Gadolinium-enhanced magnetic resonance imaging in temporal bone lesions

A 2-year experience with an enhancement agent in magnetic resonance imaging (MRI) is examined through case presentations. Characteristics of the agent Gadolinium DTPA/Dimeglumin are reviewed. Radiographic capabilities in enhanced versus unenhanced MRI are compared. Temporal bone lesions, including acoustic neuromas and facial nerve neuromas, are presented. Recent experience with facial nerve enhancement in Bell's palsy is also presented. Greater accuracy in defining small temporal bone lesions and increased delineation of facial nerve involvement appear to be significant benefits with enhanced MRI.     

HLA-B27-associated uveitis with a chorioretinitis manifestation.

A 29-year-old man who had been treated for acute anterior uveitis in a local medical office and observed for 1 month presented complaining of distorted vision in his left eye for 1 week. On ophthalmic examination, the anterior segment was relatively quiet with few cells. A posterior segment examination revealed cystoid macular edema and multiple splinter retinal hemorrhages. Results of all laboratory and imaging studies were negative, except for a positive HLA-B27 haplotype. Fluorescein angiography revealed massive leakage in the mid and late phase, consistent with chorioretinitis. Periocular corticosteroid injections and oral prednisolone were administered. The patient responded to the treatment well with subsequent resolution of chorioretinitis 2 months later. Although rare, chorioretinitis can occur in the setting of uveitis associated with HLA-B27 and seems to respond well to corticosteroid treatment.     

The CarboMedics Prosthetic Heart Valve in the Mitral Position: Results of the Multicenter International Trial

A bstract Isolated mitral valve replacement using the CarboMedics prosthetic mitral valve (CarboMedics, Inc., Austin, TX) was studied in 13 centers in the United States, Canada, and Scandinavia between 1987 and 1993 in 428 patients with a mean age of 57 ± 14 years. Actuarial survivals at 1, 2, and 5 years were 88.2% and 75.8%. Freedom from events at 5 years were 94.8% for major thromboembolism, 96.6% for thrombosis, and 96.7% for endocarditis. Linearized morbidity rates (events per 100 patient years) for events at > 30 days postoperatively were .51 thrombosis, 1.1 major thromboembolism, and .37 endocarditis. These results at early to mid-term compare favorably with the first generation bileaflet valve.     

Passive electrical properties of motoneurons in aged cats following axotomy

The objective of this study was to determine whether the aging process influences the changes in the electrophysiological properties of motoneurons that occur as a consequence of axotomy. Accordingly, using intracellular recording and stimulating techniques, the basic electrical properties of control (unaxotomized) and axotomized spinal cord motoneurons of aged cats were determined. Compared with control motoneurons, axotomized motoneurons exhibited increases in input resistance (R_in), membrane time constant (τ_b) and the equalizing time constant (τ_c). While the electrotonic length (L) remained unchanged, axotomy induced a decrease in the total cell capacitance (C_cell. The post-axotomy reduction of C_cell indicates that the motoneuron surface area was reduced and the increased membrane time constant indicates that there was an increase in membrane resistivity (R_m). The post-axotomy conservation of L accompanied by an increase in R_m suggests that aged axotomized motoneurons undergo geometrical changes. Furthermore, calculations based on cable theory suggest that the diameter of the equivalent cylinder (d) decreased following axotomy, whereas the equivalent cylinder length (l) remained unaffected. It is concluded that axotomy produces significant alterations in the soma-dendritic portion of aged spinal motoneurons, as indicated by the changes found in their passive electrophysiological properties, and that the pattern of the response that occurs in axotomized motoneurons of adult cats is also present in axotomized motoneurons of aged animals.     

Cancer risk due to occupational exposure to polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) demonstrate carcinogenic activity in animal models. Although some epidemiologic studies have implicated PAHs as risk factors for human cancer, the evidence reported to date has not been consistent. The purpose of this report is to describe the associations between occupational exposure to PAHs in the workplace and each of 14 types of cancer. A population-based, case-control study was carried out in Montreal to investigate associations between a large variety of environmental and occupational exposures on the one hand, and several types of cancer on the other. A detailed job history was obtained from each subject along with information on a number of potential confounders. Each job history was reviewed by a team of experts, who used this information to construct a corresponding history of occupational exposures. Among the PAH exposures considered were benzo(a)pyrene (B(a)P) and five categories of PAHs defined on the basis of the source material, namely, wood, petroleum, coal, other sources, and any source. Altogether, 3,730 cancer patients and 533 population controls were interviewed and their job exposure histories coded. For each of 14 types of cancer analyzed, three control groups were available: other cancer patients, population controls, and the pooled set of cancer and population controls. The associations between 14 cancer types and 6 PAH exposures were analyzed using logistic regression methods. For most types of cancer evaluated, there was no evidence of excess risk due to PAHs at the levels encountered in the occupations in which PAH exposure has been prevalent in the Montreal area. For a few cancer sites–the esophagus, the pancreas, and the prostate gland–there were suggestions of excess risk; these observations are noteworthy hypotheses for further investigation. For lung cancer, there appeared to be an increased risk due to PAHs among nonsmokers and light smokers, but not among heavy smokers.     

Multidisciplinary preoperative assessment and late function in dysvascular amputees.

During a three-year period, 95 adults were treated by lower-extremity amputations for peripheral vascular insufficiency. A multidisciplinary team for presurgical evaluation determined all to be potentially independent walkers with a prosthesis. Patients were graded for level of independent walking before amputation and again at a minimum two-year follow-up examination using a seven-level functional grading system. Seventy-six of 90 patients (84%) ambulated within one functional level of their preamputation status. This return to preamputation level of function was maintained whether comparing preamputation functional level or surgical amputation level. Prosthetic use increased and the use of walking aids decreased with increased functional ambulation levels, but did not correlate with surgical levels. Peripheral vascular insufficiency patients can maintain walking independence. Multidisciplinary presurgical evaluation helps selection of the amputation level and correct prosthetic limb fitting.