Blink-associated contralateral eccentric saccades as a rare sign of unilateral brain injury.

Abstract

To describe a rare sign of unilateral brain injury as a form of unwanted blink-associated contralateral eccentric saccades. A 62-year-old patient who underwent an ischemic stroke affecting the entire right middle cerebral artery territory came to our attention 1 year after stroke, manifesting with transient contralateral conjugate gaze deviations associated with spontaneous blinking. We complemented the regular neurologic evaluation with brain MRI, study of evoked potentials, electroneurography of the facial nerve, and infrared video-oculoscopy. The patient had left-sided hemiparesis, hypoesthesia, hemianopia, and hemispatial neglect. He also showed the occurrence of a rapid leftward conjugate deviation of the eyes, followed by a corrective movement to the primary ocular position. MRI showed a wide malacic area spanning the right frontal, temporal, and parietal cortical and subcortical regions, with signs of wallerian degeneration of the descending right corticospinal tract. Motor and somatosensory evoked potentials were centrally altered on the right side. Electroneurography of the facial nerves was normal. Infrared video-oculoscopy indicated persistence of the same blink-related saccades even in darkness. It is known that unilateral cerebral lesions may manifest with a contralateral conjugate gaze deviation evoked by closure of the lids. This sign, known as spasticity of conjugate gaze, may be due to the suppression of the fixation reflex. In our case, the persistence of this sign in the darkness allowed us to exclude this diagnosis. We hypothesized that the blink-related neural pathways may improperly activate the oculomotor circuitry at both the cortical and subcortical levels.