INTRODUCTION
Scalp arteriovenous malformations (AVMs) are very rare vascular anomalies. A prevalence of 200 cases over 15 years worldwide has been reported; they are also reported to account for 8.1% of all arteriovenous malformations [1,3,9,10,15,18,22,23]. The first accurate description was provided by Hunter in 1757. The case presented in this paper is the third scalp AVM managed at our center but the first of a large scalp AVM. Scalp AVMs are also called “cirsoid aneurysms” meaning varix, due to the serpentine shape of the draining veins [2,13,18]. This pathology is characterized by an abnormal connection between feeding arteries and draining veins without an interposed capillary network. Two main causes are identified: congenital and traumatic. There are reports of AVMs following hair transplants, craniotomies, infections, inflammation, and infusions through scalp veins [10,14-16,18,22]. Spontaneous AVMs are often present at birth but are not noticed until they cause aesthetic problems in adulthood [4,18]. Treatment options include endovascular approaches or surgical excision. Surgery is the most frequently used method to address cosmetic concerns and bleeding. Endovascular techniques include sclerotherapy and embolization utilizing coils, balloons, glue, and various liquid agents [7,16,17,21].
In lower-middle income countries, like Senegal, surgery might be the only practicable treatment for scalp AVMs. We hereby report a case of a spontaneous AVM managed at our center, discussing the challenges faced and how we addressed some of these issues.
CASE DESCRIPTION
A 35-year-old man presented on the 2nd of May, 2024 with a large pulsating mass localized in the occipital region of the scalp. The mass had been present since birth and had progressively increased in size over the years. There was reported history of intermittent headaches which had worsened in frequency and intensity. There was no history of trauma to the scalp or visual disturbances. The family also reported a gradual onset of behavioral disturbances including incoherent speech but these were attributed to a known psychiatric disorder for which he was being followed. He had smoked for over 10 years, the pack-year was not specified. His past surgical history was unremarkable.
On examination, The Glasgow Coma Scale (GCS) was 14/15 (M6V4E4), with pupils equal and reactive to light. There were no motor or sensory deficits. Local examination revealed a median occipital mass, slightly lateralized to the right, approximately 8 cm in maximum diameter, 4 cm in height, with a circumference of about 25 cm. The mass was soft, painless, pulsatile on palpation and seemingly attached to deep structures. There was a systolic bruit on auscultation.
The patient benefited from a brain computed tomography (CT) scan and CT angiography which showed an occipital, contrast-enhancing mass, mostly lateralized to the right, and fed by the right occipital artery (Fig. 1). Regarding the veinous drainage, as per what was visible on the CT-angiography, the nidus was drained by the right parietal vein.
Due to recurrent troubling headaches and aesthetic concerns, a decision was made to surgically excise the mass.
The patient was initially positioned supine for general anesthesia and endotracheal intubation. Following which, he was then turned into the prone position, with a pillow placed under the chest, iliac crest and ankles, and his head stabilized using a round headrest made from theatre drapes. This was followed by shaving the surgical site and preparing it under strict aseptic conditions.
The first step was geared at controlling hemorrhage, hence a linear incision facing the right occipital artery was made, followed by meticulous dissection of the subcutaneous tissue with adequate hemostasis. Dissection was continued to expose the right occipital artery on which a temporary clip was placed to decompress the swelling (Fig. 2), as it was identified as the main feeding artery to the nidus per the CT angiography. This provided partial decompression of the mass but was not complete.
Next, a horseshoe-shaped incision was made around the swelling, with the hinge towards the neck of the patient. Careful dissection of the subcutaneous tissue was performed, followed by meticulous dissection and devascularization of the lesion (Fig. 3). During dissection, we noticed that the left occipital artery was also feeding the lesion, explaining why adequate decompression was not achieved with clipping of the right occipital artery. The left occipital artery was then ligated. Complete excision of the AVM nidus, along with the adjacent galea, was performed, including coagulation or ligation of all feeding vessels (Fig. 4). The total estimated blood loss was 250 cc, most of which occurred during dissection of the lesion before the left occipital artery was identified as a feeder and ligated. Intraoperatively, we observed that the nidus was also drained by the right occipital vein, in addition to the right parietal vein that was seen on the CT-angiography.
Following excision, we noted hyperostosis of the external occipital protuberance. An osteotomy was performed with the aid of a Gigli saw, followed by hemostasis using bone wax. The incisions were then closed, starting with the subcutaneous tissue and then the skin. We would like to note at this point that following excision of the lesion en bloc, no trimming of the excess skin flap or plastic reconstruction was performed (Fig. 4). A drain was left in situ.
The procedure lasted approximately 4 hours and 30 minutes, with no intraoperative complications. The excised specimen was sent for histopathological analysis, confirming an arteriovenous malformation.
The patient was then turned and extubated immediately after surgery with no complications. The immediate postoperative period was uneventful. He was discharged home on postoperative day 4.
Follow-up was, however, marked by the development of skin necrosis of about 2.5 cm in diameter, ten days after surgery (Fig. 5). This was managed successfully with initial debridement followed by wound dressings every other day. No infection was observed during the last follow-up and the patient was doing well. At 6 months follow-up, he reported no headaches, the ulcer had healed completely and satisfactory aesthetic results were achieved. His Glasgow was 15/15.
The excess skin observed initially regressed spontaneously on subsequent follow-ups (Fig. 5).
DISCUSSION
Congenital Scalp AVMs are usually present at birth. Patients may have a red or purple skin pigmentation at the lesion site, but the lesions only clinically manifest themselves in late childhood, adolescence, or adulthood [8,9]. Spontaneous scalp AVMs tend to have a more complex vascular network than post-traumatic AVMs. The latter results from trauma to normal scalp, leading to direct connections between an artery and a vein, or due to canalization of thrombus and does not involve a complex vascular network [8,13,14].
Spontaneous scalp AVMs usually present in the third decade of life as an enlarging, pulsatile mass associated with throbbing headaches [14]. Other symptoms may include bruit, local pain, pulsatile tinnitus, palpable bruits, numbness, recurrent hemorrhage, scalp necrosis, congestive heart failure, epilepsy, mental retardation and intracranial ischemia [1,4,6,14-16,18,21,22]. These symptoms are dependent on the size and severity of the AVM. Our patient was in his fourth decade of life and he presented with headaches and a progressively enlarging, painless pulsating mass along with an auscultatory bruit.
rontal, temporal, occipital, or parietal regions. They may be midline or lateralized; lateral lesions are usually fed by the ipsilateral artery, while midline lesions are fed bilaterally [1]. In our case, the lesion was midline, slightly lateralized to right, and intraoperatively, it was found to be fed bilaterally.
Angio-tomography, magnetic resonance angiography (MRA), and digital subtraction angiography (DSA) are key in the diagnosis of scalp AVMs, with DSA being the gold standard [1,3,4,6,8,11,12,14,16,22,23,25]. DSA is not only essential in the diagnosis but also aids in delineating the lesion, identifying feeders, excluding intracranial extension and also helps differentiate scalp AVMs from other vascular lesions [3,6,8,11,14]. Hence, playing a role in both diagnosis and management.
Our patient did only an angio-tomography, due to the fact that DSA is very expensive and available in only a few facilities. Unavailability or unaffordability of essential neurosurgical imaging is cited as one of the challenges to the practice of neurosurgery in low- and middle-income countries [20]. Lack of DSA led to failure to identify all feeders to the nidus pre-operatively. Hence, the initial intraoperative attempt to control hemorrhage, involving temporary clipping of right occipital artery, was not satisfactory because there was another feeder, the left occipital artery, which was missed.
In the case of unavailability of DSA, meticulous interpretation of available imaging, angio-tomography in our case, is important in order to identify all feeders. We recommend diligent reviewing of the angio-CT images with the radiologist on the computer monitor to identify all feeders as well as the venous drainage of the AVM rather than relying on the angio-CT scan films alone.
Cosmetic concerns are cited as the most common indication for treatment of scalp AVM; other indications include; persistent headaches, tinnitus, prevention of hemorrhage, and other symptoms [1,4,6,15]. This is similar to our case, in which the indications for treatment were cosmetic concerns and recurrent headaches.
Treatment options include surgical excision, ligation, sclerotherapy, and embolization. Embolization is commonly used to slow blood flow to the malformation, thereby decreasing excessive hemorrhage. Endovascular intervention is increasingly used for lesions without intracranial extension, as a preoperative adjunct or for definitive management [11]. Embolization alone, whether endovascular or percutaneous, can effectively manage small AVMs with few feeding arteries. It may also be the intervention of choice when considering extremely large or diffuse AVMs in patients whose comorbidities would preclude them as surgical candidates [15]. Preoperative embolization of large AVMs facilitates subsequent resection by preventing massive hemorrhage [8,11], one of the feared events in the excision of scalp AVMs.
Surgical excision remains one of the most successful treatment for scalp AVMs, it minimizes the risk of recurrence and resolves the cosmetic problem. The aim is to remove the nidus, the associated galea from the pericranium and to ligate the feeding vessels [12,23]. Surgery is the treatment of choice in the case of large AVMs or those with multiple afferences [1]. In fact, surgical excision is preferred for lesions greater than 4 cm and endovascular embolization for lesions less than 4 cm [22]. There has however been a shift towards endovascular treatment with combined treatment preferred for huge lesions or lesions for whom satisfactory esthetic control was not attained via endovascular treatment alone [1,15,22].
Our patient certainly met the criteria for a two-step management i.e., pre-operative embolization followed by surgical resection. The lesion was bigger than 4 cm hence making him a candidate for surgical resection, and the huge size presents a significant risk of massive bleeding intra-operatively thereby making him a candidate for pre-operative embolization. Furthermore, there was no intracranial extension of the lesion, hence, no contraindication to embolization. However, our patient did not benefit from such a procedure because it was not available in our country during the time period concerned.
We had to refer to other means of controlling hemorrhage since we did not have the facilities to carry out pre-operative embolization in our patient and we needed a means to control hemorrhage.
Variable techniques had been used to control hemorrhage during surgery, including percutaneous sutures of the feeding vessels, interlocking suture along the line of incision, use of tourniquet and intestinal clamp over the base of the flap, and use of temporary clipping of feeding arteries [4,6]. In our case, temporary clipping of the right subcutaneous occipital artery, the main feeding artery, was performed at the onset of the surgery. This led to slight decompression of the lesion which, nonetheless, remained tense. During dissection, we noticed that the left occipital artery was also feeding the lesion, explaining why adequate decompression of the mass was not achieved. It should however be noted that the technique helped in keeping bleeding at 250 cc. Furthermore, studies suggest that adequate intra-operative hemorrhage controlling techniques obviate the need for pre-operative embolization [1,6].
Regarding complications; necrosis, infection, and recurrence following incomplete resection are the most common complications of surgical intervention [1,5,24]. In our case, the patient developed a small area of skin necrosis which was initially debrided and subsequently managed by wound dressing every other day. This complication was due to ligation of scalp vessels that compromised blood supply. Satisfactory wound healing is achieved following adequate wound care of scalp necrosis [19]. Certain authors managed skin necrosis with wound dressing alone and achieved good results [14] while others had to resort to secondary wound closure or wound grafting especially when the area of necrosis is significant [4].
Recurrence is a complication much more common with embolization than with surgical resection and most recurrences occur within the first year post-treatment [11]. Complete surgical excision eliminates the risk of such occurrence [6]. Our patient is now one-year post-surgical excision and follow-up will continue, but until now there is no sign of recurrence of the AVM.
As a novelty for this study, the excess skin flap following excision of the scalp AVM was left in situ and it regressed completely with subsequent follow-ups. This would suggest that plastic reconstruction may not be obligatory for best aesthetic results.
CONCLUSIONS
Management of large scalp AVMs is possible even in resource strained environments like ours. In the absence of DSA, good knowledge of the behavior of the feeders with regard to lateral or midline disease coupled with meticulous interpretation of available imaging will aid in identifying all feeders to the nidus of the AVM. Lack of access to pre-operative embolization for primary treatment or for control of intra-operative bleeding can be solved by early temporary clipping or ligation of the main feeders. Then one can proceed with complete surgical resection of the lesion.
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