Magnetic resonance imaging-based measurements of cerebrospinal fluid and blood flow as indicators of intracranial compliance in patients with Chiari malformation

OBJECT: The diagnosis of Chiari malformation (CM) is based on the degree of tonsilar herniation, although this finding does not necessarily correlate with the presence or absence of symptoms. Intracranial compliance (ICC) and local craniocervical hydrodynamic parameters derived using magnetic resonance (MR) imaging flow measurements were assessed in symptomatic patients and control volunteers to evaluate the role of these factors in the associated pathophysiology. METHODS: Seventeen healthy volunteers and 34 symptomatic patients with CM were studied using a 1.5-tesla MR imager. Cine phase-contrast images of blood and cerebrospinal fluid (CSF) flow to and from the cranium were used to quantify local hydrodynamic parameters (for example, cord displacement and systolic CSF velocity and flow rates) and ICC. The ICC was derived using a previously described method that measures the small, natural changes in intracranial volume and pressure with each cardiac cycle. Differences in the average cord displacement and systolic CSF velocity and flow, comparing healthy volunteers and patients with CM were not statistically significant. Note, however, that a statistically significant lower ICC (20%) was observed in patients compared with controls. CONCLUSIONS: Previous investigators have focused on CSF flow velocities and cord displacement to explain the pathogenesis of CM. Analysis of results have indicated that ICC is more sensitive than local hydrodynamic parameters to changes in the craniospinal biomechanical properties in symptomatic patients. The authors concluded that decreased ICC better explains CM pathophysiology than local hydrodynamic parameters such as cervical CSF velocities and cord displacement. Low ICC also better explains the onset of symptoms in adulthood given the decline in ICC with aging.     

Repair of pig dura in vivo using temperature controlled CO(2) laser soldering

BACKGROUND AND OBJECTIVES: The purpose of this study was to demonstrate that laser soldering might be successfully used for closing holes or cuts in the dura layer, which encapsulates the brain. STUDY DESIGN/MATERIALS AND METHODS: A temperature controlled fiberoptic CO(2) laser system and albumin solder were used for spot soldering of fascia patches to holes in the dura of farm pigs, in vitro and in vivo. RESULTS: The mean burst pressure of the soldered patches in the in vitro experiments was 190 +/- 88 mm Hg-significantly higher than typical maximum CSF pressure of 15 mm Hg. In the in vivo experiments the pigs showed no postoperative complications. Histopathological studies exhibited an accepted level of inflammatory reaction and showed no thermal damage to the underlying brain tissue. CONCLUSIONS: It has been clearly demonstrated that temperature controlled laser soldering is a very useful technique for the repair of the dura. It provides significant advantages over standard closure techniques: it is easy to apply, the bond is strong and watertight and the procedure is likely to be much faster than suturing. This research work will lead to clinical trials.     

Dental management of patients with myasthenia gravis: a literature review

Myasthenia gravis is a chronic neuromuscular disease characterized by muscular weakness and fatigability. Dental management of patients diagnosed with myasthenia gravis presents a challenge to the dental profession. A MEDLINE search of the English medical (limited to provision in dental care) and dental literature on myasthenia gravis and dental management published between 1975 and 2004 was conducted. In the dental literature, 12 articles were found, and only a few focused on myasthenia gravis and dental care. The purpose of this article was to review and summarize the clinical signs and symptoms associated with myasthenia gravis, highlighting the role of the dental profession in the process of the diagnosis and management of the oral and dental complications that might be associated with the disease, while avoiding myasthenic crisis.     

Endoscopic sinus surgery: where we are-and where we're going

PURPOSE OF REVIEW: Improved understanding of sinonasal mucociliary function as well as technological advancements have led to a renaissance in the management of sinonasal disease. The current techniques, and adjunctive intraoperative technologies, have allowed for a more precise and safer surgical dissection, extending this surgical application to include the routine endoscopic management of skull base lesions and sinonasal malignancies. The anatomic boundaries of the nasal endoscope continue to be redefined. This paper will review the recent advances in the field of surgical rhinology as well as discuss directions for the future. RECENT FINDINGS: Advancements in imaging technology including image acquisition, three-dimensional reconstruction, stereotactic navigation, and CT-MRI fusion have aided in more thorough preoperative planning, enabling safer and more precise endoscopic surgical dissection. Refinement of endonasal powered instrumentation including microdebriders and high-speed suction irrigation drills have minimized trauma to normal tissues and accelerated postoperative healing. Increased experience with the endoscope has broadened the endoscopic ventral skull base exposure from the odontoid process to foramen ovale to the olfactory bulb. SUMMARY: Endoscopic sinus surgery is no longer exclusively for the management of chronic rhinosinusitis and nasal polyposis. Sinonasal malignancies, as well as anterior skull base lesions have become part of the rhinologist's responsibility. Furthermore, selective lesions managed through traditional craniotomies may now be accessed via trans-sinonasal transcranial endoscopic routes.     

When blue is larger than red: colors influence numerical cognition in synesthesia

In synesthesia, certain stimuli ("inducers") may give rise to perceptual experience in additional modalities not normally associated with them ("concurrent"). For example, color-grapheme synesthetes automatically perceive achromatic numbers as colored (e.g., 7 is turquoise). Although synesthetes know when a given color matches the one evoked by a certain number, colors do not automatically give rise to any sort of number experience. The behavioral consequences of synesthesia have been documented using Stroop-like paradigms, usually using color judgments. Owing to the unidirectional nature of the synesthetic experience, little has been done to obtain performance measures that could indicate whether bidirectional cross-activation occurs in synesthesia. Here it is shown that colors do implicitly evoke numerical magnitudes in color-grapheme synesthetes, but not in nonsynesthetic participants. It is proposed that bidirectional coactivation of brain areas is responsible for the links between color and magnitude processing in color-grapheme synesthesia and that unidirectional models of synesthesia might have to be revised.     

The effect of repeated isoflurane anesthesia on spatial and psychomotor performance in young and aged mice

Exposure to general anesthesia may contribute to postoperative cognitive impairment in elderly patients, but the relationship remains poorly understood. We investigated whether aged mice, 18-19 mo, are more susceptible to postanesthetic cognitive impairment than young mice, 3-4 mo, using spatial memory (Barnes maze) and psychomotor (rotarod) tasks. Initially we studied the effect of a single anesthetic episode on asymptotic maze performance. We then tested whether repeated anesthesia would impair spatial memory and psychomotor performance to a greater extent in aged mice. Mice were anesthetized with isoflurane (1.4% atm) for 30 min; controls received 90% oxygen. Anesthesia, administered during the asymptotic period of maze learning, did not impair performance tested the following day (P > 0.05). Repeated anesthesia, 2-3 h after each session, did not impair overall maze or rotarod performance in young or aged mice (P > 0.05). Spatial learning appeared to be facilitated by anesthesia, F(1,204) = 7.97, P < 0.01 for pooled results. Asymptotic performance-when learning had stabilized-remained unimpaired in both the maze and rotarod tasks. These results suggest that an age-related risk of anesthetic-induced impairment appears to be limited to acquisition of a novel motor skill and that anesthesia alone does not lead to prolonged cognitive impairments in aged mice. IMPLICATIONS: This study demonstrates that repeated isoflurane general anesthesia impaired psychomotor performance in aged mice during the initial learning period; however, spatial learning improved and, overall, spatial memory and psychomotor performance were unimpaired. Thus, general anesthesia alone does not appear to result in prolonged cognitive deficits in aged mice.     

Glucuronidation as a mechanism of intrinsic drug resistance in colon cancer cells: contribution of drug transport proteins

We have recently shown that drug conjugation catalysed by UDP-glucuronosyltransferases (UGTs) functions as an intrinsic mechanism of resistance to the topoisomerase I inhibitors 7-ethyl-10-hydroxycamptothecin and NU/ICRF 505 in human colon cancer cells and now report on the role of drug transport in this mechanism. The ability of transport proteins to recognise NU/ICRF 505 as a substrate was evaluated in model systems either transfected with breast cancer-resistance protein 1 (Bcrp1), multidrug-resistance protein 2 (Mrp2) or Mrp3, or overexpressing MRP1 or P-170 glycoprotein. Results from chemosensitivity assays suggested that NU/ICRF 505 was not a substrate for any of the above proteins. In drug accumulation studies in human colon cancer cell lines NU/ICRF 505 was taken up avidly and retained in cells lacking UGTs (HCT116), whereas, following equally rapid uptake, it was cleared rapidly from cells displaying UGT activity (HT29) as glucuronide metabolites. HT29 cells were shown to express MRP1 and 3, but not P-170 glycoprotein, MRP2 or breast cancer-resistance protein. The major glucuronide of NU/ICRF 505 inhibited ATP-dependent transport of estradiol 17-beta-glucuronide in Sf9 insect cell membrane vesicles containing MRP1 or MRP3, while co-incubation of HT29 cells with the MRP antagonist, MK571, significantly restored intracellular concentrations of NU/ICRF 505. These data lead us to conclude that the presence of a glucuronide transporter is essential for glucuronidation to represent a major de novo resistance mechanism and that UGTs will contribute more as a primary resistance mechanism when the parent drug (e.g. NU/ICRF 505) is not itself recognised by transport proteins.