Читать книгу Vestibular Disorders - Группа авторов - Страница 14

First check if the patient has a head tilt, which is ipsilesional to a peripheral vestibular loss [4, 7]. Is there a Horner’s syndrome, which could be indicative of a lesion affecting the descending sympathetic pathways such as a brainstem infarction (Fig. 1a)? Vertical misalignment of the eyes in the absence of an extraocular muscle palsy (skew deviation) can occur in peripheral and central vestibular loss, but is thought to occur more commonly in the latter. Ocular tilt reaction (OTR) refers to the triad of skew deviation, head tilt (toward the hypotropic eye), and ocular counter-roll (Fig. 1b). These 3 findings are attributed to a unilateral lesion of the “graviceptive pathways” arising from the utricle [7]. A vestibular or lower brainstem lesion causes an ipsiversive OTR whereas an upper brainstem lesion causes a contraversive OTR. To check for skew deviation, alternate cover test should be performed; when each eye is covered in turn, a corrective vertical saccade occurs in the uncovered eye, bringing the hypotropic (down) eye upwards or the hypertropic (up) eye downwards. Otoscopy is performed to evaluate the tympanic membrane directly and rule out active ear disease (infection or cholesteatoma) as a cause of vertigo.