MRI of the intrinsic muscles of the hand: spectrum of imaging findings and clinical correlation.

OBJECTIVE: The purpose of our study was to describe the spectrum of intrinsic hand muscle abnormalities on MRI in patients with clinically evident abnormalities of the intrinsic hand muscles and to correlate clinical and radiologic findings. MATERIALS AND METHODS: MRI of 21 hands was performed in 19 patients with clinically evident or suspected intrinsic hand muscle abnormalities. All MRI was performed on a 1.5-T scanner using transaxial T1-weighted, T2-weighted, or STIR as well as contrast-enhanced T1-weighted sequences. Two observers reviewed all MR images retrospectively in a blinded fashion with regard to the exact anatomic location of the muscle abnormality, signal abnormalities, muscle atrophy, and the cause. Kappa statistics were used to calculate interobserver variability. MRI findings were compared with clinical findings using Spearman's rank test. A panel of experts assessed the impact of MRI on the diagnostic workup. RESULTS: On the basis of MRI findings, abnormalities (either MR signal abnormality or atrophy) of both the lumbrical and interosseus muscles were noted in 10 (48%) of 21 hands, of the thenar muscles in eight (38%) of 21 hands, and of the hypothenar muscles in 12 (57%) of 21 hands. The correlation between clinical and MRI findings was moderate to strong for the interosseus, thenar, and hypothenar muscles (0.43-0.84). MRI was judged to be useful for establishing the final diagnosis in 17 (81%) of 21 hands. CONCLUSION: MRI of the hands is useful and correlates well with clinical findings in patients with intrinsic hand muscle abnormalities.

Neurotropism revisited.

The purpose of this study is to re-examine the probable directive effect of the distal stump of a severed peripheral nerve on regenerating axons. Forssman postulated the existence of such a directive influence and Cajal interpreted it as chemotactic in nature. This view was subsequently refuted by Weiss and Taylor. In our study the proximal stumps of transected rodent sciatic nerve were inserted into the single inlet end of a Y-shaped autogenous inferior vena cava graft. Into one limb of the double outlet end, namely the common iliac nerve bifurcation, the distal stump of the same sciatic nerve was inserted, while the counter limb was ligated in one group, left open in the second group, inserted with a segment of autogenous tendon in the third, and grafted with a segment of autogenous nerve in the fourth group. Both outlets were left unoccupied in yet another group as the control. The vena cava conduit was prepared so that a 1.5 cm gap existed between the proximal stumps of the sciatic nerve and the distal sciatic nerve stumps and the tendon grafts respectively. The grafted sciatic nerves were explored and biopsied after 12 weeks. The direction of nerve tissue regeneration in each group was analyzed histologically. Predilection of the regenerating nerve fibers toward the distal stumps was observed in each of the test groups. These results indicate the existence of a guiding influence at the distal stump toward the regeneration nerve fibers.

Functional, electrophysiologic, and morphometric evaluation of nerve regeneration from coaptation on regenerated nerve fibers: experimental study in rabbits.

The importance of a sufficient number of nerve fibers at a proximal coaptation site is indisputable for the successful repair of nerves; however, the quality of nerve fibers required at this site has yet to be defined. The present study deals with the question of whether it is necessary to trim nerves back to unaffected neuronal tissue or whether the coaptation on recently regenerated nerve fibers, commonly believed to produce a poor quality of repair can, in fact, produce adequate nerve regeneration. Twenty New Zealand White rabbits received a standardized crush lesion on the peroneal nerves of both hind legs. Four weeks later, the nerves of the left hind legs (n = 20) were transected 10 mm distal to the previous crush lesion and coapted to the freshly regenerated nerve fibers. For comparison, on 10 right hind legs, the nerves were transected at the site of previous crushing (Group A, superimposition) or 10 mm proximal to the site of crushing on unscathed nerve fibers (Group B). Eleven weeks later, the quality of nerve regeneration was assessed by the toe-spreading reflex, electrophysiologic data, muscle weight, and histomorphologic evaluation. In the animals of Group A, the quality of nerve regeneration following coaptation on the regrown axons did not differ in any of the examined parameters from the quality of nerve fibers outgrown from the site of the superimposed lesion. Both lesions led to a completely functional reinnervation. Also in Group B, nerve action potential recording and histologic data on both sides did not reveal a significant difference between the number and maturation of nerve fibers equidistant from the suture site, shortly before muscle entrance. With this coaptation model, it could be demonstrated in the peroneal nerve of rabbits, that coaptation to recently regenerated nerve fibers leads to a significant functional regeneration.

Incidence of the superficial fascia and its relevance in skin-sparing mastectomy.

BACKGROUND: With the move away from classical radical mastectomy to ever more skin-sparing procedures, there has been an ongoing discussion about how much skin and subcutaneous tissue should be resected to perform an adequate mastectomy while leaving viable skin flaps. One of the common recommendations is to dissect just superficial to the superficial layer (SL) of the superficial fascia of the breast. This, in turn, has revived the old, unsolved controversy about the existence or absence of the SL, a fascia that reportedly encloses the mammary gland ventrally. In skin-sparing mastectomies (SSM), which combine tumor resection with immediate breast reconstruction, the ideal would be to create skin flaps that are thin enough to remove all breast tissue but at the same time are thick enough to preserve flap circulation. The feasibility of meeting these two goals simultaneously and the possible role and relevance of the SL as a guide to dissection in SSM was examined in this study. METHODS: Sixty-two breast resection specimens from 31 women who underwent breast reduction were examined histologically to determine whether the SL was present, whether breast tissue could be detected within or beyond this SL, the measured distance between the caudal border of the dermis and the SL or the breast tissue, and whether the thickness of the subcutaneous fat layer was correlated with the patients' physical data, such as body weight or body mass index (BMI). RESULTS: The SL was absent in 44% of resection specimens. When the SL was present, 42% of specimens contained several islands of breast tissue within the SL. No breast tissue was found beyond the SL. The minimal distance between the SL and the dermis varied from 0.2 mm to 4.0 mm; the minimal distance between the breast tissue and the dermis was 0.4 mm. In 50% of specimens, the minimal distance between the dermis and the SL or breast tissue was < 1.1 mm. A distance of > or = 5 mm was encountered in only 17% of specimens, and a distance of > or = 10 mm was encountered in only 5% of specimens. No significant correlation between the right and left breast was found with any of the parameters examined. A weak negative correlation was seen between the BMI and the mean thickness of the subcutaneous fat (P = 0.049; correlation coefficient [r] = -0.39; Spearman rank correlation). CONCLUSIONS: Histologic evaluation revealed that the SL is not present in all breasts and, thus, cannot serve as a reliable plane of dissection. Furthermore, if the SL is present microscopically, then it often is too thin and delicate to be detectable macroscopically. Finally, even if the SL is present and visible macroscopically, the distance to the overlying skin is so small in the majority of patients that a dissection superficial to the SL would not leave viable skin flaps in skin-sparing mastectomies.