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Diffusion-weighted and transversal relaxation time (T,)-weighted magnetic resonance imaging were used to study the relationship between the duration of hypoxia-ischemia [unilateral common carotid artery (CCA) ligation and exposure to 8% oxygen] and the in vivo visualization of brain edema in 7-d-old rats. After CCA ligation, 35 animals were divided into five groups according to the length of exposure to 8% oxygen: no exposure (n = 9), 15 min (n = 12), 30 min (n = 5), and 1 h (n = 9) exposure; six animals served as controls. Diffusion weighted images were acquired 2 h after the hypoxic-ischemic insult, sequential T, weighted images were recorded for up to 7 d and the outcome was documented by histologic examination at 21 d. The apparent diffusion coefficient of water in the ipsilateral cortex was significantly decreased in all animals recovering from prolonged hypoxic-ischemic insult (30 min and longer), whereas this was the case in only 40% of animals exposed to 15 min of hypoxia. Moreover, T, prolongation of brain tissue occurred only in the former group. These results indicate transient and reversible alterations of physiologic water compartmentation for short term hypoxia-ischemia, but irreversible edema formation for long term hypoxia-ischemia. They support the hypothesis that the duration of hypoxia-ischemia determines whether a vasogenic edema and infarction follows the initial cytotoxic edema. 38: 113-118, 1995) Abbreviations ADC,, apparent diffusion coefficient of water CCA, common carotid artery DWI, diffusion weighted imaging ECMO, extracorporeal membrane oxygenation GFAP, glial fibrillary acidic protein MRI, magnetic resonance imaging RARE, rapid acquisition with relaxation enhancement T,, transversal relaxation time T2W1, T, weighted imaging T, , mixing time T,, time to echo T,, time to repeat Over the past few years, a large number of animal studies have contributed to a better understanding of the pathogenesis of perinatal hypoxic-ischemic brain damage (1-8) and accompanying cerebral edema (2). This is largely due to the adaptation of the Levine preparation (9)-unilateral CCA ligation with subsequent hypoxia-to 7-d-old neonatal rats (I), whereby unequivocal unilateral brain damage can be produced. This animal model admits to titrate the severity of hypoxicischemic lesions by varying the duration of hypoxia (exposure to 8% oxygen). The extent of brain damage to the ipsilateral hemisphere was classified as mild cerebral edema after 1 h of hypoxia, or progressively increasing edema after 3 h of hypoxia (2). In particular, no brain damage was observed after CCA ligation alone (1, 2). This is an important observation, e.g. in the context of ECMO for severe respiratory failure in newborn infants, which involves permanent unilateral CCA ligation (10). In this regard, ECMO bears the risk of hypoxicischemic encephalopathy resulting from the combination of hypoxia and hypoperfusion during or after the procedure (11,12). (Pediatr ResThe noninvasive nature of MRI together with the sensitivity of the contras...

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The aim of this study was to collect information about the incidence of leg-length discrepancy, axis deviation and instability resulting from fractures about the knee in childhood. We reviewed 43 patients with a clinical and radiological examination after a mean follow-up period of 13 years. The fractures were divided into four subgroups, each one presenting typical problems. Growth disturbance (shortening and axis deviation) making secondary procedures necessary was seen in 5 out of 14 (36%) distal femoral epiphyseal fractures. Complex instability was observed in 3 out of 7 (43%) proximal tibial epiphyseal fractures. In the tibial spine fractures anatomical reduction often did not prevent moderate cruciate ligament insufficiency; and in the metaphyseal fractures 2 of the 7 cases showed leg-lenghtening. In conclusion, the Salter classification seems to be of little prognostic value at the knee as Type-II fractures are frequently followed by asymmetric growth arrest. Open reduction is not reliable in avoiding this complication. Associated ligament injuries are not rare and deserve more attention.