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Biomedical subjects

R B North

Publications and source records attributed to R B North.

At least 19 recordsLinked to original sources
PubMed1992

Spinal cord stimulation evoked potentials during thoracoabdominal aortic aneurysm surgery.

Although monitoring of somatosensory evoked potentials elicited from stimulation of lower extremity peripheral nerves has been suggested as a method for assessing neural function during thoracoabdominal aortic aneurysm surgery, this technique has been reported to yield a large number of false positives. It was believed that direct stimulation of the spinal cord would eliminate some of the problems associated with peripheral evoked potentials. The present study compared in 18 patients the use of scalp recorded evoked potential following stimulation of either the posterior tibial nerve via percutaneous needles or the spinal cord via an epidural electrode previously placed fluoroscopically. In 10 patients in whom distal bypass or shunt was not used, peripheral evoked potentials totally disappeared within 5-30 min of aortic clamping. Spinal cord stimulation evoked potentials disappeared permanently in 2 patients shortly after aortic cross-clamping; 1 died shortly after the procedure, and the other awoke densely paraplegic and died the next day. When distal perfusion was maintained by shunt or bypass, the disappearance of both peripheral and spinal evoked potentials accurately predicted the neurologic outcome of 1 paralyzed patient. Loss of spinal cord stimulation evoked potentials was found to be correlated with adverse neurologic outcome. Over the period of aortic clamping a gradual decrease in mean amplitude (50% at 45 min [P less than 0.05]) and a 20% increase in mean latency time were observed. Maintenance of adequate distal perfusion may permit the use of peripheral evoked potentials in the assessment of spinal cord ischemia during aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Patient-interactive, computer-controlled neurological stimulation system: clinical efficacy in spinal cord stimulator adjustment.

Over the past 20 years, continuing technical advances have rendered spinal cord stimulation an easily implemented low-morbidity technique for the management of chronic intractable pain in properly selected patients. Percutaneous methods for the insertion of arrays of multiple epidural electrodes, which are driven by noninvasively programmable "multichannel" implanted devices, have been among the most important of these technical improvements. The same implanted electronics may be used with peripheral nerve or intracerebral electrodes. If the capabilities of this new hardware are to be used to full advantage, a major investment of time and effort is required to adjust the system postoperatively for optimum effect. Ideally, these adjustments should be based upon psychophysical data, obtained in a manner that minimizes influences such as potential operator bias or stimulus presentation-order effects. These requirements have been met by the development of a computerized system designed for direct patient interaction and for greater ease of operation than the standard external devices used with these implants. The system has been tested clinically in 25 patients with spinal cord stimulation for pain. It rapidly tests the available electrode combinations and stimulus pulse parameters at a rate comparable to or greater than that of a skilled human operator using the standard device. It records detailed graphic data and patient analog ratings at varying thresholds and implements "pain drawing" methods with novel input and analytical techniques. This patient-interactive computerized system has proved to be safe and effective clinically. The time required by the average patient working with this system to adjust the stimulator is comparable to or less than the time required by the same patient working with a physician's assistant. Psychophysical data collected by the system may be correlated with clinical observations. Ongoing development will permit delivery of novel pulse sequences and protocols to assess the mechanisms by which stimulation affords relief from pain.

Electric Stimulation Therapy↗
PubMed1991

Monitoring of spinal cord stimulation evoked potentials during thoracoabdominal aneurysm surgery.

Repair of a thoracoabdominal aneurysm involves a significant risk of ischemic injury to the spinal cord. Standard monitoring of somatosensory evoked potentials, which relies upon peripheral nerve stimulation, becomes nonspecific and insensitive during this surgery when aortic cross-clamping produces lower extremity ischemia causing a peripheral conduction block. Techniques for the insertion of percutaneous epidural electrodes, developed originally for pain management, have been adapted to this setting to permit direct stimulation of the spinal cord for intraoperative monitoring of evoked potentials. The clinical outcome in patients monitored by this technique has been consistent with evoked potential findings.

Aorta, Abdominal↗
PubMed1991

Spinal cord compression complicating subarachnoid infusion of morphine: case report and laboratory experience.

The intraspinal administration of morphine has been employed increasingly in the management of intractable pain of malignant as well as benign origin. We have encountered a previously unreported clinical complication: spinal cord compression by an inflammatory tissue mass surrounding a subarachnoid infusion catheter administering morphine, leading to paraplegia. The patient was referred to our institution after catheter and pump implantation for chronic, intractable pain associated with pre-existing lumbar arachnoid fibrosis, after multiple myelograms and surgeries. The patient may, therefore, have had an underlying propensity to foreign body reactions. We have encountered a similar phenomenon, however, in a canine laboratory model. The pathological features in both our patient and our laboratory preparation, with inflammatory tissue masses around the tip of the catheter but not around proximal subarachnoid segments, suggest an effect related to infusion, as opposed to infection or the presence of the catheter. We review the pathological features in both settings and the pertinent literature.

Adult↗
PubMed1991

Fusion of the occiput to the upper cervical spine. A review of 37 cases.

This is the first report of a large series of patients undergoing preoperative traction to reduce spinomedullary compression from cranial settling. In all cases, an attempt was made to reduce the malalignment with Gardner-Wells or halo traction before posterior fusion. One patient required an anterior retropharyngeal decompression of the odontoid performed as a one-stage procedure at the time of the posterior operation, and two required subsequent anterior transoral-transpharyngeal resection of the odontoid. From 1974 to 1989, 37 patients underwent posterior occipital cervical arthrodesis. All cases presented with neurologic deficit, and most had signs of brain stem compression, such as L'hermitte's sign or Ondine's curse. The most common cause of basilar impression was rheumatoid arthritis, neoplastic destruction, previously failed C1-C2 fusion, or Down's syndrome. Mean postoperative follow-up was 2 years and 10 months; the patients with less than 2 years' follow-up were followed until successful fusion. Eight of 9 patients with L'hermitte's sign or Ondine's curse and 10 of 12 patients with intractable occipital pain were relieved of their symptoms after reduction and triple-wire stabilization-fusion. Eighteen of 25 patients with long tract signs improved after surgery. Interestingly, 14 (93.3%) of 15 patients with myelopathy improved when successful preoperative reduction of their deformity occurred, whereas only 4 (40%) of 10 patients with fixed basilar impression improved (chi 2 = 8.57, P = .014). Symptoms such as Ondine's curse, L'hermitte's sign, intractable occipital headache, and myelopathy are usually relieved by skeletal traction and posterior fusion without need of an additional transmucosal anterior procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Dorsal root ganglionectomy for failed back surgery syndrome: a 5-year follow-up study.

Dorsal root ganglionectomy has been suggested as a method for the treatment of chronic intractable radicular pain, with theoretical advantages over dorsal rhizotomy, which does not interrupt ventral root afferents. The indications for these procedures in patients with persistent pain following lumbosacral spine surgery are not well established. Long-term results have been reported infrequently, and no published series has a mean follow-up period of more than 30 months. The authors have reviewed their experience with a series of 13 patients with failed back surgery syndrome, in whom dorsal root ganglionectomy was performed. Patients were selected on the basis of clinical presentation and diagnostic root blocks suggesting a monoradicular pain syndrome. Follow-up data were obtained at a mean of 5.5 years following dorsal root ganglionectomy. Follow-up interviews to assess outcome were conducted by a disinterested third party. Treatment "success" (at least 50% sustained relief of pain and patient satisfaction with the result) was recorded in two patients at 2 years after surgery and in none at 5.5 years. Equivocal success (at least 50% relief, without clearcut patient satisfaction) was recorded in one patient at 2 and at 5.5 years postoperatively. Improvements in activities of daily living were recorded in a minority of patients. Loss of sensory and motor function was reported frequently by patients. A minority of patients had reduced or eliminated analgesic intake. These results suggest that dorsal root ganglionectomy has a limited role in the management of failed back surgery syndrome, and that methods to select patients to receive this procedure should be refined or alternative approaches should be considered.

Activities of Daily Living↗
PubMed1991

Failed back surgery syndrome: 5-year follow-up in 102 patients undergoing repeated operation.

The indications for repeated operation in patients with persistent or recurrent pain after lumbosacral spine surgery are not well established. Long-term results have been reported infrequently, and in no case has mean follow-up exceeded 3 years. We report 5-year mean follow-up for a series of repeated operations performed between 1979 and 1983. Patient characteristics and modes of treatment have been assessed as predictors of long-term outcome. One hundred two patients with "failed back surgery syndrome" (averaging 2.4 previous operations), who underwent a repeated operation for lumbosacral decompression and/or stabilization, were interviewed by a disinterested third party a mean of 5.05 years postoperatively. Successful outcome (at least 50% sustained relief of pain for 2 years or at last follow-up, and patient satisfaction with the result) was recorded in 34% of patients. Twenty-one patients who were disabled preoperatively returned to work postoperatively; 15 who were working preoperatively became disabled or retired postoperatively. Improvements in activities of daily living were recorded, overall, as often as decrements. Loss of neurological function (strength, sensation, bowel and bladder control) was reported by patients more often than improvement. Most patients reduced or eliminated analgesic intake. Statistical analysis (including univariate and multivariate logistic regression) of patient characteristics as prognostic factors showed significant advantages for young patients and for female patients. Favorable outcome also was associated with a history of good results from previous operations, with the absence of epidural scar requiring surgical lysis, with employment before surgery, and with predominance of radicular (as opposed to axial) pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1991

Failed back surgery syndrome: 5-year follow-up after spinal cord stimulator implantation.

Spinal cord stimulation, in use for more than 20 years, has evolved into an easily implemented technique, with percutaneous methods for electrode placement. We have reviewed our experience with this technique in treating "failed back surgery syndrome," and have assessed patient and treatment characteristics as predictors of long-term outcome. A series of 50 patients with failed back surgery syndrome (averaging 3.1 previous operations), who underwent spinal cord stimulator implantation, was interviewed by impartial third parties, at mean follow-up intervals of 2.2 years and 5.0 years. Successful outcome (at least 50% sustained relief of pain and patient satisfaction with the result) was recorded in 53% of patients at 2.2 years and in 47% of patients at 5.0 years postoperatively. Ten of 40 patients who were disabled preoperatively returned to work. Improvements in activities of daily living were recorded in most patients for most activities; loss of function was rare. Most patients reduced or eliminated analgesic intake. Statistical analysis (including univariate and multivariate logistic regression) of patient characteristics as prognostic factors showed significant advantages for female patients and for those with programmable multi-contact implanted devices. These results, in patients with postsurgical lumbar arachnoid and epidural fibrosis and without surgically remediable lesions, compare favorably with the results in two separate series of patients with failed back surgery syndrome, in whom 1) surgical lesions were diagnosed and repeated operation performed; and 2) monoradicular pain syndromes were diagnosed and dorsal root ganglionectomies performed at our institution. This suggests the need for further assessment of selection criteria, critical analysis of treatment outcome, and prospective study of spinal cord stimulation and alternative approaches to failed back surgery syndrome.

Activities of Daily Living↗
PubMed1990

Multiple spinal metastases from paraganglioma.

Isolated vertebral body metastases from paraganglioma are exceedingly rare. They have been reported to occur in the presence of active primary tumor in the neck, local recurrence, or widespread metastases. A unique case of carotid body tumor (paraganglioma) is reported with the following features: (1) multiple vertebral body metastases (C6, T9, and L3) presenting with spinal cord compression, and no evidence of local recurrence or other metastatic disease; (2) absence of mitoses on the original specimen or the metastatic deposit; and (3) a prolonged interval (9 years) to the development of symptomatic metastases.

Adult↗
PubMed1990

Low-grade cerebral astrocytomas. Survival and quality of life after radiation therapy.

Of 77 patients with supratentorial Grades I and II astrocytoma diagnosed from January 1975 to December 1984, 66 were treated with postoperative radiation therapy. The patients received a tumor dose of 5000 to 5500 cGy in 180 cGy fractions, five fractions per week, over 5.5 to 6 weeks. Overall actuarial survival at 2, 5, and 10 years was 71%, 55%, and 43%, respectively. Progression-free survival at 2, 5, and 10 years was 69%, 50%, and 39%, respectively. Survival for patients receiving postoperative radiation therapy in the range of 4500 to 5900 cGy was 78% and 66% at 2 and 5 years, respectively. Quality of life was determined at two points in time: 1 to 2 years postoperatively, and at last follow-up (2-12 years postoperatively). The occurrence of mental retardation was specifically addressed in long-term survivors, and was observed in 50% of children. Overall, however, 80% of short-term survivors and 67% of long-term survivors were intellectually and physically intact, without major neurologic deficit. Specific prognostic factors were assessed by multivariate analysis. Improved survival was observed with young patients, females, normal preoperative mental status, surgical resection (versus biopsy alone), involvement of only one lobe with tumor, and a history of preoperative seizures. A weighted prognostic factor score derived from these observations permits a clinically useful assessment of risk for individual patients.

Adolescent↗
PubMed1990

Occult, bilateral anterior sacral and intrasacral meningeal and perineurial cysts: case report and review of the literature.

None of the more than 180 cases of anterior sacral meningocele reported in the past 150 years has been bilateral, and only two have been associated with occult intrasacral meningocele. We report a unique case of bilateral anterior sacral cysts, communicating with the subarachnoid space, associated with occult intrasacral meningeal and perineurial (Tarlov's) cysts, in an asymptomatic woman. The pertinent clinical and diagnostic imaging literature is reviewed.

Adult↗
PubMed1990

Percutaneous retrogasserian glycerol rhizotomy. Predictors of success and failure in treatment of trigeminal neuralgia.

Eighty-five medically intractable trigeminal neuralgia patients treated by percutaneous retrogasserian glycerol rhizotomy (PRGR) were followed for 6 to 54 months. The median time to recurrence of symptoms refractory to medical therapy and requiring further intervention was 3 years (by Kaplan-Meier survival analysis). The median time to recurrence of symptoms requiring some form of medical treatment was 2 years. Following repeat PRGR for recurrent symptoms, the median time to recurrence was 1 year. Univariate log rank statistics and multivariate Cox proportional hazards modeling revealed significant associations between favorable outcome and female sex, absence of atypical features or associated cluster headache symptoms, success of prior carbamazepine therapy, duration of symptoms, and cerebrospinal fluid return during the procedure. A scoring system using prognostic factors has been developed based upon these findings. Assessment of published studies of PRGR and of other treatments for trigeminal neuralgia is made difficult by the variety of outcome measures employed and variable follow-up intervals. The present study attempts to address these issues by definition of endpoints, statistical analysis of the data, and identification of important prognostic factors in a manner useful to the clinician.

Adult↗
PubMed1987

Computer-controlled, patient-interactive, multichannel, implanted neurological stimulators.

Programmable implantable neurological stimulation systems with multiple electrodes have many advantages in clinical use, but time-consuming postoperative adjustment of stimulation parameters is a distinct disadvantage. A personal computer interface to standard commercial radiofrequency-coupled devices has been developed, permitting direct patient interaction to expedite this process. In addition, the system permits simulated multichannel operation and implementation of various modulation schemes.

Electric Stimulation Therapy↗
PubMed1985

CT myelography for outpatients. An inpatient/outpatient pilot study to assess methodology.

The diagnostic usefulness, limitations, and adverse reactions associated with computed tomographic myelography using metrizamide were assessed for broad outpatient application. The initial approach was to examine inpatients (n = 38) with low-dose metrizamide (100 mgI/ml). This low dose was believed less likely to be associated with side effects. They were then treated as if they were outpatients, with the liberties this entailed. The consequences of needle puncture were minimized by using a 25-gauge disposable needle. Thirty-four (89%) patients remained free of side effects after the procedure. Subsequently, this technique was extended to 42 outpatients, 38 (90.5%) of whom remained asymptomatic. For comparison, 170 mgI/ml was used in another 25 outpatients, who evidenced more symptoms. The potential medical, economic, and therapeutic benefits of obviating hospitalization by safer outpatient CT myelography seem clear.

Ambulatory Care↗