**Acknowledgements**

The authors would like to express their gratitude to Dr. Mitsuru Matsuki (Radiology, Kindai University), Dr. Takafumi Hosokawa (Neurology, Osaka Medical College), Dr. Shinichi Haginomori (Otorhinolaryngology, Osaka Medical College), Dr. Hiroshi Ymamamoto (Radiology, Sumitomo Hospital), and Dr. Mitsuyosi Ayabe and Dr. Kazuhito Noda (Neurology, Kurume University) for providing the information of the cases.

This work was supported by JSPS KAKENHI, Grant Number 16 K09704, from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
