Case Report

Microvascular Decompression of the for Paroxysmal and Deficit Dirk De Ridder1, Mary Jane Sime2, Peter Taylor3, Tomas Menovsky4, Sven Vanneste1,5

Key words - BACKGROUND: Microvascular decompression is standard neuro- - Microvascular decompression surgical practice for treating trigeminal neuralgia and hemifacial spasm. Most - Optic nerve - Paroxysmal phosphenes other cranial nerves have been decompressed for paroxysmal intermittent hy- - Visual field deficit peractivity of the affected cranial nerve or in very long-standing compressions to treat cranial nerve hypofunctioning. Abbreviations and Acronyms ICA: Internal carotid artery - CASE DESCRIPTION: We describe a case of intermittent paroxysmal unilat- MRI: Magnetic resonance imaging eral phosphenes (i.e., light flashes) associated with worsening visual field de- MVD: Microvascular decompression VEP: Visually evoked potential fects. Magnetic resonance imaging showed a sandwiched optic nerve/chiasm between an inferior compression of the internal carotid artery and a superior From the 1Departments of Surgical Sciences, Section of compression of the anterior communicating artery. The patient was successfully Neurosurgery, 2Ophthalmology, and 3Internal Medicine, Section of Neurophysiology, Dunedin School of Medicine, treated by microvascular decompression and anterior clinoidectomy plus optic University of Otago, Dunedin, New Zealand; 4Department of canal unroofing. Neurosurgery, University Hospital Antwerp, Belgium; and 5School of Behavioral and Brain Sciences, The University of - CONCLUSIONS: This case report adds to the few previous case reports Texas at Dallas, Dallas, Texas, USA combining 2 previously described techniques (i.e., microvascular decompres- To whom correspondence should be addressed: sion and anterior clinoidectomy plus optic canal unroofing). Dirk De Ridder, M.D., Ph.D. [E-mail: [email protected]] Citation: World Neurosurg. (2016) 85:367.e5-367.e9. fi 14-18 19 fl http://dx.doi.org/10.1016/j.wneu.2015.09.094 de cits, and 1 case report described ashes were present only at night or in phosphenes, or flashes of light, to be darkness and were not triggered by sun- Journal homepage: www.WORLDNEUROSURGERY.org related to vascular compression of the light or other visual stimuli. He had had Available online: www.sciencedirect.com optic nerve by an anterior communicating long-standing (since childhood) esotropic ª 1878-8750/$ - see front matter 2016 Elsevier Inc. artery aneurysm. Whereas the 4 case strabismus, which caused intermittent All rights reserved. reports caused by an ectatic carotid artery diplopia when he was tired. Further describe improvements after surgical ophthalmologic testing showed that un- INTRODUCTION decompression, 2 case reports from the aided acuities were 4/6 on the right not Microvascular compression syndromes are era before magnetic resonance imaging improved by pinhole and 4/6 on the left well-known entities in neurosurgery and are (MRI) describing fusiform aneurysm improving to 4/4 with pinhole. He had a commonly treated by surgical microvascular compression failed to improve after right-sided inferonasal field defect decompression (MVD). Whereas vascular surgical decompression.20,21 (Figure 1). compression of the trigeminal nerve Here, we describe a case of a patient On clinical neurologic examination, no and facial nerve and its respective de- presenting with unilateral flashes of light gross visual loss or field defect could be compressions are mainstream treatments associated with a progressive visual field detected. He had strabismus but his for trigeminal neuralgia and hemifacial deficit treated by insertion of Teflon be- movements were normal. Other cranial spasm,1-3 similar conditions affecting other tween the anterior communicating artery nerve, motor, and sensory examinations cranial nerves have attracted less attention or and the chiasm complemented by anterior were normal, as were his reflexes. are considered controversial.4 For most clinoidectomy, transection of the falciform An MRI scan showed an ectatic distal other cranial nerves, only case reports or ligament, and unroofing of the optic right internal carotid artery (ICA) abutting small case series have been described. canal. the undersurface of the right optic nerve Microvascular compressions and surgical and a compression of the optic chiasm by decompressions of the oculomotor,5 the anterior communicating artery trochlear,6 abducens,7 vestibulocochlear,4,8 CASE REPORT (Figure 2). The right-sided optic nerve and intermediate,9 glossopharyngeal,10 vagal,11 A 73-year-old man presented at the eye chiasm thus appeared to be sandwiched accessory,12 and hypoglossal13 nerve have clinic with photopsia at night or in the between these 2 compressions. been reported. dark, with short paroxysms of white light, Visually evoked potentials (VEP) were A recent addition is the surgical lasting less than a second, and only in his performed using full-field and half-field decompression of the optic nerve or right eye. The flashes became more stimulation. Delays were found after chiasm for progressive visual field frequent but not longer lasting. The right eye stimulation, with both temporal

WORLD NEUROSURGERY 85: 367.e5-367.e9, JANUARY 2016 www.WORLDNEUROSURGERY.org 367.E5 CASE REPORT DIRK DE RIDDER ET AL. MICROVASCULAR DECOMPRESSION OF THE OPTIC NERVE

the vascular compression and the right side of the chiasm to perform the MVD (see Figure 3B). Subsequently, the dural ring over the carotid was incised anteriorly so that the optic nerve became detached from the dura and could be stretched more by the carotid artery. An indentation could be seen in the nerve where the optic strut and the anterior clinoid were located (see Figure 3B). Subsequently, the operative field was thoroughly rinsed and the dura was reconstructed with artificial dura. After this, the orbitozygomatic fi Figure 1. Preoperative visual fields. The inferonasal field defect worsened in 2014, extending to the craniotomy was replaced and xed with superonasal field and becoming a hemifield deficit, at which time surgical treatment was proposed. plates and screws, followed by weaning Soon after surgery, the inferior and superior defects improved. of anesthesia and extubation. On the night after the MVD and optic nerve release, the flashes of white light in his right eye disappeared and did not re- and nasal fields affected. The delays were had deteriorated, which turn. A postoperative computed tomogra- mild to moderate and consistent with early troubled him when reaching for items phy scan performed on day 1 showed the optic nerve disease. No abnormalities such as a cup of coffee. He denied orbitozygomatic approach with anterior were present on the left. changes in or other visual clinoidectomy, optic canal decompres- In view of the typical history, nasal field disturbances. He mentioned that the sion, and the Teflon in situ (Figure 4). Five defect, VEP, and MRI, the diagnosis of flashes had become more brilliant and days after his surgery, he was discharged microvascular compression of the optic longer lasting. The flashes were triggered home and followed up in the outpatient nerve was withheld and the patient was by eye movements. In view of his clinical clinic after 6 weeks and 3 months. At informed that conservative management deterioration, confirmed by visual field follow-up, he had no more phosphenes/ would be maintained except if the symp- testing, he was offered an MVD. photopsia and subjectively had the toms worsened. impression that his vision had improved. Six months later, the patient presented His strabismus on the other hand subjec- SURGERY for routine follow-up at the eye clinic and tively felt worse, even although his a dramatic worsening of his visual field After induction of anesthesia, intubation, diplopia had not worsened. He denied any defect was noted, with both inferior and and ventilation, the patient was put in a headaches, concentration problems, or  superior defects (see Figure 1). He also supine position with his head rotated 40 memory problems, but still had some fa- had the impression that his depth to the left. His head was pinned in a tigue at 6 weeks. Mayfield headrest. An incision was made VEP postoperatively showed an in the hairline across the midline for 3 improvement in the P100 latency of the cm. A single-piece orbitozygomatic right eye nasal half-field VEP from 118 craniotomy was elevated, to minimize milliseconds preoperatively to 110 milli- retraction of his temporal and frontal seconds postoperatively. The temporal lobe. Subsequently, the sphenoid wing half-field VEP remained unchanged at 110 was removed as well as the anterior cli- milliseconds. noid and the orbital roof posteriorly, overlying the optic nerve. After this, the dura was incised over the anterior part of DISCUSSION the temporal lobe and inferior part of the Microvascular compression syndromes, frontal lobe. Subsequently, the sylvian irrespective of the cranial nerve involved, fissure was split widely. Without the use share a common clinical picture, which of retractors, the carotid artery was permits a clinical diagnosis, with MRI to exposed and followed posteriorly to confirm the vascular compression22 or to where the A1 branches off from the ca- exclude another cause for the typical 23,24 Figure 2. Preoperative magnetic resonance rotid and a vascular compression can be clinical picture. imaging showing the sandwiched right optic seen from the A1 as well as the anterior of a microvascular compression syndrome nerve/chiasm. AcoA, anterior communicating artery on the superior can be summarized by unilateral, communicating artery; ICA, internal carotid part of the chiasm (Figure 3AeC). paroxysmal, and intermittent hyperactivity artery; MVC, microvascular compression. Shredded Teflon was inserted between of a cranial nerve, which is often triggered

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