De novo development of gliomas in a child with neurofibromatosis type 1, fragile X and previously normal brain magnetic resonance imaging.

Fifteen to 20% of children with neurofibromatosis type 1 develop low-grade glial neoplasms. However, since neuroimaging is not routinely obtained until a child is clinically symptomatic, little is known about presymptomatic radiographic characteristics of gliomas in this at-risk population. Herein, we describe a child with neurofibromatosis type 1 who initially had normal brain imaging before the development of multifocal gliomas. Comparison of these serial images demonstrated that brain tumors can arise de novo in children with this cancer predisposition syndrome, further underscoring the limited prognostic value of normal baseline magnetic resonance imaging.

The impact of surgeon specialization on patient mortality: examination of a continuous Herfindahl-Hirschman index.

OBJECTIVE: To examine the effect of surgeon specialization on patient outcomes, controlling for volume. BACKGROUND: There is great interest in the degree to which surgical specialization affects outcomes, particularly considering drives to measure and reward quality in healthcare. Although surgical specialization has been previously analyzed with respect to outcomes, most studies have treated it as a dichotomous variable based on academic credentials. We treat it here as a continuous variable defined quantitatively by procedural diversity. METHODS: We used 2002 to 2005 patient data from the National Surgical Quality Improvement Program for the Department of Surgery, Barnes Jewish Hospital, St. Louis, Missouri. To quantitate procedural specialization, Herfindahl-Hirschman indices for surgeons were calculated using billing codes. These indices were calculated according to 3 different levels of procedural aggregation. Using conditional logit models, we examined the relationship between these indices and 30-day postoperative mortality rates. RESULTS: Surgeon specialization was inversely related to mortality rates after adjusting for case volume when indices were calculated using medium procedural aggregation (odds ratio for mortality = 0.580 per 0.1 unit Herfindahl increase; P = 0.025) or low aggregation (odds ratio for mortality = 0.510 per 0.1 unit Herfindahl increase; P = 0.015). No relationship was observed at the high level of aggregation. CONCLUSIONS: The procedural concentration component of surgical specialization is correlated with improved mortality rates independently of case volume. However, how broadly or narrowly "specialization" is defined has an impact on this relationship.

Temporal characteristics of semantic perseverations induced by blocked-cyclic picture naming.

When unimpaired participants name pictures quickly, they produce many perseverations that bear a semantic relation to the target, especially when the pictures are blocked by category. Evidence suggests that the temporal properties of these "semantic perseverations" may differ from typical lexical perseverations in aphasia. To explore this, we studied semantic perseverations generated by participants with aphasia on a naming task with semantic blocking [Schnur, T. T., Schwartz, M. F., Brecher, A., & Hodgson, C. (2006). Semantic interference during blocked-cyclic naming: Evidence from aphasia. Journal of Memory and Language, 54, 199-227]. The properties of these perseverations were investigated by analyzing how often they occurred at each lag (distance from prior occurrence) and how time (response-stimulus interval) influenced the lag function. Chance data sets were created by re-shuffling stimulus-response pairs in a manner that preserved unique features of the blocking design. We found that the semantic blocking manipulation did not eliminate the expected bias for short-lag perseverations (recency bias). However, immediate (lag 1) perseverations were not invariably the most frequent, which hints at a source of inconsistency within and across studies. Importantly, there was not a reliable difference between the lag functions for perseverations generated with a 5s, compared to 1s, response-stimulus interval. The combination of recency bias and insensitivity to elapsed time indicates that the perseveratory impetus in a named response does not passively decay with time but rather is diminished by interference from related trials. We offer an incremental learning account of these findings.