Hyo-Jung Kim1, Jong Hee Lee2, Ji-Soo Kim3. 1. Kangwon National University College of Medicine, Chuncheon, South Korea; Biomedical Research Institute, Seoul National University Bundang Hospital, South Korea. 2. Department of Neurology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea. 3. Department of Neurology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea. Electronic address: jisookim@snu.ac.kr.
Abstract
OBJECTIVE: The central pathways responsible for ocular vestibular evoked myogenic potentials (VEMPs) to forehead tapping remain to be determined. This study aimed to determine whether the medial longitudinal fasciculus (MLF) carries the signals for ocular VEMPs (oVEMPs) in response to this mode of stimulation. METHODS: Twelve patients with isolated unilateral internuclear ophthalmoplegia (INO) due to brainstem infarction underwent evaluation of the ocular tilt reaction (ocular torsion and skew deviation), tilt of the subjective visual vertical (SVV), cervical VEMPs (cVEMPs) in response to tone burst sound, and oVEMPs induced by tapping the forehead. RESULTS: Eight (67%) patients showed abnormal oVEMPs that included no wave formation (n=4) and decreased amplitude (n=3) in the lesion side, and bilaterally absent responses in the remaining patient. Furthermore, the patients showed diminished oVEMPs responses in the lesion side compared with normal side (6.0 ± 5.6 vs. 11.7 ± 5.5 μV, paired t-test, p=0.001) and increased IADamp(%) of the oVEMPs compared with normal controls (43.6 ± 41.2 vs. 9.1 ± 6.2, t-test, p=0.018). In contrast, cVEMPs were abnormal in only three (25%) patients, decreased (n=2) or no response in the lesion side. Eleven (92%) patients showed contraversive ocular tilt reaction or SVV tilt. CONCLUSION: Patients with INO frequently show impaired formation of ipsilesional oVEMPs in response to forehead tapping. The occasional abnormality and decreased amplitude of ipsilesional cVEMPs also suggest a modulatory pathway for the inhibitory sacculocollic reflex descending in the MLF. SIGNIFICANCE: This study suggests that the MLF contains the fibers for the otolith-ocular reflex from the contralateral ear.
OBJECTIVE: The central pathways responsible for ocular vestibular evoked myogenic potentials (VEMPs) to forehead tapping remain to be determined. This study aimed to determine whether the medial longitudinal fasciculus (MLF) carries the signals for ocular VEMPs (oVEMPs) in response to this mode of stimulation. METHODS: Twelve patients with isolated unilateral internuclear ophthalmoplegia (INO) due to brainstem infarction underwent evaluation of the ocular tilt reaction (ocular torsion and skew deviation), tilt of the subjective visual vertical (SVV), cervical VEMPs (cVEMPs) in response to tone burst sound, and oVEMPs induced by tapping the forehead. RESULTS: Eight (67%) patients showed abnormal oVEMPs that included no wave formation (n=4) and decreased amplitude (n=3) in the lesion side, and bilaterally absent responses in the remaining patient. Furthermore, the patients showed diminished oVEMPs responses in the lesion side compared with normal side (6.0 ± 5.6 vs. 11.7 ± 5.5 μV, paired t-test, p=0.001) and increased IADamp(%) of the oVEMPs compared with normal controls (43.6 ± 41.2 vs. 9.1 ± 6.2, t-test, p=0.018). In contrast, cVEMPs were abnormal in only three (25%) patients, decreased (n=2) or no response in the lesion side. Eleven (92%) patients showed contraversive ocular tilt reaction or SVV tilt. CONCLUSION:Patients with INO frequently show impaired formation of ipsilesional oVEMPs in response to forehead tapping. The occasional abnormality and decreased amplitude of ipsilesional cVEMPs also suggest a modulatory pathway for the inhibitory sacculocollic reflex descending in the MLF. SIGNIFICANCE: This study suggests that the MLF contains the fibers for the otolith-ocular reflex from the contralateral ear.
Authors: Hyo Jung Kim; Seong Ho Park; Ji Soo Kim; Ja Won Koo; Chae Yong Kim; Young Hoon Kim; Jung Ho Han Journal: J Clin Neurol Date: 2016-01 Impact factor: 3.077
Authors: Ji-Soo Kim; David E Newman-Toker; Kevin A Kerber; Klaus Jahn; Pierre Bertholon; John Waterston; Hyung Lee; Alexandre Bisdorff; Michael Strupp Journal: J Vestib Res Date: 2022 Impact factor: 2.354