Projecting seismicity induced by complex alterations of underground stresses with applications to geothermal systems.

Seismicity associated with subsurface operations is a major societal concern. It is therefore critical to improve predictions of the induced seismic hazard. Current statistical approaches account for the physics of pore pressure increase only. Here, we present a novel mathematical model that generalises adopted statistics for use in arbitrary injection/production protocols and applies to arbitrary physical processes. In our model, seismicity is driven by a normalised integral over the spatial reservoir volume of induced variations in frictional Coulomb stress, which-combined with the seismogenic index-provides a dimensionless proxy of the induced seismic hazard. Our model incorporates the classical pressure diffusion based and poroelastic seismogenic index models as special cases. Applying our approach to modeling geothermal systems, we find that seismicity rates are sensitive to imposed fluid-pressure rates, temperature variations, and tectonic conditions. We further demonstrate that a controlled injection protocol can decrease the induced seismic risk and that thermo-poroelastic stress transfer results in a larger spatial seismic footprint and in higher-magnitude events than does direct pore pressure impact for the same amount of injected volume and hydraulic energy. Our results, validated against field observations, showcase the relevance of the novel approach to forecast seismic hazards induced by subsurface activities.

[The emotional burnout effect on labor efficiency of stomatologists].

The article presents the results of the study of factors effecting on professional deformation of stomatologists and its relationship with their personal characteristics, labor experience and medical specialization. the information is compiled with purpose of elaborating comprehensive recommendations on diagnostics of phases of development of syndrome of emotional burnout in this category of medical specialists at the initial stages of its occurrence and proposing measures of its adjustment including social and personal prevention.

[Influence of monotony of work on psychophysiological health of drivers of electric rolling stock of railway transport].

The article presents the results of the author's research that determines the degree of influence of monotonous (monotonous) labor processes on the drivers (and their assistants) of traction rolling stock of railway transport. Information is collected in order to develop a set of measures to overcome the monotony of work, improve the quality of working life and psychophysiological health of employees, and as a result, ensure traffic safety, improving the safety system for drivers and improving the quality of passenger transport.

Normal blood flow response and vasomotion in the diabetic Charcot foot.

Vasomotion, the spontaneous rhythmic contraction exhibited by small arteries and arterioles is dysregulated in patients with diabetic neuropathy. We examined the relationship between Charcot arthropathy and vasomotion at the dorsum of the foot. We studied nine diabetic patients with clinically diagnosed neuropathy and Charcot arthropathy in 13 feet (n=13), twelve subjects with diabetic neuropathy and no Charcot deformity (n=12), and 11 healthy controls (n=11). Following neuropathy assessment, blood flow was measured by laser Doppler flowmetry with local skin warming. Fast Fourier transformation was performed to provide an index of vasomotion. Subjects with Charcot osteoarthropathy had more severe somatic neuropathy and higher circulating levels of serum calcium (9.8+/-0.1 versus 9.3+/-0.1 mg/dL). Raising local temperature increased skin blood flow and vasomotion in both control subjects and Charcot subjects, but not in diabetic patients with neuropathy alone (p < 0.05 for blood flow, p < 0.02 for vasomotion). Patterns of peripheral vasomotion and blood flow which are clearly disordered in diabetic neuropathy are intact in patients with a Charcot osteoarthropathy, despite a more severe sensory nerve impairment. These findings suggest that the loss of peripheral blood flow and vasomotion often seen in diabetic neuropathy may actually be protective against Charcot arthropathy by preventing bone resorption. It remains unclear then whether the Charcot arthropathy is a direct result of a failure to decrease blood flow to bone, or is the manifestation of some other pathology.

Spinal instrumentation with a low complication rate.

BACKGROUND: Spinal instrumentation has become an increasing part of the armamentarium of neurosurgery and neurosurgical training. For noncontroversial indications for spine fusion the arthrodesis rate seems to be better. For both noncontroversial and controversial indications, the reported complication rate with spinal instrumentation tends to be greater than that with noninstrumented spine surgeries. These reported complications include a 2-3% neurologic injury rate, 3-45% reoperation rate for implant failure, and inflection rates of 5-10%. Therefore, we report on 299 cases that have undergone spinal instrumentation placed exclusively by neurosurgeons with a very low complication rate. METHODS: Two hundred ninety-nine consecutive spinal instrumentation cases performed exclusively by neurosurgeons at Indiana University Medical Center were analyzed for complications related to spinal instrumentation. The spinal instrumentation placed consisted of 195 anterior cervical locking plates, 22 cases of posterior cervical instrumentation, 9 cases of combined anterior locking plates with posterior cervical instrumentation, 14 anterior thoracolumbar plates, 51 posterior thoraco-lumbar instrumentation cases, and 8 combined anterior/posterior thoracolumbar instrumentation cases. RESULTS: The mean follow-up is 40 months (6-95). There was one perioperative death unrelated to the spinal instrumentation. There were no neurologic injuries and there has been no hardware infection to date. There were two dural tears, three superficial wound infections, and three minor wound breakdowns successfully treated. Hardware complications included three cervical plate/screw extrusions reoperated, one cervical plate fracture reoperated, one posterior cervical screw backout not reoperated, one case of broken pedicle screw not reoperated, one vertebral body failure not reoperated, and one posterior rod case reoperated for excessive rod length and protrusion. The overall complication rate attributable to placement of spinal instrumentation was 10/299 (3%) with a reoperation rate of 2%. The arthrodesis rate was 298/299 (99%). CONCLUSION: The complication rate for using spinal instrumentation can be less than previously reported. Lessons learned and discussed should reduce the rate even more. Spinal instrumentation is a safe and useful adjunct to fusion in treating degenerative, traumatic, infectious, and neoplastic diseases of the spine.

Impairment of peripheral blood flow responses in diabetes resembles an enhanced aging effect.

OBJECTIVE: To test the hypothesis that skin blood flow responses in the fingertip of diabetic patients are impaired and to examine the role of aging in both healthy control subjects and diabetic patients. RESEARCH DESIGN AND METHODS: We measured cutaneous blood flow using laser Doppler techniques in 40 people with diabetes and in 20 age- and sex-matched healthy control subjects. To induce vasoconstriction, subjects were asked to perform three 1-min stressor tasks: mental arithmetic, contralateral hand grip, and immersion of the contralateral hand in ice water. To induce vasodilatation, a local heat stimulus of 45 degrees C was applied for 5 min. RESULTS: Basal blood flow did not differ between groups, but vasoconstrictive responses induced by arithmetic or immersion of the contralateral hand in ice-cold water and vasodilatation induced by local heating were severely impaired in diabetic subjects, compared with healthy control subjects (P < 0.01). These responses correlated with autonomic nerve function and deteriorated significantly with advancing age in control subjects, but not in diabetic subjects. Blood flow in younger diabetic subjects resembled that of older control subjects. CONCLUSIONS: These data demonstrate that diabetes has effects on precapillaries that may by direct or mediated via autonomic nerves, which result in a deficit that resembles premature aging.

Impaired peripheral vasomotion in diabetes.

OBJECTIVE: To test the hypothesis that vasomotion, the rhythmic contraction exhibited by small arteries and arterioles, is impaired in diabetic subjects compared with healthy control subjects. RESEARCH DESIGN AND METHODS: We mathematically modeled the oscillations in laser Doppler microvascular measurements taken from the pulpar surface of the index finger in 20 healthy control subjects and 20 age-matched diabetic subjects (8 with type I and 12 with type II diabetes). The mean duration of diabetes was 17.1 +/- 2.3 years, and mean HbA1c was 9.1 +/- 0.4%. Blood flow was measured for 5 min as subjects rested quietly in a closed room. Fast Fourier transformation was performed to provide the frequency power spectrum of each recording. Amplitude of vasomotion was correlated with six quantitative measurements of neuropathy. RESULTS: Diabetic subjects had impaired low-frequency oscillation vasomotion in 75% of age-matched patients (15 of 20 patients), with mean amplitudes of 24.9 +/- 6.4 vs. 129.0 +/- 33.2 (P < 0.0039). Of six somatic and autonomic neuropathy variables, only the warm thermal sensory threshold correlated significantly with the mean amplitude of vasomotion (r = -0.75, P < 0.0009). CONCLUSIONS: Patterns of peripheral vasomotion are clearly disordered in diabetes. The loss of low-frequency oscillations observed here suggests a peripheral vascular abnormality that extends past the capillary network to arterial vessels. It is uncertain whether the accompanying small unmyelinated nerve C-fiber dysfunction is a cause or consequence of the impaired microvascular function. Measurement of vasomotion may prove useful as a novel test for peripheral neurovascular function.

Sarcoid myelopathy.

A 45-year-old woman with history of iritis, uveitis, and sarcoidosis of the skin presented with a subacute cervical myelopathy. Magnetic resonance imaging (MRI) showed patchy, multifocal, gadolinium-enhancing intramedullary lesions of the spinal cord, and extramedullary lesions of the basal cisterns and fourth ventricle. Symptoms and MRI abnormalities were improved within 1 month of corticosteroid therapy.

Hemorrhagic dilation of the fourth ventricle: an ominous predictor.

Very little is known about the effect of computerized tomography (CT)-documented fourth intraventricular hemorrhage (IVH). An analysis of 50 patients with CT-documented fourth IVH treated between 1987 and 1992 is presented. The various etiologies included intraparenchymal hemorrhage with secondary fourth IVH (19 cases), spontaneous subarachnoid hemorrhage (18 cases), spontaneous IVH (seven cases), and trauma (six cases). Overall, 28 patients (56%) had hemorrhagic dilation of the fourth ventricle and all 28 suffered brain death, despite aggressive therapy in 79% of cases. Twenty-two patients (44%) had fourth IVH without dilation; of these, nine (41%) died and 13 (59%) experienced functional survival, despite aggressive care in 90% of cases. The survival rate was significantly worse for patients with dilation of the fourth ventricle (p < 0.01, chi-squared test). Of the 28 patients with fourth IVH associated with dilation, 25 (89%) had diffuse clot, involving the lateral and third ventricles as well, and three (11%) had isolated fourth IVH. Of the 22 patients with fourth IVH and no dilation, 13 (59%) had diffuse IVH (eight of these died and five had functional recovery) and nine (41%) had isolated fourth IVH (one died and eight had functional recovery). Diffuse ventricular clot was associated with an increased mortality rate for patients with fourth IVH and no dilation (p < 0.05). Of the 28 patients with fourth IVH associated with dilation, 24 (86%) presented with a Glasgow Coma Scale (GCS) score of 3 or 4, one with a GCS score of 6, and three with a GCS score of 13 to 15; all 28 died. For the 22 patients with fourth IVH and no dilation, nine presented with a GCS score of 3 to 5 (eight died and one had functional recovery), three had a GCS score of 6 to 8 (all three had functional survival), two had a GCS score of 9 to 12 (both had functional survival), and eight had a GCS score of 13 to 15 (one died and seven had functional survival). There was a greater chance of higher GCS scores in patients with fourth IVH and no hemorrhagic dilation (p < 0.01). Logistic regression multivariate analysis showed hemorrhagic fourth ventricular dilation to be the most significant outcome predictor (p = 0.0001), followed by GCS score (p = 0.007) and the presence of diffuse IVH (p = 0.0279).

Management of unilateral locked facet of the cervical spine.

Twenty-four patients with unilateral cervical locked facets were treated between 1986 and 1990. The primary mechanisms of injury were vehicular accidents (58%) and altercations (38%). The level of unilateral facet dislocation was C5-C6 (41%), C6-C7 (25%), C3-C4 (17%), and C4-C5 (17%). Seventeen (70%) came to the hospital with radiculopathy, five (20%) were normal, and two (10%) had spinal cord injuries. Plain films showed subluxation but no fracture. All patients had a cervical computed tomographic scan. Fracture in addition to facet locking was seen in 12 (50%) of 24 scans: 5 with facet fracture, 4 with facet/laminar fractures, 2 with facet/laminar/body fractures, and 1 foramen transversarium fracture. On the basis of CT findings, closed reduction was thought to be contraindicated in two cases. Five patients (22%) underwent successful closed reductions. Two of the patients with closed reductions were placed in a halo but again had subluxation. Thus, 24 patients underwent surgery for open reduction, posterior spinous process wire fixation, and facet wiring to struts of the iliac crest for bony fusion. The initial surgery was successful in 23 (96%) of 24 patients. One patient experienced subluxation and underwent further surgery for anterior cervical fusion/plating. Two wound infections were treated, and there were no deaths or neurological worsening. At 1 year, all deficits had improved. Of 16 radiculopathies, 3 (19%) had persistent 4/5 weakness, and the rest were normal, including 2 delayed-diagnosis patients who both showed improvement from 2/5 to 5/5 strength within 1 week of surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Closed continuous drainage of cerebrospinal fluid via a lumbar subarachnoid catheter for treatment or prevention of cranial/spinal cerebrospinal fluid fistula.

One hundred and seven patients who had a lumbar subarachnoid catheter (teflon or silicone) placed for closed continuous cerebrospinal fluid (CSF) drainage between 1983-1991 are presented. Overall, the drain was successful in achieving the desired goal in 101 of 107 (94%) cases. There were no deaths. Five of 107 (5%) patients developed infections including two cases (2%) of meningitis. There were three cases (3%) of overdrainage with temporary neurologic decline, but all recovered. Five of fifteen (33%) teflon catheters required replacement because of occlusion, but only 5 of 92 (5%) silicone catheters required replacement. Transient lumbar nerve root irritation was seen in 15 of 107 (14%) patients treated for a CSF fistula, and all symptoms resolved after drain removal. CSF fistula/pseudomeningocele after spine surgery was cured by CSF drainage in 36 of 39 (92%) cases; there was a 10% incidence of infection (1 wound, 2 discitis, 1 meningitis). CSF fistula after cranial surgery was cured in 22 of 25 (87%) cases; there was 1 case of (4%) infection and 1 case (4%) of overdrainage. A drain was used to augment a tenuous dural closure in 38 patients with 100% success; no infection occurred and there were 2 cases (5%) of overdrainage. Five patients were successfully treated for traumatic CSF rhinorrhea/otorrhea without complications. The silicone catheter appears superior to the teflon catheter; however, both are simple, safe, and efficacious for the treatment or prevention of CSF fistulas.

Efficacy of dorsal longitudinal myelotomy in treating spinal spasticity: a review of 20 cases.

The authors report their experience using dorsal longitudinal myelotomy in treating spasticity in 20 patients with complete spinal cord injuries. These patients suffered from severe painful flexor/extensor spasms that prevented them from wheelchair ambulation and/or their decubitus ulcers healing. All were receiving large doses of various oral drugs, including baclofen, which had failed to control their spasticity, and all underwent a modification of a posterior T-myelotomy as first described by Bischof. All 20 patients enjoyed immediate complete relief of their painful spasms, although two (10%) eventually experienced return of their spasms and are thus classified as long-term failures. Seventeen patients succeeded in markedly reducing, or being completely weaned from, their antispasmodic medications. In 11 of 14 patients, nonhealing decubitus ulcers subsequently healed with treatment. Bladder function was unchanged from the preoperative status in all patients. Chronic intrathecal baclofen infusion has recently been reported as an effective treatment of the spasticity of paraplegia. The results of this study, along with previous reports advocating dorsal longitudinal myelotomy, suggest that this approach is an efficacious alternative to chronic baclofen infusion in reducing spasticity for complete paraplegics. Considering the cost of the infusion pump, along with the fact that chronic intrathecal baclofen therapy necessitates long-term medical supervision, it appears that myelotomy is superior for this select group of patients who have no hope of regaining voluntary motor function.

Cranioplasty, vertebral body replacement, and spinal fusion with tobramycin-impregnated methylmethacrylate.

A prospective analysis of cranioplasty, vertebral body replacement, and spinal fusion using tobramycin-impregnated methylmethacrylate in 65 patients is presented. Cranioplastic methacrylate (1 packet) was mixed with 1.2 g of powdered tobramycin and placed into the desired location. The polymer was irrigated with bacitracin until it became solid. All patients received prophylactic medication with intravenously administered nafcillin and cephalosporin perioperatively and for 48 hours postoperatively. The follow-up time ranged from 7 to 57 months (mean, 32.2 months). Serum tobramycin levels remained below 0.5 microgram/ml in all patients tested, regardless of the time interval. Blood urea nitrogen and creatinine levels remained within normal limits in all patients, and there has been no nephrotoxicity or ototoxicity. There has been 1 infection among the 65 patients (1%) to date. It occurred in a patient who had a previously treated local infection. Cranioplasty, vertebral body replacement, or spinal fusion with tobramycin-impregnated methylmethacrylate is safe and may reduce the incidence of infection.

Suprascapular nerve entrapment. A series of 27 cases.

Suprascapular nerve entrapment is an acquired neuropathy secondary to compression of the nerve in the bony suprascapular notch. A series of 27 cases, the largest reported to date, is presented and examined as to the best and most appropriate method of diagnosis and treatment. The entity is described in detail as to its origin, anatomy, and pathophysiology.

Quantitation of human melanoma, carcinoma and sarcoma tumor cell adhesion to lymphatic endothelium.

We have used an in vitro adhesion assay to study the interaction of tumor cells with lymphatic endothelium, a dynamic event that leads to tumor metastasis in vivo. 3H-thymidine-labeled human tumor cells from: one primary Ewing sarcoma, two established melanoma cell lines, two colon and two breast carcinomas (one established line and one primary culture of each) were added to 24-well culture dishes containing confluent monolayers of bovine lymphatic endothelium. Radioactivity associated with either the cells in suspension or the attached cells was assessed and compared at frequent intervals up to 360 minutes. Generally, tumor cell attachment increased as a function of time reaching a plateau between 180 and 360 minutes. the modular media system described here facilitates the primary and secondary culture (or co-culture) of a variety of normal and transformed cells. Primary cultures with a rounded morphology (one breast and one colon carcinoma) showed the lowest preferential attachment for lymphatic endothelium. All established cell lines and the primary Ewing sarcoma cell line displayed a more fibroblastic morphology and achieved the highest adhesion profiles. There was a correlation between the malignancy and attachment potential for the melanoma and breast carcinoma cell lines. Collectively, these data show that established tumor cell lines with fibroblastic-like morphology exhibit more rapid adhesion than primary tumor cell cultures with more rounded morphologies. While this property may reflect in vitro selection and/or adaptation, it does correlate with the metastatic propensity for some human tumor cells.

Sentinel symptoms and signs of intracranial aneurysms.

Despite advances in the management and surgery of aneurysmal subarachnoid hemorrhage, fewer than half of the patients surviving to hospital admissions have favorable outcomes. This is due to the primary and secondary effects of the hemorrhage. Studies have shown that as many as 40% of ruptured aneurysms had preceding warning symptoms and signs. These warnings include severe headache and cranial nerve palsies, especially the third cranial nerve. Seizures, focal deficits or transient ischemic attacks are rarely warnings. Evaluation should include, in this order, computed tomography scan, lumbar puncture and angiography as indicated. Surgery on symptomatic non-ruptured aneurysms is associated with a greater than 95% chance of a very good outcome and less than 1% mortality rate.