CT and MRI features of endolymphatic sac tumor / 中华放射学杂志

ABSTRACT

Objective:To explore CT and MRI features of the endolymphatic sac tumor (ELST).Methods:The CT and MRI morphology confirmed by surgical pathology for 19 patients with ELST were retrospectively analyzed from June 2011 to May 2019 in Eye & ENT Hospital of Fudan University. The features of CT and MRI included location, size, adjacent structures invasion, CT values, bone destruction, features of T 1WI and T 2WI, enhancement distribution characteristics, dynamic enhancement curve morphology, DWI signal characteristics. The ADC values of the lesions and ipsilateral medial pterygoid muscles were compared using a paired t test. Results:Nineteen ELST patients (one with bilateral diseases) were included. Totally 20 ears (right 9 and left 11) of 13 females and 6 males were studied. The masses with slightly high-density and obscure boundary were located around the vestibular aqueduct at the posterior edge of the petrosal bone. Bone destruction involved mastoid process of the middle ear (16 ears), jugular foramen (11 ears), semicircular canal (10 ears), facial nerve canal (7 ears) and internal auditory canal (9 ears). A large amount of residual bone could be found in the interior of nineteen masses. The CT value was (78.6±21.9) HU. The lesion showed central iso-intensity and peripheral hyperintensity on T 1WI and T 2WI in 16 ears, while no obvious hyperintensity on T 1WI in the other 4 ears. The hyperintensity on T 1WI was around the margin of the lesion in 10 ears, situated at lateral side in 5 ears and all over the lesion in 1 ear. Flow voids signals could be seen in 9 ears as well. Liquid-liquid plane was seen on T 2WI in 2 ears. The solid mass portion which showed iso-intensity on both T 1WI and T 2WI presented marked enhancement on contrast-enhanced T 1WI, while other part of the mass no enhancement. DWI of 14 ears illustrates no evidence of restricted diffusion, and the ADC value [(1.25±0.08)×10 -3 mm 2/s] was slightly higher than that of the medial pterygoid muscles ( t=4.437, P=0.001). The style of time-signal intensity curves of the dynamic contrast-enhanced MRI was rapidly ascending followed by descending curves in 2 ears. Conclusion:Imaging findings of ELST have some characteristics, including located around the vestibular aqueduct at the posterior edge of the petrosal bone, bone destruction, peripheral hyperintensity on T 1WI and no restricted diffusion, which is helpful for its diagnosis.