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Show Journal of Neuro- Ophthalmology 17( 4): 231- 239, 1997. © 1997 Lippincott- Raven Publishers, Philadelphia Cavernous Internal Carotid Artery Aneurysms Treated With Electrolytically Detachable Coils Van V. Halbach, M. D., Randall T. Higashida, M. D., Christopher F. Dowd, M. D., Ross W. Urwin, M. D., Peter A. Balousek, M. D., Todd E. Lempert, M. D., and Grant B. Hieshima, M. D. Objectives: To report the results of treatment of aneurysms involving the cavernous segment of the internal carotid artery treated with a new device, the electrolytically detachable platinum coil. Materials and Methods: Between 1991 and 1995,220 patients with intracranial aneurysms were treated with the electrolytically detachable platinum coils. Thirty- five patients ( 16%) harbored aneurysms involving the cavernous segment of the internal carotid artery and are the subject of this report. The presenting symptoms were cranial nerve palsies in 19 ( 54%), epistaxis in 4 ( 11%), and subarachnoid hemorrhage in 3 ( 9%). The age ranged from 31 to 80 years, with a mean of 58 years, and included 26 women and 9 men. The aneurysm size ranged from 5 to 22 mm, with an average of 11.6 mm. Results: Of the seven patients who presented with bleeding ( epistaxis in four, subarachnoid bleeding in three), none had bleeding after treatment. Of patients who presented with cranial nerve palsy, 58% had complete resolution of signs and symptoms and 38% showed dramatic improvement. Only one patient who presented with severe visual, loss and optic atrophy was slightly worse after treatment. Two patients died from causes unrelated to their cavernous aneurysms or their endovascular treatment. Conclusions: In patients who harbor a symptomatic aneurysm arising from the cavernous segment of the internal carotid artery with a definable neck, electrolytically detachable coils offer an excellent treatment modality that permits aneurysm closure with preservation of flow in the carotid artery. Key Words: Cavernous sinus- Cavernous aneurysm- Embolization- Electrolytically detachable coils. Aneurysms that involve the cavernous segment of the internal carotid artery are rare, composing only 3% to 5% Manuscript received November 25, 1996; accepted February 28, 1997. From the Department of Radiology, Neurointerventional Section ( V. V. H., R. T. H., C. F. D., R. W. U., P. A. B., T. E. L., G. B. H.), and the Department of Neurological Surgery ( V. V. H., R. T. H., C. F. D., G. B. H.), University of California, San Francisco, San Francisco, California, U. S. A. Address correspondence and reprint requests to Van V. Halbach, M. D., Department of Radiology, L352, UCSF Medical Center, 505 Parnassus Avenue, San Francisco, CA 94143- 0628, U. S. A. of all intracranial aneurysms ( 1). Although occasionally asymptomatic, most produce symptoms that prompt evaluation, often by an ophthalmologist. Ruptured cavernous aneurysms can rarely produce both subarachnoid hemorrhage ( 1,2) and massive epistaxis ( 3,4), but usually result in a carotid cavernous fistula with the classic findings of proptosis, bruit, chemosis, and cranial neuropathy ( 2,5). Carotid cavernous fistulas are usually treated with detachable balloons. Unruptured cavernous aneurysms may produce retro-orbital headache, fifth nerve dysfunction, diplopia, and occasionally ischemic ( 2) and embolic events ( 2,6). Although conservative treatment has been advocated for asymptomatic cavernous aneurysms ( 7), the management of symptomatic aneurysms has evolved considerably over the past 50 years. The earliest surgical attempts at treatment included deconstructive ( parent vessel occlusion) procedures including common carotid artery ligation ( 5,8,9), internal carotid artery ligation ( 5,8,9), and carotid trapping procedures ( 5). These procedures could often reduce or eliminate the patient's symptoms but carried both short- and long- term complications of stroke ( 10- 12). Recent endovascular techniques have evolved that have drastically reduced the risk of stroke and identify patients who may be at high risk for stroke from deconstructive procedures such as carotid occlusion. These techniques include balloon test occlusion with induced hypotension, or blood flow perfusion evaluation, and the development of endovascular carotid occlusion techniques with detachable silicone and latex balloons ( 2,13- 20). Despite these impressive advances, immediate and delayed stroke after carotid occlusion can still occur. In the past 10 years, the ability to navigate a detachable silicone or latex balloon into the aneurysm sac with preservation of the parent vessel has been reported ( 5,13,16,18- 20) in patients whose aneurysm demonstrated a definable neck. We are reporting the results of treatment of this same population with a new occlusion device, the electrolytically detachable platinum coil, which has been recently approved by the U. S. Food and Drug Administration ( FDA) for the treatment of surgically difficult aneurysms. 231 232 V. V. HALBACH ETAL. PATIENTS AND METHODS Patient Population Thirty- five patients with aneurysms that involved the intracavernous segment of the internal carotid artery were treated with electrolytically detachable coils between December, 1991 and December, 1995. Aneurysms that occur at the distal portion of the cavernous sinus or project inferiorly into the cavernous sinus were excluded from this study. This includes carotid ring or paraclinoid aneurysms, sometimes referred to as superior hypophyseal and carotid ophthalmic aneurysms. Although these aneurysms can rarely originate entirely within the cavernous sinus, they typically arise distal to the carotid ring above the cavernous sinus. Most ( 30 patients) were treated under an FDA- approved investigational device exemption protocol designed to evaluate use of the electrolytically detachable coil in intracranial aneurysms that fail surgical clipping, are surgically inoperable because of location or size, or present a high surgical risk. The protocol was approved by the institutional review board for human subjects at the University of California at San Francisco. All subjects had signed informed consent before treatment. The electrolytically detachable coil received FDA approval for the treatment of surgically difficult aneurysms in September of 1995. The patients' ages at the time of treatment ranged from 31 to 80 years, with an average of 58 years. This group included 26 women and 9 men. Presenting Symptoms Nineteen patients presented with mass effect symptoms from compression of the adjacent cranial nerves by the aneurysm sac. Five patients presented with a third FIG. 1. A 56- year- old woman who presented with severe visual angiogram, lateral projection, demonstrates a cavernous aneurysm ( arrows). B: Angiogram postembolization with coils ( arrows) demc parent artery. nerve palsy alone, eight patients had sixth nerve involvement, and one patient suffered from fifth nerve dysfunction. Three patients had involvement of the third and sixth nerves, and the remaining two patients had involvement of the third and fourth nerves. One patient had severe visual loss in the left eye secondary to an anteriorly projecting aneurysm arising from the carotid siphon ( Fig. 1). Two patients had rupture of the cavernous aneurysm, producing a direct carotid cavernous fistula. They both had bruit, proptosis, and chemosis, in addition to their cranial nerve palsies. Four patients presented with massive epistaxis from medially projecting cavernous aneurysms. Two of the patients had undergone prior transsphenoid surgery for pituitary adenoma at an outside institution, and massive bleeding was encountered at the time of the surgery. In these two individuals, the source of bleeding was suspected to be a pseudoaneurysm, although surgical trauma to a medially directed cavernous aneurysm could not be excluded ( 21,22). One patient presented with minor epistaxis from a medially projecting cavernous aneurysm. Three patients presented with subarachnoid hemorrhage from an intracavernous aneurysm. In one patient, an aneurysm projected medially into Meckel's cave and produced a large subarachnoid hemorrhage ( see Fig. 4). A second patient had type IV Ehlers- Danlos disease and the bleeding site may have been a dissecting aneurysm that ruptured through the cavernous sinus into the subarachnoid space at the level of Meckel's cave. The third aneurysm arose from the proximal carotid siphon and extended toward the carotid ring. Two patients had aneurysms that extended medially into the sella turcica and were thought to be at risk for subarachnoid bleeding. loss and optic atrophy on the left. A: Left common carotid injection arising from the carotid siphon projecting anteriorly into the optic canal mstrates complete occlusion of the aneurysm with preservation of the J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 CAVERNOUS INTERNAL CAROTID ARTERY ANEURYSMS 233 The remaining patients presented with severe, ipsilat-eral, unrelenting retro- orbital headaches. Aneurysm Morphology The angiographic lumen of the intracavernous aneurysms ranged from 5 to 22 mm, with a mean of 11.6 mm. Six patients had a large amount of thrombus present as determined by computed tomography ( CT) or magnetic resonance imaging ( MRI). The neck of the aneurysm was large ( 4 mm or larger) in 27 patients ( 77%). In the remaining eight patients ( 23%), the neck was smaller than 4 mm. Technique Thirty patients were treated with neuroleptic anesthesia, whereas the remaining patients underwent general anesthesia. All patients underwent four- vessel arteriography to exclude aneurysms at other locations. Patients who harbored wide neck aneurysms underwent balloon carotid test occlusion for 30 minutes. All diagnostic and therapeutic procedures were performed from a trans-femoral arterial access. Six- or 7- Fr sheaths were placed in the femoral artery for arterial access. Specialized projections of the internal carotid artery were obtained to permit optimal visualization of the aneurysm sac and to separate it from the parent vessel. This view permits accurate measurement of the aneurysm neck ( see Fig. 2C). To permit accurate measurement of the aneurysm dimensions and its attachment to the parent vessel ( neck), 1- cm washers were placed on either side of the head in the angiographic plane most suitable to visualize the neck. After accurate delineation of the aneurysm morphology, systemic anticoagulation with 75 U/ kg of porcine heparin was administered by intravenous bolus. Activated clotting times ( Hemochron; International Technidyne, Edison, NJ) were obtained before and after the administration of heparin and the heparin dose was titrated to achieve a clotting time more than twice baseline. The diagnostic catheter was exchanged for a 6- Fr guiding catheter ( Cordis Corporation, Miami Lakes, FL) positioned in the proximal cervical internal carotid artery. This large- caliber guiding catheter permits repeat roadmapping ( freezing the images to permit navigation and placement of coils into the aneurysm sac) with concurrent placement of a soft microcatheter ( Target Therapeutics, Corporation, Fremont, CA; and Cordis Corporation) coaxially through it. Under fluoroscopic guidance, the variable- stiffness microcatheter was carefully advanced into the aneurysm sac. Soft, electrolytically detachable platinum coils ( Target Therapeutics Corporation) were then delivered into the aneurysm sac. The coils have a circular memory with diameters ranging from 2 to 25 mm, and range in length from 2 to 30 cm. The platinum coil is soldered to a stainless steel delivery wire that permits repositioning and removal of the coil if needed. When the coil was positioned in a perfect position, a positive current ( 1 mA, 3 V) was applied to the delivery wire that dissolves the junction between the platinum coil and the delivery wire. Sequentially smaller- diameter coils were then positioned in the aneurysm sac to produce complete thrombosis of the sac. The microcatheter and guide catheters were then removed and the anticoagulation either reversed with protamine sulfate or continued for a short duration, typically less than 24 hours. Postembolization arteriography was performed to delineate the result of endovascular aneurysm thrombosis by the coils. RESULTS Nineteen patients presented with objective signs from mass effect of the intracavernous aneurysm on adjacent cranial nerves. Eleven patients ( 58%) had complete resolution of the presenting cranial nerve dysfunction without development of new signs or symptoms. Seven patients ( 39%) experienced dramatic improvement in their presenting cranial nerve palsies. One patient who presented with severe visual loss secondary to an aneurysm projecting forward into the optic canal has had slight worsening in her acuity after treatment, but has had stable vision for the past 53 months ( Fig. 1). Four patients suffered massive epistaxis, and one patient had minor epistaxis before treatment. None has had any bleeding episodes after coil treatment, although one patient died 1 month after treatment, presumably from unrelated causes ( 21). Three patients experienced subarachnoid bleeding before treatment, and all had 100% occlusion of their aneurysms without any subsequent bleeding episodes post-therapy. The two patients with symptoms of carotid cavernous fistulas have had complete resolution of their proptosis, chemosis, bruit, and cranial nerve palsies. The clinical follow- up ranges from 8 to 56 months, with an average of 28.8 months. The angiographic results were grouped into percentage occlusion of the aneurysm sac by the detachable coils and associated thrombus. Twelve patients ( 34%) had complete angiographic occlusion of the aneurysm. Fifteen patients ( 40%) had 90- 99% occlusion. The remaining four patients had 75%, 85%, 85%, and 30% occlusion on follow- up arteriography. Thirty- one follow-up arteriograms were performed on 23 patients. The parent artery was patent in 30 patients, and in the 1 patient with Ehlers- Danlos syndrome, it was intentionally closed at the time of treatment because of severe narrowing of the carotid artery produced by the adjacent aneurysm. Six patients required additional treatment with coils to provide maximal occlusion of the aneurysm sac. Complications A groin hematoma developed in one patient after removal of the femoral catheter. She remained hemody-namically stable and was treated conservatively with no permanent morbidity. In two patients, a malpositioned coil unraveled during withdrawal from the aneurysm sac. In the first case, the coil was snared and removed. In the second case, the end of the unraveled coil was implanted in the puncture site. The patient was subsequently treated with aspirin 325 mg/ day for several months. The foliow- J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 234 V. V. HALBACH ETAL. up arteriogram was unremarkable and the patient's presenting symptoms abated. One patient experienced a transient ischemic event immediately after treatment and was treated with aspirin for several months, but suffered no permanent sequelae and has had no further events. A 77- year- old woman presented with diplopia and was noted to have a right third nerve palsy. Angiographic workup revealed an unruptured, asymptomatic right middle cerebral aneurysm and a partially thrombosed left cavernous aneurysm. She underwent successful detachable coil treatment of the left cavernous aneurysm and several weeks later had complete resolution of her diplopia. Although surgical clipping of the contralateral remaining middle cerebral aneurysm was strongly recommended, she refused additional treatment. Two years later, she died from a subarachnoid hemorrhage produced by rupture of the middle cerebral aneurysm. One patient who initially presented with massive ep-istaxis was successfully treated with detachable coils and had no rebleeding. He had a series of strokes 1 month after treatment. A series of blood cultures proved positive and the strokes were thought to be caused by subacute bacterial endocarditis, although infected coils in the aneurysm could not be entirely excluded. He was treated successfully with antibiotics and discharged home. This 78- year- old man died the following month from unknown causes, and this is the only case in this series that has been previously reported ( 21). ILLUSTRATIVE CASES Case 1 A 65- year- old woman presented with severe retro-orbital headaches accompanied by diplopia of 6 weeks' duration. Physical examination was remarkable for the presence of a right sixth nerve palsy. An MRI and magnetic resonance angiography examination ( Fig. 2B) revealed a partially thrombosed, 10- mm aneurysm. Arteriography in the right anterior oblique projection ( Fig. 2C) showed the aneurysm had a wide but definable neck. Four electrolytically detachable coils, a total length of 120 mm, were navigated into the aneurysm sac and detached, producing 95% occlusion of the volume of the aneurysm. Over the ensuing 2 months her headaches subsided and the diplopia resolved. A follow- up arteriogram at 6 months revealed some compaction of the previously placed coils with refilling of the aneurysm neck. This was retreated with four additional coils, resulting in 95% occlusion of the aneurysm sac ( Fig. 2D). The patient's examination remained negative and she had no further episodes of headache or diplopia. She remains well at 27 months after treatment. Case 2 A 77- year- old woman presented with a 1- month history of diplopia. On ophthalmologic examination, she was noted to have a third nerve palsy and ptosis on the right. A contrast- enhanced CT scan showed a large, partially thrombosed aneurysm involving the right cavernous sinus ( Fig. 3A). Arteriography confirmed the presence of a partially thrombosed aneurysm ( Fig. 3B). Ten electrolytically detachable coils were delivered into the aneurysm sac on two separate treatment sessions separated by 5 months. On the final postembolization arteriogram and late follow- up arteriogram at 8 months ( Fig. 3C), most of the aneurysm (> 90%) remained thrombosed. The patient had dramatic improvement in her diplopia and only experiences occasional diplopia when she is tired. Case 3 A 49- year- old woman began experiencing retro-orbital headaches, diplopia, and ptosis 10 weeks before discovery of a giant aneurysm involving the cavernous segment of the left internal carotid artery. On physical examination, there was total ophthalmoplegia. On MRI examination, the aneurysm measured 30 mm and contained a considerable amount of thrombus. Arteriography revealed a partially thrombosed left cavernous aneurysm, a small left carotid ophthalmic aneurysm, and a fusiform aneurysm arising from the proximal basilar artery ( Fig. 4A, B). A balloon test occlusion of the left carotid artery was performed and tolerated for 30 minutes. Although the patient tolerated the test occlusion, carotid occlusion was not thought to be the optimal treatment because it would increase collateral flow through the fusiform basilar aneurysm. Electrolytically detachable coils were therefore navigated into, the aneurysm sac and detached with preservation of the parent artery ( Fig. 4C, D). The patient subsequently has had considerable improvement in her ocular motility, and 4 months after treatment has had resolution of her ptosis and third nerve palsy, with diplopia only on far lateral gaze. Slight recanalization of the thrombus in the aneurysm was noted on a follow- up arteriogram 6 months later, and this was successfully treated with additional detachable coils. DISCUSSION Most cavernous aneurysms present with symptoms of retro- orbital headache or mass effect with dysfunction of the third, fourth, fifth, and sixth cranial nerves ( 2,5). Medially or superiorly projecting cavernous aneurysms can produce optic nerve dysfunction ( Fig. 1) or subarachnoid hemorrhage ( 2,4,5,7). Cavernous aneurysms can also erode medially into Meckel's cave and produce subarachnoid bleeding, which occurred in three patients ( 9%) in our series. Aneurysms that project medially into the sphenoid sinus can present with life- threatening ep-istaxis, which occurred in four ( 11%) patients in this study ( 2,4,5). Aneurysm rupture in this location most often produces a direct carotid cavernous fistula, which currently is most often treated with detachable silicone or latex balloons. Therapeutic decision making regarding intracavernous aneurysms is difficult. Cavernous aneurysms, as a general rule, are less life threatening than intracranial aneurysms. The location at the skull base, surrounded by the adjacent sphenoid bone, cavernous sinus, and cranial J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 CAVERNOUS INTERNAL CAROTID ARTERY ANEURYSMS 235 FIG. 2. A 65- year- old woman who presented with severe retro- orbital headaches and diplopia. A: T1- weighted coronal magnetic resonance image ( MRI; TR 500, TE 15) demonstrates a partially thrombosed aneurysm arising from the intracavernous segment of the right internal carotid artery. B: Three- dimensional time- of- flight MR angiography ( TR 45, TE 5); volume of interest demonstrates an interiorly directed aneurysm ( arrows) arising from the proximal horizontal segment of the right internal carotid artery. C: Right internal carotid, arteriogram 45° anterior oblique projection, demonstrates a wide- neck ( arrows) aneurysm arising from the proximal horizontal segment of the internal carotid artery. D: Angiogram, same injection and projection as Figure 1C, postembolization, demonstrates that the electrolytically detachable coils have produced 95% occlusion of the aneurysm sac. nerves, has complicated the direct surgical management of this disease. The management of an aneurysm involving the cavernous segment of the internal carotid artery has evolved considerably over the past few decades. Carotid occlusion by surgical ligation techniques has been performed for a variety of anterior circulation aneurysms; however, the acute and long- term complication rates have prompted the development of alternative treatments. The complication rates for internal carotid and common carotid ligation have been reported to be 6% and 11%, respectively ( 12). Delayed complications with carotid ligations have been reported, including a delayed stroke rate of between 6% and 7.5% ( 10,11). Direct surgical attack of the aneurysm with hypothermic arrest has also been reported ( 23), as well as direct exposure of the cavernous sinus through a variety of approaches to permit direct surgical clipping ( 24- 28). Recently created surgical bypass procedures with vein graft bypass from the petrous carotid to the supraclinoid carotid artery have also been described; however, these techniques have not been widely accepted ( 29,30). Direct surgical approaches to intracavernous aneu- J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 236 V. V. HALBACH ETAL. ' T& i *, i-"£ ~ ! * j * . . » , b ^£ S&? •", . ~^ . - J . f • •••'. l . 3IJS J « ' ^ ^ \ j < ^ ^ * * • R J& o1 • | " ^ fa ' T. r *? T^: ** mat L f .: Ti1i • • Hflfe . Ex " U^" '-" J *• • '• FIG. 3. A 77- year- old woman who presented with diplopia and ptosis of the right eye. A: Contrast- enhanced computed tomography scan at the level of the sella turcica demonstrates a partially thrombosed aneurysm in the right cavernous sinus ( arrows). B: Right internal carotid injection angiogram, lateral projection, demonstrates a cavernous aneurysm ( arrows) originating from the lateral aspect of the carotid siphon. The patient was treated with 10 detachable coils over two treatment sessions. C: A late follow- up arteriogram, right internal carotid injection, lateral projection, demonstrates thrombosis of most of the aneurysm sac by the coils. The patent internal carotid artery can be seen through the coil mass. rysms have been reported ( 23- 28,31), and the morbidity and mortality associated with these treatments has been reduced with increasing experience. Dolenc ( 31) recently reported the largest series of cavernous aneurysms treated by direct surgical clipping. He reported 64 patients treated over a 10- year period, with more than half of the patients harboring asymptomatic aneurysms. The reported complications included three ( 5%) postoperative deaths ( two patients with traumatic aneurysms), four patients ( 6%) with mild hemiparesis, two patients ( 3%) with a permanent sixth nerve palsy, and two additional patients ( 3%) with a permanent third nerve palsy, for a total complication rate of 20%. He advocated that the initial attempt at treatment be made by a neuroradiologist from an endovascular approach, with the goal of complete exclusion of the aneurysm and preservation of the adjacent carotid artery ( 31). We agree that endovascular treatment should be the primary treatment for symptomatic cavernous aneurysms, and that electrolytically detachable coils have been shown in this series to be the most suitable occlusion device. Endovascular procedures developed to treat symptomatic cavernous aneurysms include balloon test occlusion and carotid sacrifice with detachable balloons ( 13- 20) as well as fibered and detachable coils. Although the complication rates of carotid occlusion with detachable balloons have been lower than with surgical ligation or trapping procedures, there are still disadvantages to this technique. Delayed complications from carotid occlusion still exist despite the development of ancillary tests, including cerebral perfusion blood flow scans, transcranial Dopp-ler, and CT blood flow imaging. The extra demand placed on the collateral vessels also theoretically increases the chance for additional aneurysms to develop. Techniques have been described in the past 10 years for placement of detachable latex or silicone balloons into an aneurysm sac with preservation of the parent vessel ( 18- 20). In treating cavernous aneurysms, our group has reported success in alleviating the mass effect, but a complication rate of 5% stroke and 10% transient cerebral ischemia has prompted the evaluation of alternative intravascular occlusion devices. The electrolyti- J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 CAVERNOUS INTERNAL CAROTID ARTERY ANEURYSMS 237 FIG. 4. A 49- year- old woman who had complete ophthalmoplegia and severe retro- orbital pain secondary to a giant partially thrombosed aneurysm. Left internal carotid injection angiograms, anteroposterior ( A) and lateral ( B) projections, demonstrate a partially thrombosed aneurysm ( arrows) arising from the proximal cavernous internal carotid artery. Postembolization left internal carotid angiograms, same injection, anteroposterior ( C) and lateral ( D) projections, demonstrate complete thrombosis of this aneurysm with preservation of the parent artery flow by the coils. The unruptured 3- mm carotid ophthalmic aneurysm was treated with surgical clipping at a later time. cally detachable platinum coil has emerged as an excellent alternative in patients who are diagnosed with an intracavernous aneurysm that has an angiographically definable neck. The ability to reposition and retrieve coils before detachment has provided greater accuracy in aneurysm occlusion. The ability to deliver these coils through small microcatheters can permit treatment of aneurysms previously untreatable with detachable balloons. There are recent preliminary reports of treatment of intracranial aneurysms using this device ( 32- 35), but only a single case report describes treatment of a cavernous aneurysm ( 34). This larger series suggests that the treatment of cavernous aneurysms is both feasible and effective. In patients diagnosed with a cavernous aneurysm without a definable neck and who tolerate balloon test occlusion, we prefer to use detachable silicone balloons ( 2,18). One patient in this series who harbored an underlying collagen deficiency syndrome ( Ehlers- Danlos syndrome, type IV) underwent intentional carotid sacrifice with the electrolytically detachable coils. In this unusual case, the smaller- caliber catheter that delivered the detachable coils was judged to be less likely to damage her thin, fragile arteries than the larger- caliber catheters that are required to deliver detachable balloons. Twenty percent of the patients in this series presented with bleeding: 11% with epistaxis and 9% with subarachnoid bleeding. Intracavernous aneurysms have been reported to produce both epistaxis and subarachnoid bleeding ( 2- 7). These events demand urgent and definitive therapy because they are associated with a high risk of rebleeding and very high mortality. All seven of the patients with hemorrhage had 100% occlusion of the aneurysm sac. This series probably overestimates the incidence of hemorrhage for several reasons. First, two of the patients had undergone prior transsphenoid surgery J Neuro- Ophthalmol, Vol. 17, No. 4, 1997 238 V. V. HALBACH ETAL. for pituitary tumors. The surgery could have damaged a preexisting cavernous aneurysm or directly injured the carotid artery. Also important to consider is that this series reflects the treatment of patients with aneurysms with a definable neck referred to a tertiary medical center for treatment. Patients with fusiform aneurysms are usually treated with detachable balloons for parent vessel occlusion, and patients with more mild symptoms or no symptoms do not undergo therapy. It is important to remember that cavernous aneurysms that project medially into the sphenoid sinus or Meckel's cave, or superiorly through the carotid ring are at risk for rupture and fatal epistaxis or subarachnoid bleeding, and deserve more urgent treatment. Some medially projecting aneurysms can erode the bone owing to pressure and gain access to the sphenoid sinus ( 21). In some instances, the bone overlying the medial carotid artery is congenitally absent. We usually obtain a thin- section CT examination of the skull base in any patient who harbors a medially projecting cavernous aneurysm to evaluate whether this bony barrier of the sphenoid sinus has been eroded. Rarely, a medially projecting cavernous aneurysm can gain access to the space around the pituitary gland and rupture permits blood to escape into the subarachnoid space through the diaphragma sellae. Coronal MRI is the most useful modality to define the relationship of the aneurysm to the sella turcica, but is inadequate to evaluate the integrity of the bony walls surrounding the sphenoid sinus. Cavernous aneurysms classically present with retro-orbital pain and cranial nerve dysfunction. Thrombosis of the aneurysm after carotid occlusion may transiently aggravate these symptoms but usually results in long-term improvement of the presenting symptoms as the thrombus organizes and undergoes fibrosis ( 2,9,14,15, 17,18,20). Long- term follow- up usually shows reduction in size of the aneurysm after acute thrombosis after 4- 6 weeks. It seems counterintuitive that placement of a space- occupying material, such as a detachable balloon or detachable coil, would improve the mass effect produced by the aneurysm. However, our experience has shown that improvement in mass effect symptoms does follow successful endosaccular occlusion of the aneurysm. Our experience with detachable balloons placed into the aneurysm sac with preservation of the parent vessel has also shown complete resolution of presenting objective neurologic signs in 50% of patients and improvement in objective neurologic signs in 42.3% of patients on long- term ( mean, 60 months) follow- up ( 36). The current series has demonstrated similar results, with 58% of patients showing complete resolution of their presenting cranial nerve signs, and 38% showing substantial improvement. It must be underscored that although most patients will have improvement over time (> 6 months), transient ( weeks to several months) aggravation of symptoms is common. The use of corticosteroids can decrease this acute response presumably from diminishing the inflammatory effects produced by the intraluminal thrombus induced by the detachable coils or balloons. The electrolytically detachable platinum coil is a significant improvement over previously available endovas-cular occlusion devices. The coil can be repositioned or removed before detachment and a variety of sizes permits treatment of a large range of aneurysms. If positioned in the ideal location, it can be detached electrolytically without displacement or traction on the aneurysm. Comparisons with previously reported series using alternate embolic devices are not easy because the detachable coil sometimes permits treatment of aneurysms previously unbeatable with other devices. Our own experience with detachable balloons for the treatment of cavernous aneurysms with preservation of the parent vessel had previously shown a stroke rate of 5%, with transient ischemic events in 10% ( 2). In this series, there was a transient ischemic event in one patient ( 3%) and no permanent morbidity or mortality associated with the detachable coil treatment. 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