Epidermoid cyst in the cerebellopontine angle region invading adjacent neurovascular: a MRI study

Abstract

Objective To explore the advantages of MR imaging sequences displaying the epidermoid cyst (EC) with adjacent neurovascular invasion in the cerebellopontine angle region.Methods Petrospective analysis on clinical and MR imaging data of 8 patients with ECs in the cerebellopontine angle region confirmed by surgery and pathology was performed. T1WI, T2WI, FLAIR,DWI, T1 enhancement scanning, and both 3D-FIESTA and 3D-TOF-MRA sequences, especially, were performed to investigate the normal neurovascular signal features, epidermoid cyst and its neurovascular invasion features in cerebellopontine angle region and the advantages of 3D-FIESTA and 3D-TOF-MRA sequences in demonsuating these features were analyzed too. Results Conventional sequences showed poor results on nerves and vessels, but 3D-FIESTA showed clear results. Vessels were clearly showed under 3D-TOF-MRA, but nerves shown under 3D-TOF-MRA were not as clear as those under 3D-FIESTA. Eight ECs showed isointensity in 3D-FIESTA, and the border of the lesions could be delineated clearly from peripheral CSF. However, hypointensity was showed in 3D-TOF-MRA, and the borders of the lesions could not be identified from CSF. All of the 8 patients with ECs (100%) showed trigeminal nerve encasement on 3D-FIESTA, including 4 thinning and 2 fold distortion. In the 8 patients with ECs, 3 (37.5%) showed facial and acoustic nerves encasement (1 was also diagnosed as having dysaudia by clinical manifestations), 1 (12.5%) displacement, 2 (25%) tight relationship, and 2 (25%)non-touching. Clinically, all 8 patients with ECs had trigeminal neuralgia; of them, the 2nd and 3ndtrigeminal nerves were involved in 4 patients and the 1at, 2nd and 3nd trigeminal nerves were all involved in the other 4 patients; the imaging features and clinical manifestations were 100% coincident. Conclusion 3D-FIESTA sequence is superior to other MR imaging sequences in demonstrating the ECs with neurovascular invasion; combined with 3D-TOF MRA, 3D-FIESTA can give precise preoperative evaluation. Key words: Cerebellopontine angle; Epidermoid cyst; Neurovascular complex; Magnetic resonance imaging