Pseudoabducens Palsy of Lutz

A 40-year-old woman presented with a 2-year history of nonfluctuating diplopia on left gaze. Her medical history included 3 years of left facial numbness. On examination, visual acuity, color vision, pupils, lids, funduscopic examination, and automated visual fields were normal.

Photo and Video Essay Section Editors: Melissa W. Ko, Dean M. Cestari, Peter Quiros, Kimberly M. Winges, MD MD MD MD Pseudoabducens Palsy of Lutz Amit K. Sharma, MD, David D. Kim, MD, J. Alexander Fraser, MD A 40-year-old woman presented with a 2-year history of nonfluctuating diplopia on left gaze. Her medical history included 3 years of left facial numbness. On examination, visual acuity, color vision, pupils, lids, funduscopic examination, and automated visual fields were normal. Smooth pursuit in the right eye was normal, whereas the left eye had very slight abduction limitation. Rightward saccades from primary position (Fig. 1A) to right gaze (Fig. 1B) were normal, but there was a striking abduction lag in the left eye with voluntary leftward saccades (Fig. 1C showing the eyes midsaccade; Fig. 1D showing the eyes at the end of the same saccade; Video) and contralateral adduction nystagmus (see Video, Supplemental Digital Content 1, http://links.lww.com/WNO/A570). Vestibulo-ocular reflexmediated saccades, however, were completely normal. Crosscover testing revealed orthophoria in primary and right gaze but a 10 prism diopters esotropia on left gaze. Neurological examination was notable only for a 30% reduction in sen- FIG. 1. Abduction lag of the left eye during leftward saccade. A. Eye position at rest in primary gaze, showing orthotropia. B. Eye position on rightward saccades. C. Eye position 0.2 seconds after the initiation of a leftward saccade which had started from the eye position seen in panel B; owing to abduction lag, the left eye has travelled only part way into its abducting saccade, whereas the right eye has already achieved full adduction. D. Eye position approximately 1.5 seconds after saccade initiation; the patient’s left eye has just completed its abduction saccade, with good final amplitude. Department of Clinical Neurological Sciences (AKS, DDK, JAF), Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and Department of Ophthalmology (JAF), Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. The authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the full text and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). Signed informed patient consent, including explicit consent for publication, was obtained. Address correspondence to Amit K. Sharma, MD, Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, 339 Windermere Road, London, ON N6A 5A5, Canada; E-mail: [e-mail] e598 sation in the left forehead and chin. MRI of the brain, including thin-slice (1.8 mm) FLAIR sequences through the brainstem, was unremarkable (Fig. 2). Acetylcholine receptor antibody testing was negative. INTERPRETATION OF FINDINGS She was diagnosed with a “pseudoabducens palsy of Lutz” (PAPOL), a term which we believe improves on the previous name of “internuclear ophthalmoplegia (INO) of Lutz” (a misnomer), but nevertheless, distinguishes this characteristic entity from other forms of pseudoabducens palsy (an abduction deficit unrelated to abducens nerve dysfunction) (1) such as thalamic esotropia and myasthenia Sharma et al: J Neuro-Ophthalmol 2022; 42: e598-e599 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay FIG. 2. Thin-slice MRI of the brainstem. Panels A (most rostral) through (D) (most caudal) depict the midbrain and rostral pons at consecutive levels and do not reveal a visible macroscopic lesion. gravis. Consistent with a presumed central localization, her abducting left eye saccades had developed a subtle torsional component and associated mild eyelid retraction at the follow-up 3 years later (see Video, Supplemental Digital Content, http://links.lww.com/WNO/A570), despite normal repeat thin-slice MRI. Mild cases of PAPOL may lack nystagmus. Orthophoria in primary gaze, worsening of abduction with saccades vs. pursuit, and preservation of reflexive saccades differentiate it from an abducens nerve, neuromuscular junction, or lateral rectus problem. A lack of globe retraction or palpebral fissure narrowing during eye movements distinguishes it from variants of Duane syndrome. In 1923, Anton Lutz first described the characteristic dual eye movement findings of ipsilateral abduction slowing and contralateral dissociated adducting nystagmus—the converse of a typical INO (2). He originally called this a “posterior INO” based on a mistaken assumption that posterior supranuclear fibers for horizontal gaze divided into 2 branches, one synapsing with lateral rectus neurons and another synapsing with contralateral medial rectus neurons(3). The true localization of PAPOL remains debated, although older hypotheses proposing a lesion affecting the paramedian pontine reticular formation or its connections are incorrect because this would cause gaze limitation. One hypothesis postulates a burst of convergence tone during a saccade that accelerates the adducting eye and slows the abducting eye, thereby producing a PAPOL (3). Alternatively, more intrinsic defects in antagonist medial rectus inhibition may be responsible, analogous to what has been demonstrated in typical INO using infrared oculography4. Regardless of mechanism, the responsible lesion localizes best to the midbrain or rostral pons. This is supported by Sharma et al: J Neuro-Ophthalmol 2022; 42: e598-e599 electrophysiological studies, even in cases without imaging abnormalities (4). Our patient’s ipsilateral trigeminal findings suggest the rostral pons localization, where we presume she has a microstructural lesion below the resolution of the MRI. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: A. K. Sharma, D. D. Kim, and J. A. Fraser; b. Acquisition of data: J. A. Fraser; c. Analysis and interpretation of data: A. K. Sharma, D. D. Kim, and J. A. Fraser; Category 2: a. Drafting the manuscript: A. K. Sharma; b. Revising it for intellectual content: A. K. Sharma, D. D. Kim, and J. A. Fraser; Category 3: a. Final approval of the completed manuscript: A. K. Sharma, D. D. Kim, and J. A. Fraser. ACKNOWLEDGMENTS The authors thank the patient for providing consent to publish her case. REFERENCES 1. Caplan LR. Top of the basilar syndrome. Neurology. 1980;30:72–79. 2. Nij Bijvank JA, Balk LJ, Tan HS, Uitdehaag BMJ, van Rijn LJ, Petzold A. A rare cause for visual symptoms in multiple sclerosis: posterior internuclear ophthalmoplegia of Lutz, a historical misnomer. J Neurol. 2017;264:600–602. 3. Thömke F, Hopf HC. Abduction paresis with rostral pontine and/ or mesencephalic lesions: pseudoabducens palsy and its relation to the so-called posterior internuclear ophthalmoplegia of Lutz. BMC Neurol. 2001;1:4. 4. Feldon SE, Hoyt WF, Stark L. Disordered inhibition in internuclear opthalmoplegia: analysis of eye movement recordings with computer simulations. Brain. 1980;103:113– 137. e599 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.