T2-SPACE imaging of the cauda equina for the assessment of leptomeningeal metastatic disease

Abstract

The diagnosis of leptomeningeal metastatic disease (LMD) is frequently challenging and MRI of the spine is an important part of the diagnostic paradigm. We sought to examine the value of adding 3-dimensional, heavily T2-weighted, Sampling Perfection with Application optimised Contrasts using different flip angle Evolution (T2-SPACE) imaging of the lumbar spine to the MRI protocol for patients with suspected LMD. MRI spine examinations including T2-SPACE imaging of the lumbar spine performed for suspected or known LMD were retrospectively reviewed by a neuroradiologist to determine the additional benefit of the T2-SPACE sequence. The accuracy of T2-SPACE was also compared to contrast-enhanced T1-weighted imaging (ceT1WI) and standard T2-weighted imaging (T2WI). 59 patients with T2-SPACE were identified over a 20-month period, 17 having abnormal appearances on ceT1WI, including 12 with appearances consistent with LMD. In eight of these 12 patients, nodules visible on T2-SPACE were visible on T2WI, though T2-SPACE improved the temporal comparison of slowly progressive cauda equina nodules in two cases. In three patients, T2-SPACE identified nodules which were not readily identifiable on T2WI, though were visible on ceT1WI. In one patient, LMD visible on ceT1WI was not appreciable on T2-SPACE or T2WI due to the lack of a nodular component. In six patients, T2WI showed equivocal nodularity, which could be confidently attributed to facet joint arthropathy or a tortuous vessel. In conclusion, T2-SPACE has high sensitivity and specificity for the detection of nodular lesions of the cauda equina and can confidently characterise equivocal findings on standard T2WI.