Deviation of the subjective visual vertical (SVV) in anterior cerebral artery infarction

Healthy humans can determine what is „upright“ within a mean error of less than±2.5 degrees of the earth vertical¹. Errors in verticality perception, reflected in a deviation of subjective visual vertical (SVV), frequently occur in labyrinthine and peripheral vestibular nerve lesions², as well as in brainstem and thalamic lesions involving central vestibular pathways^1–4. So far, SVV deviation in supratentorial cortical lesions has only been reported in patients with middle cerebral artery infarctions affecting vestibular cortical areas^5,6. Here, we present two cases of SVV deviation in anterior cerebral artery (ACA) infarction.

Case 1: A 49 year-old right-handed confectioner was admitted to our stroke unit for ACA infarction. The day prior to admission he and his family suddenly noticed him to be unable to „get his words out“. Moreover, his gait was unsteady and he was falling to the right. The patient's past medical history is notable for hypertension, diabetes, and hypercholesterolemia. He never had any balance or posture disorders. On admission, the patient demonstrated speech inhibition, a mild right-sided facial palsy and impaired fine motor skills of the right hand. Lateropulsion with a body tilt to the right was documented. Cranial MR imaging showed infarction confined to the left ACA territory with left ACA occlusion at the A2 segment; there were no other brain lesions, in particular, thalamus and brainstem were unaffected.

Case 2: A 59-year old wood worker with no past medical history of balance or posture disorders was admitted to our hospital for sudden-onset weakness of his left leg and, to a lesser degree, his left arm. On admission, left hemiparesis and lateropulsion with body tilt to the left were noted. Cranial MR-imaging revealed infarction confined to the right ACA territory. Doppler sonography demonstrated right carotid artery occlusion.

To assess the patients' perception of upright, the static subjective visual vertical was determined as previously described⁵. SVV was deviated to the right by 3.2±0.9 deg in patient 1 (binocular vision, mean±standard deviation; monocular vision: left eye 3.1±0.9 deg, right eye 3.8±1.4 deg), and to the left by 4.4±0.9 deg in patient 2 (monocular vision left eye, right eye blind). Verticality perception returned to normal several weeks after the infarction with no SVV deviation present on follow-up exams.

To our knowledge, this is the first report of a deviation of the subjective visual vertical in anterior cerebral artery infarction. It indicates that structures in the ACA territory contribute to the neural network constructing verticality perception.

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