Stereotactic and functional neurosurgery
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In order to provide a data bank to allow a more precise and effective implementation of spinal cord stimulation, a computerized analysis of 1,375 combinations obtained from electrode arrays located in the thoracic and cervical epidural area was performed. 67 electrode arrays implanted in 34 subjects were subjected to analysis. During the stimulation trial, all the available combinations were systematically tested and the results entered into a computerized database. ⋯ Analysis of the data allow the surgeon (1) to define the characteristics of the stimulation-induced paresthesiae; (2) to define the spectrum of the electrical parameters used to stimulate the spinal cord; (3) to define the population of implanted electrode arrays/contacts; (4) to study objectively how the position of the electrodes within the spinal canal, their vertebral level and the interelectrode distance affect the electrical parameters and the stimulation-induced responses. The multifactorial systematic analysis of such a large number of combinations provides the basis for further developments in the area of electrical stimulation of the nervous system.
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Stereotact Funct Neurosurg · Jan 1991
Case ReportsFunctional neurosurgery--a future for the gamma knife?
The Gamma Knife is currently the only radiosurgical device which has been used in functional neurosurgery. This mode of utilization is possible because the instrument can make lesions in normal brains with a volume as small as 50 mm3. ⋯ The important role of stereotactic MRI localization in functional radiosurgery is pointed out, and a preliminary report of the recent experience with stereotactic magnetoencephalography combined with stereotactic MRI for physiological and anatomic target localization is given. It is concluded that functional radiosurgery should only be performed with radiation of very small volumes of brain, as the very high doses required would be devastating if delivered to even small volumes.
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Stereotact Funct Neurosurg · Jan 1991
Comparative StudyContact combinations in epidural spinal cord stimulation. A comparison by computer modeling.
The geometrical characteristics of longitudinal fiber populations in the dorsal columns (DC), recruited by various contact combinations in epidural spinal cord stimulation (SCS), were compared in a theoretical study. A 3-dimensional computer model was used, representing the geometry and electrical conductivity of the low-thoracic spinal cord and surrounding tissues, in combination with a model representing the electrical properties of a myelinated nerve fiber. It was calculated that, among usual dorsomedial contact combinations, the ratio of mediolateral and dorsoventral extent of the recruited area in DC only varied by 2-5%. ⋯ It is concluded that the optimal combination varies with distance between cathode and DC and that a unique 'best contact combination' does not exist. When both a decrease of primary afferent diameter in DC and collateral branching near their entrance are considered, the model predicts that recruitment of cutaneous afferents will start in lateral DC and proceed medially at increasing stimulus, which fits clinical observations on the spread of paresthesia. The model predicts that large fibers in the posterior spinocerebellar tract will also be recruited in SCS.
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Stereotact Funct Neurosurg · Jan 1991
Case ReportsPercutaneous retroperitoneal stimulation of the sacral plexus. Initial report and technical note.
A new percutaneous approach to stimulate the sacral plexus for the treatment of pain is described. The percutaneous electrode is inserted under fluoroscopy through the chosen dorsal and ventral sacral foramen and is advanced into the retroperitoneal layer where the plexus lies. The electrode, can be advanced several centimeters and lies in close proximity to the branches of the sacral plexus. ⋯ We report our initial experience with a new approach to stimulation of the peripheral nervous structures. That is stimulation of the sacral plexus through electrodes implanted percutaneously along the plexus in the retroperitoneal area. This initial report is not meant to give clinical results of this methodology, but simply to point to another route to apply electrical stimulation safely to various parts of the nervous system.
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Stereotact Funct Neurosurg · Jan 1991
How do geometric factors influence epidural spinal cord stimulation? A quantitative analysis by computer modeling.
Effects of both anatomic and electrode geometry on the recruitment of rostrocaudal fibers in the spinal cord were investigated by computer simulation of epidural spinal cord stimulation. A three-dimensional model was used, representing the geometry and electrical conductivity of the spinal cord and surrounding tissues, in combination with a model representing the electrical properties of a myelinated nerve fiber. Recruitment contours in the dorsal columns were calculated at various spinal geometries as a function of electrode position, combination and area. ⋯ Recruitment areas resulting from different contact combinations of a mediodorsal array were almost identical. It was shown that perception threshold largely depends on both dorsal cerebrospinal fluid width and fiber size. The usual bipolar contact separation appeared to approximate the theoretically optimal value, resulting in maximum fiber recruitment at minimum stimulus.