Midbrain Infarction Causing Diplopia and Atypical Neurological Symptoms: An Abducens Palsy Review A 68 year old white male reports distance horizontal diplopia immediately following a cerebrovascular accident. Neuroimaging shows acute right midbrain infarction. While rarely associated with stroke, neurologic sixth nerve palsies occur and entail further workup. i. CASE HISTORY a. PT DEMOGRAPHICS: 68 year old white male b. CHIEF COMPLAINT: On 8/12/16 patient reports recent onset of horizontal diplopia in the distance for two weeks and reduction of right gaze. Noted diplopia, dizziness, and trace left sided extremity/facial weakness after recent stroke on 07/28/16, but reported no pain, visual field loss, or ataxia. c. OCULAR HISTORY: i. Mild Non-Proliferative Diabetic Retinopathy OS (10-2015) d. MEDICAL HISTORY i. 1999: Diabetes Mellitus ii. 1999: Hypertension iii. 1999: Hyperlipidemia iv. 2009: Cerebrovascular accident v. 2009: Right vertebral artery stent vi. 2014: Transient ischemic attack vii. 2014: Severe posterior circulation disease e. MEDICATIONS i. Metformin ii. Amlodipine iii. Hydrochlorothiazide iv. Lisinopril v. Tamsulosin vi. Clopidogrel bisulfate f. OTHER SALIENT INFORMATION i. MRI 06-26-09; Subacute infarction in left ventral pons ii. MRI 04-20-16; Subacute infarction of left caudate iii. CT Brain without contrast 06-25-09; Subacute infarction in left ventral pons iv. CT Brain without contrast 01-02-16; unremarkable ii. PERTINENT FINDINGS a. CLINICAL i. Vision 1. OD: 20/20-1 cc 2. OS: 20/20 cc ii. Pupils: equal, round and reactive to light with no afferent defect iii. Cover Test (thru habitual Rx) 1. Distance: 10^ Right Esotropia 2. Near: ~4^ Right Esotropia iv. Maddox Rod: 15^ Base Out OD at distance v. Subjective Prism: 12^ base out OD eliminated diplopia vi. Extraocular Motility: Limited right abduction by approximately 30% (IMAGE OF PATIENT) 1. (+) right gaze diplopia, (-) pain vii. Confrontations: Full to finger count viii. Anterior Segment: Unremarkable with (-) ptosis, iris neovascularization ix. Posterior Segment: Unremarkable with (-) optic nerve pallor, neovascularization, hemes, cotton wool spots, exudates b. PHYSICAL i. Results from neurology examination 07-29-16 (Summarized) c. SELECTED LABORATORY STUDIES i. Vitals- 08/04/16 1. Blood Pressure: 148/72 2. Pulse: 58 ii. Labs 1. Glucose -08/03/16 a. 113 2. HbA1C- 07/30/16 a. 6.1% d. RADIOLOGY STUDIES i. CT Brain with contrast 07-29-16 1. No pertinent findings ii. MRI Brain without contrast 07-29-16 (IMAGE OF PATIENT’S MRI) 1. Radiology Impression “Acute infarct right paramedian pontomedullary junction with multiple remote infarcts and chronic microangiopathy” iii. DIFFERENTIAL DIAGNOSIS a. PRIMARY/LEADING i. Gaze paresis secondary to vascular disease 1. Most common cause of CN 6 palsy b. OTHERS i. Aneurysm ii. Tumor iii. Muscle entrapment iv. Giant cell arteritis v. Myasthenia Gravis vi. Raymonds Syndrome vii. Millard Gubler Syndrome viii. Foville’s Syndrome ix. Internuclear ophthalmoplegia iv. DIAGNOSIS AND DISCUSSION a. FINAL DIAGNOSIS: Cranial nerve 6 palsy with neurological findings secondary to midbrain infarction i. MRI confirms acute right infarct, at the right paramedian pontomedullary junction b. ELABORATE ON CONDITION—Cranial Nerve 6 Palsy i. Signs and Symptoms 1. Horizontal diplopia greater in distance 2. Abduction defect 3. Esotropia at distance a. Ipsilateral to abduction defect ii. Epidemiology 1. 11.3 in 100,0004 a. Most common of all Cranial Nerve Palsies 2. 15% of all CN 6 palsies caused by Stroke5 3. Literature reveals 5.8% of stroke cohort had a CN 6 palsy8 4. 47% of all stroke causing CN palsies occur in brainstem cerebellum8 c. EXPOUND ON UNIQUE FEATURES—Cranial Nerve 6 Palsy due to midbrain infarction i. Nuclear 6th Cranial Nerve Palsy 1. Ipsilateral gaze palsy that cannot be overcome by vestibular testing a. Contralateral abduction weakness b. Ipsilateral peripheral facial nerve palsy i. One and a half syndrome ii. Foville’s syndrome iii. Gaze palsy ii. Fascicular 6th Cranial Nerve Palsy 1. Results from location of surrounding structures in the Pons a. Contralateral hemiplegia i. Raymond’s syndrome b. Ipsilateral facial weakness with contralateral hemiplegia i. Millard Gubler Syndrome 2. **UNIQUE FEATURES OF THIS PATIENT** a. trace contralateral limb weakness b. trace contralateral facial weakness iii. Recommended Neuro-Ophthalmic Evaluation 1. Cranial nerve testing 2. Vestibular system and cerebellum testing 3. Evaluation of deep tendon reflexes and peripheral motor system 4. Optic nerve head evaluation v. TREATMENT AND RESPONSE TO TREATMENT a. TREATMENT OPTIONS i. Patching paretic eye or frosting spectacle lens ii. Temporary Fresnel Prism iii. Injection of Botulinum Toxin in ipsilateral medial rectus muscle iv. Surgical intervention 1. Indicated after 6 months of stable deviation b. PROGNOSIS i. Approximately 50% of all CN6 palsies resolve spontaneously after onset (within 3 months) 4 1. Vasculopathic etiologies resolve more rapidly (4-6 weeks) 4 ii. 31-35% recurrence rate for vasculopathic patients 4 c. MANAGEMENT OF CASE i. 12^ BO Fresnel Prism placed on right lens ii. Patient to Return to Clinic on 9/12/16 for follow up vi. CONCLUSION a. Sixth cranial nerve palsies are the most common oculomotor cranial nerve palsies i. Most often caused by vasculopathic disorders in at risk patients over 50 years old. 1. Current treatment protocol does not indicate neuroimaging for these patients. b. When neurological findings are present with cranial nerve palsy, more severe diagnoses should be considered such as cerebrovascular accident, neoplasm or aneurysm. c. Midbrain infarctions causing a sixth cranial nerve palsy are rare and are often associated with additional gaze deficits, facial paresis, or hemiplegia. d. Any patient diagnosed with CN6 palsy and presenting with additional neurological symptoms should be sent for neuroimaging and a further neurological workup regardless of age or presence of vascular risk factors. References: 1 Azarmina, Mohsen, MD, and Hossein Azarmina, MD. "The Sixth Syndromes of the Sixth Cranial Nerve." Journal of Ophthalmic and Vision Research (2012): 160-71. Web. 2 "Does a Patient with an Isolated Vasculopathic Ocular Motor Cranial Nerve Palsy Need a Neuorimaging Study?" Controversies in Neuro- Ophthalmology (2009): 100-03. Web. 3 Ehlers, Justis P., and Chirag P. Shah. "10: Neuro-ophthalmology." The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease. Philadelphia: Lippincott Williams & Wilkins, 2008. 254-56. Print. 4 Goodwin, Denise. "Differential Diagnosis and Management of Acquired Sixth Cranial Nerve Palsy." Optometry - Journal of the American Optometric Association 77.11 (2006): 534-39. Web. 5 "IV. Neuropathies and Nuclear Palsies." Canadian Neuroophthalmology Group. June 2008. Web. 6 Kim, J. S., J. K. Kang, S. A. Lee, and M. C. Lee. "Isolated or Predominant Ocular Motor Nerve Palsy as a Manifestation of Brain Stem Stroke." Stroke 24.4 (1993): 581-86. Web. 7 O'Donnell, Thomas J., MD, and Edward G. Buckley, MD. "Sixth Nerve Palsy." Comprehensive Ophthalmology Update 7.5 (2006): 1-7. Web. 8 Rowe, F. "Prevalence of Ocular Motor Cranial Nerve Palsy and Associations following Stroke." Eye 25.7 (2011): 881-87. Web. 9 Sanders, Scott K., Aki Kawasaki, and Valerie A. Purvin. "Long-term Prognosis in Patients with Vasculopathic Sixth Nerve Palsy11InternetAdvance Publication at Ajo.com Feb 28, 2002." American Journal of Ophthalmology 134.1 (2002): 81-84. Web. 10 Tamhankar, Madhura A., Valerie Biousse, Gui-Shuang Ying, Sashank Prasad, Prem S. Subramanian, Michael S. Lee, Eric Eggenberger, Heather E. Moss, Stacy Pineles, Jeffrey Bennett, Benjamin Osborne, Nicholas J. Volpe, Grant T. Liu, Beau B. Bruce, Nancy J. Newman, Steven L. Galetta, and Laura J. Balcer. "Isolated Third, Fourth, and Sixth Cranial Nerve Palsies from Presumed Microvascular versus Other Causes." Ophthalmology 120.11 (2013): 2264-269. Web. 11 Yanoff, Myron. "Part II: Neuro-ophthalmology." Yanoff: Ophthalmology. 4th ed. S.l.: Elsevier Mosby, 1998. 1319-321. Print. .