MRI features of cervical nodal necrosis in metastatic disease

Magnetic resonance imaging (MRI) is increasingly used to evaluate head and neck tumours but its place in the assessment of nodal metastasis is still unclear. This study compares the MRI findings with the computed tomography (CT) sign of nodal necrosis in 114 patients with confirmed nasopharyngeal carcinoma (NPC). Ninety-one (80%) patients showed neck node enlargement on both MRI and CT. Thirty-one (34%) of these patient with lymphadenopathy showed nodal necrosis. Seventy-two necrotic nodes were seen on CT. Using CT as the standard, the sensitivity and specificity of individual MRI sequences are as follows: T1-weighted (36%, 100%), T2-weighted (47%, 98%) and enhanced T1 (67%, 100%). In combination (when one or more sequences are positive), the sensitivity and specificity are as follows: T1 and T2-weighted (60%, 99%), T1-weighted and enhanced scan (67%, 100%) and T1-, T2-weighted and enhanced scan (78%, 99%). Only 26 (36%) nodes with nodal necrosis could be recognised on T1-weighted MRI as an area of low signal intensity. Paradoxically, eleven (15%) nodes, showed slightly hyperintense necrotic areas. Contrast enhanced MRI showed 48 (67%) NN thus improving detection rate. High signal intensity with or without a rim of lower signal intensity could be seen in 39 (54%) nodes on T2-weighted images. Five nodes (7%), curiously showed low signal necrotic centres. Ideally, staging of the primary tumour and nodes should be performed using a single modality. The tumour is often more advantageously evaluated by MRI. However, CT should be considered if MRI findings of nodal involvement are equivocal.