Congenital Third Nerve Palsy Associated With Midbrain Hypoplasia Due to Bilateral Segmental Internal Carotid Artery Agenesis

A 15-year-old girl, diagnosed with a partial right third nerve palsy, was found to have bilateral internal carotid artery agenesis. Neuroimaging with 3D-constructive interference in steady state scanning identified the possible etiology of the third nerve palsy as midbrain hypoplasia.

Photo Essay Section Editor: Timothy J. McCulley, MD Congenital Third Nerve Palsy Associated With Midbrain Hypoplasia Due to Bilateral Segmental Internal Carotid Artery Agenesis Rebika Dhiman, MD, Bhavya Gorimanipalli, MBBS, Deepa R. Swamy, MD, Sanjay Sharma, MD, Ajay Garg, MD, Rohit Saxena, MD, PhD FIG. 1. Eye movements reveal an exotropia with limitation of elevation, depression, and adduction of the right eye and mild right ptosis. Abstract: A 15-year-old girl, diagnosed with a partial right third nerve palsy, was found to have bilateral internal carotid artery agenesis. Neuroimaging with 3D-constructive interference in steady state scanning identified the possible etiology of the third nerve palsy as midbrain hypoplasia. Journal of Neuro-Ophthalmology 2018;38:483-485 doi: 10.1097/WNO.0000000000000666 © 2018 by North American Neuro-Ophthalmology Society A 15-year-old girl was evaluated for outward deviation of her right eye, which had been present since birth without evidence of progression. Her only other complaint was recurrent episodes of right-sided occipital headache for 9 months. Strabismus and Neuro-Ophthalmology Services (RD, BG, DRS, RS), Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India; and Department of Radiology (SS, AG), All India Institute of Medical Sciences, New Delhi, India. The authors report no conflicts of interest. Address correspondence to Professor Rohit Saxena, MD, PhD, Strabismus and Neuro-Ophthalmology Services, Dr. R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India; E-mail: [e-mail] Dhiman et al: J Neuro-Ophthalmol 2018; 38: 483-485 On examination, visual acuity was counting fingers in the right eye and 20/20 in the left eye. Pupillary reactions were normal, and there was no anisocoria. Anterior and posterior segments were normal in both the eyes. There was exotropia of 65-prism diopters in primary gaze with limitation of adduction, elevation, and depression of the right eye and mild right ptosis (Fig. 1). The function of all other cranial nerves was normal. The patient had mild hypoplasia of the right side of her face. Based on these findings, a clinical diagnosis of right-sided partial congenital pupil-sparing third nerve palsy was made. Postcontrast brain computed tomography revealed an enhancing vascular lesion in the suprasellar space. Digital subtraction angiography demonstrated an aberrant course of the petrous portion of the right internal carotid artery (ICA), aplasia of the choroidal segment with reformation of the terminal ICA using multiple collaterals from right middle meningeal and right internal maxillary arteries (Fig. 2A). There was agenesis of the left ICA (Fig. 2B) with reformation of terminal left ICA from branches of the left external carotid artery (ECA), middle meningeal, accessory middle meningeal, and terminal branches of internal maxillary arteries (Fig. 2C). These findings were consistent with bilateral segmental ICA 483 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo Essay FIG. 2. Digital subtraction angiography. A. Right common carotid artery injection shows multiple collaterals at skull base (arrow) reconstituting the terminal internal carotid artery and (arrowhead) intracranial arteries. B. Lateral view of left common carotid artery shows absence of left internal carotid artery. C. Injection of left common carotid artery shows multiple collaterals at skull base (arrow) reconstituting terminal internal carotid (arrowhead) and intracranial arteries. agenesis (more severe on left) with multiple collaterals from the ECAs at the skull base reconstituting terminal ICAs. Brain MRI revealed atrophy of the right half of the brainstem, and compression of right cerebral peduncle by aneurysmally dilated right posterior communicating artery (Fig. 3). With highresolution 3D-constructive interference in steady state (CISS), the left third nerve was visualized (Fig. 4), but the right third nerve was not. These findings were suggestive of bilateral segmental ICA agenesis with collaterals and congenital right third nerve hypoplasia, thus causing partial right third nerve palsy. Agenesis of ICA is a rare occurrence (1), and its association with third nerve palsy is even rarer. Most patients with ICA agenesis remain asymptomatic because of collateral circulation from the contralateral ICA and vertebrobasilar system (2), but some may present with headache, subarachnoid hemorrhage, and transient ischemic attacks (1). Mechanical or hemodynamic insults to the developing embryo have been postulated as the causative factor of ICA agenesis (3). Elazab et al (4) reported a 2-month-old girl with a third nerve palsy found to have ipsilateral ICA agenesis and a basilar artery aneurysm. Compression of the third nerve by the aneurysm was the presumptive cause of the third nerve palsy. Cherungottil et al (5) reported 2 FIG. 3. Axial T2 MRI (A) and magnetic resonance angiogram (B) demonstrate a dilated right posterior communicating artery (arrows). There is hypoplasia of the right side of the midbrain. 484 Dhiman et al: J Neuro-Ophthalmol 2018; 38: 483-485 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo Essay FIG. 4. Axial 3D-CISS sequence reveals normal left third nerve (arrows) with prominent vascular flow void in interpeduncular cistern. The right third nerve is not visualized. girls aged 40 days and 7 years, with agenesis of the left ICA and right posterior communicating aneurysms causing right third nerve palsies. In both reports, the third nerve palsies were complete with pupillary involvement. By contrast, our patient had a bilateral ICA agenesis and a partial third nerve palsy without apparent pupillary involvement. Neuroimaging with 3D-CISS scanning was unable to visualize the right third nerve. In our patient, the extensive anomaly of the intracranial vascular system (bilateral segmental ICA agenesis) leading to vascular disruption to the developing brain may have caused right-sided hypoplasia of the midbrain leading to a partial right third nerve palsy. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: R. Saxena and S. Sharma; b. acquisition of data: B. Gorimanipalli and D. R. Swamy; c. analysis and interpretation of data: R. Dhiman and R. Saxena. Category 2: a. Drafting the manuscript: R. Dhiman, B. Gorimanipalli, D. R. Dhiman et al: J Neuro-Ophthalmol 2018; 38: 483-485 Swamy, and A. Garg; b. revising it for intellectual content: R. Dhiman, S. Sharma, A. Garg, and R. Saxena. Category 3: a. Final approval of the completed manuscript: S. Sharma, A. Garg, and R. Saxena. REFERENCES 1. Lee JH, Oh CW, Lee SH, Han DH. Aplasia of the internal carotid artery. Acta Neurochir (Wien). 2003;145:117-125. 2. Neves WS, Kakudate MY, Centola CP, Garzon RP, dÀgua AP, Sanches R. Agenesis of the internal carotid artery: a case report. Radiol Bras. 2008:4166. 3. Keen JA. Absence of both internal carotid arteries. Clin Proc. 1945;4:588. 4. Elazab NE, Riel-Romero RM, Gonsalez-Toledo E. Internal carotid artery agenesis and basilar artery aneurysm with third nerve palsy. Pediatr Neurol. 2010;42:451-454. 5. Cherungottil L, Shetty S, Vijayalakshmi P, Dwivedi MK, Srinivasan KG, Saravanan M. Congenital oculomotor nerve palsy due to effects of carotid artery agenesis. JAAPOS. 2014;18:507-509. 485 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.