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Biomedical subjects

G B Jacobs

Publications and source records attributed to G B Jacobs.

At least 19 recordsLinked to original sources
PubMed2006

Serotyping and genotyping of HIV-1 infection in residents of Khayelitsha, Cape Town, South Africa.

It is estimated that between 5.5 and 6.1 million people are infected with HIV/acquired immunodeficiency syndrome (AIDS) in South Africa, with subtype C responsible for the majority of these infections. The Khayelitsha suburb of Cape Town has one of the highest HIV prevalence rates in South Africa. Overcrowding combined with unemployment and crime in parts of the area perpetuates high-risk sexual behavior, which increases exposure to infection by HIV. Against this background, the objective of this study was to characterize HIV-1 in residents confirmed to be seropositive. Serotyping was performed through a competitive enzyme-linked immunosorbent assay (cPEIA). Genotyping methods included RNA isolation followed by RT-PCR and sequencing of the gag p24, env gp41 immunodominant region (IDR), and env gp120 V3 genome regions of HIV-1. With the exception of a possible C/D recombinant strain, all HIV-1 strains were characterized as HIV-1 group M subtype C. One individual was shown to harbor multiple strains of HIV-1 subtype C. In Southern Africa, the focus has been to develop a subtype C candidate vaccine, as this is the major subtype found in this geographical area. Therefore, the spread of HIV-1 and its recombinant strains needs to be monitored closely.

Adult↗
PubMed1999

Visceral and vascular complications resulting from anterior lumbar interbody fusion.

OBJECT: The literature on abdominal and general surgery-related complications following anterior lumbar interbody fusion (ALIF) is scant. In this retrospective review of 60 patients in whom ALIF was performed at their institutions between 1996 and 1998, the authors detail the associated complications and their correlation with perioperative factors. The causes, strategies for their avoidance, and the clinical course of these complications are also discussed. METHODS: The study group was composed of 31 men and 29 women whose mean age was 42 years (range 29-71 years). The preoperative diagnosis was discogenic back pain in 33 patients (55%); failed back syndrome in 11 (18.3%); pseudarthrosis in five (8.3%); postlaminectomy syndrome in four (6.6%); spondylolisthesis in three (5%); burst fracture in two (3.3%); and malignancy in two (3.3%). A retroperitoneal approach to the spine was used in 57 of the 60 patients. One interspace was exposed in 28 patients (46.6%), two in 28 (46.6%), and three in four (6.6%). Discectomy and interbody fusion in which the authors placed titanium cages or bone dowels was performed in 56 patients and corpectomy with instrumentation in four. Seven (11.6%) of 60 patients had undergone previous abdominal surgery and 29 (48.3%) had undergone previous spinal surgery. The follow-up period averaged 12+/-4 months (mean+/-standard deviation). Twenty-four general surgery-related complications occurred in 23 patients (38.3%), including sympathetic dysfunction in six; vascular injury in four; somatic neural injury in three; sexual dysfunction in three; prolonged ileus in three; wound incompetence in two; and deep venous thrombosis, acute pancreatitis, and bowel injury in one patient each. There were no deaths. The incidence of complications was not associated with underlying diagnosis (p>0.1), age (p>0.5), previous abdominal or spinal surgery (p>0.1), or the number of levels exposed (p>0.1). CONCLUSIONS: This report provides a detailed analysis of the general surgery-related complications following ALIF. Although many of these complications have been recognized in the literature, the significance of sympathetic dysfunction appears to have been underestimated. The high incidence of complications in this series likely reflects the strict criteria. Many of these complications were minor and resolved over time without long-term sequelae.

Adult↗
PubMed1997

Persistently electrified pedicle stimulation instruments in spinal instrumentation. Technique and protocol development.

STUDY DESIGN: A prospective review was done of a new intraoperative technique developed to detect and prevent neurologic compromise during pedicle screw insertion. OBJECTIVES: To describe in sufficient detail the technique of persistently electrified pedicle stimulation instruments, so that this technique will be available generally to all clinical neurophysiologists and spine surgeons; and to demonstrate the use, typical results, interpretation, and protocol of the technique. SUMMARY AND BACKGROUND DATA: Fusion techniques that use pedicle instrumentation have the potential to cause nerve root injury. Several authors have proposed imaging and neurophysiologic methods to improve outcome. The present method represents a significant theoretical departure and advance from previously reported methods. METHODS: All relevant instruments used during pedicle instrumentation were converted easily, inexpensively, and quickly into monopolar stimulators with appropriate stimulus voltages to identify broaches of pedicle bone via evoked-electromyograms from relevant muscle groups. RESULTS: The persistently electrified pedicle stimulation instrument technique provided accurate intraoperative neurophysiologic information concerning pedicle, integrity in the patients studied. The protocol is standardized and adaptable easily, inexpensively, and quickly to most clinical applications. CONCLUSIONS: The persistently electrified pedicle stimulation instrument technique described here is useful for monitoring instrumented lumbar fusion procedures. The use of this protocol may help confirm intraosseous placement of pedicle screws and prevent neurologic injury.

Bone Screws↗
PubMed1997

Frameless stereotactic guidance for surgery of the upper cervical spine.

OBJECTIVE: The goal was to evaluate and describe the use of a frameless, computed tomography-guided, stereotactic technique in complex procedures involving the craniocervical junction. METHODS: Eleven procedures, including transoral odontoid resection, posterior atlantoaxial fusion with transarticular C1-C2 screw fixation, and spinal tumor resection, were performed in the preceding 26 months. In each case, frameless stereotaxy was used to plan the incision, to define resection margins, and to determine the appropriate orientation of instrumentation. RESULTS: There were no intraoperative complications noted. Each patient underwent adequate resection of the pathological lesion and satisfactory placement of instrumentation. The stereotactic system provided detailed anatomic visualization, which increased the confidence of the surgeon during the procedure. The system limited the need for extensive surgical exposure, reduced fluoroscopy time, and decreased the risk of neurovascular injury. CONCLUSION: Frameless stereotaxy provided the surgeon with intraoperative information regarding the extent of bone and soft tissue resection. It provided a multidimensional view of anatomic relationships in the operative field, which significantly increased surgical accuracy and safety.

Adult↗
PubMed1997

Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study.

The neuroanatomical structures that approximate the bony pedicles of the lumbar spine allow little room for technical error or compromise of the bone during pedicle screw insertion. Currently available neurophysiological monitoring techniques detect compromised bone and nerve root injury after it occurs. The purpose of this prospective study is to evaluate the reliability and efficacy of a unique neurophysiological monitoring technique. This technique provides immediate evaluation of pedicle cortical bone integrity in patients undergoing lumbar fusion with instrumentation by using electrified surgical instruments throughout the pedicle screw fusion procedure. Spontaneous electromyographic (EMG) activity was also monitored. Intraoperative evoked EMG stimulation was performed using a pedicle probe and feeler as monopolar stimulators during the insertion of 164 pedicle bone screws in 32 patients. The EMG response to subthreshold stimulation intensities indicated cortical bone compromise. Immediate and conclusive feedback via evoked EMG activity using stimulating pedicle probes in appropriate muscle groups was successful in identifying pedicle cortical bone compromise in four patients. One false-negative evoked EMG study was noted but was identified via spontaneous EMG activity. Intraoperative EMG monitoring alerted the surgeon that redirection of the pedicle probe or screw was necessary to avoid nerve root irritation or injury and served as an early warning system. Evoked EMG stimulation proved to be reliable and efficacious, especially when used in combination with spontaneous EMG. This technique may provide an added safeguard during implant placement procedures at centers where intraoperative neurophysiological monitoring is routinely performed.

Adult↗
PubMed1995

Frameless stereotactic guidance. An intraoperative adjunct in the transoral approach for ventral cervicomedullary junction decompression.

METHODS: The application of a video-interactive frameless stereotactic guidance system for the treatment of ventral cervicomedullary junction compression is described in a patient with basilar invagination, odontoid dysgenesis, and a Chiari malformation who had irreducible impingement on the ventral brainstem by a partially fused mass of bone made up of the malformed odontoid peg, the inferior clivus, and dorsally protruding osteophytes at the odontoid-clival junction. RESULTS: This technology permitted instantaneous feedback of the surgeon's orientation in all planes, facilitating extensive removal of the dens and clival tip to achieve adequate ventral brainstem decompression. In view of the distortion of the craniovertebral anatomy produced by the patient's anomalies, the ability to visualize three dimensionally the location of the vertebral arteries also added an element of safety to the lateral bone removal. Similarly, the ability to localize the rostral limit of the clivus that needed to be resected and the caudal extent of C2 that needed to be removed to achieve an adequate decompression helped ensure that the extent of bone removal was appropriately tailored to the patient's anatomy. CONCLUSION: The authors believe this technique represents a significant advance over standard radiographic intraoperative localization techniques during transoral approaches to the ventral cervicomedullary junction for patients in whom the odontoid is fixed in position in relation to the clivus. This is based on the speed with which localization can be obtained, the accuracy of the information provided, the ability to obtain localization in multiple planes simultaneously, and the lack of radiation exposure during the procedure.

Brain Stem↗
PubMed1995

Surgery for metastatic spinal disease.

Cancer is a leading cause of death in the United States. Despite the development of advanced treatment for many malignancies, a large number of patients will require evaluation and possible surgical intervention for lesions which have metastasized to or directly invaded the spinal column. The recommendations for operative intervention on these patients should be made following evaluations by multiple specialties, both medical and surgical. An improved understanding of the pathophysiology of malignancy and the development of advanced adjunctive treatment modalities have improved the quality and duration of life in many patients. Recent studies have demonstrated the utility of early surgery when combined with other treatment modalities. Surgical techniques for tumor resection and spine stabilization have improved the outcome of patients reported in multiple surgical series. A multidisciplinary approach to treatment of cancer patients with spinal involvement affords the patient an optimal outcome.

Aged↗
PubMed1995

Isolated toxoplasmosis of the thoracic spinal cord in a patient with acquired immunodeficiency syndrome. Case report.

Toxoplasmosis and lymphoma are the two most common causes of intraparenchymal cerebral mass lesions in patients with acquired immunodeficiency syndrome (AIDS). The clinical and radiographic features of the intracranial lesions have been well described. Because of the high frequency of toxoplasmosis in the AIDS population, common therapy for patients presenting with intracranial mass lesions consists of an empirical trial of anti-Toxoplasma chemotherapy, with biopsy reserved for cases demonstrating features considered to be more consistent with lymphoma, or for lesions that do not improve despite adequate anti-Toxoplasma treatment. A similar treatment algorithm does not exist for intramedullary lesions of the spinal cord. The authors describe a patient who presented with paraparesis resulting from an isolated thoracic intramedullary lesion. An open biopsy of the lesion revealed characteristic structures containing Toxoplasma tachyzoites. The clinical and radiographic presentation of the lesion is discussed, the available literature is reviewed, and a treatment strategy for spinal cord lesions in AIDS patients is proposed.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Dynamic cardiomyoplasty for treatment of idiopathic dilatative cardiomyopathy in a dog.

In a dog with advanced dilatative cardiomyopathy, dynamic cardiomyoplasty resulted in improvement in clinical status and systolic function. Dynamic cardiomyoplasty involved surgical isolation of the right latissimus dorsi muscle on its neurovascular pedicle, transposition of the muscle into the thoracic cavity, wrapping the ventricles with the muscle, and implantation of a myostimulator for cardiosynchronous stimulation of the muscle. After a 2-week period, the latissimus muscle underwent a 50-day period of progressive burst stimulation to transform the muscle to a fatigue resistant phenotype. Thereafter, the muscle received cardiosynchronous stimulation at a 3:1 R-wave-to-burst ratio. This procedure may offer hope for long-term treatment of dilatative cardiomyopathy in dogs.

Animals↗
PubMed1994

Systemic malignancy presenting as neck and shoulder pain.

Systemic malignancy can be manifested by musculoskeletal complaints. We review the history, physical examination, and diagnostic imaging studies of a patient whose chief complaints were neck and shoulder pain. This patient also had significant weight loss and a history of tobacco abuse. Aggressive physical therapy and appropriate medications failed to provide symptomatic relief of neck and shoulder pain. Further studies revealed lung cancer. Systemic malignancy can cause referred musculoskeletal pain without obvious metastatic involvement at the symptomatic area, and should be considered in patients with persistent symptoms.

Cervical Vertebrae↗
PubMed1994

Artificial reflex arc: a potential solution for chronic aspiration. III: Stimulation of implanted cervical skin as a functional graft triggering glottic closure in the canine.

Stroke often impairs the ability of the vocal cords to close during deglutition, resulting in aspiration. The current study is a further advance on the application of the concept of an artificial reflex arc during swallowing. The second and third cervical branches were bilaterally isolated in four dogs and baseline sensory nerve traffic was detected via tripolar perineural electrodes. Cervical skin pressure-induced suprathreshold signals were used to trigger vocal cord contraction via bipolar electrodes passed around the recurrent laryngeal nerves. Skin subtended by the cervical nerves was implanted over the lateral aspect of the pyriform sinuses for 1 week. After reexploration, glottic closure was verified on videotape as surges in sensory nerve traffic were induced by mechanical stimulation of the pharynx. The possibility of artifactual stimulation was ruled out by lack of electrode motion during pharyngeal stimulation, spontaneous firing in the sensory nerve during light anesthesia, and sensory frequency differing from ambient 60-Hz noise. This article introduces the concept of autogenous functional graft as a basis for afferent information in electronic systems for dynamic rehabilitation of swallowing disorders.

Animals↗
PubMed1993

Electronic control of laryngeal spasm. II. Selective blockage of glottic adduction by a closed-loop circuit in the canine.

This work is the continuation of an earlier pilot study in which specially designed electrodes were used to block their own induced action potentials to restrain spasticity. In the current series of experiments, strap muscle and thyroarytenoid contraction (glottic closure) elicited by supramaximal ansa hypoglossi (N = 6) and recurrent laryngeal nerve (N = 4) stimulation (30 to 50 Hz, 0.1 to 6 mA, 0.1 to 1 msec), respectively, allowed afferent information via intramuscular sonomicrometer crystals to trigger a circuit that, in turn, stimulated blocking electrodes passed around the nerves downstream. Simultaneous videorecording of strap and vocal cord motion during direct laryngoscopy with their corresponding excursion tracings demonstrated near-total suppression of contractions within given stimulation "windows." These encouraging results may eventually permit selective restraint of erratic contractions involving laryngeal and other cervical musculatures in the human.

Action Potentials↗
PubMed1991

CNS effects on cardiomyoplasty in goats: preliminary study.

Following cardiomyoplasty, the latissimus dorsi (LD) muscle contracts in response to both pacemaker and central nervous system (CNS) derived action potentials. To evaluate the effect of this dual stimulation on cardiac function, six goats (56 kg to 80 kg) underwent treadmill tests 4 to 5 months after surgery. Sonomicrometer crystals were used to measure changes in the left ventricular short-axis dimension (LVSAD) and regional length changes in the LD muscle. Pacing mediated stimulation resulted in 17 +/- 4% fractional shortening of the muscle pedicle lasting 400 +/- 17 msec. Walking at speeds of 0.8 and 2.4 km/hr produced muscle contractions of variable duration and intensity. LVSAD was decreased by both pacing (14%) and walking (up to 10%). Pacing in combination with walking caused erratic muscle contractions with concomitant changes in LVSAD suggestive of impaired ventricular filling. No arrhythmias were noted during exercise.

Action Potentials↗
PubMed1991

Dynamic rehabilitation of the paralyzed face: III: Balanced coupling of oral and ocular musculature from the intact side in the canine.

We have recently demonstrated the feasibility of artificial agonist/antagonist coupling between intact facial and reinnervated strap muscles in the rabbit. The present study broadens this principle to involve bi-level cross-facial innervation. After severing the facial innervation unilaterally in four dogs, a nerve pedicle from a cervical motor nerve was implanted into the orbicularis oris and from the deep temporal nerve into the orbicularis oculi. After neurotization (5.6 months), the pedicles were electrically stimulated to verify muscular response. Graded contraction on the intact side was induced by stimulating the ipsilateral facial nerve with currents of various pulse widths. The resulting compression of a strain gauge on the intact face triggered a two-channel, opto-isolated, pulse width-modulated stimulator to produce agonistic graded contraction at one level of the reinnervated side (e.g., oral) and reciprocal relaxation in its reinnervated counterpart (e.g., ocular). The sophistication of the present model--as compared to the original pilot study--brings us one step closer to dynamic human facial rehabilitation.

Animals↗
PubMed1990

Electronic control of laryngeal spasm. I. Blockage of orthodromically induced action potentials in intact canine recurrent laryngeal nerves.

Spastic dysphonia is a central nervous system phenomenon of unknown etiology characterized by uncoordinated voice tremor with erratic patterns of laryngeal contraction. Standard treatments have not been entirely satisfactory. The authors propose to apply a concept of selective nerve activity blockage, which leaves normal contractions undisturbed, as the basis for suppression of laryngeal spasticity. Single pulses of constant duration and increasing amplitude were injected into specially designed blocking electrodes placed around six recurrent laryngeal nerves (three dogs). Vocal cord adduction was reduced or arrested within given "windows" of stimulation levels of the blocking electrodes, while it increased with higher amplitudes when the current was injected via standard bipolar electrodes (controls). Although this study demonstrates the feasibility of blocking action potentials passing along recurrent laryngeal nerves, it might eventually allow control of laryngeal spasm from information taken directly from the affected musculature.

Action Potentials↗
PubMed1990

Artificial restoration of voice. I: Experiments in phonatory control of the reinnervated canine larynx.

Coordinated electronic pacing of implanted nerve pedicles into paralyzed laryngeal muscles has allowed selective dynamic control of abduction, adduction, and elongation of the vocal cords. Modifications of the original circuit in a cervical muscle model has added fine tuning to basic "all-or-none" pacing. Rehabilitation of phonation illustrated the sophisticated nature of voice and the need for restoration of fine tuning. Five mongrel dogs received nerve-muscle pedicles into the thyroarytenoideus, cricothyroideus, and posterior cricothyroideus after denervation of one hemilarynx. Following appropriate reinnervation time, pedicles and intact recurrent laryngeal nerves were injected with currents of variable amplitudes and pulse widths to achieve graded vocal fold control while air was blown intratracheally towards the glottic chink. Videoscopic and spectral analyses indicated that artificial phonation could be restored to frequencies measured in the normal state. These experiments suggested that rehabilitation of the impaired voice by servocontrol might eventually be feasible.

Animals↗
PubMed1989

Excitation thresholds for nerve pedicles: a preliminary report.

Ongoing interest in the rehabilitation of paralyzed musculature in the head and neck has focused on the electronic stimulation of nerve-muscle pedicles that have been reimplanted into the incapacitated effector(s). Despite visual and histochemical evidence of reinnervation, it is still not known whether the excitability of a nerve-muscle pedicle (or for that matter a direct nerve implant) is equivalent to or better than that of reinnervated or normal muscle. Such information is necessary for the eventual construction of an implantable stimulator. Eighteen rabbits were anesthetized with intramuscular xylazine and ketamine and the ansa hypoglossi nerve was cut on one side. A crossover nerve-muscle pedicle was brought in from the opposite sternothyroid muscle to the sternohyoid in nine animals; the other nine received a direct nerve implant. After a minimum neurotization period of 3 months and reexploration, an electrical stimulator capable of delivering square wave pulses of variable amplitude and width was used to determine the thresholds of contraction of the nerve pedicles, an intact motor nerve of similar size, a normal muscle, and the reinnervated strap in 16 evaluable rabbits. Strength duration curves were established. The data indicate that thresholds for nerve pedicles are equivalent to those of normal nerves and are significantly lower than those of muscle.

Animals↗