Focal amyloidosis of the head and neck: evaluation with CT and MR imaging.

Localized amyloidosis of the head and neck was found retrospectively in the nasopharynx (n = 3) and orbit (n = 1) of four female patients (mean age, 32 years), three of whom had a prior history of antigenic stimulation. In all patients, computed tomography revealed a slightly high absorption and a relatively homogeneous, partially calcified mass. In the one patient who underwent magnetic resonance (MR) imaging, a distinctive loss of signal intensity was seen on the long repetition time/echo time sequence. This enhanced T2 relaxation may be due to (a) static or slowly fluctuating internal magnetic fields arising from adjacent amyloid protons held in relatively fixed positions within the beta-pleated sheet, resulting in quick phase dispersion; (b) chemical exchange and spin-spin interaction with adjacent water protons; and (c) diffusion through differences in diamagnetic susceptibility. This unusual appearance at MR imaging may improve the ability of radiologists to distinguish focal amyloidosis from many other diseases that affect the head and neck.