|Year : 2014 | Volume
| Issue : 4 | Page : 164-166
Computed tomographic angiography: An alternative to catheter-angiography in the evaluation of a scalp arterio-venous malformation
Anas Ismail, Muhammad Abba Suwair, Mustaha Shuaibu Hikima
Department of Radiology, Bayero University, Aminu Kano Teaching Hospital, Kano, Kano State, Nigeria
|Date of Web Publication||11-Dec-2014|
Department of Radiology, Bayero University, Aminu Kano Teaching Hospital, PMB 3452, Kano, Kano State
Source of Support: None, Conflict of Interest: None
Arterio-venous malformation (AVM) is an uncommon abnormality, characterized by abnormally dilated pathologic vessels resulting in shunting of blood from arteries to veins without intermediary capillaries. The management of AVM is challenging because of high shunt flow and complex vascular anatomy. A 28-year-old female patient presented with a pulsatile occipital swelling. Sonographic findings of the AVM were confirmed on computed tomographic angiography, showing dilated, and tortuous vessels in the occipital region with feeders from the vertebral arteries and the right external carotid, which drained to the right internal jugular vein. She was treated by ligating the feeders.
Keywords: Arterio-venous malformation, computed tomographic angiography, scalp
|How to cite this article:|
Ismail A, Suwair MA, Hikima MS. Computed tomographic angiography: An alternative to catheter-angiography in the evaluation of a scalp arterio-venous malformation. Sahel Med J 2014;17:164-6
|How to cite this URL:|
Ismail A, Suwair MA, Hikima MS. Computed tomographic angiography: An alternative to catheter-angiography in the evaluation of a scalp arterio-venous malformation. Sahel Med J [serial online] 2014 [cited 2022 Jul 5];17:164-6. Available from: https://www.smjonline.org/text.asp?2014/17/4/164/146823
| Introduction|| |
Arterio-venous malformation (AVM) is characterized by abnormally dilated tortuous pathologic vessels resulting in shunting of blood from arteries to veins, bypassing capillaries.  Scalp AVMs, usually enlarged progressively over time by recruiting feeders from intracranial arteries.  The feeding arteries and draining veins of these lesions are usually of normal regional vasculature. As a result of abnormal hemodynamics, they become progressively dilated. Occasionally, they undergo aneurysmal dilatation due to increased flow pressure. 
The scalp AVMs arise spontaneously or following trauma. Clinical symptoms include pulsatile mass, headache, local pain, tinnitus; and less frequently, hemorrhage and necrosis. ,,
Arterio-venous malformation of the scalp is uncommon, and its management is challenging because of high shunt flow and complex vascular anatomy. This report reiterates roles of noninvasive techniques of Doppler ultrasound scan and computed tomographic angiography (CTA) in detailed characterization of AVMs.
| Case report|| |
AR is a 28-year-old woman, who presented with progressive pulsatile occipital scalp swelling for 3 years, headache and local pain; with no history of trauma.
Examination revealed a soft, dark and nontender lesion in the occipital region of the scalp. The overlying skin is coarse and dry; however, there was neither ulceration nor active hemorrhage. Bruit was heard on auscultation of the lesion. The vital signs were stable and all other systems were normal. The blood investigations were unremarkable.
Ultrasound examination revealed a soft tissue mass with multiple tortuous sonolucent tubular structures. On Doppler interrogation, they showed a mosaic color appearance [Figure 1] and high bi-directional velocity flow on spectral Doppler analysis.
|Figure 1: Color Doppler scalp sonogram, showing a mosaic color appearance of the arterio-venous malformation|
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The CT scanogram showed an occipital soft tissue swelling that measured 101.4 mm by 49.7 mm in size. There were no calcification or lucency is seen within it. The underlying bone is intact.
The axial and reconstructed CTA were obtained with dynamic injection of contrast. They showed grossly dilated and tortuous vessels in the occipital region that formed the earlier noted scalp swelling. Their diameter ranged from 4.7 mm to 10.7 mm [Figure 2]. These vessels are fed by the vertebral arteries bilaterally and the right external carotid artery. Their draining veins joined the right internal jugular vein at the base of the skull. There was no evidence of communication with intracranial circulation. The circle of Willis and the cerebral and cerebellar hemispheres are within the normal limits.
|Figure 2: A sagittal (a) and axial (b) reformatted computed tomographic angiography images showing the dilated and tortuous vessels. Note the feeders from the branches of the vertebral arteries from the foramen magnum (arrows)|
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The diagnosis of primary (Group 1) occipital scalp AVM was made and the patient had ligation of the feeding arteries with a remarkable symptomatic improvement.
| Discussion|| |
An AVM of the scalp is an abnormal fistulous connection between the feeding arteries and draining veins, without an intervening capillary bed within the subcutaneous layer.  AVMs of the scalp are relatively rare and there is a paucity of reliable data from developing nations. However, according to the preliminary reports of New York Islands AVM study, the average annual AVM detection rate was 1.34/100,000 person-years.  Nevertheless, their precise natural course is still unclear. 
The etiology of scalp AVMs may be spontaneous or traumatic. They generally develop in the trauma background and in patients older than 30 years. Spontaneous AVM of the scalp may present at birth, but may remain asymptomatic until adulthood. Trauma, pregnancy, or hormonal change causes deterioration of the symptoms. Traumatic AVM of the scalp develops months or years after the scalp trauma. About 10-20% of scalp AVMs develop following penetrating or nonpenetrating trauma to the scalp.  Though this patient presents in her third decade of life, 80% of AVMs are seen by the end of the fourth decade, 20% <20 years. 
The most frequent sites of involvement are frontal, temporal, and parietal regions with the occipital region as seen in the index case rarely affected.  Extracranial AVMs accounts for only 8.1% of the cases. , AVMs are 20 times more common in the brain involving or supplied by intracranial vasculature than in that from the external carotid arteries.  Cervico-facial involvement is most common in the cheeks, ears, nose, and less commonly forehead.  Nevertheless, this case showed an unusual cervico-occipital pattern.
In a report by Fisher-Jeffes et al.  in 24 patients with cirsoid aneurysms of the scalp, the lesions were related to trauma in nine patients (38%). Each of their patients presented with a pulsatile scalp swelling with a bruit. The symptoms usually were bruit, transient hemiparesis and Gerstmann's syndrome in addition to the symptoms due to raised intracranial pressure.  In this case however, there was no history of trauma and her symptoms were mostly headache and the deformity and dry skin/alopecia.
The quality of the diagnosis is important for the surgical procedure to be performed, and catheter angiography is of great significance for diagnosis and treatment options. It is particularly employed for the determination of cranial feeders. However, it is expensive, invasive, time consuming and requiring skills for intra-arterial manipulation of catheters with associated risks of stroke. On the other hand, recent developments of CTA with multi-slice technology have provided significant improvements in vascular applications allowing noninvasive vascular evaluation. Advantages of CTA include shorter acquisition times, retrospective creation of thinner sections from source data, improved three-dimensional rendering with diminished artifacts. CTA can also provide a very high temporal resolution and visualization of the related adjacent bony structures, which may be important in surgical planning. Even though CTA has some drawbacks, such as the use of contrast material and the lack of information about blood flow direction, it can be used as a diagnostic alternative for extracranial and intracranial vascular diseases.
The speed and accuracy of the CTA exam of this patient, combined with the ease of rapid generation of three-dimensional images using the very good reporting console played a great role in establishing the diagnosis and in identifying feeder vessels, draining veins and planning the surgical removal of the AVM. It has also ruled out any other significant pathology, which may have impacted on the management of the patient. ,,
Among the treatment options include surgical excision, ligation of feeding vessels, transarterial and transvenous embolization and injection of sclerosant into the nidus. The index case had ligation of the feeders, which resulted in resolution of symptoms.
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[Figure 1], [Figure 2]