Added value of magnetic resonance spectroscopy for diagnosing childhood cerebellar tumours.

1 H-magnetic resonance spectroscopy (MRS) provides noninvasive metabolite profiles with the potential to aid the diagnosis of brain tumours. Prospective studies of diagnostic accuracy and comparisons with conventional MRI are lacking. The aim of the current study was to evaluate, prospectively, the diagnostic accuracy of a previously established classifier for diagnosing the three major childhood cerebellar tumours, and to determine added value compared with standard reporting of conventional imaging. Single-voxel MRS (1.5 T, PRESS, TE 30 ms, TR 1500 ms, spectral resolution 1 Hz/point) was acquired prospectively on 39 consecutive cerebellar tumours with histopathological diagnoses of pilocytic astrocytoma, ependymoma or medulloblastoma. Spectra were analysed with LCModel and predefined quality control criteria were applied, leaving 33 cases in the analysis. The MRS diagnostic classifier was applied to this dataset. A retrospective analysis was subsequently undertaken by three radiologists, blind to histopathological diagnosis, to determine the change in diagnostic certainty when sequentially viewing conventional imaging, MRS and a decision support tool, based on the classifier. The overall classifier accuracy, evaluated prospectively, was 91%. Incorrectly classified cases, two anaplastic ependymomas, and a rare histological variant of medulloblastoma, were not well represented in the original training set. On retrospective review of conventional MRI, MRS and the classifier result, all radiologists showed a significant increase (Wilcoxon signed rank test, p < 0.001) in their certainty of the correct diagnosis, between viewing the conventional imaging and MRS with the decision support system. It was concluded that MRS can aid the noninvasive diagnosis of posterior fossa tumours in children, and that a decision support classifier helps in MRS interpretation.

A clinical and radiological assessment of incisional hernias following closure of temporary stomas.

AIMS: The rate of incisional hernia at stoma closure sites is unclear. This study aimed to describe this rate in patients with closed stomas who had definitive post-operative imaging of their abdominal wall. METHODS: A retrospective review of patients who had undergone stoma reversal and had a CT or MRI scan of the abdomen ≥2 months following reversal was performed. A radiologist, blinded to the original radiological report and clinical results, reviewed all scans for abdominal wall herniation. This was correlated to documented clinical findings. RESULTS: Fifty-nine patients were included: 49 loop ileostomy and 10 end colostomy reversals. CT scans were performed for 57 patients and MRI for two. The median time from closure to imaging was 10 months (range 3-32 months). The combined clinical and radiological hernia rate was 34% (20/59). Imaging alone produced a rate of 31% (18/59). The clinical rate of hernia detection was 14% (8/59). Using the rate of clinical herniation as the detection standard, imaging had a low positive predictive value (33%, 6/18) but a high negative predictive value (95%, 39/41). Four patients required surgical repair of their stoma site hernia (20%, 4/20). CONCLUSIONS: One in three patients undergoing stoma closure developed an incisional hernia. One in five of those with a hernia underwent surgical repair. Definitive imaging may provide an early surrogate marker for late clinically relevant hernias. Consideration of methods to prevent stoma closure site hernias should be considered.