Introduction

   Aneurysms of the paraclinoid segment have presented unique challenges in surgical management. Before the development of microsurgical cranial base techniques, the approach to treating these aneurysms often was made difficult by the obstructing anterior clinoid process. Advances in surgical techniques and cranial base approaches have greatly improved surgical outcomes with paraclinoid aneurysms.³⁾ In addition, endovascular procedures have become a treatment alternative in the management of these lesions, although total obliteration with endovascular treatment is not as likely as it with surgery.⁹⁾
   In cases of giant paraclinoid aneurysms, the worsening of visual acuity after aneurysmal neck clipping has been observed in up to 17% of patients.⁴⁾⁷⁾ Hoh et al.⁸⁾ demonstrated that the overall rate of worsened or new visual deficits after the endovascular coiling of paraclinoid aneurysms was 4%, as compared to a rate of 3% after open surgery. Here, we report a case of a large aneurysm in the paraclinoid artery segment, which was treated via endovascular coiling, and resulted in a progressive visual defect.

Case Report

   A 53-year-old woman was admitted to our clinic complaining of sudden-onset blurred vision in her left eye, coupled with a headache. An examination revealed visual field defects in the temporal side and lower quadrant of the nasal side in the patient's left eye, and in the upper quadrant of the temporal side of the patient's right eye (Fig. 1A). We determined that visual acuity in the patient's left eye had decreased to 20/200. We then conducted a magnetic resonance imaging scan, and this revealed a 1.6×1.9 cm sized globoid lesion, which was consistent with a large paraclinoid aneurysm of the left internal carotid artery (Fig. 2). Angiography confirmed this diagnosis, showing a 22×18×19 mm large aneurysm of the paraclinoid segment in the left internal carotid artery (Fig. 3).
   The authors of this paper then performed a coil embolization, in order to obliterate the aneurysm. Because the patient was alert and well cooperated, we performed procedure under local anesthesia to lesser the complication of general anesthesia. The patient's right femoral artery was punctured, and the coils were impacted into the aneurysm through the microcatheter, which was positioned in the neck of the aneurysm. A total of 16 coils were inserted into the lumen of the aneurysm. The post-embolization angiography revealed a 90% obliteration of the aneurysm, and adequate blood flow in the ACA, MCA, and distal branches (Fig. 4). 
   Five days after the completion of the coiling procedure, the patient began to complain of further visual loss, albeit with no headache, and we then assessed the patient's visual acuity and visual field. These examinations revealed that the patient had incurred total blindness in the left eye, such that we were unable to check her visual field. The patient also had manifested temporal hemianopsia in her right eye, which had become worse than when it was previously checked (Fig. 1B). The patient was treated with corticosteroids, because she had no symptoms except than those of visual loss, and we believed that surgery might do quite a bit more harm to her than any help it might provide. Three months later, the patient returned to our clinic, with slightly improved visual acuity in her left eye, such that light perception was possible. Unfortunately the patient refused an assessment of her visual field at this time, and thus we have no data regarding that issue.

Discussion

   In addition to the prevention of aneurysmal rebleeding, the rationale for open surgical treatment of giant aneurysms is to restore neurological function by decompressing the surrounding neural structures.²⁾¹⁰⁾ However, for patients who undergo endovascular treatment of high-risk giant aneurysms, signs of expansive aneurysmal mass effect may be alleviated after stable obliteration has been achieved.⁵⁾ Drake²⁾ reported the "paradox of great improvement, even recovery, from severe brain stem compression" after intra-aneurysmal thrombosis after deliberate occlusion of the basilar artery. The author concluded that "removal of the pulse pressure and thrombosis must somehow reduce the size of the mass slightly but significantly, even in the first few weeks and even though there may not be much change in size in the computed tomographic scan." Similarly, GDC embolization improved the clinical signs of aneurysmal mass effect for 53% of nongiant lesions treated.¹¹⁾ Tsuura et al.¹²⁾ observed aneurysmal shrinkage to approximately 30% of initial volumes, 2 to 12 months after occlusion of the parent vessel, whereas endovascular coiling led to a volume reduction to 57% of the initial volume, at 18 months after the intervention. Hoh et al.⁸⁾ reported patients who had paraclinoid aneurysms presented with visual complaints displayed excellent visual outcomes. One hundred eighty aneurysms were treated by direct surgery, 57 were treated by endovascular occlusion, and one was treated by surgical extracranial-intracranial bypass and endovascular internal carotid artery balloon occlusion. Of the 12 patients in the surgical group who manifested visual symptoms, 8 patients exhibited improved visual acuity after surgery, 3 patients experienced no changes, and 1 manifested a worsening of visual impairment. Four patients, who had no prior visual symptoms, postoperatively developed new visual deficits. The overall rate of worsened or new visual deficits after surgery was determined to be 3%. Of the four patients in the endovascular group who manifested visual symptoms, three experienced improved visual outcomes after endovascular procedures, one reported no change, and none of the patients' visual symptoms became more prominent. Two patients, however, with no prior visual symptoms, developed new visual deficits after receiving endovascular treatment for their aneurysms. The overall rate of worsened or new visual deficits after receiving endovascular treatment was 4%. Berenstein stated 26 patients with visual loss and giant inoperable aneurysms, in which 19 were treated by endovascular mean.¹⁰⁾ Vision improved in seven patients, remained unchanged in seven, and worsened in one patient. The patient in whom the symptoms worsened was found to respond well to corticosteroids.¹⁾ It is reasonable to surmise that, in these cases, thrombosis may have eliminated the pulsatile pressure within the aneurysm, thereby causing shrinkage to occur as the result of the organization of the saccular thrombus, and the retraction of the aneurysmal wall.
   By way of contrast, the aggravation of the giant aneurismal mass effect has been described to occur after spontaneous thrombosis or endovascular treatment.¹⁰⁾ It has been suggested, therefore, that the combination of the organized thrombus and the noncompressible coils did not allow the natural shrinkage of the aneurysm to occur in a timely fashion.¹⁰⁾ Some reports have shown that visual deficits as the result of retinal embolisms constituted unique complications which are encountered in the endovascular treatment of ophthalmic artery aneurysms.⁶⁾⁹⁾ But it remains currently unknown. However we clearly must recognize that it happens, and be cautious about it when we attempt to manage paraclinoid aneurysms with endovascular treatment.

Conclusion

   Endovascular treatment has emerged as a promising alternative to surgical clipping in selected patients manifesting intracranial aneurysms. The results of a host of studies have indicated that endovascular treatment constitutes a safe and effective therapeutic alternative for the treatment of ruptured and unruptured paraclinoid aneurysms. However, complications have also been reported in relation to endovascular treatment of both ruptured and unruptured paraclinoid aneurysms. Visual symptoms related to the mass effects of giant paraclinoid aneurysm are normally reported to be improved after coil embolization, but symptoms have also been reported to worsen after the procedure, in some cases. Here, the authors report an unusual case of progressive visual loss occurred after the performance of endovascular coiling treatment for a large paraclinoid aneurysm. 

REFERENCES

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