Examining the frontal subcortical brain vulnerability hypothesis in children with neurofibromatosis type 1: Are T2-weighted hyperintensities related to executive dysfunction?

OBJECTIVE: It was hypothesized that neuropsychological impairments in children with neurofibromatosis type I (NF1) are associated with brain areas of increased T2-weighted signal intensity on MRI. Systematic and extensive examination of this hypothesis remains however scarce, particularly regarding executive dysfunction whereas hyperintensities are located preferentially in frontal-sub-cortical networks. In this study, we compared the executive functioning profile with characteristics of brain hyperintensities in children with NF1. METHOD: A sample of 36 school-age children with NF1 (7-12 years) underwent a detailed examination of executive function, including performance-based tests and child's behavior rating in daily life. Executive function measures were compared with the characteristics of the T2-weighted hyperintensities on parallel MRI scans. The presence, number, and size of hyperintensities in the whole brain were considered as well as their main cerebral locations. RESULTS: Executive dysfunction including traditional cognitive and ecological measures in children with NF1 is not significantly influenced by T2-weighted hyperintensities, in terms of presence or not, number, size, and location, whether in the whole brain or according to involved specific brain areas. CONCLUSION: T2-weighted hyperintensities, as they are currently measured, cannot be used as a strong indicator of executive dysfunction in children with NF1. Based on the available NF1 cognitive impairment pathogenesis models, a critical discussion on anatomical-functional relationships between hyperintensities and neuropsychological profile is proposed, especially the executive dysfunction.

Relationships between bone mass and micro-architecture at the mandible and iliac bone in edentulous subjects: a dual X-ray absorptiometry, computerised tomography and microcomputed tomography study.

OBJECTIVES: To compare bone volume, bone mineral density, cortical thickness and bone micro-architecture in a series of paired mandibular and iliac bone samples analysed by various imagery techniques to see whether relationships exist between the various techniques and between mandibular and iliac bone. MATERIALS AND METHODS: Bone samples from the mandible and ilium were harvested in 20 cadavers and analysed by dual energy X-ray absorptiometry (DXA), computerised tomography (CT) on a conventional hospital machine and microCT. RESULTS: Significant correlations were found between Hounsfield density obtained by CT, and bone mass determined by microCT but not with DXA values. Cortical thickness measurements were well correlated between CT and microCT. No relationships were found between mandibular and iliac bone, when considering mineral density, cortical thickness, bone volume or micro-architecture. CONCLUSION: In clinical practice, CT remains the most appropriate routine means for bone qualitative and quantitative evaluation at the mandible. In this ex vivo study, these results confirm that mandibular bone status does not reflect the axial skeletal one and assist in the placement of implants with dental prostheses in old or osteoporotic patients.

Correlating implant stability to bone structure.

OBJECTIVES: The aim of this study was to demonstrate a possible correlation between bone microarchitecture and primary implant stability. MATERIAL AND METHODS: Twenty-two implants (Ankylos((R)) and Straumann((R))) were inserted into the maxillae and mandibles of human cadavers. Bone structure was determined by computed tomography in three specimens (male, age 53; female, 67; female, 80). A strict clinical protocol was used for implantation. Primary implant stability was measured by resonance frequency analysis (Osstell Mentor). The bone structure was analyzed by micro-computed tomography (CT). Bone histomorphometrical parameters were calculated and correlated to primary implant stability. RESULTS: Implant stability quotients (ISQ) ranged from 50 to 70% depending on the specimens and sites. Histomorphometry indicated differences in the bone microstructures of the specimens. However, ISQ values were not related to trabecular bone histomorphometrical parameters. The sole correlation was found between ISQ values and cortical bone thickness. CONCLUSION: This study confirms the relevance for primary stability of cortical thickness around implants. The thickness of cortical bone can be assessed using a standard clinical CT.

Spontaneous sphenoid sinus mucocele revealed by meningitis and brain abscess in a 12-year-old child.

Sphenoid sinus mucocele is an uncommon lesion related to inflammatory disease that is diagnosed after surgery or a traumatic event. This report describes an unusual case revealed by bacterial meningitis and cerebral abscess in a 12-year-old child. CT and MR imaging allowed precise extension to the skull base in preoperative management and follow-up investigations. Endoscopic transnasal marsupialisation of the mucocele and antibiotic therapy led to complete remission. There was no evidence of recurrence after 6 months, which suggests that sphenoid mucoceles, regardless of size and complications, can be treated by endoscopic sinus surgery.

[Non-invasive evaluation of an injectable bone substitute]. / Méthods non invasive d'évaluation d'un substitut osseux injectable.

Despite the increasing number of techniques for the preservation of bone ridges after dental avulsion, no precise evaluation of alveolar filling has been performed to date. The criteria of available measurement techniques (probes, retroalveolar or panoramic radiography, and lateral teleradiography) are not sufficiently reliable and precise. This study investigated the reliability of evaluation based on CT images in comparison with retroalveolar radiography (the most precise radiographic technique, providing standardised images), direct measurements, and images obtained in scanning electron microscopy. After a preliminary investigation ex vivo, a study was performed in vivo on three beagles. Mandibular premolars were extracted, and the corresponding alveoli were filled with an injectable bone substitute composed of a calcium phosphate mineral load associated with hydroxypropyl methylcellulose. Measurements performed on CT images relative to visual and automatic detection of density changes and studies of density curves provided better precision than those obtained by retroalveolar radiography.