• Yu Iida, Hidetoshi Murata, Ken Johkura, Testuhiro Higashida, Takahiro Tanaka, and Kensuke Tateishi.
• Department of Neurosurgery, Yokohama City University, Yokohama, Kanagawa, Japan.
• World Neurosurg. 2018 Mar 1; 111: 367-372.

BackgroundBow hunter's syndrome (BHS) is rare and typically induced by mechanical compression of the dominant vertebral artery (VA) during head rotation. We report a case of BHS induced by nondominant VA compression in which contralateral VA patency was preserved. Definite diagnosis of BHS is not often feasible because of transient symptoms and nonspecific clinical features, such as vertigo or dizziness, especially in nondominant VA compression. We discuss the diagnostic clues of BHS and clinical features of BHS caused by nondominant VA compression through a literature review.Case DescriptionA 65-year-old man suffered repeated bouts of dizziness whenever his head was rotated to the left. This dizziness was consistently accompanied by downbeat nystagmus (DBN). Radiography revealed left VA compression by a lateral osteophyte at the C3-C4 level only during left head rotation. In contrast, patency of the right VA, which was almost equivalent in size to the left VA, was preserved during head rotation. The distinctive clinical finding of head rotation-induced DBN, which is usually associated with lesions involving the caudal midline cerebellum, was observed. Symptoms disappeared immediately after left VA decompression with osteophytectomy and C3-C4 fusion.ConclusionsDespite excellent flow through the contralateral VA, occlusion of the nondominant VA occasionally induces BHS. According to a review of the literature, BHS cases do not always depend on the VA on one side for blood supply. Head rotation-induced DBN can be useful for diagnosis of BHS, even in cases of nondominant VA compression.Copyright © 2018 Elsevier Inc. All rights reserved.

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