The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.

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trauma. These metaphyseal abnormalities were identified from postmortem radiography and correlated with microscopy. The authors concluded the metaphyseal alterations represented partial or complete planar microfractures that transected the primary spongiosa adjacent to the growth plate. These microfractures usually resembled a "bucket-handle" or a "corner fracture," depending on the angulation of the x-ray beam relative to the true long axis of the extremity. These injuries are in distinction to the well-recognized SalterHarris type II injuries that are also commonly referred to as "corner" fractures.Recent case series have reported the presence of infantile rickets in young infants being evaluated for unexplained fractures mim- AJR 2014; 202:185-196 OBJECTIVE. The purpose of this study was to review the hypothesis that classic metaphyseal lesions represent traumatic changes in abused infants and compare these lesions with healing rickets. A Critical Pe d i a t r ic I m ag i ng • O r ig i n a l R e s e a rc hMATERIALS AND METHODS. Using a PubMed search, a multidisciplinary team reviewed studies that reported the histopathologic correlation of classic metaphyseal lesions. Selective studies of growth plate injury and rickets were cross-referenced.RESULTS. Nine identified classic metaphyseal lesion studies were performed by the same principal investigator. Control subjects were inadequate. Details of abuse determination and metabolic bone disease exclusion were lacking. The presence of only a single radiology reviewer prevented establishment of interobserver variability. Microscopy was performed by two researchers who were not pathologists. Classic metaphyseal lesions have not been experimentally reproduced and are unrecognized in the accidental trauma literature. The proposed primary spongiosa location is inconsistent with the variable radiographic appearances. Classic metaphyseal lesions were not differentiated from tissue processing artifacts. Bleeding and callus were uncommon in spite of the vascular nature of the metaphysis. The conclusion that excessive hypertrophic chondrocytes secondary to vascular disruption were indicative of fracture healing contradicts the paucity of bleeding, callus, and periosteal reaction. Several similarities exist between classic metaphyseal lesions and healing rickets, including excessive hypertrophic chondrocytes. "Bucket-handle" and "corner fracture" classic metaphyseal lesions resemble healing rickets within the growth plate and the perichondrial ring, respectively. The age of presentation was more typical of bone fragility disorders, including rickets, than reported in prior child abuse series.CONCLUSION. The hypothesis that classic metaphyseal lesions are secondary to child abuse is poorly supported. Their histologic and radiographic features are similar to healing infantile rickets. Until classic metaphyseal lesions are experimentally replicated and independently validated, their traumatic origin remains unsubstantiated.Ayoub et al.

Quantitative analysis of Golgi-stained neurons in the preoptic area of the brain of prepuberal Macaca fascicularis monkeys indicated structural differences between males and females. Neurons of males had more dendritic bifurcations and a higher frequency of spines. The bifurcation difference appeared in all cell types and was concentrated in the ventrolateral preoptic area. The spine difference was greatest in the central region of the preoptic area. No differences in gross measurements of this brain region were found. These results suggest that sexual dimorphism in the function of the monkey preoptic area may be based on differences in neuronal structure.