Biomedical subjects

N E Simmons

Publications and source records attributed to N E Simmons.

18 recordsLinked to original sources

PubMed2001

Serum cortisol response to transsphenoidal surgery for Cushing disease.

OBJECT: Transsphenoidal surgery remains the optimal treatment for Cushing disease, but the definitions of surgical cure and failure remain debatable. In this study the authors evaluated serum cortisol levels in patients before and after they underwent transsphenoidal surgery to elucidate the patterns of cortisol decrease and the optimal time and criteria for determining surgically induced remission. METHODS: Twenty-seven patients were evaluated throughout an 8-month period. Serum cortisol levels were obtained before surgery and at 6-hour intervals postoperatively. No exogenous steroid medications were administered until after cortisol sampling was discontinued, following diagnosis of remission. Twenty-one (78%) of 27 cases were labeled initial surgically induced remissions. Twenty-two (81%) of 27 cases were deemed surgically induced remissions at follow-up examination. Following surgery, initial remissions and failures demonstrated divergent patterns of cortisol levels. No patient whose condition was deemed an initial surgically induced remission has experienced definitive relapse of disease since discharge. One patient whose condition was initially deemed a surgical failure, eventually was found to exhibit surgically induced remission without further intervention. CONCLUSIONS: Given such findings, exogenous steroid medications do not appear to be required for patients until after the determination of remission. During the 1st postoperative day, there is a time period during which serum cortisol values significantly differ between the categories of surgically induced remissions and surgical failures. Surgically induced remissions were identified when postoperative values of cortisol were lower than preoperative midnight levels and when absolute values of cortisol were less than 10 microg/dl. In a small proportion of patients remission on a delayed basis may also be demonstrated. These data allow for a simple and rapid determination of postoperative remission in patients undergoing transsphenoidal surgery for Cushing disease.

Adenoma↗

PubMed2000

Transthoracic approaches to thoracic disc herniations.

The transthoracic approach to herniated thoracic discs is an important procedure in the management of these uncommonly encountered lesions. Whereas posterior and posterolateral microsurgical approaches and thoracoscopic procedures have been widely advocated in the recent neurosurgical literature, the transthoracic operation continues to offer significant advantages in appropriately selected cases. The authors discuss the preoperative considerations, relevant anatomical structures, and surgical technique.

Calcinosis↗

PubMed2000

Cerebral atrophy in Cushing's disease.

BACKGROUND: Cushing's disease causes significant pathological changes throughout the body as a result of elevated cortisol levels. Very few systematic investigations have focused on the morphologic effects of hypercortisolism on the central nervous system. The validity of using premature cerebral atrophy as a diagnostic tool for Cushing's disease remains unknown. METHODS: This study includes 63 patients with Cushing's disease who were evaluated and treated at the University of Virginia Medical Center. Radiologists randomly compared these individuals with age- and sex-matched controls in a blinded protocol, assessing the degree of cerebral atrophy on computed tomography and magnetic resonance scans. RESULTS: Patients with Cushing's disease showed significant premature atrophy when compared with controls. This trend continued after subdividing the groups based on age and duration of symptoms except in the following groups: age greater than 60, duration of symptoms less than 1 year, and symptoms lasting between 4-5 years. CONCLUSIONS: Excluding the three aforementioned groups, the hypercortisolemic state manifested in patients with Cushing's disease promotes the premature development of cerebral atrophy, which can be identified on routine radiologic imaging and may assist in the clinical diagnosis of the condition.

Adult↗

PubMed2000

Complications of posterior lumbar interbody fusion when using a titanium threaded cage device.

OBJECT: The authors reviewed their series of patients to quantify clinical and radiographic complications in those who underwent a posterior lumbar interbody fusion (PLIF) procedure in which a threaded interbody cage (TIC) was implanted. METHODS: Sixty-seven patients underwent a posterior lumbar interbody fusion procedure in which a TIC was used. The authors excluded patients who underwent procedures in which other instrumentation was used or a nondorsal approach was performed. Fifteen percent of the cases (10 patients) were complicated by laceration of the dura. In three cases, bilateral implantation could not be performed. The average blood loss was 670 ml for all cases, and blood transfusion was required in 25% of the cases (17 patients). The rate of minor wound complication was 4.5% (three patients). One patient died. The average period of hospitalization was 4.25 days. Twenty-eight patients (42%) experienced significant low-back pain 3 months postoperatively, and in 10 (15%) of these cases it persisted beyond 1 year. In 10 patients postoperative radiculopathy was demonstrated, and magnetic resonance imaging revealed epidural fibrosis in six patients, arachnoiditis in one, and a recurrent disc herniation in one. One patient incurred a permanent motor deficit with sexual dysfunction. Pseudarthrosis was suggested radiographically with evidence of motion on lateral flexion-extension radiographs (10 cases), lucencies around the implants (seven cases), and posterior migration of the cage (two cases). Additional procedures (in 14 patients) consisted primarily of transverse process fusion with pedicle screw and plate augmentation for persistent back pain and radiographically demonstrated signs of spinal instability. In two patients with radiculopathy, migration of the TIC required that it be removed. Graft material that extruded from one implant necessitated its removal. In one patient scarectomy was performed. CONCLUSIONS: Our high incidence of TIC-related complications in PLIF is inconsistent with that reported in previous studies.

Adolescent↗

PubMed2000

Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy.

OBJECT: The authors undertook a study to explore the predisposing risk factors, frequency of occurrence, and clinical implications of kyphosis following laminectomy for cervical spondylotic myelopathy (CSM). METHODS: Preoperative radiological studies were available in 46 patients with CSM who had undergone laminectomy. Records were reviewed to obtain demographic data and operative reports. Preoperative radiographs were assessed to determine spinal alignment. In a follow-up interview the authors established clinical outcome and patient satisfaction. Postoperative cervical alignment and mobility was also determined by assessing lateral neutral, flexion, and extension x-ray films. Preoperatively, the cervical spine was shown to be kyphotic in four (9%) of 46, straight in 20 (43%) of 46, and lordotic in 22 (48%) of 46 patients. Nine (21%) of 42 patients with either straight or lordotic alignment demonstrated in the preoperative period developed kyphosis after surgery. Kyphosis developed in six (30%) of 20 patients in whom straight spinal alignment was demonstrated preoperatively and in only three (14%) of 22 patients in whom lordosis was found preoperatively. Clinically, 13 (29%) of 45 patients improved and 19 (42%) of 45 remained unchanged after an average 4-year follow-up period; 36 (80%) patients believed that their surgery was successful (one patient, who was mentally retarded, could not respond to the follow-up questionnaire). Spinal alignment was not predictive of outcome; cervical mobility as demonstrated on flexion and extension, however, correlated with improved functional performance (p = 0.005). CONCLUSIONS: Kyphosis may develop in up to 21% of patients who have undergone laminectomy for CSM. Progression of the deformity appears to be more than twice as likely if preoperative radiological studies demonstrate a straight spine. In this study, clinical outcome did not correlate with either pre- or postoperative sagittal alignment.

Cervical Vertebrae↗

PubMed1999

Small cell lung carcinoma causing epidural hematoma: case report.

BACKGROUND: Epidural hematoma usually stems from trauma, yet it may occur from other etiologies, including neoplasms. We present a case of small cell lung carcinoma with focal hemorrhagic central nervous system metastasis producing an epidural hematoma, and review the associated literature. CLINICAL PRESENTATION: A 67-year-old man was undergoing chemotherapy for small cell carcinoma of the lung. Acute neurologic deterioration resulted from a large parietal epidural hematoma of non-traumatic origin. INTERVENTION: The clot was evacuated via craniotomy with marked improvement in his clinical state. Metastatic tumor was present in the scalp, muscle, bone, and dura. No gross brain invasion was apparent. CONCLUSIONS: This case illustrates the wisdom of including metastatic disease in the differential diagnosis of intracranial hemorrhage. Even epidural hematoma may result from metastatic cancer. The prevalence of lung carcinoma and the aging of the population may produce an increased appearance of this phenomenon. Appropriate evaluation and rapid intervention will aid the patient in both the acute and long-term phases, and should improve the quality of survival.

Aged↗

PubMed1999

Estrogen receptors in prolactinomas: a clinico-pathological study.

BACKGROUND: Antiestrogens are effective in the treatment of estrogen receptor (ER) positive breast carcinoma. The use of antiestrogen therapy in pituitary adenomas, however, has not been explored. This study attempted to identify a population who may benefit from antiestrogen therapy. MATERIALS & METHODS: Prolactinomas from 29 patients (10 men, 19 women) were analyzed for ER and Ki-67 labeling index using immunohistochemistry. Nine of the 19 women were either amenorrheic or had not received exogenous estrogen for at least one year. Ten women were menstruating either spontaneously or as a result of estrogen administration. Factors including age, serum prolactin level, tumor size, evidence of tumor invasiveness and recurrence of tumor were evaluated to determine if they were predictive of ER expression. RESULTS: Tumors from 6/10 (60%) men were positive for ER. Among women who were having menses, 9/10 (90%) tumors were positive, whereas 6/9 (67%) tumors from amenorrheic women were positive. Statistical analysis revealed that none of the variables: gender, age, menstrual status, Ki-67 proliferative rate, exposure to dopamine agonists, preoperative prolactin level, tumor size, or invasiveness was predictive for the presence of the receptor. The incidence of ER, however, was significantly reduced in recurrent tumors (p = 0.03). CONCLUSIONS: ER expression is less likely in recurrent tumors. The efficacy of ER antagonists cannot be inferred by gender or estrogen exposure.

Adult↗

PubMed1998

Glioma occurrence after sellar irradiation: case report and review.

OBJECTIVE: Tumor neogenesis is an uncommon but known consequence after therapeutic irradiation of the central nervous system. Causative agents for glioma induction remain unknown, but laboratory and clinical data suggest a possible role for radiation as a promotor. In the treatment of both pituitary adenomas and craniopharyngiomas, adjunctive conventional radiation therapy has long played a role. CLINICAL PRESENTATION: This report details two cases in which patients received standard sellar irradiation for growth hormone-secreting pituitary adenomas and later were diagnosed with gliomas, after a latency period of 11 and 18 years, respectively. Additionally, a comprehensive review of the literature with 30 reports of gliomas developing after conventional radiation for treatment of pituitary adenomas and craniopharyngiomas is presented. The mean dose for craniopharyngiomas (n = 8) was 5800 cGy, with a mean latency of 11.5 years from initial diagnosis to the eventual discovery of the gliomas. The mean dose for the treatment of pituitary adenomas (n = 24) was 5300 cGy, with a mean latency of 10.4 years. CONCLUSION: Typical features of the resulting gliomas included presentation in young patients, histologically high grades, and occurrence within the temporal lobe. A large proportion of gliomas were associated with growth hormone-secreting adenomas. This review assesses the implication of doses of conventional radiotherapy that were previously thought to be benign and concludes that although radiation-associated gliomas are uncommon, they represent a potentially devastating long-term risk. Based on this analysis, treatment of sellar tumors with conventional fractionated radiotherapy should be carefully considered and perhaps used primarily in those cases for which radiosurgery is not appropriate.

Adenoma↗

PubMed1998

Use of preoperative computed tomography-angiography in cranial remodeling: technical note.

UNLABELLED: OBJECTIVE/IMPORTANCE: One of the most severe complications of craniosynostosis repair is dural sinus laceration. Massive hemorrhage and air embolism are potentially life-threatening sequelae that can result from such an event. The aberrant anatomy of patients with craniosynostosis only accentuates this risk, because separation of the calvaria from the underlying dura is often performed without direct visualization of the sinuses. METHODS: Three-dimensional computed tomography was combined with computed tomographic angiography in the preoperative assessment of patients with craniofacial abnormalities. RESULTS: A clear understanding of the dural sinus anatomy in relation to the overlying bony landmarks became available to the operating surgeon. Six patients underwent this procedure, with excellent visualization of the bony and sinus anatomy achieved in all cases. CONCLUSION: It is thought, that the benefit of combining these procedures has been significant by allowing the visualization of the dural sinus anatomy and overlying bony landmarks. This procedure conveys minimal concomitant morbidity or expense to the patient, yet offers valuable insight toward operative planning and complication avoidance.

Cerebral Angiography↗

PubMed1997

Utilization of type I collagen gel, demineralized bone matrix, and bone morphogenetic protein-2 to enhance autologous bone lumbar spinal fusion.

Autologous bone grafts are currently considered "gold standard" material for achieving long-term spinal arthrodesis. The present study was performed to determine whether demineralized bone matrix (DBM), type I collagen gels, or bone morphogenetic protein-2 (BMP-2) can improve autologous bone spinal fusions. Using a unilateral decompression-contralateral fusion technique in dogs, each of these materials was added to an autologous bone graft. Volumetric analysis, histological analysis, and biomechanical testing were performed to assess the effectiveness of each material. The DBM had an inhibitory effect on solid bone fusion of the spine, whereas the type I collagen gels improved the bony interface between the graft and the host spine. The BMP-2 strongly enhanced the amount of bone deposition at the fusion site and increased the number of intervertebral levels that were solidly fused. This study strongly supports the use of BMP-2 as an additive to autologous bone grafts in spine stabilization.

Animals↗

PubMed1996

The accessory optic system in the frog, Rana Pipiens: an electron microscopic study of the retinal afferents utilizing the anterograde tracer biocytin.

The retinal afferents to the basal optic nucleus in the frog, Rana Pipiens, were labeled anterogradely with biocytin and subsequently studied at the electron microscopic level. Labeled synaptic terminals in the nucleus varied in size from 0.5 microns to 2.0 microns and made symmetric synaptic contacts with large and small dendrites, although very rare axospinous and axosomatic contacts were also demonstrated.

Animals↗

PubMed1996

Molecular methods of enhancing lumbar spine fusion.

OBJECTIVE: An optimal method for spinal fusion would induce rapid growth of bone via an osteoconductive and osteoinductive implant. This study examines the spinal fusion enhancement potential of some osteoconductive and osteoinductive biomaterials. METHODS: Four similar canines received unilateral posterolateral fusions on the left side at T13-L1 and L4-L5 and on the right side at L2-L3 and L6-L7. The experiments were grouped as follows: Group A, autogenous bone harvested from the iliac crest; Group B, autogenous bone and collagen; Group C, no implant; and Group D, autogenous bone, collagen, and recombinant human bone morphogenetic protein-2. Radiographic assessment, three-dimensional computed tomographic volumetric analysis, and biomechanical testing were performed at each level. RESULTS: For Groups A and B, the fusions demonstrated moderate bone formation at 6 and 12 weeks postoperatively. Group D fusions exhibited earlier and more dramatic increases in volume and radiodensity and eventually were comparable in size to the vertebral bodies. Average fusion volumes computed from three-dimensional computed tomographic analysis were: Group A = 1.243 cc, Group B = 0.900 cc, Group C = 0.000 cc, and Group D = 6.668 cc (P = 0.003 compared to Group A). Group D exhibited flexion and extension biomechanical properties much greater than controls. The addition of recombinant human bone morphogenetic protein-2 consistently yielded the strongest fused segments and, on average, enhanced extension stiffness by 626% and flexion stiffness by 1120% over controls. CONCLUSION: The most advantageous spinal fusion implant matrix consisted of recombinant human bone morphogenetic protein-2, autogenous bone, and collagen. Future investigators, however, need to examine the appropriate quantities of the individual components and clarify the efficacy of the matrix for the various types of spinal fusion approaches.

Animals↗

PubMed1996

Treatment of lumbar spinal stenosis by extensive unilateral decompression and contralateral autologous bone fusion: operative technique and results.

A new surgical technique for the treatment of lumbar spinal stenosis features extensive unilateral decompression with undercutting of the spinous process and, to preserve stability, uses contralateral autologous bone fusion of the spinous processes, laminae, and facets. The operation was performed in 29 patients over a 19-month period ending in December of 1991. All individuals had been unresponsive to conservative treatment and presented with low-back pain in addition to signs and symptoms consistent with neurogenic claudication or radiculopathy. Nine had undergone previous lumbar decompressive surgery. The minimum and mean postoperative follow-up times were 2 and 2 1/2 years, respectively. The mean patient age was 64 years; only two patients were younger than 50 years of age. Of the patients with neurogenic claudication, 69% reported complete pain relief at follow-up review. Of those with radicular symptoms, 41% had complete relief and 23% had mild residual pain that was rated 3 or less on a pain-functionality scale of 0 to 10. For the entire sample, this surgery decreased pain from 9.2 to 3.3 (p < 0.0001) on the scale. Sixty-nine percent of patients were satisfied with surgery. Low-back pain was significantly relieved in 62% of all patients (p < 0.0001). Low-back pain relief correlated negatively with number of levels decompressed (p < 0.05). To assess fusion, follow-up flexion/extension radiographs were obtained, and no motion was detected at the surgically treated levels in any patient. The results suggest that this decompression procedure safely and successfully treats not only the radicular symptoms caused by lateral stenosis but also the neurogenic claudication symptoms associated with central stenosis. In addition, the procedure, by using contralateral autologous bone fusion along the laminae and spinous processes, can preserve stability without instrumentation.

Adult↗

PubMed1994

Magnetic resonance imaging of neuronal grafts in the primate.

This preliminary study demonstrates the vital role that magnetic resonance imaging plays in the study of neuronal grafts in a nonhuman primate model of Huntington's disease. MRI scans were used to accurately locate and stereotactically lesion the anterior putamen of an adult rhesus monkey, thereby mimicking the anatomical and biochemical changes in Huntington's disease. Follow-up scans were utilized to confirm correct placement of the lesion and to stereotactically implant primate fetal neuronal tissue precisely into the lesion. Additionally, MRI appeared capable of imaging the fetal striatal grafts in rhesus monkeys. While the precise cellular composition of growing grafts was not identifiable on MRI scans, differentiation between normal, lesioned, and engrafted tissue was possible. Correlation of the magnetic resonance images of the grafted regions with actual graft tissue in perfused sections of the brain was shown. The use of magnetic resonance imaging, as indicated in these neuronal implantation studies, allows for a wide variety of future research possibilities where noninvasive and precise localization of the graft is mandated.

Animals↗

PubMed1993

Degeneration of long-term fetal neostriatal allografts in the rhesus monkey: an electron microscopic study.

Primate fetal neostriatal neurons were implanted into the ibotenic acid-lesioned primate striatum and the animals were allowed to survive for 8 months. Light microscopic examination of the transplanted tissue demonstrated that the grafts were between 1.0 and 1.5 mm in diameter. The transplants were highly gliotic, but contained both normal appearing and degenerating neurons. At the electron microscopic level, the transplanted neurons displayed ultrastructural features identical to those of medium spiny, medium aspiny, and large aspiny striatal neurons. However, the majority of the grafted neurons showed evidence of degeneration. The grafts' neuropil demonstrated numerous glial processes, as well as mature axodendritic and axospinous synapses. Although this study was limited to only two graft recipients, the degenerative changes seen in the long-term primate allografts suggest that extension of these techniques into the clinical setting may be premature at the present time.

Animals↗

PubMed1993

A method for utilizing biocytin to study retinofugal pathways at the light and electron microscopic levels.

Numerous methods have been utilized in the past to study the retinofugal pathway at both the light and electron microscopic levels. However, many of these techniques have technical drawbacks that make them difficult to use in electron microscopic studies. We present herein a method for utilizing the anterograde tracer biocytin to study the retinal pathways at both the light and electron microscopic levels. Biocytin is an especially useful tracer since it clearly labels very small axons and boutons in addition to the larger fibers. In addition, the synaptic ultrastructure is left intact and the technique can be utilized in numerous double-labeling neuroanatomical studies.

Animals↗

PubMed1993

Carotid artery revascularization following Crutchfield clamp placement. Report of two cases.

Several types of adjustable clamp have been widely utilized to gradually occlude the carotid artery for the treatment of various intracranial vascular lesions. A fairly large number of patients, many of whom have not been adequately followed, have these clamps still in place. The authors report two patients, initially treated with a Crutchfield clamp for an intracranial aneurysm, in whom carotid artery system revascularization occurred through the clamp many years later, leading to continued filling of the aneurysm. Recommendations are given on monitoring patients with Crutchfield clamps in order to minimize long-term complications.

Aged↗

PubMed1992

Descriptive morphology of developing fetal neostriatal allografts in the rhesus monkey: a correlated light and electron microscopic Golgi study.

Primate fetal striatal neurons were transplanted into the ibotenic acid lesioned rhesus monkey striatum. Ten weeks after transplantation the monkeys were transcardially perfused and graft tissue was histologically stained. Golgi impregnated, and processed for electron microscopy. The monkeys received magnetic resonance imaging (MRI) scans before lesioning, after lesioning, and ten weeks after transplantation to noninvasively study the striatal grafts. The study demonstrated that fetal striatal grafts, measuring up to 0.4 x 0.8 cm, can survive for extended periods of time in the non-human primate. Hematoxylin-eosin stained sections of the transplant demonstrated that neuronal, glial, vascular, and lymphocytic cells were present in the graft. The majority of the neurons had somatic diameters between 8 and 20 microns and were characterized by nuclei containing multiple nucleoli. A few neurons within the graft had somatic diameters up to 40 microns. These larger neurons exhibited more mature cytoplasm containing a moderate amount of Nissl substance. Some of the blood vessels within the graft were surrounded by a large number of plasma cells, but there was no evidence of hemorrhage or necrosis. Bielschowsky staining and Golgi impregnation of the transplanted tissue demonstrated that there were neurons at various degrees of differentiation. Some of the neurons had varicose dendrites, growth cones, and filopodia, which are all characteristics of immature neurons, while others had a much more mature appearance, including a moderate number of dendritic spines. Some of these neurons had an appearance typical of differentiating "medium spiny" neurons of the normal striatum. Electron microscopic analysis of the transplanted tissue and individual Golgi-impregnated neurons within the transplant confirmed that there were developing neurons within the graft. These neurons had an increased nuclear-to-cytoplasmic ratio and had nuclei containing multiple nucleoli. The neuropil surrounding these neurons was loosely organized and contained large areas of extracellular space. The neuropil exhibited developing dendrites, numerous growth cones, and mature synapses. In summary, the study demonstrated that fetal striatal allografts can survive for up to three months in the rhesus monkey and undergo normal differentiation as assessed by Golgi impregnation and electron microscopy.

Animals↗