Imaging of the Craniocervical Junction: A Pictorial Review.

The craniocervical junction (CCJ) is a complex anatomical structure comprising the occiput, the atlas, and the axis. The CCJ plays an important role in maintaining stability, providing protection, and supporting neurovascular structures. The CCJ can be affected by a wide range of congenital variants and traumatic, degenerative, inflammatory, and tumoral pathologies. This pictorial review the normal anatomy of the CCJ and presents the most common anatomical variants and pathologic conditions affecting the CCJ.

An observational cohort study of histological screening for BK polyomavirus nephropathy following viral replication in plasma.

Systematic screening for BKPyV-DNAemia has been advocated to aid prevention and treatment of polyomavirus associated nephropathy (PyVAN), an important cause of kidney graft failure. The added value of performing a biopsy at time of BKPyV-DNAemia, to distinguish presumptive PyVAN (negative SV40 immunohistochemistry) and proven PyVAN (positive SV40) has not been established. Therefore, we studied an unselected cohort of 950 transplantations, performed between 2008-2017. BKPyV-DNAemia was detected in 250 (26.3%) transplant recipients, and positive SV40 in 91 cases (9.6%). Among 209 patients with a concurrent biopsy at time of first BKPyV-DNAemia, 60 (28.7%) biopsies were SV40 positive. Plasma viral load showed high diagnostic value for concurrent SV40 positivity (ROC-AUC 0.950, 95% confidence interval 0.916-0.978) and the semiquantitatively scored percentage of tubules with evidence of polyomavirus replication (pvl score) (0.979, 0.968-0.988). SV40 positivity was highly unlikely when plasma viral load is below 4 log10 copies/ml (negative predictive value 0.989, 0.979-0.994). In SV40 positive patients, higher plasma BKPyV-DNA load and higher pvl scores were associated with slower viral clearance from the blood (hazard ratio 0.712, 95% confidence interval 0.604-0.839, and 0.327, 0.161-0.668, respectively), whereas the dichotomy positivity/negativity of SV40 immunohistochemistry did not predict viral clearance. Although the pvl score offers some prognostic value for viral clearance on top of plasma viral load, the latter provided good guidance for when a biopsy was unnecessary to exclude PyVAN. Thus, the distinction between presumptive and proven PyVAN, based on SV40 immunohistochemistry, has limited clinical value. Hence, management of BKPyV-DNAemia and immunosuppression reduction should be weighed against the risk of occurrence of rejection, or exacerbation of rejection observed concomitantly.

Lunotriquetral Coalition.

Lunotriquetral (LT) coalition is the most common carpal coalition. Four morphological types of LT coalition have been described. LT coalition is usually asymptomatic, but rarely a fibrocartilaginous type may cause ulnar wrist pain. We report a case of bilateral asymptomatic LT coalition that was seen incidentally on conventional radiography taken after a wrist injury. Conventional radiography is the first imaging technique to detect and classify this type of LT coalition. Magnetic resonance imaging is a useful tool to investigate possible associated pathology of the carpal joints, particularly if surgical treatment of a symptomatic patient is anticipated.

The Ankle Fleck Sign Indicating Fibular Avulsion of the Superior Peroneal Retinaculum.

Teaching point: A linear flake of bone at the posterolateral aspect of the distal fibula indicates avulsion of the superior peroneal retinaculum and warrants further investigation by dynamic ultrasound.

Chondroid Lipoma Mimicking Malignancy.

Teaching Point: A chondroid lipoma is a rare benign adipocytic neoplasm, containing a chondromyxoid matrix, that may mimic a myxoid liposarcoma and myxoid chondrosarcoma.