Oculomotor Nerve Palsy Due to Unusual Causes

Background: An isolated oculomotor nerve (CN III) palsy is a diagnostic concern because of the potential for serious morbidity or life-threatening causes. We present 5 unusual causes of oculomotor nerve palsy that escaped initial diagnosis in order to raise awareness of their associated features that will facilitate correct diagnosis. Methods: This study consisted of a retrospective analysis of clinical features and imaging of 5 patients who were referred for neuro-ophthalmologic evaluation with presumed diagnosis of oculomotor nerve palsy of unknown reasons. Results: A complete CN III palsy and an inferior division CN III palsy were diagnosed with a schwannoma in the cavernous sinus and orbital apex portion, respectively; a middle-aged woman with aberrant regeneration was found to have a small meningioma; an adult man with ptosis was diagnosed with cyclic oculomotor paresis with spasms; and a patient after radiation was diagnosed with neuromyotonia. Conclusions: Localizing the lesion of oculomotor nerve palsy and careful examination of the imaging is crucial. Aberrant regeneration, cyclic pupil changes, and past medical history of amblyopia, strabismus, or radiation are also very helpful for diagnosis.

Worldwide Neuro-Ophthalmology Section Editors: Kathleen B. Digre, MD Meagan Seay, DO Oculomotor Nerve Palsy Due to Unusual Causes Background: An isolated oculomotor nerve (CN III) palsy is a diagnostic concern because of the potential for serious morbidity or life-threatening causes. We present 5 unusual causes of oculomotor nerve palsy that escaped initial diagnosis in order to raise awareness of their associated features that will facilitate correct diagnosis. Methods: This study consisted of a retrospective analysis of clinical features and imaging of 5 patients who were referred for neuro-ophthalmologic evaluation with presumed diagnosis of oculomotor nerve palsy of unknown reasons. Results: A complete CN III palsy and an inferior division CN III palsy were diagnosed with a schwannoma in the cavernous sinus and orbital apex portion, respectively; a middle-aged woman with aberrant regeneration was found to have a small meningioma; an adult man with ptosis was diagnosed with cyclic oculomotor paresis with spasms; and a patient after radiation was diagnosed with neuromyotonia. Conclusions: Localizing the lesion of oculomotor nerve palsy and careful examination of the imaging is crucial. Aberrant regeneration, cyclic pupil changes, and past medical history of amblyopia, strabismus, or radiation are also very helpful for diagnosis. A may be missed with conventional neuroimaging or when the benefit of the patient’s history and examination findings are not adequately conveyed to the radiologist interpreting the imaging study. With less common etiologies, important details of the history and examination that point to the diagnostic cause may not be fully appreciated, such as aberrant regeneration, oculomotor nerve paresis with cyclic spasm, and postirradiation diplopia, and should also be considered in the differential diagnosis of isolated oculomotor paralysis that do not spontaneously resolve. We present 5 unusual causes of oculomotor nerve palsy that escaped initial diagnosis in order to raise awareness of their associated features that will facilitate correct diagnosis. n isolated oculomotor nerve (CN III) palsy is a diagnostic concern because of the potential for serious morbidity or life-threatening causes. Benign, pupil-sparing ischemic third nerve palsies in patients older than 50 years are the most common (1). However, neuroimaging is usually performed because of the concern for aneurysmal compression of CN III and pituitary apoplexy that are relatively rare (6%) but requires timely diagnosis and urgent interventions due to the potential for high morbidity and lifethreatening consequences. To diagnose and localize lesions causing oculomotor palsies with high sensitivity, the oculomotor nerves are imaged and evaluated along their anatomic pathway with thin 1-mm coronal views, in addition to axial, sagittal imaging, and angiographic approaches for diagnosing vascular lesions when indicated. When present, most lesions causing oculomotor nerve dysfunction occur in the subarachnoid space (32%) and cavernous sinus (23%) (2,3). Small aneurysms, schwannomas, meningiomas, inflammatory processes, and radiation-induced changes Supported by grants from the top priority of the Clinical Medicine Center of Shanghai (2017ZZ01020). 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 HTML and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). Consent: Written informed consent was obtained from all 5 patients for publication of this manuscript and any accompanying images. A copy of the written consent is available for review by the editor of this journal. Ethics approval and consent to participate: The Institutional Ethics Review Board of the Eye, Ear, Nose, and Throat Hospital of the Fudan University Shanghai approved the study protocol, and written informed consent was obtained from all participants. Consent for publication: Participants gave consent to have anonymous data used for publication in this case series report. Availability of data and materials: The data sets used and/or analyzed during this study are available from the corresponding author on reasonable request. e244 Case 1: Schwannoma of CN III With Acute Worsening Due to Hemorrhage A 28-year-old woman presented with a left ptotic eyelid that occurred immediately on awakening, 4 months before. She denied headaches or periorbital pain. History revealed amblyopia at age 3 years and strabismus surgeries at age 7 years and 22 years, for exotropia of the left eye. A review of systems was unremarkable. A review of her family photographic album showed gradual progression of exotropia and ptosis of the left eye (Fig. 1A). Her best-corrected visual acuity (BCVA) was 20/20 in the right eye (21.50–1.25 · 5) and 20/40 in the left eye (+1.50–1.25 · 115). Pupils measured 2.5 mm in the right eye and 6 mm in the left eye in a brightly lit room with a lack of pupil light reflex on the left eye, and no sectoral iris sphincter palsy on slit-lamp examination. The left eyelid was almost completely ptotic. No evidence of aberrant regeneration was present on examination. The left eye elevation, adduction, and depression were almost completely lacking (Fig. 1B). Normal abduction and intorsion on attempted downgaze provided evidence for the lack of involvement of the sixth and fourth nerves; the right eye motility was normal. Brain MRI, Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology MRA, computed tomography angiography (CTA), and orbital MRI with and without gadolinium contrast were interpreted as normal by the neuroradiologist. However, after review of the imaging study with specific attention to the course of the oculomotor nerve by the neuroophthalmologist, a small intrinsic focal enlargement of oculomotor nerve was identified that enhanced with gadolinium and also showed signal abnormalities consistent with intrinsic hemorrhage of a schwannoma (4.8 mm) in the left cavernous sinus portion (Fig. 1C–E). Case 2: Orbital Schwannoma of CN III With Sparing of Levator Palpebrae A 37-year-old woman presented with a gradual outward deviation of her left eye for 2 years and double vision for 6 months. She was diagnosed with a left Adie pupil at an outside hospital. She denied amblyopia or ocular pain. Her BCVA was 20/20 in both eyes. The left eye showed exotropia on primary gaze with reduced adduction and infraduction and slightly impaired supraduction, consistent with an incomplete oculomotor nerve palsy with sparing of the eyelid (Fig. 2A). There was no upper eyelid ptosis or weakness of the levator palpebrae. Abduction was normal, and intorsion was present on attempted downgaze. The pupils were 2.5 mm in the right eye and 5 mm in the left eye in room light with a lack of pupil light reflex on the left eye, and no sectoral iris sphincter contractions on slit-lamp examination; there was evidence of supersensitivity of the left pupil to low concentration pilocarpine (Fig. 2B, 2C). There was no pupil constriction with near effort. Orbital and brain MRI were interpreted as normal by the neuroradiologist (Fig. 2D). However, when the coronal sections were carefully reviewed by the neuro-ophthalmologist, an intrinsic enlargement of the orbital portion of the oculomotor nerve in the orbital apex that enhanced with gadolinium FIG. 1. Schwannoma of CN III with acute worsening due to hemorrhage. A 28-year-old patient with a history of slowly progressive oculomotor nerve palsy presenting with sudden worsening and a complete CN III palsy due to acute hemorrhage into an intrinsic schwannoma (A), a family photographic album showed titled headed at age 7 years, narrowed fissure in left eye with progressive ptosis with sudden complete ptosis in September 2017. B. Shows ptosis, restriction of elevation, adduction, and depression of the left eye, and left pupillary involvement. Orbital MRI with T1WI images after gadolinium injection showed (C) slight thickening of the left cavernous sinus and a small enhanced nodule near the internal carotid artery on the axial section. D. Coronal section showed a small mass with intrinsic hemorrhage indicative of a schwannoma (red arrow). E. The T2WI image presented a mixed signal of the tumor with an old hemorrhage. Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 e245 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology was appreciated, consistent with a third nerve schwannoma (4.3 mm) (Fig. 2E–2G). Strabismus surgery with splitting and transposition of the lateral rectus to the inferior rectus muscle was performed. One month after the surgery, she was able to fuse in primary gaze without double vision. Case 3: Meningioma of CN III With Primary Aberrant Regeneration A 48-year-old woman presented with an outward deviation of her left eye for 5 years. She had to turn her head to the right to focus on a target without double vision. A review of systems was noncontributory. Her BCVA was 20/20 in both eyes. The left upper eyelid showed retraction in primary gaze and slight retraction in downgaze due to aberrant regeneration. The left eye showed exotropia on primary gaze. Ocular motility showed reduced adduction, elevation, and depression, and normal abduction with no significant change in the pattern of exotropia on upgaze and downgaze; there was intorsion on attempted downgaze in the left eye with normal versions in the right eye (Fig. 3A). Pupils measured 4.0 mm in the right eye and 5 mm in the left eye in light and 4.5 mm in the right eye and 5.5 mm in the left eye in darkness with an intact pupil light reflex but slightly diminished in the left eye compared with the right eye (Fig. 3B) Orbital and brain MRI was originally read as normal (Fig. 3D), but further review by the neuro-ophthalmologist was undertaken due to the chronicity and presence of aberrant regeneration of the eyelid. A small enhancing lesion surrounding the oculomotor nerve in the anterior cavernous sinus with dural enhancement was found, consistent with a meningioma (6.8 mm) (Fig. 3E, F). Case 4: Oculomotor Nerve Paresis With Cyclic Spasms A 20-year-old man was referred for neuro-ophthalmology evaluation and eyelid surgery. History revealed a “small” right eye compared with the fellow eye noted by his parents FIG. 2. Orbital schwannoma of CN III with sparing of levator palpebrae. A 37-year-old patient with a history of slowly progressive diplopia and an isolated palsy of the left CN III with normal levator function and relative sparing of the superior rectus (A), there was no left upper eyelid ptosis. Adduction and depression were restricted in the left eye with a mild supraduction deficit. There was pupillary involvement. B. The infrared video captured the left pupil dilated in room light, with (C) left pupil contraction after the 0.1% pilocarpine test. D. T1WI axial orbit MRI with gadolinium was unremarkable, but (E) T2WI coronal, (F) T1WI coronal, and (G) T1WI parasagittal after contrast images showed a hyperintense enhancing lesion, consistent with a small schwannoma (red arrow) of the left inferior orbital apex. e246 Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology FIG. 3. Meningioma of CN III with primary aberrant regeneration. A 48-year-old patient with oculomotor nerve palsy and primary aberrant regeneration. A. There was left upper eyelid retraction with exotropia and restricted adduction, elevation, and depression, together with pupillary involvement. B, C. The infrared video showed the dilated left pupil in room light (B) and in dim light (C). D–F. T1WI images of orbital MRI after gadolinium injection showed (D), no apparent lesion on axial sections, but coronal sections (E, F) showing enhancement of a small nodule at the left inferior apex and anterior cavernous sinus with adjacent dural enhancement and a tail sign, indicative of meningioma (red arrow). during infancy with frequent right eyelid twitching movements noticed, even during sleep. Strabismus surgery was performed twice for the right eye exotropia. His BCVA was 20/20 in both eyes. There was right ptosis, exotropia, and accompanying pupillary mydriasis during some parts of the examination (paretic phase, Fig. 4A, C), however, periodically there was a slight “twittering” and elevation of the right eyelid, less exotropia, and simultaneous pupillary constriction without light (spasm phase, as shown in Supplemental Digital Content, Video 1, http://links.lww.com/ WNO/A427). Orbit and brain MRI with thin cuts were devoid of pathology. The patient was diagnosed as having congenital oculomotor nerve paresis with cyclic spasm. Case 5: Radiation-Induced CN III Palsy With Neuromyotonia A 63-year-old woman presented with paroxysmal double vision lasting 10 seconds to several minutes with a Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 frequency of 40–50 times per day. On examination, the left eyelid showed slight ptosis with a very small exotropia of the eye. Adduction, elevation, and depression were slightly reduced in the left eye (Fig. 5A). The pupil examination showed normal pupil reactions with no anisocoria in clinic room light and only a very slight anisocoria in bright light where the left pupil was slightly larger. Abduction was normal, and the left eye exhibited intorsion on attempted downgaze, indicating normal sixth and fourth nerve function. During episodes of diplopia, the left eye deviated inward and abduction became greatly reduced (Fig. 5B and Supplemental Digital Content, Video 2, http:// links.lww.com/WNO/A428). During the examination, the patient related that these episodes were often precipitated by bright sunlight. This was verified by opening the examination room window shade and having her look out into the bright sunlight, which indeed precipitated another episode. On further questioning, she recalled that 20 years ago she had surgery for pituitary tumor, followed by radiation e247 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology FIG. 4. Oculomotor nerve paresis with cyclic spasms. A 20-year-old patient with right cyclic oculomotor nerve paresis with spasms. A, C. paretic phase and (B, D) spasm phase. During the paretic phase, there was (A) complete ptosis of the right upper eyelid and (C) pupillary dilation. During spasms, (B) the eyelid retracted slightly and demonstrated a “twittering” movement with simultaneous (D) pupillary constriction (See Supplemental Digital Content, Video 1, http://links.lww.com/ WNO/A427). treatment. Orbital and brain MRI with gadolinium was originally read as normal, but review of the imaging study by the neuro-ophthalmologist showed evidence for slight enhancement of the left CN III in the subarachnoid cistern (Fig. 5C, D) consistent with radiation-induced neuropathy. The patient was diagnosed with radiation-induced neuromyotonia and treated with carbamazepine. The frequency of the episodes was significantly reduced. Patients with isolated oculomotor palsy due to unknown causes are increasingly referred to tertiary hospitals for neuro-ophthalmologic evaluation. Most patients complete comprehensive evaluation, which includes a brain MRI/ MRA or CTA workup to exclude compressive lesions, including aneurysms. Neuroimaging studies read as normal with a persistent CN III palsy provide diagnostic dilemmas that require more extensive history and appreciation of nuances on examination that may have been originally overlooked. Amblyopia and gradual progressive ptosis and recurrence of exotropia after strabismus surgery in Patient 1 increased the suspicion for a congenital, slow-growing tumor (in this case, schwannoma) and not an aneurysm and prompted re-evaluation of the previous imaging that was originally read as normal. The sudden worsening of CN III palsy with complete ptosis in the setting of a previous FIG. 5. Radiation-induced CN III palsy with neuromyotonia. A 63-year-old patient with acquired neuromyotonia of the left CN III medial rectus with a history of radiation to pituitary adenoma 20 years before. A. (upper panel) During the “quiet” phase, the left eye showed normal adduction and abduction on versions. B. (lower panel) During episodes of neuromyotonia with diplopia (often brought on by exposure to sunlight), the left eye developed esotropia with reduced abduction (See Supplemental Digital Content, Video 2, http://links.lww.com/WNO/A428). C, D. T1WI images of orbital MRI after gadolinium injection showed a slight enhancement (red arrow) of the left oculomotor nerve in the subarachnoid cistern. e248 Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology long-standing, slowly progressing oculomotor nerve palsy raised the suspicion of schwannoma with intertumoral hemorrhage, a known complication of these intrinsic oculomotor nerve tumors (4–6). An isolated CN III schwannoma in the absence of neurofibromatosis is rare and was described in 40 patients (7,8). Yang et al (9) classified these tumors into 4 types based on their location— cisternal, cavernous, cisterno-cavernous, and intraorbital. Cisternal schwannomas are the most common, and cavernous schwannomas are infrequently diagnosed (10,11). CN III is located in the lateral dural folds of the cavernous sinus and is lateral to the carotid artery. Knowledge of this anatomy along with this patient’s history and examination in combination with high-resolution, thin slice MR sequences helped with tumor localization in Case 1. Diagnosis of schwannoma of the orbital apex portion of CN III in Case 2 was aided by the history of slowly progressive palsy of the medial rectus, inferior rectus, and iris sphincter with only mild paresis of supraduction and sparing of levator function. Sparing of an extraocular muscle within a division of the oculomotor nerve (sparing of the levator with mild involvement of the superior rectus) may be an important sign of intrinsic tumors of the oculomotor nerve that may be compressing some nerve bundles and sparing others. Case 3 demonstrated eyelid retraction in the setting of a chronic CN III palsy pointing toward a diagnosis of primary aberrant regeneration, a relatively uncommon phenomenon resulting from chronic compression of CN III by tumors or aneurysms, in the absence of antecedent trauma (12,13). Eyelid signs of aberrant regeneration include eyelid retraction that can be accentuated with attempted gaze in adduction, infraduction, or supraduction. Pupillary signs that can be present include miosis in dim light, accentuated by adduction, infraduction, or supraduction and lessened by abduction. Ocular motility signs of aberrant regeneration consist of lessening of exotropia (or induced esotropia) on supraduction or infraduction, Eyelid, pupil, or motility signs of primary aberrant regeneration in the absence of trauma point more toward a lesion caused by chronic compression of the oculomotor nerve, with meningioma being the most common cause. Schwannomas, which originate from the intrinsic components of the peripheral oculomotor nerve, rarely cause aberrant regeneration (14,15). Slowgrowing aneurysms may also produce primary aberrant regeneration but are an uncommon cause. The important aspect of Case 3 is that primary aberrant regeneration of the oculomotor nerve usually indicates a slow-growing compressive lesion and neuroimaging studies read as “normal” should be reviewed with heightened suspicion for an extrinsic, compressive lesion of CN III. The history and examination findings in Case 4 helped make the diagnosis of oculomotor nerve paresis with cyclic spasm, which is a rare congenital condition that is usually not associated with tumors, except in rare cases of a glioma Tian et al: J Neuro-Ophthalmol 2021; 41: e244-e250 (16). Therefore, neuroimaging studies are usually normal. History will reveal congenital onset CN III dysfunction with repeated episodes of CN III activation, resulting in “twittering” of the eyelid, pupil miosis, and lessening of exotropia. There is often a history of several childhood strabismus surgeries. The eyelid movements during episodes of CN III spasm often occur during sleep and were recalled by the parents in this case when specifically questioned. Case 5 had examination findings and history that pointed toward adult onset neuromyotonia, which can occur after brain or orbit radiation (17,18) or rarely in patients with thyroid orbitopathy (19). The repeated episodes of activation of one or more muscles innervated by CN III can occur spontaneously or can be provoked by extreme gaze or by light stimuli, as in this case. A careful review of the patient history, examination, and radiologic imaging is recommended in cases of chronic CN III palsy with “normal” neuroimaging studies, as a CN III lesion is often present that has escaped previous diagnosis. Important historical and examination clues include gradual progression, findings of primary aberrant regeneration, or intermittent CN III activation. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: M. Wang, G. H. Tian, and R. H. Kardon; b. Acquisition of data: C. Y Feng, J. R. Hong, Y. Sha, and G. H. Tian; c. Analysis and interpretation of data: G. H. Tian, R. H. Kardon, M. Wang, and X. H. Sun. Category 2: a. Drafting the manuscript: R. H. Kardon, G. H. Tian, M. Wang, and C. Y. Feng; b. Revising it for intellectual content: G. H. Tian, X. H. Sun, M. Wang, and R. H. Kardon. Category 3: a. Final approval of the completed manuscript: C. Y. Feng, R. J. Hong, Y. Sha, X. H. Sun, M. Wang, G. H. Tian, and R. H. Kardon. Guohong Tian, MD, PhD Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Visual Impairment and Restoration, Shanghai, China Randy Kardon, MD, PhD Department of Ophthalmology and Visual Sciences, University of Iowa and Veterans Affairs Hospital, Iowa City, Iowa Chaoyi Feng, MD, PhD Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China Rujian Hong, MD Yan Sha, MD, PhD Department of Radiology, Eye and ENT Hospital, Fudan University, Shanghai, China e249 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Worldwide Neuro-Ophthalmology Xinghuai Sun, MD, PhD Min Wang, MD, PhD Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China NHC Key Laboratory of Myopia (Fudan University), Key Shanghai Laboratory of Visual Impairment and Restoration, Shanghai, China REFERENCES 1. Fang C, Leavitt JA, Hodge DO, Holmes JM, Mohney BG, Chen JJ. Incidence and etiologies of acquired third nerve palsy using a population-based method. JAMA Ophthalmol. 2017;135:23– 28. 2. Margolin E, Freund P. Third nerve palsies: review. Int Ophthalmol Clin. 2019;59:99–112. 3. Keane JR. Third nerve palsy: analysis of 1400 personallyexamined inpatients. Can J Neurol Sci. 2010;37:662–670. 4. Fatehi Hassanabad M, Akagami R. Sudden neurological deterioration due to repeated intratumoral hemorrhage in a patient with a vestibular schwannoma. J Clin Neurosci. 2019;61:304–307. 5. Sato M, Fujio S, Takajo T, Kamimura K, Hiraki T, Yamahata H, Arita K, Yoshimoto K. 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