Upbeat Nystagmus due to a Small Pontine Lesion: Evidence for the Existence of a Crossing Ventral Tegmental Tract

• Published in: European neurology Vol. 54; no. 4; pp. 186 - 190
• Main Authors: Pierrot-Deseilligny, C., Milea, D., Sirmai, J., Papeix, C., Rivaud-Péchoux, S.
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Karger 01.01.2005; S. Karger AG
• Subjects: Biological and medical sciences; Brain Injuries - complications; Brain Injuries - pathology; Development. Senescence. Regeneration. Transplantation; Electrooculography - methods; Fundamental and applied biological sciences. Psychology; Humans; Injuries of the nervous system and the skull. Diseases due to physical agents; Magnetic Resonance Imaging - methods; Male; Medical sciences; Middle Aged; Models, Biological; Neural Pathways - pathology; Neurology; Nystagmus, Pathologic - etiology; Nystagmus, Pathologic - pathology; Original Paper; Pons - pathology; Reflex, Vestibulo-Ocular - physiology; Traumas. Diseases due to physical agents; Ventral Tegmental Area; Vertebrates: nervous system and sense organs; Vertical nystagmus; Upbeat nystagmus; Ventral tegmental tract; Vestibulo-ocular reflex; Eye disease; Nervous system diseases; Vestibuloocular reflex; Oculomotor syndrome
• ISSN: 0014-3022; 1421-9913
• DOI: 10.1159/000090295

We report a patient with an isolated large upbeat nystagmus (UBN) in the primary position of gaze. Eye movements were filmed and recorded using electro-oculography. The upward vestibulo-ocular reflex gain, evaluated by pitching the head forward, was markedly reduced compared to when pitching the head back. The lesion was a probable lacunar infarction located in the paramedian and posterior part of the basis pontis, at the upper pons level. This UBN case, with one of the smallest brainstem lesions reported so far, supports the existence in humans of the crossing ventral tegmental tract, described in the cat and transmitting excitatory upward vestibular signals to the third nerve nucleus. It is also suggested that the decussation of this tract lies at the same upper pons level as in the cat but in a slightly more ventral location, i.e. in the posterior basis pontis.