MR imaging of Schmorl's nodes: Imaging characteristics and epidemio-clinical relationships.

PURPOSE: The purpose of our prospective study was to assess the presentation of Schmorl's nodes (SN) on magnetic resonance imaging (MRI) and investigate their possible association with demographic and clinical findings. MATERIALS AND METHODS: Three hundred and thirty-three patients were prospectively included. Thirteen (3.9%) patients were excluded because of contraindication to MRI and/or Scheuermann's disease. The final study population included 320 patients. T1-weighted and short TI inversion recovery sequences were performed to assess SN prevalence, the vertebral level and their anatomical distribution in vertebra. Medical history was recorded focusing on previous diseases including degenerative, rheumatoid and neoplastic disease, and any existing spinal traumatism. Epidemiological information was also obtained, including age, gender, ethnicity, professional and sporting activity. RESULTS: The final study population included 320 patients (172 men, 148 women) with a mean age of 54 years±17.5 (SD) (range: 19-87 years). A total of 421 SN were found in 158/320 patients (49.4%). SN were localized in thoracic spine for 48%, in lumbar spine for 46% and cervical spine for 6%. The middle part of the thoracic vertebra was the most affected area (80%), mostly in the middle superior endplate (41%). SN were more frequently observed in manual workers who worked more than 10 years (P<0.0001) and less frequently in patients of the 30-39-year-old age group (P=0.0048). No significant associations were found with gender (P=0.17) and remarkable medical history (P=0.21). SN were less frequently observed in patients with sport activities of 1-5hours/week (P=0.04) and those with an African origin (P<0.0001). CONCLUSION: Our study suggests a potential role for ethnical and physical factors in the pathogenesis of SN. Furthers studies are mandatory to evaluate their clinical relevance, especially in patients such as Caucasian manual workers in whom SN have a high prevalence.

Imperfect genes, Fisherian mutation and the evolution of sex.

In this paper we present a mathematical model of mutation and selection that allows for the coexistence of multiple alleles at a locus with very small selective differences between alleles. The model also allows for the determination of fitness by multiple loci. Models of this sort are biologically plausible. However, some previous attempts to construct similar models have assumed that all mutations produce a decrease in fitness, and this has led to a tendency for the average fitness of population members to decline when population numbers are finite. In our model we incorporate some of the ideas of R. A. FISHER, so that both deleterious and beneficial mutations are possible. As a result, average fitness tends to approach a stationary distribution. We have used computer simulation methods to apply the Fisherian mutation model to the problem of the evolution of sex and recombination. The results suggest that sex and recombination can provide very large benefits in terms of average fitness. The results also suggest that obligately sexual species will win ecological competitions with species that produce a substantial fraction of their offspring asexually, so long as the number of sites under selection within the genomes of the competing species is not too small and the population sizes are not too large. Our model focuses on fertility selection in an hermaphroditic plant. However, the results are likely to generalize to a wide variety of other situations as well.

Surgery for the treatment of locally recurrent disease.

BACKGROUND AND METHODS: Total pelvic exenteration is a salvage procedure done in the effort to eliminate completely pelvic cancer. Low colorectal anastomosis and continent urinary diversion are two new procedures that allow complete pelvic evisceration without the need for external appliances. From 1984 through 1994, 67 patients have undergone rectosigmoid colectomy and low-colorectal anastomosis. Sixteen patients underwent surgery as part of a total pelvic exenteration for recurrent cervical cancer, and 51 patients underwent surgery for either primary or recurrent ovarian carcinoma as part of an optimal debulking procedure. Between 1988 and 1995, 55 patients have received continent urinary diversion with the Miami Pouch. Fifty-two patients underwent surgery for recurrent cervical cancer, two patients for advanced vulvar cancer, and one patient for a vesico-vaginal fistula. All of the patients with recurrent cervical cancer had previously received radiation therapy for gynecologic cancer. RESULTS: Of the 16 patients with recurrent cervical cancer who had a low colorectal anastomosis, 14 had a temporary colostomy. Of these 14 patients, eight had a colostomy takedown and have maintained fecal continence. Of the 51 patients with ovarian cancer who had a low colorectal anastomosis, all achieved fecal continence. With the Miami Pouch, a urinary continence rate of 86% was obtained. Twenty-four (44%) patients had early complications, including ureteral obstruction, ureterocolonic anastomotic leak, reservoir cutaneous fistula, small bowel obstruction, and pyelonephritis. Nineteen (35%) patients had late complications, including ureteral reflux, urinary incontinence, difficult catheterizations, and reservoir stones. There was a perioperative mortality rate of 5%. CONCLUSIONS: Low-colorectal anastomosis is an attractive alternative to permanent colostomy, allowing all patients who had the protective colostomies taken down to achieve fecal continence. Continent urinary diversion with the Miami Pouch is also a worthwhile procedure because of its high continence rate. Although survival advantage for either procedure has not been proven, the quality of life of patients undergoing such procedures has been substantially improved because of the avoidance of external appliances. This has been achieved with acceptable morbidity and mortality rates.