Abstract
Abstract: :
Purpose: To describe the vertical deviation differences in a group of patients with fourth cranial nerve palsy in erected and supine position. Methods: We included patients with unilateral fourth cranial nerve palsy who underwent full ophthalmologic exploration and measurement of the vertical deviation with prisms and alternate occlusion performing Bielschowsky's test (primary position with the head aligned with its vertical axis, and with the head tilted first to the right side and then to the left side), the exploration was performed while the patient was sitting (erected), and then we asked them to lay down repeating the same exploration (supine position). Results: Ten patients were explored; the mean vertical deviation with their head aligned in its vertical axis, in the sitting position was 7.7 prismatic diopters (pd), and 4.2 pd in the lying position. The vertical deviation observed performing Bielschowsky’s test (head tilted to the paretic side) was minor when the patient was explored in the supine position: The average deviation in the erected patient was 18.1 pd and 7.3 pd in the supine position. Conclusions: The response to the Bielschowsky's test was less important in the supine position than in the erected patient The vestibule-ocular reflexes responsible of the larger vertical deviation when tilting the head trough the paretic side are attenuated in the supine position; the physiologic justification for this phenomenon is based on the otholit 's role in the control of the ocular movements, this receptors are stimulated according to their position in relation to gravity, this clinical observation supports the explanation proposed by Bielschowsky related to the role of the vestibular system in one of the main clinical signs of this entity.
Keywords: vestibulo-ocular reflex • ocular motor control • eye movements