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Endovascular platinum coil embolization of incompletely surgically clipped cerebral aneurysms
Surg Neurol 1994 ;41 :4-8
Endovascular Platinum Coil Embolization of Incompletely Surgically Clipped Cerebral Aneurysms Kenneth W. Fraser, M .D., Van V. Halbach, M .D., George P. Teitelbaum, M.D., Tony P. Smith, M .D., Randall T . Higashida, M .D ., Christopher F . Dowd, M.D., Charles B. Wilson, M.D., and Grant B . Hieshima, M .D. Department of Radiology and Department of Neurological Surgery, UCSF Medical Center, San Francisco, California
Fraser KW, Halbach VV, Teitelbaum GP, Smith TP, Higashida RT, Dowd CF, Wilson CB, Hieshima GB . Endovascular platinum coil embolization of incompletely surgically clipped cerebral aneurysms . Surg Neurol 1994 ;41 :4-8 . The natural history of incompletely clipped intracranial aneurysms is largely unknown. The authors present two cases of residual aneurysm filling after surgical clipping which were successfully managed by intravascular placement of platinum coils . Management of residual aneurysms and possible future role of transcatheter therapy are discussed . KEYWORDS :
Aneurysm ; Endovascular therapy
The natural history of incompletely clipped intracranial aneurysms with residual contrast filling is largely unknown [11,16] . Residual aneurysm filling probably represents a continued risk of rupture and hemorrhage if not completely obliterated . The current treatment for a residual cerebral aneurysm neck or incomplete clipping is reoperation [6-9,16,191 . However, some patients may not be medically stable or may have a remnant aneurysm that is not anatomically approachable for reoperation . In recent years, endovascular treatment of aneurysms using detachable balloons and coils has increased . We present two cases of residual aneurysm filling after surgical clipping that were managed by means of transcatheter placement of platinum coils . The more recent case involved aneurysm embolization with an electrolytically detached Guglielmi coil (Target Therapeutics, Fremont, CA) . This approach may be of benefit in a selected
Address reprint requests to : Kenneth W . Fraser, M .D ., Department of Radiology, UCSF Medical Center, 505 Parnassus Avenue, San Francisco, CA 94143-0628 . Received March 29, 1993 ; accepted May 25, 1993 .
0 1994 by Elsevier Science Inc .
population of patients who are unable or unwilling to undergo the rigors of a second craniotomy .
Material and Methods Patient #1 A 51-year-old, right-handed female experienced the acute onset of headache, an intracranial rushing sound, and subsequent nausea and vomiting. A noncontrast head computed tomography (CT) scan was performed approximately 48 hours after the onset of symptoms demonstrated subarachnoid hemorrhage without evidence of hydrocephalus . Cerebral arteriography revealed the presence of a 1 .5-cm basilar tip aneurysm (Figure 1 A) . The patient was initially treated conservatively with Amicar, Nimodipine, and volume expansion for 8 days . After her clinical improvement, she underwent craniotomy for treatment of the ruptured aneurysm . The surgical approach was complicated by inclusion of the P-1 segment of the right posterior cerebral artery into the aneurysm neck . Initially, placement of a McFadden fenestrated clip was attempted but failed to completely include the neck of the aneurysm without compromising the posterior cerebral artery . A Sugita clip with a 7-mm blade and 3 .5-mm fenestration was then placed across the aneurysm neck with the P-1 segment included within the fenestration . Postoperatively the patient was arousable but was noted to have slight right third nerve palsy . However, over the next 24 hours she became less responsive with loss of right side pupillary light reflex and a moderately dense right hemiparesis . A noncontrast head CT scan revealed slight right temporal lobe edema. Angiography was performed that excluded vasospasm but demonstated residual filling of the aneurysm through the fenestrated clip (Figure 1B) . The patient subsequently became hypoxic, secondary to pneumonia with associated pulmonary edema, and was reintubated on the fourth postoperative day . She underwent conservative medical management and improved 0090-3019/94/57 .00
Endovascular Platinum Coil Embolization
Surg Neurol 1994 ;41 :4-8
5
A
Figure 1 . (A) Left vertebral arteriogram in frontal seen , demonstrating basilar tip aneurysm . (B) Left vertebral aerteriogram in frontal view after application of clip (curved arrow) with residual contrast filling ofaneurysm (arrows) . (C) Left vertebral arteriogram in frontal view after transcaeheter coil embolization of residual aneurysm (arrows) .
C
neurologically, becoming more alert and moving her right side . Due to her complicated postoperative course, it was decided to treat the residual aneurysm by endovascular approach on the tenth postoperative day . A 2 .2 F coaxial microcatheter (Tracker-18, Target Therapeutics, Fremont, CA) was maneuvered through the fenestrated
aneurysm clip using digital road-mapping and a steerable 0 .14" guidewire for placement of two 3 mm (helical diameter) by 10 mm (length) platinum Hilal coils (Cook Inc ., Bloomington, IN) . A postembolization arteriogram and subsequent follow-up angiogram 2 weeks later demonstrated total occlusion of the residual aneurysm (Fig-
6
Surg Neurol 1994 ;41: 4-8
ure 1 C) . Follow-up physical examination at approximately I year demonstrated mild right spastic hemiparesis with normal speech and intellect . She continues to have mild diplopia, although this is improving .
Fraser et al .
postembolization demonstating a lack of recurrence of either aneurysm .
Discussion Incomplete treatment of cerebral aneurysm may result in
Patient #2
Patient #2, a 47-year-old, right-handed male, presented with an asymptomatic right cavernous internal carotid and left supraclinoid carotid aneurysms . These were initially diagnosed by MRA screening exam due to his strong family history of cerebral aneurysms . The patient's mother and two maternal uncles died of subarachnoid hemorrhage secondary to aneurysmal rupture . Additionally, the patient has two first cousins who developed subarachnoid hemorrhage and subsequently underwent surgical repair of cerebral aneurysms . The patient underwent a left frontal temporal craniotomy for the left supraclinoid carotid artery aneurysm that was partially intracavernous on inspection . The anterior clinoid process was drilled off with opening of the dura along the course of the internal carotid artery (ICA) in an effort to visualize the entire aneurysm neck . At first, a portion of the aneurysm appeared to be inaccessible in the cavernous sinus, but by working slowly on the proximal side of the neck a curved 3-mm Yasargil clip was placed across the neck of the aneurysm . Followup angiography performed 5 days postoperatively and prior to the planned endovascular obliteration of the right cavernous carotid aneurysm demonstrated slow residual filling of the left supraclinoid aneurysm . Therefore, before beginning treatment of the right cavernous carotid aneurysm, conservative therapy with Amicar, 1 .5 g Qlh for 7 days, was initiated to attempt to thrombose the residual filling of the left carotid aneurysm . At the end of 1 week, follow-up angiography demonstrated continued filling of the left supraclinoid aneurysm (Figure 2 A) . A 2 French Tracker 10 microcatheter (Target Therapeutics) was advanced through the left ICA aneurysm clip and into the residual aneurysm cavity using digital road mapping and a steerable 0 .010" guidewire . A single 3 mm x 8 cm GDC electrolytically detachable coil was deposited within the residual aneurysm cavity through the Tracker 10 catheter . Upon detachment of the GDC coil there was no evidence of residual filling of the aneurysm (Figure 2B)_ Endovascular embolization of the right cavernous aneurysm was then performed 1 day later using GDC coils deposited through a Tracker 18 catheter (Target Therapeutics) . At the completion of both aneurysm embolizations, the patient was neurologically intact . Follow-up angiography 3 days later demonstrated continued obliteration of both aneurysms . A follow-up cerebral angiogram was performed 1 year
a small but definite risk of new or recurrent hemorrhage . Most reports have discussed remnant aneurysm filling below the clip with regard to "regrowth or rehemorrhage ." The management of incomplete clipping of an aneurysm neck with contrast filling of its residual aneurysm cavity above the clip has been a clinical situation rarely reported in the literature [2] . This does not represent the same category of patient as those with clipping of the aneurysm with only the residual neck of the aneurysm filling with contrast [1,5,7,11,16) . Detection of incompletely clipped aneurysms can be discovered in the operating suite by piercing the aneurysm with a needle or incising with a knife [3] . More recently, the use of intraoperative angiography can aid in evaluation of post-clipping results [4,13,17) . However, these methods are not without risk or false-negative identification of residual filling of the aneurysm lumen . Intraoperative angiography has been shown to have a 4% false negative rate with failure to identify residual aneurysm filling [4] . Factors responsible for failure to identify residual filling of clipped aneurysms with intraoperative angiography include inadequate projections, inability to image parallel to the clip blades, poorer resolution of portable systems, and clip migration . As Drake points out, repeat angiography is advisable even after intraoperative angiography has demonstrated the aneurysm to be obliterated [7] . The issue of how to manage a residual aneurysm remains difficult . The primary treatment of the residual aneurysm should be surgical . Drake et al have recommended reoperation and reclipping to obtain complete aneurysm occlusion [6-7,8,16] . The risk of not fully clipping an aneurysm in younger patients over the course of a lifetime may be significant, particularly with the suggestion of younger patients' aneurysms growing more rapidly than older persons [10,18,20] . Incomplete clipping of the aneurysm neck may be secondary to broad neck of the aneurysm, atheromatous plaque, perforating branches, or adjacent anatomic constraints [3,8,9,19] . The practice of wrapping or reinforcing the aneurysm is not an assurance of protection . Fujiwara et al cite a 10year rebleed rate 17% higher in nontreated aneurysm in comparison to the wrapped aneurysm [12] . Todd et al's follow-up of 60 patients with single anterior circulation aneurysms who underwent wrapping, demonstrated an early rebleeding rate (<6 mo) of 8 .6% and a late rebleeding rate (6 months to 10 years) of 1 .5% per annum,
Surg Neurol 1994 ;41 :4-8
Endovascular Platinum Coil Embolization
B Figure 2 . (A) Lateral left internal carotid arteriogram demonstrating
residual filling (arrow) ofsuperelinoid aneurysm after surgical clipping and I week of Amicar treatment . (B) Lateral left internal carotid arteriogram demonstrating obliteration of residual aneurysm with GDC platinum coil (arrow) .
significantly higher than aneurysms not completely clipped [21 ]. Evaluating where forces act upon the aneurysm gives some prediction of site of subsequent rupture . In Crawford's series, rupture occurred at the apex of the aneurysm in 64%, body in 17%, and in the neck of the aneurysm in 2% of autopsied cases [5] . Therefore, with the aneurysm still filling its apex and body, the risk of rupture continues to be significant . By using the Bernoulli Theorem, calculation of approximate pressure inside an incompletely clipped aneurysm is approximately as follows . Assuming blood as incompressible or nearly incompressible fluid flowing in a tube (blood vessel), the static pressure acting on the wall of the tube and measured by a side tap (inside pressure of the aneurysm) is related to the total pressure (systemic blood pressure) in the flow by the Bernoulli Theorem : p + hug + g
(1/2)dv2 = constant
= Gravitational constant (980.62 cmlsec 2)
where p is the pressure, h is the height above a reference point, d is the density of liquid, and v is the velocity of flow . Considering a horizontal tube with no change in elevation or for that matter, taking two pressure readings at the same location with h, = h2 = 0, the Bernoulli equation becomes :
p, + (1/2)dv, 2 = p 2 = ( 1/2)dv22 and setting the velocity ov v2 = 0 (approaching static flow within the aneurysm) the case of measuring the total pressure p, in the flow, and referring to p, as the static pressure p, then P, = p, + (1/2)dv2. Note p, _ total pressure within lumen of systemic artery For example : for water flowing at 60 cm/sec 2 (approx. velocity in MCA) with d = 1 .0 glcm 3 P, = p, + 1/2(1 .0 g/cm3)(1/980 .62 cm/sec 2)(60 cm/sec 2)2 =p, + 1,84g/cm 2 or p, = p, + (1 .84 g/cm2)(0 .7356 mm Hg/g/cm 2) = p, + 1 .36 mm Hg. These calculations suggest the total difference in static blood pressure between the systemic pressure in the artery and the lumen of the incompletely clipped aneurysm is only 1-2 mm Hg . Therefore, the risk of rupture secondary to blood pressure constraints is likely to remain significant . Endovascular treatment of residual cerebral aneurysms should be considered in those patients who are not felt to be reoperative candidates for medical reasons, have difficult reoperative anatomy, or refuse a second craniotomy procedure . The first patient was treated with the more conventional platinum coil that was guided and placed with a coil pusher . The second patient was treated with a newer, more controllable coil that can be inserted, withdrawn, and repositioned as necessary to conform to the confines of the residual aneurysm [15] . This newer delivery system will allow more precise control as well
8
Surg Neurol 1994 ;41 :4-8
as optimal positioning of the coil at the time of detachment . In addition, the coil has a possible secondary effect of electrothrombosis with acceleration of clot formation within a aneurysm by the passage of a low level direct current through the delivery wire for the GDC coil [ 14] . This results in a net positive charge upon the platinum wire of the GDC coil, thus attracting negatively charged components of red and white blood cells, platelets, and fibrinogen . The combination of partial surgical clipping followed by endovascular treatment of the remaining aneurysm may prove to be a new therapy for difficult aneurysms that cannot be treated by either modality alone . The electrolytically detachable coil has proven to be most effective in aneurysms with a well-defined neck 1151 . In aneurysms with a wide neck, complete obliteration of the aneurysm sac by electrolytically detachable coils has proven difficult [15] . Often fenestrated encircling clips or vessel reconstruction by direct surgical techniques are effective in treating fusiform or wide-necked aneurysms . However, the presence of heavy calcification in the vessel wall, tortuous anatomy, or extension of the aneurysm neck into inaccessible locations can preclude complete surgical treatment. If partial clipping of an aneurysm could be performed with surgical creation of a neck or barrier achieved, then subsequent endovascular treatment could be performed with a higher chance of success . Long-term follow-up data continue to be collected with regard to endovascular treatment of aneurysms with platinum coils . These two cases of residual aneurysm obliteration will also require the scrutiny of time- We believe the utility of an endovascular approach will continue to offer an alternative in a select patient population in which reoperation is considered contraindicated or unacceptable to the patient .
Fraser
et
al .
in opening and closing pressures of cerebral aneurysm clips . Neurosurgery 1990 ;26(1) :80-5 . 4 . Barrow DL, Boyer KL, Joseph GJ . Intraopemtive angiography in the management of neurovascular disorders . Neurosurgery 1992 ;30 :153-9 . 5 . Crawford T . Some observations on the pathogenesis and natural history of intracranial aneurysms . J Neurol Neurosurg Psychiatr 1959 ;22 :259-66. 6 . Drake CG, Vanderlinden RG . The late consequences of incomplete surgical treatment of cerebral aneurysms . J Neurosurg 1967 ;27 :226-38 . 7 . Drake CG, Allcock JM . Postoperative angiography and the slipped clip . J Neurosurg 1973 ;39 :683-9 . 8 . Drake CG, Friedman AH, Peerless 5J . Failed aneurysm surgery : reoperation in 115 cases . J Neurosurg 1984 ;61 :848-56 . 9 . Ehina K, Suzuki M, Andoh A, Saitoh K, Iwabuchi T . Recurrence of cerebral aneurysm after initial neck clipping . Neurosurgery 1982 ;2(6) :764-8 . 10 . Ferguson GC . Physical factors in the initiation, growth, and rupture of human intracranial saccular aneurysms . J Neurosurg 1972 ;37 :666-7 . 11 . Feurherg 1, Lindquist C, Lindquist M, Steiner L . Natural history of postoperative aneurysm rests . J Neurosurg 1987 ;66 :30-4 . 12 . Fujiwara S, Fujii K, Nishiu S ., et al . Long-term results of wrapping of intracranial ruptured aneurysms. Acta Neurochir (Wien) 1990 ;103(1-2) :27-9 . 13 . Hieshima GB, Reicher MA, Higashida RT, Halbach VV, Cahan LD, Martin NA, Frazee JG, Rand RW, Bentson JR . Intraoperarive digital subtraction neuroangiography : a diagnostic and therapeutic tool . AJNR t987 ;8 :759-67 . 14 . Guglielmi G, Vinuela F, Sepetka 1, Marcellari V . Elecrrothrombosis of saccular aneurysms via endovascular approach . Part 1 : Electrochemical basis, technique, and experimental results . J Neurosurg 1991 ;75 :1-7 . 15 . Guglielmi G, Vinuela F, Dion J, Duckwiler G . Electrothrombosis of saccular aneurysm via endovascular approach . Part 2 : Preliminary clinical experience . J Neurosurg 1991 ;75 :8-14 . 16 . Lin T, Fox AJ, Drake CG . Regrowth of aneurysm sacs from residual neck following aneurysm clipping . J Neurosurg 1989 ;70 :556-60 . 17 . Martin NA, Bentson J, Vinuela F, Hieshima G, Reichter M, Black K, Dion J, Becker D . intraoperative digital subtraction angiography and the surgical treatment of intracranial aneurysms and vascular malformations . J Neurosurg 1990 ;73 :526-33 . 18 . Ostergaard Jr . HOG. Incidence of multiple intracranial aneurysms . Influence of arterial hypertension and gender . j Neurosurg 1985 ;63 :49-55 .
References 1 . Allcock JM, Drake GG . Postoperative angiography in cases of ruptured intracranial aneurysm . J Neurosurg 1963 ;20 :752-9 . 2 . Black SP, German WJ . Observations on the relationship between the volume and size of the orifice of experimental aneurysms . J Neurosurg 1960 ;17 :984-90 . 3 . Atkinson JL, Anderson RE, Piepgras DG . A comparative study
19. Sato S, Suzuki S . Prognosis in cases of intracranial aneurysm after incomplete direct operations . Acts Neurochir 1971 ;24 :245-52 . 20 . Suzuki J, Ohara H . Clinicopathological study of cerebral aneurysms. Origin, rupture, repair and growth . J Neurosurg 1978 ; 48 :505-14 . 21 . Todd NV, Tocher JL, Jones PA, Miller JD . Outcome following aneurysm wrapping: a 10-year follow-up review of clipped and wrapped aneurysms . J Neurosurg 1989 ;70 :841-6 .
Endovascular Platinum Coil Embolization of Incompletely Surgically Clipped Cerebral Aneurysms Kenneth W. Fraser, M .D., Van V. Halbach, M .D., George P. Teitelbaum, M.D., Tony P. Smith, M .D., Randall T . Higashida, M .D ., Christopher F . Dowd, M.D., Charles B. Wilson, M.D., and Grant B . Hieshima, M .D. Department of Radiology and Department of Neurological Surgery, UCSF Medical Center, San Francisco, California
Fraser KW, Halbach VV, Teitelbaum GP, Smith TP, Higashida RT, Dowd CF, Wilson CB, Hieshima GB . Endovascular platinum coil embolization of incompletely surgically clipped cerebral aneurysms . Surg Neurol 1994 ;41 :4-8 . The natural history of incompletely clipped intracranial aneurysms is largely unknown. The authors present two cases of residual aneurysm filling after surgical clipping which were successfully managed by intravascular placement of platinum coils . Management of residual aneurysms and possible future role of transcatheter therapy are discussed . KEYWORDS :
Aneurysm ; Endovascular therapy
The natural history of incompletely clipped intracranial aneurysms with residual contrast filling is largely unknown [11,16] . Residual aneurysm filling probably represents a continued risk of rupture and hemorrhage if not completely obliterated . The current treatment for a residual cerebral aneurysm neck or incomplete clipping is reoperation [6-9,16,191 . However, some patients may not be medically stable or may have a remnant aneurysm that is not anatomically approachable for reoperation . In recent years, endovascular treatment of aneurysms using detachable balloons and coils has increased . We present two cases of residual aneurysm filling after surgical clipping that were managed by means of transcatheter placement of platinum coils . The more recent case involved aneurysm embolization with an electrolytically detached Guglielmi coil (Target Therapeutics, Fremont, CA) . This approach may be of benefit in a selected
Address reprint requests to : Kenneth W . Fraser, M .D ., Department of Radiology, UCSF Medical Center, 505 Parnassus Avenue, San Francisco, CA 94143-0628 . Received March 29, 1993 ; accepted May 25, 1993 .
0 1994 by Elsevier Science Inc .
population of patients who are unable or unwilling to undergo the rigors of a second craniotomy .
Material and Methods Patient #1 A 51-year-old, right-handed female experienced the acute onset of headache, an intracranial rushing sound, and subsequent nausea and vomiting. A noncontrast head computed tomography (CT) scan was performed approximately 48 hours after the onset of symptoms demonstrated subarachnoid hemorrhage without evidence of hydrocephalus . Cerebral arteriography revealed the presence of a 1 .5-cm basilar tip aneurysm (Figure 1 A) . The patient was initially treated conservatively with Amicar, Nimodipine, and volume expansion for 8 days . After her clinical improvement, she underwent craniotomy for treatment of the ruptured aneurysm . The surgical approach was complicated by inclusion of the P-1 segment of the right posterior cerebral artery into the aneurysm neck . Initially, placement of a McFadden fenestrated clip was attempted but failed to completely include the neck of the aneurysm without compromising the posterior cerebral artery . A Sugita clip with a 7-mm blade and 3 .5-mm fenestration was then placed across the aneurysm neck with the P-1 segment included within the fenestration . Postoperatively the patient was arousable but was noted to have slight right third nerve palsy . However, over the next 24 hours she became less responsive with loss of right side pupillary light reflex and a moderately dense right hemiparesis . A noncontrast head CT scan revealed slight right temporal lobe edema. Angiography was performed that excluded vasospasm but demonstated residual filling of the aneurysm through the fenestrated clip (Figure 1B) . The patient subsequently became hypoxic, secondary to pneumonia with associated pulmonary edema, and was reintubated on the fourth postoperative day . She underwent conservative medical management and improved 0090-3019/94/57 .00
Endovascular Platinum Coil Embolization
Surg Neurol 1994 ;41 :4-8
5
A
Figure 1 . (A) Left vertebral arteriogram in frontal seen , demonstrating basilar tip aneurysm . (B) Left vertebral aerteriogram in frontal view after application of clip (curved arrow) with residual contrast filling ofaneurysm (arrows) . (C) Left vertebral arteriogram in frontal view after transcaeheter coil embolization of residual aneurysm (arrows) .
C
neurologically, becoming more alert and moving her right side . Due to her complicated postoperative course, it was decided to treat the residual aneurysm by endovascular approach on the tenth postoperative day . A 2 .2 F coaxial microcatheter (Tracker-18, Target Therapeutics, Fremont, CA) was maneuvered through the fenestrated
aneurysm clip using digital road-mapping and a steerable 0 .14" guidewire for placement of two 3 mm (helical diameter) by 10 mm (length) platinum Hilal coils (Cook Inc ., Bloomington, IN) . A postembolization arteriogram and subsequent follow-up angiogram 2 weeks later demonstrated total occlusion of the residual aneurysm (Fig-
6
Surg Neurol 1994 ;41: 4-8
ure 1 C) . Follow-up physical examination at approximately I year demonstrated mild right spastic hemiparesis with normal speech and intellect . She continues to have mild diplopia, although this is improving .
Fraser et al .
postembolization demonstating a lack of recurrence of either aneurysm .
Discussion Incomplete treatment of cerebral aneurysm may result in
Patient #2
Patient #2, a 47-year-old, right-handed male, presented with an asymptomatic right cavernous internal carotid and left supraclinoid carotid aneurysms . These were initially diagnosed by MRA screening exam due to his strong family history of cerebral aneurysms . The patient's mother and two maternal uncles died of subarachnoid hemorrhage secondary to aneurysmal rupture . Additionally, the patient has two first cousins who developed subarachnoid hemorrhage and subsequently underwent surgical repair of cerebral aneurysms . The patient underwent a left frontal temporal craniotomy for the left supraclinoid carotid artery aneurysm that was partially intracavernous on inspection . The anterior clinoid process was drilled off with opening of the dura along the course of the internal carotid artery (ICA) in an effort to visualize the entire aneurysm neck . At first, a portion of the aneurysm appeared to be inaccessible in the cavernous sinus, but by working slowly on the proximal side of the neck a curved 3-mm Yasargil clip was placed across the neck of the aneurysm . Followup angiography performed 5 days postoperatively and prior to the planned endovascular obliteration of the right cavernous carotid aneurysm demonstrated slow residual filling of the left supraclinoid aneurysm . Therefore, before beginning treatment of the right cavernous carotid aneurysm, conservative therapy with Amicar, 1 .5 g Qlh for 7 days, was initiated to attempt to thrombose the residual filling of the left carotid aneurysm . At the end of 1 week, follow-up angiography demonstrated continued filling of the left supraclinoid aneurysm (Figure 2 A) . A 2 French Tracker 10 microcatheter (Target Therapeutics) was advanced through the left ICA aneurysm clip and into the residual aneurysm cavity using digital road mapping and a steerable 0 .010" guidewire . A single 3 mm x 8 cm GDC electrolytically detachable coil was deposited within the residual aneurysm cavity through the Tracker 10 catheter . Upon detachment of the GDC coil there was no evidence of residual filling of the aneurysm (Figure 2B)_ Endovascular embolization of the right cavernous aneurysm was then performed 1 day later using GDC coils deposited through a Tracker 18 catheter (Target Therapeutics) . At the completion of both aneurysm embolizations, the patient was neurologically intact . Follow-up angiography 3 days later demonstrated continued obliteration of both aneurysms . A follow-up cerebral angiogram was performed 1 year
a small but definite risk of new or recurrent hemorrhage . Most reports have discussed remnant aneurysm filling below the clip with regard to "regrowth or rehemorrhage ." The management of incomplete clipping of an aneurysm neck with contrast filling of its residual aneurysm cavity above the clip has been a clinical situation rarely reported in the literature [2] . This does not represent the same category of patient as those with clipping of the aneurysm with only the residual neck of the aneurysm filling with contrast [1,5,7,11,16) . Detection of incompletely clipped aneurysms can be discovered in the operating suite by piercing the aneurysm with a needle or incising with a knife [3] . More recently, the use of intraoperative angiography can aid in evaluation of post-clipping results [4,13,17) . However, these methods are not without risk or false-negative identification of residual filling of the aneurysm lumen . Intraoperative angiography has been shown to have a 4% false negative rate with failure to identify residual aneurysm filling [4] . Factors responsible for failure to identify residual filling of clipped aneurysms with intraoperative angiography include inadequate projections, inability to image parallel to the clip blades, poorer resolution of portable systems, and clip migration . As Drake points out, repeat angiography is advisable even after intraoperative angiography has demonstrated the aneurysm to be obliterated [7] . The issue of how to manage a residual aneurysm remains difficult . The primary treatment of the residual aneurysm should be surgical . Drake et al have recommended reoperation and reclipping to obtain complete aneurysm occlusion [6-7,8,16] . The risk of not fully clipping an aneurysm in younger patients over the course of a lifetime may be significant, particularly with the suggestion of younger patients' aneurysms growing more rapidly than older persons [10,18,20] . Incomplete clipping of the aneurysm neck may be secondary to broad neck of the aneurysm, atheromatous plaque, perforating branches, or adjacent anatomic constraints [3,8,9,19] . The practice of wrapping or reinforcing the aneurysm is not an assurance of protection . Fujiwara et al cite a 10year rebleed rate 17% higher in nontreated aneurysm in comparison to the wrapped aneurysm [12] . Todd et al's follow-up of 60 patients with single anterior circulation aneurysms who underwent wrapping, demonstrated an early rebleeding rate (<6 mo) of 8 .6% and a late rebleeding rate (6 months to 10 years) of 1 .5% per annum,
Surg Neurol 1994 ;41 :4-8
Endovascular Platinum Coil Embolization
B Figure 2 . (A) Lateral left internal carotid arteriogram demonstrating
residual filling (arrow) ofsuperelinoid aneurysm after surgical clipping and I week of Amicar treatment . (B) Lateral left internal carotid arteriogram demonstrating obliteration of residual aneurysm with GDC platinum coil (arrow) .
significantly higher than aneurysms not completely clipped [21 ]. Evaluating where forces act upon the aneurysm gives some prediction of site of subsequent rupture . In Crawford's series, rupture occurred at the apex of the aneurysm in 64%, body in 17%, and in the neck of the aneurysm in 2% of autopsied cases [5] . Therefore, with the aneurysm still filling its apex and body, the risk of rupture continues to be significant . By using the Bernoulli Theorem, calculation of approximate pressure inside an incompletely clipped aneurysm is approximately as follows . Assuming blood as incompressible or nearly incompressible fluid flowing in a tube (blood vessel), the static pressure acting on the wall of the tube and measured by a side tap (inside pressure of the aneurysm) is related to the total pressure (systemic blood pressure) in the flow by the Bernoulli Theorem : p + hug + g
(1/2)dv2 = constant
= Gravitational constant (980.62 cmlsec 2)
where p is the pressure, h is the height above a reference point, d is the density of liquid, and v is the velocity of flow . Considering a horizontal tube with no change in elevation or for that matter, taking two pressure readings at the same location with h, = h2 = 0, the Bernoulli equation becomes :
p, + (1/2)dv, 2 = p 2 = ( 1/2)dv22 and setting the velocity ov v2 = 0 (approaching static flow within the aneurysm) the case of measuring the total pressure p, in the flow, and referring to p, as the static pressure p, then P, = p, + (1/2)dv2. Note p, _ total pressure within lumen of systemic artery For example : for water flowing at 60 cm/sec 2 (approx. velocity in MCA) with d = 1 .0 glcm 3 P, = p, + 1/2(1 .0 g/cm3)(1/980 .62 cm/sec 2)(60 cm/sec 2)2 =p, + 1,84g/cm 2 or p, = p, + (1 .84 g/cm2)(0 .7356 mm Hg/g/cm 2) = p, + 1 .36 mm Hg. These calculations suggest the total difference in static blood pressure between the systemic pressure in the artery and the lumen of the incompletely clipped aneurysm is only 1-2 mm Hg . Therefore, the risk of rupture secondary to blood pressure constraints is likely to remain significant . Endovascular treatment of residual cerebral aneurysms should be considered in those patients who are not felt to be reoperative candidates for medical reasons, have difficult reoperative anatomy, or refuse a second craniotomy procedure . The first patient was treated with the more conventional platinum coil that was guided and placed with a coil pusher . The second patient was treated with a newer, more controllable coil that can be inserted, withdrawn, and repositioned as necessary to conform to the confines of the residual aneurysm [15] . This newer delivery system will allow more precise control as well
8
Surg Neurol 1994 ;41 :4-8
as optimal positioning of the coil at the time of detachment . In addition, the coil has a possible secondary effect of electrothrombosis with acceleration of clot formation within a aneurysm by the passage of a low level direct current through the delivery wire for the GDC coil [ 14] . This results in a net positive charge upon the platinum wire of the GDC coil, thus attracting negatively charged components of red and white blood cells, platelets, and fibrinogen . The combination of partial surgical clipping followed by endovascular treatment of the remaining aneurysm may prove to be a new therapy for difficult aneurysms that cannot be treated by either modality alone . The electrolytically detachable coil has proven to be most effective in aneurysms with a well-defined neck 1151 . In aneurysms with a wide neck, complete obliteration of the aneurysm sac by electrolytically detachable coils has proven difficult [15] . Often fenestrated encircling clips or vessel reconstruction by direct surgical techniques are effective in treating fusiform or wide-necked aneurysms . However, the presence of heavy calcification in the vessel wall, tortuous anatomy, or extension of the aneurysm neck into inaccessible locations can preclude complete surgical treatment. If partial clipping of an aneurysm could be performed with surgical creation of a neck or barrier achieved, then subsequent endovascular treatment could be performed with a higher chance of success . Long-term follow-up data continue to be collected with regard to endovascular treatment of aneurysms with platinum coils . These two cases of residual aneurysm obliteration will also require the scrutiny of time- We believe the utility of an endovascular approach will continue to offer an alternative in a select patient population in which reoperation is considered contraindicated or unacceptable to the patient .
Fraser
et
al .
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