Skew deviation

Abstract: Deviations of the position of the eye in the roll plane, ocular torsion (OT), and the subjective visual vertical (SVV) were systematically studied in 111 patients with acute vascular brainstem lesions. Of the 111 patients, 104 (94%) showed a direction-specific pathological tilt of the static SVV in our series. Seventy-one (83%) of 86 patients exhibited pathological static OT of one (47%) or both (36%) eyes. OT and SVV tilts are therefore sensitive signs in acute unilateral brainstem disorders. Measurements of SVV and OT may prove to be useful components of the neuro-ophthalmological evaluation. With respect to the directions of pathological tilt, SVV and OT are generally in the same direction. Based on neuroimaging, we conclude that all unilateral brainstem lesions caudal to the upper pons cause ipsiversive OT of one or both eyes, with concurrent ipsiversive tilts of SVV adjustments; all lesions rostral to this pontine level cause contraversive tilts of OT and SVV. Evidence is presented that pathological tilts of OT and SVV are secondary to a dysfunction of the tonic bilateral vestibular inputs that stabilize the eyes and head in normal upright position in the roll plane and dominate our perception of verticality.

Abstract: Central vestibular syndromes may be classified according to the three major planes of action of the vestibuloocular reflex, secondary to a lesional tone imbalance in either the horizontal yaw plane or the vertical pitch or roll plane. The clinical signs, both perceptual and motor, of a vestibular tone imbalance in the roll plane are ocular tilt reaction (OTR), ocular torsion, skew deviation and tilts of the perceived visual vertical (SVV). Either complete OTR or skew torsion without head tilt indicates a unilateral peripheral deficit of otolith input or a unilateral lesion of graviceptive brainstem pathways from the vestibular nuclei (crossing midline at the pontine level) to the interstitial nucleus of Cajal (INC) in the rostral midbrain. SVV tilts are the most sensitive sign of a vestibular tone imbalance in roll and occur with peripheral or central vestibular lesions from the labyrinth to the vestibular cortex. All tilt effects, perceptual, ocular motor and postural, are ipsiversive (ipsilateral eye undermost) with unilateral peripheral or pontomedullary lesions below the crossing of the graviceptive pathways. All tilt effects are contraversive (contralateral eye undermost) with unilateral pontomesencephalic brainstem lesions and indicate involvement of the medial longitudinal fasciculus or the rostral midbrain (INC). Unilateral lesions of vestibular structures rostral to the INC typically manifest with deviations of perceived vertical without concurrent eye-head tilt. OTR in unilateral paramedian thalamic infarctions indicates simultaneous ischemia of the paramedian rostral midbrain including the INC. Unilateral lesions of the posterolateral thalamus can cause thalamic astasia and moderate ipsiversive or contraversive SVV tilts, thereby indicating involvement of the vestibular thalamic subnuclei. Unilateral lesions of the parietoinsular vestibular cortex cause moderate, mostly contraversive SVV tilts. An SVV tilt found with monocular but not with binocular viewing is typical for a trochlear or oculomotor palsy rather than a supranuclear graviceptive brainstem lesion.

Abstract: Following inadvertent destruction of the left vestibular labyrinth during stapedectomy, a patient developed a transient abnormality of posture consisting of leftward ocular counterrolling, leftward had tilting, and a right-over-left skew deviation. This postural pattern, known as the "ocular tilt reaction," is the normal compensatory response of the dependent utricle to tilting. In this patient, the unopposed action of the intact right utricle was presumably responsible for the appearance of a normal leftward ocular tilt reaction.

Abstract: Acute unilateral peripheral and central vestibular lesions can cause similar signs and symptoms, but they require different diagnostics and management. We therefore correlated clinical signs to differentiate vestibular neuritis (40 patients) from central "vestibular pseudoneuritis" (43 patients) in the acute situation with the final diagnosis assessed by neuroimaging. Skew deviation was the only specific but non-sensitive (40%) sign for pseudoneuritis. None of the other isolated signs (head thrust test, saccadic pursuit, gaze evoked nystagmus, subjective visual vertical) were reliable; however, multivariate logistic regression increased their sensitivity and specificity to 92%.