Midbrain lesion-induced disconjugate gaze: a unifying circuit mechanism of ocular alignment?

• Published in: Journal of neurology Vol. 271; no. 5; pp. 2844 - 2849
• Main Authors: Friedrich, Maximilian U., Schappe, Laurin, Prasad, Sashank, Friedrich, Helen, Fox, Michael D., Zwergal, Andreas, Zee, David S., Faßbender, Klaus, Dillmann, Klaus-Ulrich
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2024; Springer Nature B.V
• Subjects: Anatomy; Binocular vision; Depth perception; Developmental disabilities; Eye; Eye movements; Lesions; Medicine; Medicine & Public Health; Mesencephalon; Neurology; Neuroradiology; Neurosciences; Nystagmus; Oscillations; Short; Short Commentary; Strabismus; Vestibular system; Neuroimaging; Visual system; Vestibular system; Posterior commissure; Eye movement disorders; Videooculography
• ISSN: 0340-5354; 1432-1459; 1432-1459
• DOI: 10.1007/s00415-023-12155-6

Background Disconjugate eye movements are essential for depth perception in frontal-eyed species, but their underlying neural substrates are largely unknown. Lesions in the midbrain can cause disconjugate eye movements. While vertically disconjugate eye movements have been linked to defective visuo-vestibular integration, the pathophysiology and neuroanatomy of horizontally disconjugate eye movements remains elusive. Methods A patient with a solitary focal midbrain lesion was examined using detailed clinical ocular motor assessments, binocular videooculography and diffusion-weighted MRI, which was co-registered to a high-resolution cytoarchitectonic MR-atlas. Results The patient exhibited both vertically and horizontally disconjugate eye alignment and nystagmus. Binocular videooculography showed a strong correlation of vertical and horizontal oscillations during fixation but not in darkness. Oscillation intensities and waveforms were modulated by fixation, illumination, and gaze position, suggesting shared visual- and vestibular-related mechanisms. The lesion was mapped to a functionally ill-defined area of the dorsal midbrain, adjacent to the posterior commissure and sparing nuclei with known roles in vertical gaze control. Conclusion A circumscribed region in the dorsal midbrain appears to be a key node for disconjugate eye movements in both vertical and horizontal planes. Lesioning this area produces a unique ocular motor syndrome mirroring hallmarks of developmental strabismus and nystagmus. Further circuit-level studies could offer pivotal insights into shared pathomechanisms of acquired and developmental disorders affecting eye alignment.