Bilateral oculomotor nerve palsies due to vascular conflict

Abstract

Oculomotor nerve palsy is frequently caused by an aneurismal compression and diabetes mellitus. Brainstem infarction, cavernous sinus tumors and other intracranial lesions are well known causes of oculomotor palsy also. However, neurovascular conflict causing oculomotor nerve disturbances are rare [1][2][3][4] . After the advent of high quality MRI and neuroimaging improvements, the diagnosis of such atypical neurovascular conflicts in symptomatic patients became quite simple 5,6 . The case of a patient with bilateral oculomotor disorder with MRI imaging of the head showing a right oculomotor nerve compression by the right posterior cerebral artery and a left oculomotor nerve compression by the left superior cerebellar artery is reported and discussed. CaseThis case report has been approved by the ethics committee of our institution and the patient consented with the publication. A 56 year old man with a chronic bilateral oculomotor nerve paresis was seen at our clinic. He has this non-progressive deficit for more than 15 years without any associated conditions and has been well-adapted to his condition. After an ophthalmologic evaluation, a neurological screening was suggested to exclude the possibility of intracranial mass or aneurysm. He had neither a metabolic disease nor a history of a familial neurological disorder. At physical examination, the patient showed a bilateral ophthalmoplegia, with extrinsic ocular movements depending on the activity of the IV and the VI cranial nerves and an associated partial bilateral ptosis (Fig 1). There were no pupillary abnormalities. All laboratorial results were within normal limits. An investigation to exclude myasthenia gravis was proceeded, with normal thoracic CT-scan and laboratorial tests. A therapeutic test with pyridostigmine failed to improve the III rd nerves function. A T2-weighted MRI imaging of the head revealed bilateral oculomotor nerve compression due to vascular conflicts, the right conflict caused by the right posterior cerebral artery and the left caused by the left superior cerebellar artery (Fig 2). A CTangiography showed no aneurysm or relevant abnormalities. A two-step surgical approach was suggested to the patient who refused to be operated on because he is well-adapted to the ophtalmoplegia and stated that it does not interfere on his daily activities. DisCussionVascular compression of a cranial nerve at the brainstem can cause several syndromes. Most of the neurovascular conflicts found in the literature are reported to occur within the cerebellopontine angle, with an arterial loop or a hindbrain vein compressing a cranial nerve, from the IV to the XII cranial nerves. Trigeminal neuralgia, hemifacial spasm, vertigo and glossopharyngeal neuralgia are well-known hyperactive dysfunctions secondary to a vascular compression of the V, VII, VIII and IX cranial nerves, respectively, mostly on the junction area between the central and the peripheral myelin. Surgical microvascular decompression is the approach of choice to treat many of the cases b...