Bilateral Sixth Nerve Palsy

Esotropia; Bilateral Abduction Weakness; Bilateral Sixth Nerve PalsyDouble visionThe patient is a 60 year old woman who consulted her ophthalmologist with a chief complaint of double vision looking to the left. He diagnosed of a left sixth nerve palsy. No investigations were done. Two years later she complained of diplopia looking to the right. A diagnosis of bilateral sixth nerve palsy was made. She was referred to the Neurovisual Clinic at the Massachusetts General Hospital and was admitted. Brain CT showed: A large clivus vascular tumor without bone destruction consistent with a meningioma. Neuro-ophthalmological Examination: Visual acuity 20/25 OU Visual fields, pupils and fundus examination normal. Ocular Motility: Esotropia OD > OS Bilateral abduction weakness Cranial nerves 3 and 4 normal Lower cranial nerves normal Neurological examination: Motor System: Normal Sensory System: Normal Coordination: No ataxia Diagnosis: Bilateral sixth nerve palsy Clivus meningioma Neurosurgical Consult: Advised conservative management without a biopsy. She was lost to follow-up.This patient with a clivus tumor, diagnosed as an inoperable meningioma, had bilateral sixth nerve palsies. • Esotropia OD > OS • Bilateral abduction weakness • Cranial nerves 3 and 4 normal • Lower cranial nerves normal Bilateral isolated sixth nerve palsies are generally "bad news" and when present should be considered due to a posterior fossa tumor until proved otherwise. The etiology of bilateral sixth nerve palsies include: • CNS lymphoma infiltrating the cavernous sinus(ID946-2) • Demyelination • Wernicke's encephalopathy (ID163-3) • Meningitis • Increased intracranial pressure • Other clivus tumors such as chordoma (ID26-1) • Leptomeningeal carcinomatosisNo imaging studies are available in this patientThe abducens nucleus of the sixth nerve lies in the floor of the fourth ventricle, at the level of the lower pons, and contains three groups of neurons: 1. Abducens motoneurons which innervate the ipsilateral lateral rectus muscle. 2. Abducens internuclear neurons, which project to the contralateral medial rectus subnucleus of the oculomotor nucleus via the medial longitudinal fasciculus 3. Neurons that project to the cerebellar flocculus The genu of the facial nerve curves over the dorsal and lateral surfaces of the nucleus, while the medial longitudinal fasciculus lies medial to each nucleus. The abducens nerve fascicle during its passage in the pons, lies adjacent to the motor nucleus and fascicle of the facial nerve, the motor nucleus of the trigeminal nerve, the spinal tract of the trigeminal nerve, the superior olivary nucleus, the central tegmental tract, and the corticospinal tract. The sixth nerve emerges from the brainstem between the pons and medulla, lateral to the pyramidal prominence. It then runs upwards along the ventral surface of the pons, lateral to the basilar artery, and passes between the pons and the anterior inferior cerebellar artery to ascend through the subarachnoid space along the clivus. It then pierces the dura mata, crosses around and through the inferior petrosal sinus, and passes under the petroclinoid (Gruber's ligament) in Dorello's canal to enter the cavernous sinus. In the cavernous sinus, the nerve bends laterally around the intracavernous segment of the internal carotid artery (ICA) and runs medial and parallel to the ophthalmic division (V1) of the trigeminal nerve. The ocular sympathetic fibers leave the ICA and join briefly with the abducens nerve before joining the ophthalmic division (V1) of the trigeminal nerve. Unlike the oculomotor (third nerve) and trochlear (fourth nerve), the abducens nerve does not lie within the lateral wall of the sinus, but rather it runs within the body of the sinus. The sixth nerve enters the orbit through the superior orbital fissure, passes through the annulus of Zinn, and innervates the lateral rectus muscle. See Ref (8) and (12) for full discussion.Review ref (8)Conservative1. Chen KS, Hung IJ, Lin KL. Isolated abducens nerve palsy: an unusual presentation of leukemia. J Child Neurol 2002;17:850-851. http://www.ncbi.nlm.nih.gov/pubmed/12585727 2. Currie JN, Lubin JH, Lessell S. Chronic isolated abducens paresis from tumors at the base of the brain. Arch Neurol 1983;40:226-229. http://www.ncbi.nlm.nih.gov/pubmed/6830471 3. Harada T, Ohashi T, Ohki K et al. Clival chordoma presenting as acute esotropia due to bilateral abducens palsy. Ophthalmologica 1997;21:109-111. http://www.ncbi.nlm.nih.gov/pubmed/9097318 4. Harbison JW, Lessell S, Selhorst JB. Neuro-ophthalmology of sphenoid sinus carcinoma. Brain 1984;108:855-870. http://www.ncbi.nlm.nih.gov/pubmed/6478180 5. Ikezaki K, Toda K, Abe M, Tabuchi K. Intracavernous epidermoid tumor presenting with abducens nerve paresis - case report. Neurologia Medico-Chirurgica 1992;32:360-364. http://www.ncbi.nlm.nih.gov/pubmed/1381064 6. Ilhan O, Sener EC, Ozyar E. Outcome of abducens nerve paralysis in patients with nasopharyngeal carcinoma. Eur J Ophthalmol 2002;12:55-59. http://www.ncbi.nlm.nih.gov/pubmed/11936446 7. Keane JR. Bilateral sixth nerve palsy. Analysis of 125 cases. Arch Neurol 1976;33:681-683. http://www.ncbi.nlm.nih.gov/pubmed/184766 8. Leigh RJ, Zee DS. Diagnosis of Peripheral Ocular Motor Palsies and Strabismus. Ch 9:385-474. In: The Neurology of Eye Movements, Fourth Edition. Oxford University Press, NY 2006. 9. Lopez R, David NJ, Gargano F, Post JD. Bilateral sixth nerve palsies in a patient with massive pituitary adenoma. Neurology 1981;31:1137-1138. http://www.ncbi.nlm.nih.gov/pubmed/7196535 10. Morioka T, Matsushima T, Yokoyama N. Muratami H, Fujii K, Fukui M. Isolated bilateral abducens nerve palsies caused by rupture of a vertebral artery aneurysm. J Clin Neuroopthalmol 1992;12:263-267. http://www.ncbi.nlm.nih.gov/pubmed/1287052 11. Volpe NJ, Liebach NJ, Munzenrider JE, Lessell S. Neuro-ophthalmological findings in chordoma and chondrosarcoma of the skull base. Am J Ophthalmol 1993;115:97-104. http://www.ncbi.nlm.nih.gov/pubmed/8420385 12. Wong AM. Nuclear and infranuclear ocular motor disorders. Chp 12:919-242. In: Eye Movement Disorders. Oxford University Press, 2008.curriculum_fellow; MTemspsixthabducens; MTemspsixthabducen