Introduction

Pseudoaneurysms in the scalp arteries are rare and they may be caused by infection or autoimmune disease, yet they are  most commonly the sequelae of blunt, penetrating, or surgical trauma. Most cases develop in the superficial temporal artery,2)8)10)15) and catheter angiography is the standard imaging technique that is used to diagnose scalp pseudoaneurysms.3)6)8)16) The complication rate for this technique is low, but catheter angiography can cause persistent neurological deficits,6) and certain conditions, and particularly a thrombosed aneurysm, may be misdiagnosed. Computed tomographic angiography (CTA) offers a safe, minimally invasive alternative to catheter angiography for diagnosing and treating intracranial aneurysms.1)15) However, few studies have reported on using CTA to diagnose scalp pseudoaneurysms,5)8)9)15) and the majority of the cases in those studies involved a pseudoaneurysm in the superficial temporal artery.

We report here on two cases of scalp pseudoaneurysms, one in the superficial temporal artery and the other in the occipital artery, and they were diagnosed using CTA. Surgical excision of the pseudoaneurysms was performed in the outpatient clinic with no complications.

Case Illustrations

Case 1 : A 29-year-old man was punched on the left side of his forehead. Ten days later, he felt a pulsatile mass on his forehead in the area of the superficial temporal artery. The mass had increased in size over time.

CTA was performed using a multidetector CT scanner (SOMATOM Sensation; Siemens, Berlin, Germany). The unenhanced axial CT was performed and this was followed by injecting an intravenous bolus of 100 mL of contrast material (Ultravist믱; Schering, Berlin, Germany) at a rate of 4 mL/s. The axial source data was post-processed using three-dimensional volume-rendering algorithms (WorkStream4D, Speed4DTM Technology; Siemens). The CTA revealed an 11 x 8 x 11-mm oval dye-filled sac arising from the frontal branch of the left superficial temporal artery (Fig. 1). The parent artery was located superior and medial to the aneurysmal sac. No evidence of a fistula was observed.

The CTA image was used to make an incision in the scalp along the parent artery. First, the proximal end and then the distal end of the artery were exposed and ligated. After complete ligation of the parent artery, the aneurysm was dissected from the soft tissue and resected en bloc. The aneurysm did not inadvertently rupture during surgery.

Case 2: A 36-year-old man complained of a pulsatile mass in the right suboccipital region of his head and he's had this mass for the past year. He denied a history of direct trauma. CTA revealed a 15 x 8 x 13-mm oval dye-filled sac arising from the right occipital artery and the sac was located lateral to the parent artery (Fig. 2). The lesion was surgically excised using the same procedure described in case 1.

Discussion

The clinical diagnosis of a scalp pseudoaneurysm is based on a history of direct trauma such as fist blow, sports injury, penetration, or surgery and the subsequent development of a pulsatile mass. Aneurysms, arteriovenous fistulas, vascular tumors, and aneurysms of the middle meningeal artery with bony erosion may appear as a pulsatile mass,10-12) but a pulsatile mass is not always a pseudoaneurysm or another vascular lesion. A temporal lipoma may present with similar signs and symptoms,2) so an angiographic image may be critical for making an accurate diagnosis of a pseudoaneurysm.

Catheter angiography is the standard imaging technique used to diagnose scalp pseudoaneurysms.3)6)8)16) Although this technique has a low complication rate, it can cause persistent neurological deficits.6) As a result of the advances in CT technology, CTA is a minimally invasive method for diagnosing intracranial aneurysms and it has replaced catheter angiography.1)4)5) The post-processing software is robust and it includes two- and three-dimensional assessment in an infinite number of planes. CTA accurately depicts the true size of the pseudoaneurysm, including the degree of thrombosis versus the amount of luminal opacification. The relationship of the pseudoaneurysm to the adjacent structures and landmarks such as the skull and muscles are clearly visible in CTA scans.15) Furthermore, additional information such as skull fractures and intracranial lesions can also be obtained.

Both CTA and catheter angiography can be used to diagnosis scalp pseudoaneurysms,5)15) although catheter angiography has been recommended to distinguish between an arterial pseudoaneurysm and an arteriovenous fistula.10)11) Yet Walker et al.,15) reported that asymmetric, early venous filling is a CTA sign of a fistula and there is no evidence that this suggests a diagnosis of a pseudoaneurysm. CTA can replace catheter angiography for making the diagnosis of scalp vascular lesions, but catheter angiography is useful for detecting deep arterial (internal carotid and/or ophthalmic arteries) stenosis. In cases of deep arterial stenosis, the artery involved in the pseudoaneurysm may supply the collateral circulation, and ligation could cause a neurological deficit. However, the intracranial arterial CTA images could avert this problem.

Surgical excision is the standard treatment for scalp artery pseudoaneurysms.12) Conservative treatment consists of applying pressure to the pseudoaneurysm,5) selective embolization of the proximal artery, and direct puncture embolization.16) Surgical resection includes the excision of the aneurysmal sac and the proximal and distal parent artery. Pseudoaneurysm pathology is characterized by a thin-walled, adventitial sac containing blood or organized hematoma. If the sac is entered before vascular control is obtained, it can easily rupture. To ensure a safe surgical resection, the artery should be exposed and ligated proximal and distal to the pseudoaneurysm at the beginning of the procedure. The three-dimensional CTA reconstruction allows better visualization of the pseudoaneurysm in relation to the surrounding anatomical structures than does catheter angiography.8)15) In the cases reported here, we used CTA images to guide the scalp incision over the proximal and distal artery and to ligate the parent artery. After ligation, the pseudoaneurysms were  dissected and removed. The arteries did not rupture during the surgery.

Most cases of scalp pseudoaneurysms involve the superficial temporal artery,7) and this can be explained by its anatomical location. The anterior branch of the artery has no protective cushioning where it crosses from the temporalis to the frontalis muscle, and a tethering effect of the fascia at this level limits lateral displacement of the artery in response to tangential forces.13) In the cases we report here, the pseudoaneurysm in the superficial temporal artery was the result of direct trauma, whereas the occipital artery pseudoaneurysm did not appear to be caused by head trauma. Reports of a pseudoaneurysm in the occipital artery are rare9)14) and this type of pseudoaneurysm has always developed following direct trauma such as a paintball injury9) or as a complication of placing an extension channel during surgery.14) To the best of our knowledge, we are the first in Korea to report an occipital artery pseudoaneurysm that did not result from a head injury. We used CTA images to visualize, diagnose and treat the superficial temporal artery and occipital artery pseudoaneurysms.

In summary, CTA is a useful and minimally invasive confirmatory and diagnostic tool for pseudoaneurysms arising from the superficial temporal and occipital arteries. The images allowed us to visualize the pseudoaneurysms and avoid rupturing the artery during surgery.

REFERENCES

1)   Anderson GB, Steinke DE, Petruk KC, Ashforth R, Findlay JM. Computed tomographic angiography versus digital subtraction angiography for the diagnosis and early treatment of ruptured intracranial aneurysms. Neurosurgery 45:1315-20; discussion 1320-2,1999

2)   Cheng CA, Southwick EG, Lewis EC. Aneurysms of the superficial temporal artery: literature review and case reports. Ann Plast Surg 40:668-71,1998

3)   Choo MJ, Yoo IS, Song HK. A traumatic pseudoaneurysm of the superficial temporal artery. Yonsei Med J 39:180-3,1998

4)   Dehdashti AR, Rufenacht DA, Delavelle J, Reverdin A, de Tribolet N. Therapeutic decision and management of aneurysmal subarachnoid haemorrhage based on computed tomographic angiography. Br J Neurosurg 17:46-53,2003

5)   Grasso RF, Quattrocchi CC, Crucitti P, Carboni G, Coppola R, Zobel BB. Superficial temporal artery pseudoaneurysm: a conservative approach in a critically ill patient. Cardiovasc Intervent Radiol 30:286-8,2007

6)  Heiserman JE, Dean BL, Hodak JA, Flom RA, Bird CR, Drayer BP, et al. Neurologic complications of cerebral angiography. AJNR Am J Neuroradiol 15:1401-7; discussion 1408-11,1994

7)   Isaacson G, Kochan PS, Kochan JP. Pseudoaneurysms of the superficial temporal artery: treatment options. Laryngoscope 114:1000-4,2004

8)   Ishikawa E, Sugimoto K, Yanaka K, Moritake T, Iguchi M, Ayuzawa S, et al. Giant aneurysm of the superficial temporal artery. Case report and review of the literature. Surg Neurol 53:543-5,2000

  9) John N, Leach JL, Rachana T, Mangano FT. Traumatic aneurysm of the occipital artery secondary to paintball injury. Clin Neurol Neurosurg 111: 105-108,2009

10)  Lee KS, Gower DJ, McWhorter JM. Aneurysm of the superficial temporal artery. Neurosurgery 23:499-500,1988

11)  Morioka T, Takeshita H, Nishio S, Kimura Y, Fukui M. Traumatic aneurysm of the superficial temporal artery in an elderly patient. Neurosurg Rev 20:278-81, 1997

12)  Peick AL, Nichols WK, Curtis JJ, Silver D. Aneurysms and pseudoaneurysms of the superficial temporal artery caused by trauma. J Vasc Surg 8:606-10,1988

13)  Pipinos II, Dossa CD, Reddy DJ. Superficial temporal artery aneurysms. J Vasc Surg 27:374-7,1998

14)  Tambasco N, Hamam M, Castrioto C, Calabresi P, Rossi A. Occipital pseudoaneurysm as a complication of extension channel placement for DBS in Parkinson's disease. Mov Disord 22: 1834-1836,2007

15) Walker MT, Liu BP, Salehi SA, Badve S, Batjer HH. Superficial temporal artery pseudoaneurysm: diagnosis and preoperative planning with CT angiography. AJNR Am J Neuroradiol 24:147-50,2003

16)  Yang HJ, Choi YH. Posttraumatic pseudoaneurysm in scalp treated by direct puncture embolization using N-butyl-2-cyanoacrylate: a case report. Korean J Radiol 6:37-40,2005