MR features of the denervated tongue in radiation induced neuropathy

The MR features of the denervated tongue have been described following nerv e injury from radical neck dissection and tumour invasion. The purpose of t he study was to determine whether similar features are present in the tongu e following radiation induced neuropathy (RIN). The clinical records and MR images of 12 patients with RIN of the hypoglossal nerve were reviewed retr ospectively. T-1 weighted SE images were performed in 12, T-2 weighted TSE images in 11, fat suppressed images in 10 and contrast enhanced T-1 weighte d images in nine patients. The denervated tongue revealed "oedemalike" chan ges in five, fatty infiltration in six, atrophy in 11 and pseudohypertrophy in one patient. Abnormal enhancement was not identified, and in five patie nts the signal intensity was normal on all sequences. The oedemalike change s, fatty infiltration and normal signal intensity were seen 2-48, 2-48, and 6-63 months, respectively, after the onset of RIN. In conclusion, there wa s no discernible relationship between the duration of RIN and the MR appear ance of the denervated tongue. Oedemalike changes, previously described in the acute/subacute phase of denervation, were also seen in long-standing di sease and there was no associated abnormal enhancement in any case. Further more, the signal intensity may be normal, the MR diagnosis relying on asymm etry of the size of the tongue. It is postulated that radiation causes inco mplete and ongoing damage of the nerve, the course of which is unpredictabl e.