephalography (MEG) mapping of the sensory and motor cortices. In two patients, functional MR imaging was also performed using a motor task paradigm. The functional imaging data were integrated into a frameless stereotactic database by using a three-dimensional coregistration algorithm. Subsequently, a frameless stereotactic craniotomy was performed using the integrated anatomical and functional imaging data for surgical planning. Intraoperative somatosensory evoked potentials (SSEPs) and direct stimulation were used to confirm the target and final placement of the electrode.
Direct stimulation and SSEPs performed intraoperatively confirmed the accuracy of the functional imaging data. Trial periods of stimulation successfully reduced pain in three of the five patients who then underwent permanent internal placement of the system. At a mean 6-month follow up, these patients reported an average reduction in pain of 55% on a visual analog scale. The integration of functional and anatomical imaging data allows for precise and efficient surgical planning and may reduce the time necessary for intraoperative physiological verification.
The use of epidural MCS for the treatment of refractory deafferentation pain was first described by Tsubokawa and colleagues in 1991. Since their initial reports, other groups have reported procedure-related success in treating deafferentation pain syndromes of varying causes, with success rates ranging from 50 to 80% for both central and trigeminal neuropathic pain. This procedure, in which minimal rates of morbidity have been demonstrated, is gaining increasing acceptance.
Precise intraoperative placement of the stimulating electrode over the motor cortex region corresponding to the painful body part is essential to successful outcome. Although most groups have reported intraoperative electrophysiological confirmation of motor cortex by using SSEP and/or EMG monitoring, initial localization techniques vary. The use of surface anatomical landmarks, scalp SSEPs, and computerized tomography and MR imaging-guided systems have all been reported.
Functional imaging information, such as that obtained using MEG, fMR imaging, and optical imaging, is now routinely integrated into many neurosurgical procedures, including tumor/arteriovenous malformation resection and epilepsy surgery. Sole reliance on anatomical criteria for determination of eloquent cortex has been shown to have limitations, and the integration of such functional imaging data is a useful adjunct in preoperative planning and risk assessment as well as for intraoperative guidance. We report our experience using functional imaging guidance with MEG as well as fMR imaging in patients undergoing MCS for the treatment of refractory pain.
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