Internuclear Ophthalmoplegia as an Isolated Symptom of Brainstem Wake-up Stroke Responsive to Intravenous Thrombolysis: Evidence from MRI

Abstract

Background: Internuclear ophthalmoplegia (INO) is a disorder of eye movements caused by a lesion involving the medial longitudinal fasciculus (MLF) within the brainstem, and it is characterized by adduction impairment combined with contralateral dissociated abduction nystagmus. The frequency of acute ischemic stroke (AIS) presenting with INO as a predominant symptom is very low, and many patients suffering from this brainstem AIS are precluded from intravenous thrombolysis (IVT). Objective: To provide for the first time a magnetic resonance imaging (MRI) evidence of response to the IVT in brainstem wake-up stroke presenting with INO as an isolated symptom. Methods: Here, we described a rare case of pons AIS presenting with INO as a unique symptom of awakening. In order to differentiate an ischemic stroke from other stroke mimics, and to determine whether the patient was within the therapeutic window for IVT (wake-up stroke), brain MRI including DWI and FLAIR sequences was acquired. Results: A left paramedian pontine DWI/FLAIR mismatch was detected and the patient was considered eligible for IVT. After IVT, the patient made a full recovery with complete resolution of INO. Follow-up MRI at 1 month demonstrates the absence of ischemic lesions. Conclusion: Our case provides neuroradiological evidence of IVT efficacy in brainstem stroke, and it should prompt clinicians to rapidly perform MRI in wake-up onset INO and to just as quickly administer IVT, since INO is a functionally disabling deficit. Finally, this case demonstrates the value of MRI in diagnostic, prognostic, and therapeutic workup of posterior circulation wake-up stroke.