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Giant plexiform neurofibroma (GPNF) of the scalp is an extremely rare lesion reported in association with neurofibromatosis. Occipital location of GPNF is even more infrequent, especially in association with occipital dysplasia (OD). The authors report 2 pediatric cases of GPNF associated with OD. The first case had an associated meningoencephalocele, and the second had large vascular channels within the lesion and the dominant ipsilateral transverse sinus lying in the center of the calvarial defect. The authors present these 2 unusual cases with a review of literature and discuss the radiological findings, theories of etiopathogenesis of the OD, and management dilemmas.

THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCESPropionibacterium acnes (P. acnes) is an anaerobic grampositive bacillus found as a normal component of the bacterial flora of the skin, hair follicles and sebaceous glands. Although the majority of patient isolates are thought to be contaminants, Propionibacterium acnes does cause significant disease in a small subset of patients after neurosurgical procedures. 1Ventriculoperitoneal shunt infections are the most commonly reported type of P. acnes infection in the neurosurgical literature.2,3 However, several reports describe P. acnes infections after craniotomy [4][5][6][7][8] and it has been suggested that central nervous system infections caused by P. acnes are more important than previously recognized. We report on our single ABSTRACT: Background: Propionibacterium acnes (P. acnes) is a relatively avirulent organism that is part of the normal skin flora. Most patient isolates are considered contaminants but, in a small subset of patients, particularly in the post-neurosurgery setting, the organism can cause significant infections. We reviewed our experience with the occurrence and management of P. acnes infections after cranial neurosurgical procedures over a five-year period. Methods: Patients with positive cultures for P. acnes between 1996 and 2001 were identified by review of the Saskatoon Health Region microbiology laboratory database. Of the 141 positive cultures, a review of hospital records identified six patients with P. acnes infections after neurosurgical procedures. A review of the literature related to P. acnes associated CNS infections was conducted. Results: All patients had undergone a craniotomy or burrhole placement, and one patient had received prior radiotherapy. There were no P. acnes-related ventriculoperitoneal shunt infections. All patients presented with scalp swelling and three had purulent discharge. Symptoms occurred more than two months after the initial surgery in five of six patients, while one patient developed symptoms three years post-operatively. Management for all patients included removal of the craniotomy flap and treatment with parenteral antibiotics, followed in most cases by oral antibiotics. A good response without relapse of infection was seen in five patients; one patient had recurrent infection after cranioplasty. Conclusions: P. acnes is a rare but important cause of infection after craniotomy. Wound debridement, removal of the bone flap and adequate antibiotic coverage result in cure in the majority of patients.RÉSUMÉ: Infection à Corynebacterium acnes après une neurochirurgie crânienne. Contexte : Le Corynebacterium acnes est un organisme relativement avirulent qui fait partie de la flore cutanée normale. On considère que la plupart des isolats de patients sont des contaminants. Cependant chez un petit sous-groupe de patients, particulièrement après une neurochirurgie, ce microorganisme peut causer des infections importantes. Nous revoyons notre expérience sur une période de 5 ans de l'infection à C. acnes et de son ...

In any Nash equilibrium no player will unilaterally deviate. However, many games have multiple Nash equilibria. In this paper, we survey some refinements of Nash equilibria based on the hypothesis that any player may consider a deliberate deviation from a Nash equilibrium vector while expecting other players to respond optimally to this deviation. The concepts studied here differ in the expectations players have about other players' responses to a deviation. This sort of deviations philosophy is predicated on the thought process of players. Therefore, the validity of a particular equilibrium concept to an economic model may depend upon the relevance of the thought process implied by the concept.