J Neurosurg 53:633-641, 1980 Bacterial intracranial aneurysms JOHN G. FRAZEE, M . D . , LESLIE D. CAHAN, M . D . , AND JAMES WINTER, M . D . , PH.D. Department of Surgery, Division of Neurosurgery, and Department of Radiological Sciences, Neuroradiology Section, Universityof California-Los ,4 ngeles School of Medicine, Los .4 ngeles, California The treatment of 13 patients with bacterial intracranial aneurysms is reported. The incidence of bacterial intracranial aneurysms was 4% of all patients admitted with intracranial aneurysms and 3% of all patients admitted with bacterial endocarditis. Each patient had neurological signs or symptoms suggestive of intracranial disease prior to the diagnosis of an aneurysm. Alpha Streptococcus was the most common infecting organism. All patients were treated with specific, high-dose antibiotics, and five patients underwent surgery as well. There were no surgical deaths. Six of eight nonsurgically treated patients died. A review of the literature confirms a high mortality for patients treated with only antibiotics, and a low mortality for elective surgery. The authors conclude that 1) patients with bacterial endocarditis, who develop sudden severe headache, focal neurological signs or symptoms, or seizures, should undergo serial cerebral angiography every 7 to 10 days throughout their hospitalization; 2) if an aneurysm is identified it should be excised whenever possible; and 3) patients with proximal or multiple aneurysms should be considered for surgery. KEY WORDS bacterial aneurysm 9 subarachnoid hemorrhage bacterial endocarditis 9 cerebral aneurysm 9 serial angiography 9 ACTERIAL intracranial aneurysms are uncommon, but life-threatening, lesions. Controversy has recently arisen over the appropriate management of these lesions and has motivated this review. This paper reports the experience at a single hospital with bacterial intracranial aneurysms, and includes 13 patients. Drawing from this experience and the literature, we propose to examine the following questions: 1) Are there warning signs or symptoms that suggest the diagnosis of bacterial intracranial aneurysm prior to a hemorrhage? 2) Which patients with bacterial endocarditis should have cerebral angiography? 3) What is the role of serial angiography in following patients with bacterial endocarditis? 4) If an aneurysm has been documented, is medical therapy alone adequate? 5) Is there a recommended surgical management, and is it modified by the presence of proximal or multiple aneurysms? The records were reviewed for all patients with a diagnosis of bacterial or mycotic intracranial aneurysm seen at the U C L A Center for the Health Sciences from June, 1955, to April, 1978. The diagnosis of bacterial aneurysm was established by pathological examination of surgical and autopsy specimens or by the finding of an aneurysm in the cerebral circulation of patients whose history, physical B J. Neurosurg. / Volume 53 / November, 1980 9 mycotic aneurysm 9 examination, and blood cultures led to a diagnosis of bacterial endocarditis. Illustrative Case Reports Case 1 This 20-year-old white woman was known to have congenital subaortic stenosis. The patient was well until March 31, 1978, when she had an attack of bronchitis. Treatment consisted of oral ampicillin. Over the next 12 days, she developed neck stiffness, nonpruritic, erythematous, raised lesions on her legs, swollen, sore fingers, splinter hemorrhages, and fever elevations to 40~ The patient was admitted to U C L A when she was found to be difficult to arouse. Examination revealed a temperature of 37.4~ hemorrhagic lesions on fingers, toes, palms, and soles, a small hemorrhage in the right retina, and a Grade I I I / V I aortic murmur. The patient was lethargic and had a nonfluent aphasia. The eyes were deviated to the left, the right side was paretic, and the neck was slightly stiff. The admitting diagnosis was bacterial endocarditis with a left frontal hemorrhage. The patient was started on intravenous penicillin, oxacillin, and gentamicin. All of 12 blood cultures grew Staphylococcus aureus. Computerized tomography 633 j. G. F r a z e e , L. D. C a h a n (CT) on the day of admission showed a left frontoparietal hemorrhage, and arteriography showed an embolic filling defects at the parieto-occipital branch of the posterior cerebral artery and at the bifurcation of the pericallosal artery, and narrowing of the left opercular branches (Fig. 1 left). Two weeks after admission, the patient had a generalized seizure and became unresponsive, with bilateral decerebrate posturing. A C T scan showed hemorrhage into the left temporal lobe and basal ganglia. Angiography showed aneurysms of the distal, left middle cerebral, left posterior cerebral, and the pericallosal arteries (Fig. 1 right). The hematoma was evacuated, and what was thought to be an aneurysm was clipped. Angiography 2 weeks after operation showed enlargement of the left middle cerebral aneurysm to twice the original size, with no change in the other aneurysms. The enlarging aneurysm was excised 3 days later. Angiography was repeated 10 days after the second surgery and showed no middle cerebral artery aneurysm, no change in the remaining two aneurysms, and no further emboli. The patient was treated with antibiotics for 6 weeks. Her neurological examination at discharge showed a moderate nonfluent aphasia, and a right hemiparesis. Five months later she had a mild nonfluent aphasia and Grade 4 a n d J. W i n t e r strength on the right. Soon after this examination the patient developed refractory heart failure and died. Case 2 This 47-year-old white man had a history of a heart murmur but was previously in excellent health. He was admitted to U C L A Center for the Health Sciences three times in 1 month complaining of a persistent fever. On his third admission the physical examination was normal except for a temperature of 39.4~ mental confusion, and a moderate nonfluent aphasia. Lumbar puncture showed an opening pressure of 220 mm H20, 729 white blood cells/cu cm (75% polymorphonuclear cells), 220 red blood cells/cu cm, a protein of 92 mg%, and a glucose of 58 mg% with a blood glucose of 122 rag%. Gram and acid-fast stains, india ink preparation, and cultures were all negative. The patient was admitted with a diagnosis of either meningitis or cerebral abscess, and was started on intravenous penicillin, intramuscular streptomycin, and triple antituberculous therapy. The day following admission, a Grade I I / V I systolic murmur and an Osler's node on the ball of the left foot were noted. Bacterial endocarditis was diagnosed, and a cerebral angiogram was recommended to rule out a bacterial aneurysm. FIG. 1. Case I. Left internal carotid artery angiograms. Left: On admission, embolic filling,defects are seen at the bifurcation of the pericallosal artery and the parieto-occipital branch of the posterior cerebral artery (double arrows). An anterior operculum branch is narrowed (single arrow). Right: Eleven days later, aneurysms are revealed at the locations of the previously demonstrated emboli or narrowing. 634 J. Neurosurg. / Volume 53 / November, 1980 Bacterial intracranial aneurysms TABLE 1 Patient population* Case No. Age (yrs), Sex SAH Underlying Heart Disease Possible Predisposing Factors Period BE to SAHI (days) 1 2:1: 3~ 4 5 6 7:~ 8:[: 9 10 20, F 47, M 32, F 29, F 25, M 70, M 52, M 28, M 58, M 39, F yes yes no no yes yes yes yes yes yes subaortic stenosis mitral regurgitation 12 0 unruptured unruptured 8 23 0 35 35 5 yes yes yes mitral regurgitation bronchitis -prolonged labor teeth cleaned teeth extraction urological surgery --dental work teeth cleaned, IV drugs used carious teeth teeth cleaned -- 11 12 13 37, F 29, F 52, F mitral regurgitation mitral regurgitation 28 24 6 *SAH = subarachnoid hemorrhage; BE = bacterial endocarditis; IV = intravenous. tThe number of days from the diagnosis of bacterial endocarditis to the diagnosis of subarachnoid hemorrhage. ++Casespreviously reported by Takahashi, et al. 42 Angiography confirmed a left ascending parietal branch aneurysm (Fig. 2), which was excised 2 days later. The pathological diagnosis was a bacterial cerebral aneurysm. Postoperatively, the patient was neurologically normal. Angiography was repeated 31/2 weeks after operation, and showed no new aneurysm and no filling of the previous aneurysm. The patient was discharged in good health after 6 weeks of antibiotic therapy. Summary of Cases Patient Population During the period of this study, there were 459 patients admitted with bacterial endocarditis and 296 patients with cerebral aneurysms. Thirteen patients fulfilled the requirements for bacterial intracranial aneurysm. Seven were female and six were male. Their ages ranged from 20 to 70 years, with an average age of 40 years (Table 1). Five of thirteen patients had a past history of heart disease. Nine patients had possible predisposing conditions. Examples included dental work, bronchitis, carious teeth, prolonged labor, and urological surgery (Table 1). Clinical P r e s e n t a t i o n FIG. 2. Case 2. Preoperative left internal carotid artery injection showing an ascending parietal branch aneurysm (arrows). J. Neurosurg. / Volume 53 / November, 1980 The diagnosis of bacterial endocarditis was made in all patients within 2 days of admission. This diagnosis preceded that of bacterial intracranial aneurysm in all but one case. The time from diagnosis of bacterial endocarditis to subarachnoid hemorrhage (SAH) ranged from 0 to 35 days, with an average of 18 days. Two patients with an aneurysm had not suffered an S A H . The diagnosis of bacterial intracranial aneurysm was made following the sudden onset of coma in six patients, after the onset of focal neurological findings in six patients, and after the sudden onset of severe headache in one patient. 635 J. G. F r a z e e , TABLE 2 Twelve of 13 patients had positive cultures, 11 from blood and one from an autopsy specimen (Table 2). A single organism was found in all 12 instances. The remaining patient (Case 2), who had not recently been treated with antibiotics, failed to grow organisms in spite of multiple cultures for aerobes, anaerobes, and fungi. The diagnosis of bacterial intracranial aneurysm was established in this case by pathological examination of the excised aneurysm. The most common organism was alpha Streptococcus. No. of Cases Organism Cultured alpha hemolytic Streptococcus gamma Streptococcus 5 3 2 1 1 Staphylococcus aureus beta hemolytic Streptococcus Peptostreptococcus Computerized Tomography TABLE 3 Radiographic results Total Cases 6 12 Positive Results 5 11 Results of serial angiography in six patients No. of Cases 2 1 2 1 Result enlargement of aneurysm complete resolution of aneurysm aneurysm absent after excision new aneurysm at a new site TABLE 5 Location of 19 aneurysms* Location of No. of Aneurysms Aneurysms middle cerebral artery 15 anterior cerebral artery 2 posterior cerebral artery 2 *All aneurysms were beyond the first division of each individual vessel. Three patients had multiple aneurysms. TABLE 6 Treatment and outcome in 13 patients antibiotics alone antibiotics & operation 636 Outcome Normal Disabled Computerized tomographic scans were obtained in six patients (Table 3). One was normal, one was performed 1 month after a diagnostic angiogram, and four were completed on the day of angiography. The latter four each demonstrated hematomas. The CT scan was positive for a hematoma in one patient who had no angiographically demonstrated aneurysm. The aneurysm was discovered at operation in this patient. A ngiography TABLE 4 Therapy a n d J. W i n t e r Bacteriological S t u d i e s Bacteriological findings in 12 patients Radiographic Procedure computerized tomography angiography L. D. C a h a n Dead Total Cases 2 0 6 8 2 3 0 5 Twelve patients underwent cerebral angiography, and at least one clearly defined aneurysm was seen in 11 (Table 3). A total of 19 aneurysms were found. The diagnosis of bacterial aneurysm was made at operation or autopsy in the two patients without angiographic evidence of an aneurysm. Serial angiograms were obtained in six patients. An aneurysm clearly enlarged in two cases, resolved in one case, and a new aneurysm appeared in one case (Table 4). There were three patients with multiple aneurysms. The locations included 15 middle cerebral, two anterior cerebral, and two on the posterior cerebral arteries (Table 5). All aneurysms were beyond the first major bifurcation of the involved vessel and were thus labelled as "distal." Treatment Twelve of 13 patients received a 6-week course of appropriate, high-dose, intravenous antibiotic therapy, beginning with the day of admission (Table 6). The 13th patient's treatment was started 2 days after admission, when the results of blood cultures were obtained. Craniotomy was performed in five patients. Eight patients received only antibiotic therapy. No patient received antihypertensive or antifibrinolytic therapy. Six of eight patients treated only with antibiotics died as a direct result of aneurysm rupture. The remaining two patients were neurologically normal at discharge. O f the five patients treated surgically, four were operated on after an SAH. Surgical treatment consisted of complete excision of four aneurysms and muscle-wrapping of one. There were no operative deaths and, at discharge, two patients were neurologically normal, one had a very J. Neurosurg. / Volume 53 / November, 1980 Bacterial intracranial aneurysms mild monoparesis, and two remained hemiplegic as a result of their original hemorrhages. Pathological Findings Pathological analysis of the bacterial aneurysm was obtained in eight of 13 cases. All cases were described as showing enlarged or ruptured vessels with prominent inflammation and marked attenuation of the vessel wall with wall necrosis. Discussion Bohmfalk, et al.,5 summarized 85 cases of bacterial intracranial aneurysm reported between 1954 and 1978. We have reviewed these cases from the literature ~-7,~-~,~6-28ae-29,sl-88'~~ and have compared the results with our own. Patient Population The age, sex, incidence of bacterial intracranial aneurysm in all patients with intracranial aneurysm, and the incidence of bacterial intracranial aneurysm in patients with bacterial endocarditis in our series were similar to others? -8,8'ls.',ss.sT,s9 The incidence in our patients of underlying heart disease, predisposing conditions, and the spectrum of these conditions was also similar to the literature? ,85 Pathogenesis In 1968, Nakata, et al.? ~ published experimental results showing that after the introduction of bacteria into the dog aorta, which had been isolated by temporary clamps just above the renal arteries and the aortic bifurcation, vascular wall destruction began in the layers adjacent to the vasa vasorum. They concluded that stasis and sepsis in the vasa vasorum were the necessary initiating events for the formation of a bacterial aneurysm. Molinari, et al., 24a5 pointed out that, although the original site of infection might be the vasa vasorum, this was rarely present in the cerebral vessels, particularly in distal branches where bacterial aneurysms were most likely to occur. From their own experimental model of bacterial emboli introduced into the cerebral circulation, they were able to conclude that aneurysms consistently appeared at the site of an infected embolus and that the earliest changes in the vessel wall occurred in the adventitial layer and spread to involve the media. They proposed that "in the absence of the vasa vasorum, bacteria could escape through occluded origins of the thin-walled penetrating vessels to the Virchow-Robin space and then to the adventitia of the parent vessel. T M They explained that the aneurysmal enlargement was produced by pulsations against the necrotic wall of an occluded vessel or by those same pulsations against a weakened wall of a recanalized vessel. This latter process might explain the late appearance of an aneurysm during anJ. Neurosurg. / Volume53 / November, 1980 TABLE 7 Signs and symptoms prior to hemorrhage Symptoms or Signs sudden severe headache focal deficits aphasia hemiparesis facial weakness facial numbness seizures No. of Cases 6 3 4 l l 1 tibiotic treatment, as occurred in Case 1. Molinari ~ stressed the short time period (1 to 3 days) between lodging of an infected embolus in a cerebral vessel and aneurysm formation in dogs not treated with antibiotics, or infected with virulent organisms. However, Molinari and his co-workers2s also noted that, if dogs were partially treated with an appropriate antibiotic, aneurysm rupture no longer regularly occurred in 1 to 3 days, but aneurysms were present when the dogs were sacrificed 7 or 8 days after embolization. These results would suggest that an aneurysm may develop in a patient with bacterial endocarditis who is appropriately treated, in as short a time as 1 week. Clinical Presentation and A n g i o g r a p h y The neurological signs and symptoms of patients who develop bacterial intracranial aneurysms are variable," but are often secondary to one of three processes: 1) septic embolization; 2) meningitis; and 3) SAH. The first two produce signs and symptoms before aneurysm formation, and are infectious processes that may go on to aneurysm formation, as noted by Molinari, et al., ~4a5 and Suwanwela, et al? ~ The third is a direct result of aneurysm rupture, and is frequently associated with disastrous results. Most authors have expressed concern that there are no early warning signs to herald aneurysm formation except SAH, and, thus, unless all patients with bacterial endocarditis undergo serial angiograms, the mortality rate cannot be reduced. A review of our patients suggests otherwise. Each of our cases was accompanied by premonitory signs or symptoms suggestive of intracranial disease (Table 7). In six patients who survived, these events initiated angiography. Case 2 is an example. One other patient who survived had early signs and symptoms, but angiography was not done until she suddenly became hemiplegic. The six patients who died as a direct result of an intracranial hemorrhage also had warning signs or symptoms. In two patients (Table 8), these symptoms occurred only a few hours before a catastrophic 637 J. G. F r a z e e , L. D. C a h a n a n d J. W i n t e r TABLE 8 Relationship of signs and symptoms to the diagnosis o f an aneurysm Case No. 1 2 3 4 5 6 7 8 9 10 [I 12 13 Signs or Symptoms hemiparesis,decreased mental status nonfluent aphasia, decreased mental status sudden severe headache, hemiparesis sudden severe headache sudden severe headache seizures,decreased mental status sudden severe headache facial weakness, personality change hemiparesis sudden severe headache nonfluent aphasia, personality change sudden severe headache nonfluent aphasia Delay* (days) 12 13 13 5 88 4 88 6 35 1 I 29 8 Discharge Status disabled normal disabled normal dead dead dead dead dead normal normal dead disabled *Number of days from onset of warning signs or symptoms to catastrophic hemorrhage or angiographic diagnosis of an aneurysm. event. It is doubtful whether early diagnostic procedures would have changed their clinical course. However, the remaining four patients had signs or symptoms days before a catastrophic event, which, if correctly interpreted, could have led to early angiography and definitive treatment. Our results suggest that those patients who develop a sudden severe headache, focal neurological deficits, or seizures, should be selected for angiography. It is recognized that 28% to 39% of patients with bacterial endocarditis may present with neurological signs or symptoms? 7,3BHowever, only 19% have been reported with the above signs or symptoms, ~ and one could expect that at least 25% to 33% of these patients (4% to 6% of all bacterial endocarditis patients) would have a cerebral bacterial aneurysm. Serial A n g i o g r a p h y Several points should be noted from our cases and the literature: 1) rupture of a bacterial intracranial aneurysm may occur at any point in the course of appropriate antibiotic therapy; 2) a new aneurysm may appear in subsequent angiograms even though previous angiograms were negative; and 3) new aneurysms may appear after excision of a solitary aneurysm. 4,5,17-1~,28,37,4~These facts emphasize the need for serial angiography throughout hospitalization. The experimental literature indicated that aneurysms are present 7 days after a septic embolus to the brainy s Our own experience demonstrates that there is an average of 10 days from the onset of warning signs or symptoms to a catastrophic hemorrhage or to the angiographic demonstration of a cerebral aneurysm (Table 8). Therefore, three-vessel cerebral angiography at the onset of these signs or symptoms and repeated every 7 to 10 days during 6 weeks of antibiotic therapy, even after surgical excision of one 638 aneurysm, would seem to be the method and frequency that would be most reliable for detecting bacterial cerebral aneurysms. Computerized tomography has not been helpful in establishing a diagnosis of bacterial intracranial aneurysm, and it seems unlikely that in the near future it can do little more than establish the presence of a hemorrhage, abscess, or infarct in these patients. Importantly, a 6-week course of antibiotic therapy does not insure the prevention of further aneurysm formation, ~ but, as demonstrated by our data (Table 1), most episodes of S A H occurred within 35 days of the diagnosis of bacterial endocarditis, and thus before completion of antibiotic therapy. T r e a t m e n t : S u r g i c a l or N o n s u r g i c a l Bingham, ~ in a review of 45 patients with bacterial intracranial aneurysms, emphasized that 11 of 21 patients followed with serial angiography had complete resolution of their aneurysms, and an additional six patients of this group had a decrease in aneurysm size. This led him to suggest serial angiography for all patients with a documented aneurysm. He recommended an operation only if the aneurysm enlarged, or did not change in size after 6 weeks of antibiotic therapy. He reported that three of 20 patients, who received only antibiotic therapy, died, and six of 25 patients, who received combined antibiotic and surgical treatment, died. He noted that the higher mortality rate associated with operation was not a true reflection of surgical mortality, which he estimated to be quite low. Bohmfalk, et al., 5 reviewed 85 patients, including the patients in Bingham's series. They noted that an aneurysm resolved completely i n 10 of 25 patients treated with antibiotics alone, and followed with serial angiography. This group of patients, as with J. Neurosurg. / Volume53 / November, 1980 Bacterial intraeranial aneurysms TABLE 9 TABLE 10 Bacterial intracranial aneurysms: treatment and mortality in three series Treatment and mortality in previously reported cases* Authors & Year Bingham, 1977 Bohmfalk, et aL, 1978 Frazee, et aL. 1980 Antibiotics Only Total Cases Dead Antibiotics & Surgery Total Cases Dead 20 38 8 25 30 5 3 20 6 6 8 0 Bingham's series, was a selected population and excluded the majority of patients (60 of 85 and 24 of 45, respectively) who were not followed by serial angiography. We emphasize that, although bacterial cerebral aneurysms resolve or decrease in size in some patients, the mortality of antibiotic therapy alone is high. Bohmfalk and colleagues reported that 20 of 38 patients in this group died. There were, however, no deaths for elective surgical procedures. Eight of 13 patients who required emergency operations died, but a careful examination of these eight patients confirms Bingham's earlier opinion that in most instances the deaths were not a result of surgery, but secondary to the already moribund state of the patient, rupture of a second aneurysm after the first had been successfully treated, or from unrelated causes. Our results underscore the high mortality associated with conservative therapy alone (six of eight patients) and the low mortality for craniotomy plus antibiotics (0 of five patients) (Table 9). These data suggest that therapy should consist of excision of the aneurysm as well as antibiotic treatment whenever possible. Proximal and Multiple A neurysms The most recent comprehensive review 5 suggests nonsurgical treatment for proximal and multiple aneurysms unless the latter show enlargement. A review of the treatment and outcome of the 13 cases of proximal aneurysm reported in the literature,2, ~,ea*,2s,33,86.87,'l," excluding cavernous sinus aneurysms, shows one surgical death in three patients with operation; six of 10 patients died when treated with antibiotics alone (Table 10). The outcome is unknown for one patient in this latter group. The surgical group is too small to allow us to draw conclusions, but the high mortality associated with nonoperative treatment (two-thirds of the cases) should lead one to carefully consider an operation in each case. The concern for cerebral infarction as a complication of excision of a proximal aneurysm is obvious, but several alternative approaches should be examined before relying upon antibiotic treatment alone. These would include clipping of J. Neurosurg. / Volume 53 / November, 1980 Treatment Total Cases Dead proximal aneurysms* operation 3 l nonsurgical 9 6 multiple aneurysms operation 4 Ot nonsurgical 11 0~ *Treatment and outcome is unknown for one patient. ~No surgically treated patient died as a result of operation. :~The results of treatment for two patients are unknown. the aneurysm, excision with a superficial temporal artery to middle cerebral artery bypass, trapping of the aneurysm with or without a bypass, and wrapping of the aneurysm with muscle. We have had no experience with bypass surgery in these cases. Interestingly, two of the previously reported "proximal" aneurysms were described as " b e r r y " aneurysms, not bacterial, s6 while a third occurred approximately 2 years after endocarditis. 2 Thus, these aneurysms may have been preexisting saccular aneurysms that became secondarily infected. Finally, we must consider the appropriate therapy for multiple aneurysms. A review of 15 such cases reported previously 8-Sa'~~176 shows that four patients died, and 11 recovered. Four patients were treated surgically and 11 nonsurgically (Table 10). No patient died as a direct result of treatment. It is unclear why the mortality was unusually low in the nonsurgically treated group. However, as noted before, mortality for nonsurgically treated patients in general is approximately 50%, and this fact should be kept in mind when selecting the most appropriate therapy. We believe that most patients with multiple aneurysms are surgical candidates. If multiple aneurysms are unilateral, they should be excised at one operation whenever possible. If they are bilateral, the largest aneurysm or the one presumed to have bled should be excised first. An appropriate recovery period should be allowed and angiography repeated before excision of the remaining aneurysm. Conclusions In view of the serious consequences o f a ruptured bacterial intracranial aneurysm, the high morbidity of nonsurgical therapy, the low elective surgical mortality, and the rapid appearance of new aneurysms in some patients, we would recommend aggressive management for patients with bacterial endocarditis. Specifically, we suggest that 1) those patients with the diagnosis of bacterial endocarditis, who develop sudden severe headache, focal neurological signs or 639 J. G. Frazee, L. D. Cahan and J. Winter symptoms, or seizures, should undergo serial cerebral angiography every 7 to 10 days throughout their hospitalization; 2) if an aneurysm is identified, it should be excised whenever possible; and 3) patients with proximal or multiple aneurysms should be considered for operation, but that therapy must be individualized. Acknowledgment We gratefully acknowledge the advice and assistance of Mrs. Elizabeth Kugler in preparing this manuscript. References 1. 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Ziment I, Johnson BL Jr: Angiography in the management of intracranial mycotic aneurysms. Arch Intern Med 122:349-352, 1968 Address reprint requests to: John G. Frazee, M.D., Division of Neurosurgery, University of California-Los Angeles Medical Center, Los Angeles, Calfornia 90024. 64]