Abstract

Background: Nontraumatic true superficial temporal artery aneurysm (STAA) is rare, and its characteristics and pathogenesis are unclear.

Methods: We report a case of STAA and performed a systematic review of PubMed, Scopus, and Web of Science using the keyword “superficial temporal artery aneurysm” to include studies on STAA reported through July 2022. We excluded studies on STAA associated with trauma, arterial dissection, infection, or vasculitis.

Results: A 63-year-old woman who underwent left superficial temporal artery (STA)-middle cerebral artery bypass surgery 8 years previously was diagnosed with an aneurysm located at the left STA. The blood flow volume estimated by ultrasonography was higher in the left STA than in the contralateral counterpart (114 mL/min vs. 32 mL/min). She underwent clipping surgery to prevent aneurysmal rupture without sequela. The lesion was diagnosed as a true aneurysm by histology. The systematic review identified 63 cases (including the present case) of nontraumatic true STAA. The median age of the patients was 57 (interquartile range [IQR]: 41–70) years. Most (90.5%) cases were detected as a palpable mass. Aneurysmal rupture occurred in only 1 (1.6%) case, despite the large size of aneurysms (median size: 13 [IQR: 8–20] mm) and the high frequency (33.3%) of aneurysmal growth during observation. Most (93.7%) patients underwent surgical resection of STAA without sequela.

Conclusion: Our findings suggest that the pathogenesis of true STAA is promoted by hemodynamic stress. The systematic review clarified patients’ and aneurysmal characteristics and treatment outcomes, providing further insight into the pathogenesis of nontraumatic true STAA.

Keywords: Bypass, Intracranial aneurysm, Segmental arterial mediolysis, Superficial temporal artery aneurysm, Systematic review

INTRODUCTION

Superficial temporal artery aneurysm (STAA) is an uncommon disease, and approximately 90% of STAAs are traumatic pseudoaneurysms.[ 59 ] Nontraumatic true STAA is much rarer than traumatic STAA and has mainly been presented in case reports.[ 25 , 26 ] The rarity of true STAA means that its characteristics and the underlying pathogenesis are not well clarified.

We report here a rare case of a true STAA that developed more than 2 years after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass surgery. The findings in the present case suggest the potential pathogenesis leading to the development of true STAA and show a rare complication after STA-MCA bypass surgery. We also performed a systematic review of the literature to investigate the characteristics, treatment outcomes, and potential pathogenesis of nontraumatic true STAA.

MATERIALS AND METHODS

This study was conducted following the principles of the Declaration of Helsinki and its later amendments. The patient provided written informed consent for the treatment rendered. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.[ 35 ] All datasets analyzed in this study are shown in Supplementary Tables 1 and 2 . Ethical approval was unnecessary because the present study analyzed data from published literature.

Search strategy and selection criteria

We performed a systematic review of PubMed, Scopus, and Web of Science to identify eligible studies published between the date of the databases’ inception and July 2022 using the keyword “superficial temporal artery aneurysm.” We also searched the literature referenced by eligible studies for any possible missing studies. The present systematic review aimed to analyze the characteristics, treatment outcomes, and potential pathogenesis of nontraumatic true STAA. Therefore, the inclusion criteria were studies reporting STAA. The exclusion criteria were studies on STAA associated with trauma, arterial dissection, infection, or systemic inflammatory diseases such as vasculitis. Articles written in languages other than English or Japanese were translated using Google translate (https://translate.google.co.jp/?hl=ja).

Data extraction

Two investigators (M.I. and K.S.) independently completed the database search. Any discrepancies between investigators were resolved by discussion. We extracted data from the included studies using a standardized form consisting of the following factors: patients’ characteristics (age, sex, and a history of hypertension); aneurysmal characteristics, such as size, shape (i.e., saccular or fusiform), location (e.g., the frontal branch of the STA), multiplicity, symptoms (e.g., tenderness), growth during observation, and rupture status; and factors regarding diagnosis or treatment, such as diagnostic modalities, histological findings regarding the etiology and wall thickness, treatment modalities, and treatment complications. In this study, multiplicity indicated if the patient had another aneurysm, such as an intracranial aneurysm (IA), visceral aneurysm (e.g., renal artery aneurysm), or aortic aneurysm [ Supplementary Table 1 ].

The extracted data are shown as the median (interquartile range [IQR]) or frequency (i.e., %). To assess the pathogenesis of STAA, we compared the characteristics of STAA with those of IA by referencing the International Study of Unruptured IA Investigators performed in the U.S.A, Canada, and Europe,[ 19 ] the Unruptured Cerebral Aneurysm Study by Japanese investigators,[ 37 ] and a histological analysis performed by Frösen et al.[ 15 ]

RESULTS

Case report

A 55-year-old woman with a medical history of hypertension and dyslipidemia visited our hospital complaining of weakness in the right upper extremity. A radiological examination showed cerebral infarction and hemodynamic compromise due to the left MCA stenosis. Therefore, she underwent revascularization by the left STA-MCA bypass. Two-year postoperative magnetic resonance angiography showed no aneurysm formation at the left STA [ Figure 1a ]. However, an 8-year postoperative magnetic resonance angiography demonstrated an aneurysm on the outer curvature at a sharp bend of the left STA [ Figure 1b ]. Digital subtraction angiography showed a saccular aneurysm that was 5 mm in size and an increase in the diameter of the left STA [ Figures 1c - e ]. The diameter and blood flow volume at bilateral STAs were measured in front of the external acoustic meatus by ultrasonography (LOGIQ S8 XDclear 2.0; GE Healthcare, USA) using a high-frequency linear probe (9 MHz). The diameter of the left STA was 2.6 mm, while the contralateral STA was 1.6 mm. The estimated blood flow volume was approximately 3.5 times higher in the left STA at the main trunk than in the contralateral counterpart (114 mL/min vs. 32 mL/min). Clipping surgery was performed to prevent aneurysmal rupture [ Figures 1f - i ]. The location of the aneurysm could be precisely identified by a 6-0 nylon suture used to ligate a branch from the parietal branch at the time of the previous bypass surgery [ Figures 1c and h]. A histopathological investigation showed a lack of the internal elastic lamina, and a thin and hypocellular wall in the STAA. These histological features were evident compared with a control STA of a 79-year-old man [ Figures 2a - h ]. The three layers of the arterial wall (i.e., the intima, media, and adventitia) were preserved, consistent with the diagnosis of a true STAA. She was discharged on the 13^th day postoperatively without sequela.

Figure 1:

Radiological and intraoperative findings. (a and b) Two- (a) and 8-year (b) postoperative magnetic resonance angiography shows the development of a superficial temporal artery aneurysm (STAA) between 2 and 8 years after superficial temporal artery (STA)-middle cerebral artery bypass surgery. The STAA is localized at a sharp bend of the left STA (arrows in a and b) proximal to the anastomosis. (c and d) Preoperative (c) and 8-year postoperative (d) digital subtraction angiography show a de novo saccular STAA (5 mm in size) on the outer curvature of the left STA (arrows in c and d) and a postoperative increase in the diameter of the left STA. A small branch from the STA (arrowhead in c) was ligated using a 6-0 nylon suture and cut before the anastomosis. The site of the anastomosis is indicated by an asterisk in (d). (e and f) Three-dimensional rotational angiography before (e) and after (f) clipping surgery. The STAA is indicated by an arrow in (e), and the site of the anastomosis is indicated by asterisks in (e) and (f). (g-i) Intraoperative findings of the STAA. The appearance of the STAA resembles that of usual intracranial aneurysms. A 6-0 nylon suture (arrow in h) used to ligate the branch indicated by the arrowhead in (c) remains and was useful in identifying the precise location of the STAA.

Figure 2:

Histopathological investigation of the superficial temporal artery aneurysm (STAA) and a control superficial temporal artery (STA) in a 79-year-old man. Hematoxylin and eosin (a-d) and Elastica van Gieson (e-h) staining of the STAA (a, b, e, and f) and the control STA (c, d, g, and h) are shown. The magnified views indicated by the squares in (a, c, e, and g) are shown in (b, d, f, and h), respectively. The internal elastic lamina in the control STA is indicated by arrowheads in (d and h). The internal elastic lamina was absent in the STAA. The aneurysmal wall was thin and hypocellular. Scale bar, 50 μm.

Search results

We included 45 studies in the present systematic review after full-text screening [ Figure 3 ].[ 1 , 5 , 7 - 14 , 17 , 18 , 20 - 34 , 36 , 38 - 47 , 49 , 55 , 57 , 58 , 61 - 63 ] According to the systematic review, 63 cases, including the present case, were identified after Brown first reported pathologically confirmed nontraumatic true STAA in 1942. All of the data acquired following the standardized form are shown in Supplementary Tables 1 and 2 .

Figure 3:

Study inclusion flowchart.

Patients’ and aneurysmal characteristics of STAA and IA are summarized in Table 1 and Figure 4 .[ 15 , 19 , 37 ] The median age of the patients was 57 (IQR: 41–70) years, and the median size of STAA was 13 (IQR: 8–20) mm. Approximately half of patients with STAA had a medical history of hypertension. The most common location of STAA was in the main trunk (27/56; 48.2%) followed by the frontal branch (19/56; 33.9%) [ Figure 4a ]. Most (61/63; 96.8%) of the cases were symptomatic. Fifty-seven (90.5%), 2 (3.2%), 1 (1.6%), and 1 (1.6%) case presented with a palpable mass, aneurysmal subarachnoid hemorrhage due to another aneurysm, rupture of STAA, and tenderness without a palpable mass, respectively. Atherosclerosis was the most frequent (13/21; 61.9%) etiology as indicated by histopathological findings [ Table 1 ]. An age distribution histogram of STAA shows that its incidence is positively associated with the patient’s age, peaking at the 60–70s [ Figure 4b ]. With regard to treatment, surgical resection, clipping, and endovascular embolization were chosen in 59 (93.7%), 1 (1.6%), and 2 (3.2%) cases, respectively. One patient was lost to follow-up before treatment. Treatment complications have never been reported (0%).

Table 1:

Characteristics of 63 STAAs from a systematic review.

Figure 4:

Characteristics of superficial temporal artery aneurysm (STAA) from a systematic review of 63 cases. (a) Incidence and size according to the location of STAA. Data are shown as the median and interquartile range (IQR). Among the 63 cases, data on the location and size are missing in 7 and 2 cases, respectively. (b) Age distribution histogram of patients with STAA. The numbers of patients belonging to each age group divided by every 10 years are shown in the histogram.

Among the characteristics, the similarities of STAA with IA in the International Study of Unruptured IA Investigators and Unruptured Cerebral Aneurysm Study were observed for the patients’ age, the frequency of a history of hypertension, and multiplicity of aneurysms [ Table 1 ].[ 19 , 37 ] Histological features of a degenerative change in the aneurysm wall, such as thinning and loss of mural cells, were also observed in STAA with a similar frequency to that in IA.[ 15 ] However, there was a male predominance in STAA. Although an STAA 20 mm or larger in size and aneurysmal growth during observation were frequent (31% and 33.3%, respectively), aneurysmal rupture rarely occurred in STAA (1/63; 1.6%).

DISCUSSION

In this systematic review, nontraumatic true STAA not associated with dissection, infection, or systematic inflammatory diseases was exhaustively included and analyzed. The systematic review of 63 reported cases of STAA showed that most cases were detected as a palpable mass. Intriguingly, aneurysmal rupture was rarely reported, despite the large size of aneurysms (i.e., the median size was 13 mm) and the high frequency of aneurysmal growth during observation.[ 20 ] Surgical interventions might effectively prevent rupture of STAA because growth can be easily identified by palpation, unlike asymptomatic IA.[ 6 ] Cosmetic problems, tenderness, and potential rupture should be considered as indications for surgical interventions. Meanwhile, no surgical complications were reported, although the potential risk for facial nerve palsy due to skin incision should be noted. Therefore, patients with STAA are subjected to little risk by the surgical interventions, which justify the indications for the treatments. Among the 63 reported cases, our case is the first to show the development of true STAA as a rare complication after STA-MCA bypass surgery. Besides, our case is the first to demonstrate the feasibility of neck clipping of STAA in the situation where preserving blood supply to the brain through the STA-MCA bypass is necessary.

The present systematic review showed that several vascular risk factors (i.e., aging and hypertension) were similarly associated with the development of aneurysms both in STA and intracranial arteries [ Table 1 ].[ 19 , 37 ] In addition, histological analysis showed that atherosclerosis was the most prevalent type of histological feature in STAA. Lipid accumulation in the arterial wall may be associated with degenerative changes, leading to the development of STAA, as suggested in IA.[ 16 ]

Segmental arterial mediolysis, which is a rare arteriopathy causing aneurysms in various locations,[ 56 ] was the second frequent pathological finding identified in STAA. Therefore, the pathogenesis of STAA as indicated by histological findings is in line with that of aneurysms in other locations.

Hemodynamic stress loaded on the arterial wall, which depends on blood flow volume and the morphology of the vessel,[ 50 ] may also be involved in the pathogenesis of STAA. In our case, STAA developed more than 2 years after the surgical intervention and in the context of an increase in blood flow volume and sharp bend of the STA. Therefore, a hemodynamic stress-dependent mechanism is likely to have been involved in the pathogenesis of STAA, although the effect of direct mechanical stress by the surgical intervention should also be considered. Similarly, STAA can develop in a feeder of arteriovenous malformation in the scalp or in association with porocarcinoma or hemihyperplasia, where the blood flow volume in the STA potentially increases.[ 23 , 32 , 41 ] These findings are consistent with the previous studies investigating IA in humans and animal models.[ 4 , 52 , 54 ]

The prevalence of true saccular aneurysms is diverse between locations throughout the body because of undetermined reasons, which are presumably associated with the pathogenesis. The prevalence of saccular aneurysms is highest in intracranial arteries followed by visceral arteries (e.g., the splenic artery) (3.2% vs. 0.01–0.2%).[ 3 , 60 ] The incidence rate of STAA is much lower than that of visceral artery aneurysms. Differences in the arterial structure should be considered as a reason for the differences in the prevalence of saccular aneurysms between locations. Intracranial arteries have a thinner media and adventitia, fewer elastic medial fibers, and lack the external elastic lamina and vasa vasorum.[ 48 ] However, our case is insightful in that an increase in blood demand compatible with that of an intracranial artery can also induce an aneurysm in the STA. Indeed, the previous animal studies showed that saccular aneurysms were reproducibly induced under similar conditions in intracranial and extracranial arteries.[ 2 , 51 , 53 ] These findings suggest that the blood demand of each organ may be a factor affecting the prevalence of aneurysms through the regulation of the blood flow volume in situ.

CONCLUSION

To the best of our knowledge, this is the first case to show a rare complication after STA-MCA bypass surgery (i.e., de novo aneurysm formation in the STA). In addition, the present case suggests that the pathogenesis of true STAA is promoted by hemodynamic stress, as with IA. Our systematic review clarified patients’ and aneurysmal characteristics of STAA and treatment outcomes. The analysis of 63 reported cases of STAA suggests that its characteristics are generally in line with that of saccular aneurysms in other locations, such as IA. A male predominance and high frequency of aneurysmal growth during observation in STAA should be regarded as potential differences from IA. This study provides comprehensive data regarding STAA and further insight into the pathogenesis of saccular aneurysms, including STAA and IA.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

SUPPLEMENTARY TABLES

Supplementary Table 1:

Standardized form for patients’ and aneurysmal characteristics.

Supplementary Table 2:

Standardized form for examinations and treatments.

Acknowledgment

We thank Ellen Knapp, PhD, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.

References

1. Abdelhedy I, Stephen E, Al-Maawali HT, Al-Wahahibi KN. Pulsatile temporal swelling-successful removal of a true superficial temporal artery aneurysm. Indian J Surg. 2020. 82: 725-6

2. Aoki T, Miyata H, Abekura Y, Koseki H, Shimizu K. Rat model of intracranial aneurysm: Variations, usefulness, and limitations of the Hashimoto model. Acta Neurochir Suppl. 2020. 127: 35-41

3. Barrionuevo P, Malas MB, Nejim B, Haddad A, Morrow A, Ponce O. A systematic review and meta-analysis of the management of visceral artery aneurysms. J Vasc Surg. 2019. 70: 1694-9

4. Bor AS, Velthuis BK, Majoie CB, Rinkel GJ. Configuration of intracranial arteries and development of aneurysms: A follow-up study. Neurology. 2008. 70: 700-5

5. Bozkurt G, Ayhan S, Cakici N, Celik O, Ziyal IM. Spontaneous nonpulsatile aneurysm of the superficial temporal artery mimicking a subcutaneous mass lesion. J Craniofac Surg. 2011. 22: 371-2

6. Brinjikji W, Zhu YQ, Lanzino G, Cloft HJ, Murad MH, Wang Z. Risk factors for growth of intracranial aneurysms: A systematic review and meta-analysis. AJNR Am J Neuroradiol. 2016. 37: 615-20

7. Brown R. Aneurysm of the temporal artery. Surgery. 1942. 12: 711-5

8. Brummund D, Chang A, Azimi-Ghomi O, Diaz B, Sendzischew H. Superficial temporal artery true fusiform aneurysm with several lateral feeding vessels. Cureus. 2021. 13: e13973

9. Buckspan RJ, Rees RS. Aneurysm of the superficial temporal artery presenting as a parotid mass. Plast Reconstr Surg. 1986. 78: 515-7

10. Chapman SC, Zak PW, Scaife M, Murdoch G, Eslami MH. Masson tumor (intravascular papillary endothelial hyperplasia) arising in a superficial temporal artery aneurysm. J Vasc Surg cases Innov Tech. 2019. 5: 388-91

11. Coenegrachts K, Hermans R, Poorten VV, Tthijs M, Wilms G. Non-traumatic giant aneurysm of a superficial temporal artery. JBR BTR. 2005. 88: 72-4

12. Dailey RA, Wilson DJ, Putnam D. Superficial temporal-artery aneurysm. Ophthalmic Surg. 1994. 25: 328-9

13. Delen E, Ozkara E, Aydin HE, Ozbek Z. True aneurysm of superficial temporal artery accompanying multiple intracranial aneurysm. Asian J Neurosurg. 2016. 11: 76-7

14. Endo T, Mori K, Maeda M. Multiple arteriosclerotic fusiform aneurysms of the superficial temporal artery--case report. Neurol Med Chir (Tokyo). 2000. 40: 321-3

15. Frösen J, Piippo A, Paetau A, Kangasniemi M, Niemelä M, Hernesniemi J. Remodeling of saccular cerebral artery aneurysm wall is associated with rupture: Histological analysis of 24 unruptured and 42 ruptured cases. Stroke. 2004. 35: 2287-93

16. Frösen J, Tulamo R, Heikura T, Sammalkorpi S, Niemelä M, Hernesniemi J. Lipid accumulation, lipid oxidation, and low plasma levels of acquired antibodies against oxidized lipids associate with degeneration and rupture of the intracranial aneurysm wall. Acta Neuropathol Commun. 2013. 1: 71

17. Gull S, Badawy A, Chaudhuri A The. “pulsatile” sebaceous cyst: Beware of a superficial temporal artery aneurysm. BMJ Case Rep. 2009. 2009: bcr03.2009.1698

18. Ikeda S, Watanabe T. Superficial temporal artery aneurysm associated with pathological changes mimicking cystic medial necrosis. Case report. Neurol Med Chir (Tokyo). 1988. 28: 1223-7

19. International Study of Unruptured Intracranial Aneurysms Investigato. Unruptured intracranial aneurysms--risk of rupture and risks of surgical intervention. N Engl J Med. 1998. 339: 1725-33

20. Joshi D, Klimczak K. Spontaneous rupture of superficial temporal artery aneurysm presenting as hemifacial swelling. BMJ Case Rep. 2014. 2014: bcr2013202308

21. Karam L, El Husseiny M, Abadjian G, Slaba S, Tabet G. Case report of a rare spontaneous superficial temporal artery aneurysm. J Mal Vasc. 2010. 35: 366-8

22. Kato T, Nakamizo M, Yokoshima K, Inai S, Sakanushi A, Ohashi R. Superficial temporal artery aneurysm with abdominal aortic aneurysm: Case report. Jibi Inkoka Tokeibu Geka. 2017. 89: 1111-5

23. Kawabori M, Kuroda S, Nakayama N, Kenmotsu Y, Shimizu H, Tanino M. Spontaneous giant aneurysm of the superficial temporal artery: Case report. Neurol Med Chir (Tokyo). 2009. 49: 198-201

24. Kawai H, Hamasaki T, Imamura J, Tomonori N, Odashiro T, Yamahata H. Three cases of spontaneous superficial temporal artery aneurysm with literature review. Neurol Med Chir (Tokyo). 2014. 54: 854-60

25. Kim E. True aneurysms of the superficial temporal artery: Diagnosis and treatment. Clin Neurol Neurosurg. 2014. 126: 64-8

26. Kitamura S, Horiuchi T. Superficial temporal artery aneurysm with segmental arterial mediolysis: A case report. Br J Neurosurg. 2020. p. Online ahead of print

27. Kotsis T, Christoforou P, Myoteri D, Papacharalampous P. Congenital true aneurysm of the right superficial temporal artery. Med Arch. 2018. 72: 227-9

28. Labropoulos N, Meisner RJ, Gasparis A, Tassiopoulos AK. Management of non-giant cell arteritis disease of the superficial temporal artery. J Vasc Surg. 2011. 53: 200-3

29. Lim JW, Cho KC, Kwak HJ. True aneurysm of the superficial temporal artery. J Korean Neurol Assoc. 2012. 30: 207-9

30. Locatelli D, Messina AL, Ricevuti G, Gajno TM. Superficial temporal artery aneurysms. J Neuroradiol. 1988. 15: 89-93

31. López-Ruiz P, Cuadrado M-L, Aledo-Serrano A, Alonso-Oviés A, Porta-Etessam J, Ganado T. Superficial artery aneurysms underlying nummular headache--2 cases and proposed diagnostic work-up. Headache. 2014. 54: 1217-21

32. Mahajan A, Goel G, Banga V, Das B. An unusual association of hemihypertrophy with extracranial and intracranial aneurysms. Neurol India. 2021. 69: 1481-2

33. Martin WL, Shoemaker WC. Temporal artery aneurysm. Am J Surg. 1955. 89: 700-2

34. Matkovski PD, Filho JO, Candemil PC, Zucco F, Belz WE, Loures JM. Treatment of an atherosclerotic aneurysm of the superficial temporal artery: Case report. J Vasc Bras. 2015. 14: 275-9

35. Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement. PLoS Med. 2009. 6: e1000097

36. Molinaro V, Pagliasso E, Varetto G, Castagno C, Gibello L, Rispoli P. A true aneurysm of the zygomatic orbital artery: First case report in the literature. Case Rep Med. 2012. 2012: 873168

37. Morita A, Kirino T, Hashi K, Aoki N, Fukuhara S, Hashimoto N. The natural course of unruptured cerebral aneurysms in a Japanese cohort. N Engl J Med. 2012. 366: 2474-82

38. Moriyama S, Kunitomo R, Sakaguchi H, Okamoto K, Sasa T, Tanaka M. Intravascular papillary endothelial hyperplasia in an aneurysm of the superficial temporal artery: Report of a case. Surg Today. 2011. 41: 1450-4

39. Mousa AY, Jain AK, Campbell JE, Stone PA, AbuRahma AF. Degenerative (true) superficial temporal artery aneurysm: A case report with review of literature. Vasc Endovasc Surg. 2011. 45: 568-71

40. Nair R, Varsani D, Frecker P. An unusual bump on the head: Spontaneous superficial temporal artery aneurysm. Indian J Surg. 2011. 73: 240-1

41. Nishimura T, Kubota S. A case of congenital AVM in temporoparietal muscle. No Shinkei Geka. 1996. 24: 277-80

42. Nishioka T, Kondo A, Aoyama I, Nin K, Shimotake K, Tashiro H. A case of spontaneous superficial temporal artery aneurysm. No Shinkei Geka. 1988. 16: 1009-12

43. Ohta H, Sakai H, Nakahara I, Sakai N, Nagata I, Ishibashi-Ueda H. Spontaneous superficial temporal artery aneurysm associated with multiple intracranial cerebral aneurysms--does it segmental mediolytic arteriopathy of the intra-and extra-cranial arteries?. Acta Neurochir (Wien). 2003. 145: 805-6

44. Pejkić S, Sladojevic M, Koncar I, Radmili O, Mutavdzic P, Dragaš M. Isolated true aneurysm of the superficial temporal artery: A truly enigmatic lesion. Vasa. 2014. 43: 380-4

45. Piffaretti G, Castelli P. True aneurysms of the superficial temporal artery: Report of three cases. Ann Vasc Surg. 2009. 23: 687.e15-7

46. Porcellini M, Bernardo B, Spinetti F, Carbone F. Outpatient management of superficial temporal artery aneurysms. J Cardiovasc Surg. 2001. 42: 233-6

47. Riaz AA, Ismail M, Sheikh N, Ahmed N, Atkin G, Richman P. Spontaneously arising superficial temporal artery aneurysms: A report of two cases and review of the literature. Ann R Coll Surg Engl. 2004. 86: W38-40

48. Ritz K, Denswil NP, Stam OCG, van Lieshout JJ, Daemen MJ. Cause and mechanisms of intracranial atherosclerosis. Circulation. 2014. 130: 1407-14

49. Sakamoto T, Sugimoto M, Kakigi A, Iwamura H, Kashio A, Suzuki M. A spontaneous true aneurysm of the superficial temporal artery treated by surgical resection. Auris Nasus Larynx. 2011. 38: 119-22

50. Sasaki T, Kakizawa Y, Yoshino M, Fujii Y, Yoroi I, Ichikawa Y. Numerical Analysis of bifurcation angles and branch patterns in intracranial aneurysm formation. Neurosurgery. 2019. 85: E31-9

51. Shimizu K, Imai H, Kawashima A, Okada A, Ono I, Miyamoto S. Induction of CCN1 in growing saccular aneurysms: A potential marker predicting unstable lesions. J Neuropathol Exp Neurol. 2021. 80: 695-704

52. Shimizu K, Kataoka H, Imai H, Miyata T, Okada A, Sakai N. The bifurcation angle is associated with the progression of saccular aneurysms. Sci Rep. 2022. 12: 7409

53. Shimizu K, Kataoka H, Imai H, Yamamoto Y, Yamada T, Miyata H. Hemodynamic force as a potential regulator of inflammation-mediated focal growth of saccular aneurysms in a rat model. J Neuropathol Exp Neurol. 2021. 80: 79-88

54. Shojima M, Oshima M, Takagi K, Torii R, Hayakawa M, Katada K. Magnitude and role of wall shear stress on cerebral aneurysm: computational fluid dynamic study of 20 middle cerebral artery aneurysms. Stroke. 2004. 35: 2500-5

55. Silverberg D, Teodorescu V. True aneurysm of the superficial temporal artery. EJVES Extra. 2005. 9: 126-8

56. Skeik N, Olson SL, Hari G, Pavia ML. Segmental arterial mediolysis (SAM): Systematic review and analysis of 143 cases. Vasc Med. 2019. 24: 549-63

57. Sloane J, Aziz A, Makhdoomi K. A true aneurysm of the superficial temporal artery: Is there an underlying predisposition to such rarities?. Int J Surg Case Rep. 2013. 4: 852-4

58. Uchida N, Sakuma M. Atherosclerotic superficial temporal artery aneurysm: Report of a case. Surg Today. 1999. 29: 575-8

59. Van Uden DJ, Truijers M, Schipper EE, Zeebregts CJ, Reijnen MM. Superficial temporal artery aneurysm: Diagnosis and treatment options. Head Neck. 2013. 35: 608-14

60. Vlak MH, Algra A, Brandenburg R, Rinkel GJ. Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: A systematic review and meta-analysis. Lancet Neurol. 2011. 10: 626-36

61. Wei W, Akkersdijk GP. Spontaneous aneurysm of the superficial temporal artery. Lancet. 2011. 378: 168

62. Wise M, Gibson KD. Bilateral superficial temporal artery aneurysms. J Vasc Ultrasound. 2009. 33: 192-4

63. Ysa A, Arruabarrena A, Bustabad MR, Perez E, del Campo A, Garcia-Alonso J. Images in vascular medicine. True aneurysm of the superficial temporal artery. Vasc Med. 2008. 13: 295-6