A non-internuclear cause of walled-eye ophthalmoplegia

Case presentation: A 60-year-old patient presented with a history of two days of facial palsy and binocular diplopia. Past medical history included an upper respiratory infection 1 week before. He presented right-sided hemifacial paralysis involving the superior and inferior quadrants, bilateral exotropia on primary gaze position, adduction restriction of the left eye when looking to the right, and of the right eye when looking to the left. Due to these findings, we made a hypothesis of wall-eyed bilateral internuclear ophthalmoplegia (WEBINO). However, on further examination it was noticed that the patient did not have any form of gaze-evoked nystagmus and presented with up-gaze and convergence palsy. Furthermore, the patient also presented with ataxic gait, absent osteotendinous reflexes and was unable to perform a tandem walk. Considering laboratory assessment, serum examinations were unremarkable, whereas spinal fluid analysis presented 0 cells and 57mg/dL of protein. Motor conduction studies showed reduced amplitude in the right facial nerve potential in the platism and the eye orbicularis muscles. There were no sensitive alterations. The F wave latency was increased in the tibial and normal in the ulnar nerves. The H reflex was absent bilaterally. Regarding the blink reflex, the R1 latency was increased on the right, whereas latency of the left R1 and bilateral R2 and R2c were within normal ranges. Given the clinical, laboratory and nerve conduction study findings we put forward a hypothesis of Miller Fisher syndrome (MFS). Discussion: MFS is a rare form of acute-onset immune-mediated neuropathy and is characterised by the triad: ophthalmoparesis, ataxia and areflexia. Specifically, MFS is highly associated with anti-GQ1b antibody. In that sense, both anti-GQ1b antibody and MFS have been associated with internuclear ophthalmoplegia and WEBINO. Our patient presented with several findings suggestive of MFS. Particularly, WEBINO consists of a form of bilateral internuclear ophthalmoplegia with large, wide-angle, exotropia in the primary position, bilateral adduction impairment and nystagmus of the abducting eye. Moreover, WEBINO typically presents with a wide range of vertical gaze alterations such as vertical gaze-evoked nystagmus, skew deviation and vestibular ocular reflex alterations. Lesions that cause WEBINO are frequently located in the pons and/or midbrain and are usually of inflammatory or ischemic aetiology. Particularly, the damaged structure is classically described as the middle longitudinal fasciculus. In a first assessment our patient seemed to present with WEBINO. However, the adduction paralysis,, as well as lack of abduction and gaze evoked nystagmus made the diagnosis of true WEBINO less likely. Normal MRI and alteration in nerve conduction corroborated the pseudo-WEBINO of peripheral nature. Final comments: Our patient presented with a pseudo-WEBINO of non-internuclear cause.