-Case Reports-

Unilateral Isolated Trochlear Nerve Palsy due to Ipsilateral Midbrain Infarction

Toshiyuki Hayashi^1,2, Koichi Nomura^1,2, Yasuhiro Nishiyama¹ and Kazumi Kimura¹

¹Department of Neurology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
²Department of Neurology, Shioda Hospital, Chiba, Japan

Ischemic stroke is a very rare etiology in cases of isolated trochlear nerve palsy, and no reports of ipsilateral trochlear nerve palsy caused by unilateral stroke have so far been published. However, we now report a case of isolated trochlear nerve palsy due to ipsilateral dorsal small midbrain infarction in a 70-year-old woman who presented with acute onset of diplopia. There were no other clinical manifestations, but brain magnetic resonance imaging revealed a small ischemic lesion in the right dorsal midbrain, showing that isolated trochlear nerve palsy can be caused by stroke.

J Nippon Med Sch 2021; 88: 561-563

Keywords
ischemic stroke, trochlear nerve palsy, cranial nerve palsy, magnetic resonance imaging

Correspondence to
Toshiyuki Hayashi, MD, Department of Neurology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
toshi-h-06@nms.ac.jp

Received, July 13, 2020
Accepted, December 7, 2020