Biomedical subjects
Publications and source records attributed to G Barolat.
Vagal nerve stimulation is an approved adjunctive treatment for medically intractable epilepsy. Although it is generally well tolerated, some patients experience pain, coughing, or hoarseness during stimulation. Lowering the pulse width in these patients alleviates pain and reduces voice alteration without loss of efficacy. This allows more optimal programming of stimulation intensities.
Spinal cord stimulation (SCS) has been available for about 30 years, but only in the past five years has it met with widespread acceptance and recognition by the medical community. Traditionally performed by neurosurgeons, SCS is being increasingly utilized by anesthesiologists, orthopedic surgeons and physiatrists. Pain management continues to be the most widespread application of SCS. More sophisticated technology has allowed the implanters to successfully address more complex pain syndromes such as widespread reflex sympathetic dystrophy and the failed back syndrome. Other applications are being developed, combining the ability to stimulate the spinal cord, the nerve roots and the peripheral nerves. Examples include angina pectoris, urinary incontinence and occipital neuralgia. Computer-interactive programming is gaining popularity, especially due to the extreme complexity of the implanted stimulation devices. The ability to stimulate independently multiple channels as well as multiple arrays of electrodes is today a reality. This has increased greatly the efficacy, safety and reliability of the modality. In the future, SCS will undoubtedly move several steps up in the treatment ladder of chronic pain conditions, while new applications will be discovered. The future of neural implantable technologies is bright, with an increasingly important role in the medical management of chronic conditions affecting the nervous system.
The effects of the antero-posterior and medio-lateral positions of the spinal cord in the dural sac on the perception threshold and paresthesia coverage in spinal cord stimulation were analyzed. The distributions of the dorsal cerebrospinal fluid (CSF) layer thickness, measured from transverse MR scans of normal subjects at various spinal levels, were used to calculate the distributions of threshold voltages for the stimulation of spinal nerve fibers by a computer model. These theoretical threshold distributions were shown to fit well to the corresponding distributions of perception threshold measured in patients. It is concluded that the thickness of the dorsal csf layer is the main factor determining the perception threshold and paresthesia coverage in spinal cord stimulation: an increasing thickness raises the threshold and reduces the coverage, and vice versa. The effects of an asymmetrical electrode position with respect to the spinal cord midline were also analyzed by computer modeling. It is concluded that a lateral asymmetry of less than 1 mm gives a significant reduction of perception threshold and may result in unilateral paresthesiae.
Forty-eight spinal cord injury victims were implanted with an epidural spinal cord stimulation system to treat spasms that had not satisfactorily responded to medical therapy. All the patients were at least 6 months after the injury. The protocol included assessment by independent examiners preoperatively and at 3, 6, 12 and 24 months after the implant. Pre- and postoperative data collection included the frequency and severity of the spasms. Combining the frequency and intensity scores into a 'severity' score provided a more accurate clinical picture. No patient observed neurological deterioration following the surgical procedure or the neurostimulation treatment. A statistically significant reduction in the severity of the spasms was observed in the follow-up evaluations, with results that progressively increased in time. It is appears that spinal cord stimulation is an effective and safe alternative in the management of spasms in spinal cord injury victims. Its exact role in relation to intrathecal baclofen infusion and ablative procedures remains to be defined.
This article summarizes the experience gained with implantation of 509 plate electrodes performed by a single neurosurgeon. 350 patients were subjected to implantation of plate electrodes in the dorsal epidural space. 227 patients were implanted for chronic pain management (reflex sympathetic dystrophy, failed back syndrome/arachnoiditis, pain following spinal cord injury, nerve injury pain and other miscellaneous pain conditions), 105 patients for motor disorders (spasms/spasticity following spinal cord or head injury, cerebral palsy, multiple sclerosis, spasmodic torticollis and other miscellaneous conditions) and 18 patients for both. A total of 509 electrodes were implanted in the dorsal epidural space. The electrodes types were: 442 Medtronic Resume, 39 Medtronic Resume-TL and 25 Neuromed Lamitrode. 378 electrodes were implanted for chronic pain management, 106 for motor disorders and 25 in patients presenting with both pain and motor disorders. 192 electrodes were implanted in the cervical area and 317 in the thoracic area. 3.7% of the implanted electrodes became infected and had to be surgically removed. Electrode migration occurred in 1.1% of the patients and electrode breakage in 4 patients. 288 (70%) of the implanted electrodes are still being used. Technical factors relevant to the surgical implantation of plate electrodes at various levels in the spine are presented and discussed.
A computerized statistical analysis of 3,000 implanted electrode (multi-contact, quadripolar) combinations for epidural spinal cord stimulation therapy for the management of pain was carried out in three groups: spinal levels (20 different levels, C2-L2), spinal placement (midline and lateral) and contact separation (unipolar, bipolar with a separation of 10, 20 and 30 mm) to investigate the clinically required usage ranges (difference between the perception threshold and tolerance threshold). The usage range is relatively higher at midthoracic levels (T4-T10), and for the combinations located in midline. As the contact separation increases, the usage range increases in bipolar combinations. The usage range of unipolar combinations is higher than that of bipolar combinations with 10 and 20 mm separation, and is less than that of bipolar combinations having a separation of 30 mm.
As a part of the systematic analysis of parameters involved in electrical epidural spinal cord stimulation therapy, distribution of paresthesiae in accordance with the position of contacts, as related to midline and vertebral level of contacts, was investigated. A preliminary analysis performed for 266 combinations having contacts implanted in the midcervical and low-thoracic vertebral levels showed that the topographical spread of the paresthesiae did not always cover the classical dermatomes. Significant paresthesiae spread was found as follows: C4-midline, unipolar combinations; the hand, forearm and upperarm, bipolar combinations; the hand, forearm; C4-lateral, unipolar combinations: the anterior shoulder, forearm, upper arm and hand, bipolar combinations: the hand, forearm and upper arm; T10-midline, unipolar combinations: the anterior and posterior of thigh, leg, knee, ankle and foot, bipolar combinations: the anterior and posterior thigh, leg, knee and foot; T10-lateral, unipolar combinations: the abdomen, anterior leg, knee and anterior thigh, bipolar combinations: the anterior thigh, anterior leg, knee and foot. This preliminary analysis suggests that more detailed studies would be worthwhile in the investigation of sensory responses to electrical stimulation of the spinal cord with epidural electrodes. Findings from such investigations could also be useful to extend our present anatomical knowledge of central and peripheral sensory neural structures.
A computerized statistical analysis of 1,100 quadripolar electrode combinations used in epidural spinal cord stimulation therapy for the management of pain was carried out to investigate perception and tolerance thresholds. This analysis showed that the thresholds are higher at high-cervical, mid-cervical, mid-thoracic and low-thoracic spinal levels. It is also higher for the combinations with contacts located in the midline than those implanted laterally. As the contact separation increases, the perception and tolerance thresholds increase in bipolar combinations. Unipolar combinations have the lowest thresholds.
A database is presented of sensory responses to electrical stimulation of the dorsal neural structures at various spine levels in 106 subjects subjected to epidural spinal cord stimulation. All patients were implanted for chronic pain management and were able to perceive stimulation in the area of pain. All patients entered in this study were able to reliably report their stimulation pattern. Several patients were implanted with more than one electrode array. The electrode arrays were placed in the dorsal epidural space at levels between C-1 and L-1. The structures that were likely involved include the dorsal roots, dorsal root entry zone, dorsal horn, and dorsal columns. At the present time, exact characterization of the structure being stimulated is possible only in limited instances. Various body areas are presented with the correspondent spine levels where implanted electrodes generate paresthesias. Areas that are relatively easy targets for stimulation are the median aspect of the hand, the abdominal wall, the anterior aspect of the thigh, and the foot. Some areas are particularly difficult to cover with stimulation-induced paresthesias; these include the C-2 distribution, the neck, the low back, and the perineum.
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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. The study was not meant to analyze the clinical results or the indications of epidural spinal cord stimulation. Parameters studied include position of each electrical contact as related to midline, vertebral level of each contact, distribution of stimulation-induced paresthesiae, and electrical parameters (voltage, rate, pulse width, perception threshold, discomfort threshold, usage range). 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.
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. Both motor and sensory responses can be elicited with electrical stimulation. Our initial experience with 4 implanted patients is presented and discussed. Several areas of the nervous system have been target for implantation of stimulating and recording electrodes for management of pain, as well as other indications. This includes parts of the cerebrum, brainstem, spinal cord and peripheral nerves. 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.
A 21-year-old woman had recurrent progressive weakness/hypesthesia and pain in both lower extremities. At the age of 5 and 19 years, she had undergone surgical resection of a lipomyelomeningocele at L5-S1. Surgical exploration revealed that the cord was tethered and pulled over to the side by an excessively short right S-1 nerve root. The contralateral L-5 and S-1 nerve roots were markedly stretched. Division of the right S-1 nerve root resulted in prompt disappearance of pain in the lower extremities and improvement in neurological function.
The technique of the dorsal selective rhizotomy as originally developed by Professor Fasano and by the author is described. The rhizotomy is performed through a one-level laminectomy at L-1. Exposure of the conus medullaris and the cauda equina at this level is adequate to thoroughly assess the reflex electrical response to stimulation of the lumbosacral roots and to section the selected roots/rootlets. This approach, based on over 100 surgical procedures, obviates the need for an extensive laminectomy in a growing child without compromising the clinical results.
Continuous spinal opiate administration via permanently implantable drug delivery devices has been proven to provide profound analgesia for chronic pain conditions. We present a case in which the catheter of an implantable subarachnoid device was misplaced into the subdural/extra-arachnoid space despite the free flow of cerebrospinal fluid. This was verified by x-ray dye studies. It is postulated that this misplacement of the catheter likely occurred as a result of recent lumbar punctures the patient had undergone. Extravasation of cerebrospinal fluid created a false space and contributed to the misplacement and ultimate failure of the device to provide analgesia.
Eighteen subjects with intractable pain due to reflex sympathetic dystrophy (RSD) underwent treatment by epidural spinal cord stimulation (SCS). All the patients had previously undergone multiple sympathetic blocks and/or surgical sympathectomy with either no results or only temporary therapeutic effects. Four subjects did not experience any beneficial effects during a 1-week trial and the electrode was removed, and 14 patients had the system internalized surgically. In 4 cases two separate systems (electrode + pulse generator) were implanted, in order to cover distant areas of the body involved by the disease (neck, shoulders, upper extremities, trunk and lower extremities). Follow-up varies from 4 to 14 months. In the implanted group, pain relief was absent in 3 patients, minimal in 1, moderate in 5 and good in 6. Pain relief was strictly limited to the body parts covered by the parasthesiae induced by SCS. In 3 patients, SCS produced visible changes in the swelling of the painful extremities. None of the patients was made neurologically worse. In 7 patients there were technical problems related to electrode breakage or migration, change in the pattern of paresthesiae and poor connection due to body fluid infiltration. All the problems were corrected surgically under local anesthesia. SCS has some value in the management of refractory RSD pain in selected cases. Because of the limited series and follow-up, its value in the comprehensive management of RSD requires further investigation.
A case is presented in which a solitary chondroma arose from the clivus of a patient with Ollier's disease. These tumors are rare. The diagnostic value of computerized tomography and magnetic resonance imaging is discussed.
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