Author response: Teaching Video NeuroImages: Pulsatile proptosis and wall-eyed bilateral internuclear ophthalmoplegia

We thank Lee et al. for the insightful comments on our Teaching Video NeuroImage on pulsatile proptosis and wall-eyed bilateral internuclear ophthalmoplegia (WEBINO).¹ The causative lesions for bilateral WEBINO can be located in the tegmentum of pons, pons–midbrain, or midbrain, with some injuries almost bisecting the brainstem.^2,3 As the MRI presented by Lee et al. discloses multiple hyperintense foci at the pontomesencephalic level, we reviewed the diffusion-weighted MRI, which shows a focal area of restricted diffusion at the midline of the pontine tegmentum beneath the floor of the fourth ventricle, which involves the medial longitudinal fasciculus (MLF) bilaterally (figure). The patient had presented 2 days after onset of diplopia and this lesion was consistent with an acute ischemic stroke. Although we indicated in the text and figure legend of the T2-weighted MRI that the infarction was located at the midline of the midbrain tegmentum,¹ the arrow on the MRI had been placed more anteriorly by mistake. Hence, we agree with Lee et al. that, at the pontine level, the MLF is located just ventral to the fourth ventricle, and lesions of this area can lead to bilateral WEBINO.⁴