Fig. 1

Preoperative and postoperative MR imaging. In the preoperative MR image, a well-defined, lobulated mass with a size of about 5.6 × 2.7 × 6.1 cm is seen in front of the pons to the medulla with several internal septae. The mass showed hyper-intensity on T1-weighted, hypo-intensity on T2-weighted, and hypo-intensity on diffusion-weighted images. The superior portion of this cystic lesion compresses the lower portion of the pons. The inferior portion of the lesion extends posteriorly and is surrounding the medulla, extending to the C1-C2 intervertebral level (a–e). Postoperative MR imaging after a grossly subtotal surgical resection was done through the minimal lateral supraorbital approach (f–j). In the 15-month follow-up MR images, the remnant cyst mass completely disappeared (k–o)