Spontaneous delayed migration/shortening of the pipeline embolization device: report of 5 cases.

Five patients were found to have spontaneous delayed migration/shortening of their Pipeline Embolization Devices on follow-up angiography. The device migrated proximally in 4 patients and distally in 1 patient. One patient had a subarachnoid hemorrhage and died as a result of migration of the Pipeline Embolization Device, and another patient presented with complete MCA occlusion and was left severely disabled. Mismatch in arterial diameter between inflow and outflow vessels was a constant finding. Migration of the Pipeline Embolization Device was managed conservatively, with additional placement of the device, or with parent vessel occlusion. Obtaining complete expansion of the embolization device by using a longer device, increasing vessel coverage, using adjunctive aneurysm coiling, and avoiding dragging and stretching of the device are important preventive measures. Neurointerventionalists should be aware of this potentially fatal complication and take all necessary preventive measures.

Myelopathy caused by nitrous oxide toxicity.

We describe a case of myeloneuropathy resulting from nitrous oxide abuse. MR imaging of the spine revealed symmetric abnormal signal in the posterior columns of the cervical cord. Myeloneuropathy is caused by inactivation of vitamin B12 by nitrous oxide. This syndrome can also be seen in patients with borderline vitamin B12 deficiency who have recently been anesthetized with nitrous oxide.

Improving the diagnostic accuracy of MR in the detection of infraspinatus tendon injuries.

PURPOSE: Our goal was to determine the accuracy of MRI in the diagnosis of infraspinatus tendon injury and more specifically to determine if the antero-posterior extent of a rotator cuff tear is predictive of infraspinatus tearing. METHOD: The MR images of 41 shoulders with surgically proven supraspinatus tears at surgery were retrospectively reviewed. The following were assessed for each of the 41 studies: the number of oblique coronal images on which a tendon defect could be seen, the angle subtended by the tear on axial images (the rotator cuff "axial angle"), and the extent of signal abnormality on sagittal images. RESULTS: The rotator cuff axial angle was 75.6 degrees in patients with infraspinatus tendon tears (ITTs) versus 40 degrees in those without ITTs, and this difference was significant (p < 0.001, t = 3.06). The mean number of oblique coronal images (obtained with a 4 mm slice and 1 mm gap) showing signal abnormality was 5.4 in the ITT group versus 2.9 in those without ITTs, and this difference was also significant (p < 0.001, t = 4.45). The mean sagittal extent of the tendon abnormality was 24.6 mm in the ITT group and 11.6 mm in those without ITTs, but the difference was not significant (p > 0.05, t = 1.1364). CONCLUSION: The axial angle and the number of oblique coronal images in which signal abnormality was present were significantly related to a higher incidence of infraspinatus tears.

Patterns of contrast enhancement in the pediatric spine at MR imaging with single- and triple-dose gadolinium.

PURPOSE: To assess patterns of nerve root and spinal cord contrast enhancement in the pediatric spine at magnetic resonance (MR) imaging with single- and triple-dose gadolinium. MATERIALS AND METHODS: In three control patients with no suspected pathologic spinal condition and 19 patients with a suspected condition, spinal cords were evaluated prospectively for potential spread of tumor to cerebrospinal fluid ("drop metastases") (n = 18) or Guillain-Barré syndrome (n = 1). After enhancement with 0.1 mmol/kg gadolinium, patients without definite drop metastases (n = 8) received a booster of 0.2 mmol/kg gadolinium 30-40 minutes later; clinical follow-up was obtained 12 1/2 to 19 months later. RESULTS: Drop metastases appeared as nodular areas of enhancement in 11 patients. Vascular enhancement related to the spinal cord surface and emerging nerve roots was observed in images obtained in all control patients, as well as in patients with negative findings at lumbar puncture and at clinical or MR imaging follow-up examination (n = 6). Vascular and nerve root enhancement increased with triple-dose gadolinium and was greater in patients after radiation therapy (n = 17) than in control patients (n = 3). CONCLUSION: Use of triple-dose gadolinium did not result in detection of additional cases of drop metastases.

Conspicuity of tumors of the head and neck on fat-suppressed MR images: T2-weighted fast-spin-echo versus contrast-enhanced T1-weighted conventional spin-echo sequences.

OBJECTIVE: The purpose of this study was to compare the conspicuity of tumors of the head and neck on MR images acquired with T2-weighted fat-suppressed fast-spin-echo and contrast-enhanced T1-weighted fat-suppressed conventional spin-echo sequences. MATERIALS AND METHODS: The MR images of 29 patients with 36 pathologically proved tumors of the head and neck were retrospectively analyzed. The conspicuity of these tumors was assessed on the T2-weighted sequence (4700/108 [TR/TE]) and on the contrast-enhanced T1-weighted sequence (500/16) with a 1.5-T system. Qualitative tumor-to-background contrast was graded separately against background muscle, fat, and mucosa (0 = not visualized, 1 = poorly visualized, 2 = fairly well visualized, 3 = well visualized), and the best overall sequence was noted for each tumor. Quantitative tumor-to-background ratios were measured for 10 of the tumors by using the same background markers. RESULTS: The mean overall qualitative tumor-to-background contrast grades for the T2-weighted sequence were tumor/muscle = 2.84, tumor/fat = 2.20, and tumor/mucosa = 1.23, and for the contrast-enhanced T1-weighted sequence, they were tumor/muscle = 2.02, tumor/fat = 1.58, and tumor/mucosa = 0.73. Overall, 86% of the tumors were better or equally well visualized on the T2-weighted images. The mean overall quantitative tumor-to-background ratios for the T2-weighted sequence were tumor/muscle = 7.93, tumor/fat = 3.34, and tumor/mucosa = 0.68, and for the contrast-enhanced T1-weighted sequence, they were tumor/muscle = 2.43, tumor/fat = 2.28, and tumor/mucosa = 0.85. CONCLUSION: The T2-weighted fat-suppressed fast-spin-echo sequence offers better contrast between tumors and adjacent muscle, fat, and mucosa than does the contrast-enhanced T1-weighted fat-suppressed spin-echo sequence and thus improves overall tumor conspicuity. In addition, the T2-weighted sequence does not require IV contrast material and can be performed more rapidly than can the contrast-enhanced T1-weighted sequence. The contrast-enhanced T1-weighted sequence may offer complementary information on the precise characterization of complex tumors and on the potential determination of tumor extent.

CT vs MRI in diagnosis of recurrent rectosigmoid carcinoma.

OBJECTIVE: Our goal was to compare the relative values of MRI vs. CT in diagnosing recurrent rectosigmoid cancer. MATERIALS AND METHODS: We conducted a retrospective review of 18 patients who had surgical resection of primary rectosigmoid carcinoma and suspected recurrence. They were studied with CT and MR and followed for up to 4 years. RESULTS: At the time of the initial imaging, 10 patients had recurrent tumor and 4 of the remaining 8 patients later demonstrated local recurrence. Magnetic resonance demonstrated 91% sensitivity, 100% specificity, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 89% with a 95% accuracy. Computed tomography demonstrated a sensitivity of 82% and a specificity of 50% with a PPV of 69% and an NPV of 67% with an accuracy of 68%. In three cases interpreted on CT as presacral masses, all were shown on MR to represent displaced but normal pelvic structures. In four cases MR revealed tumor involving the sacrum and sacral nerves not apparent on CT. CONCLUSION: Magnetic resonance showed superior sensitivity, specificity, and accuracy to CT and better definition of the extent of tumor.