A novel technique for safe percutaneous biopsy of a petrous apex lesion.

Lesions within the skull base are the most challenging targets for percutaneous biopsy due to the likelihood of encountering a critical structure along any needle trajectory. Due to ICA proximity, the petrous apex is considered unsafe. We describe a novel percutaneous CT-guided approach for biopsying a petrous apex lesion via a contralateral mandibular condylar notch (subzygomatic approach). To our best knowledge, this approach has not been reported and can be safely employed with thorough planning.

Chordoid glioma: a rare old foe but a new pathological and radiological presentation.

Chordoid glioma (CG) is a rare WHO Grade II neoplasm of the anterior third ventricle. We report two cases of CG with new presentation in terms of histopathology and location: a case of CG with osseous metaplasia evident on imaging, and another CG, unusually located in the posterior portion of the third ventricle.

Body Mass Index: A Reliable Predictor of Subcutaneous Fat Thickness and Needle Length for Ventral Gluteal Intramuscular Injections.

BACKGROUND: With rising prevalence of obesity, increasing number of gluteal injections would be expected to fail in intramuscular (IM) drug delivery. STUDY QUESTION: This study evaluated ventral gluteal fat thickness (VGT) on adult magnetic resonance imaging of pelvis and correlated it with the subjects' body mass index (BMI), weight, and height to establish evidence-based clinical estimates of individualized needle length and suitability of ventral gluteal site for IM injections. DESIGN: Retrospective review. STUDY DESIGN, MEASURES AND OUTCOMES: Three hundred fifty adult (224 women, 126 men) magnetic resonance imaging scans of pelvis were reviewed to measure the VGT as the distance between the skin and the nearest edge of the gluteus medius muscle at the recommended ventral gluteal injection site. VGT was correlated with BMI, weight, and height by multivariate analysis. RESULTS: Fifty-three (49 women, 4 men) subjects had VGT greater than 3.3 cm, and 146 (106 women, 40 men) subjects had VGT greater than 2.0 cm. The Pearson correlation coefficient between VGT and BMI was 0.82 for women and 0.81 for men. The difference between the VGT in men and women of comparable BMI was statistically significant (P < 0.001). BMI of 30 in women and 35 in men seem to be upper limits for successful ventral gluteal IM injections with 3.75-cm (1.5-inch) hypodermic needle. The expected failure rate of ventral gluteal IM delivery with the 3.75-cm needle is 71% in women with BMI >30, and 60% in men with BMI >35. CONCLUSION: BMI is reliably predictive of VGT in both men and women for selecting appropriate needle length for IM injections at this site. Standard needles would fail in IM delivery at this site in a considerable proportion of obese adults. Because of high prevalence of obesity in individuals with severe mental illness, our findings could significantly impact acute and maintenance therapy with injectable tranquillizers and antipsychotics.

A Large Cohort Study of 18F Fluoro-Deoxy-Glucose Uptake in Normal Spinal Cord: Quantitative Assessment of the Contamination From Adjacent Vertebral Marrow Uptake and Validity of Normalizing the Cord Uptake Against the Lumbar Thecal Sac.

PURPOSE: This study aimed (1) to assess the influence of age, sex, blood glucose, and body mass index on the F fluoro-deoxy-glucose (F-FDG) uptake in normal spinal cord; (2) to quantitatively evaluate contamination of the spinal cord SUVmax by the adjacent vertebral marrow activity; and (3) to investigate the validity of normalizing spinal cord SUVmax against lumbar thecal sac SUVmax. METHODS: Two hundred positron emission tomography-computed tomography examinations of subjects with normal spinal cord were retrospectively reviewed. SUVmax of spinal cord and vertebral body was obtained at C2, C5, T6, T12, and L3 levels. Pearson correlation coefficients (r) were obtained at each level between spinal cord SUVmax and vertebral marrow SUVmax, age, body mass index, and blood glucose. Cord to background ratio (CTB) was calculated as the ratio between SUVmax of spinal cord and SUVmax of L3 thecal sac. The coefficient of variation (CV) of spinal cord SUVmax was compared with the CV of CTB. RESULTS: Spinal cord SUVmax was highest at C2 (mean, 1.76) and lowest at T6 (mean, 1.37) with SD of 0.32 to 0.36 SUV. Sex (P > 0.45), age (r: -0.25 to -0.06), body mass index (r: 0.19 to 0.27), and blood glucose (r: -0.17 to 0.22) had no impact on the spinal cord SUVmax. A moderate to strong positive correlation (r: 0.66-0.80) was found between spinal cord SUVmax and the corresponding vertebral marrow SUVmax. The CV of CTB was greater (0.28-0.32) than the CV of spinal cord SUVmax (0.19-0.25) across all levels. CONCLUSIONS: Of the variables studied, only contamination from adjacent vertebral marrow activity significantly affected the SUVmax of spinal cord. This contamination should be corrected for when reporting spinal cord FDG uptake. Lumbar thecal sac is not a valid reference for normalizing spinal cord FDG uptake.