Dental use of cone beam computed 1 tomography in pediatric embolized 2 arteriovenous maxillofacial malformation

Objective : Pediatric facial arteriovenous malformations (AVMs) are rare but can 24 cause potentially fatal hemorrhages during dental procedures and oral surgery. In 25 this article we present a systematic review of the medical open access literature on 26 pediatric facial AVM. 28 Case report : We illustrate our purpose with clinical dental use of cone beam 29 computed tomography (CBCT) in pediatric embolized facial AVM to define the 30 presence and the position of the right upper impacted canine. 32 Conclusions : We advocate the use of CBCT as additional imaging tool in the 33 follow-up of pediatric dentomaxillofacial AVM, and for depiction of dentoalveolar 34 structures that are inaccessible by conventional dental radiography.


46
AVMs are congenital malformations of arterial and venous vessels forming 47 connections between vessels of different origins, diameters and resistance [4]. The 48 connections can be direct or pass through a cluster of small dysplastic vessels called 49 the "nidus" [1,4]. Several factors have been proposed to explain the appearance of 50 this malformation of embryonic origin: an error in the embryonic arterial and venous 51 differentiation [5,6], a combination of genetic, hormonal, biochemical factors 52 (STAT3 proteins) [6] with the presence of vascular endothelial growth factor [5], a 53 persistence of the arteriovenous ducts of the primary retiform plexus [7], a presence 54 of local ischemia [7].

57
Their expansion is the result of increased blood flow rather than cell proliferation 58 [7]. AVMs have a clear tendency to expand with age causing destruction of soft 59 tissue and adjacent bones [8]. The expansion is also associated with episodes of 60 severe bleeding, loss of function and physical deformities [8]. AVMs can appear as 61 uni-or multifocal type or a diffuse type [8]. Focal AVMs contain a well-defined 62 nidus, the simplest form of which consists of a nourishing artery associated with a 63 venous drainage [8]. Focal type is more easily accessible for surgery and the 64 diagnosis and the treatment can be done in childhood [8]. Diffuse AVMs exceed the 65 limits of topographic units, and are also associated with incomplete prior excision 66 [8]. The nidus can no longer be identified. These type is most common in adulthood 67 [8]. Enlargement of AVMs may also be due to hormonal changes during puberty [1].

68
It can occur following a stimulus: trauma with hemorrhage, following local infection 69 or tissue destruction [5,6]. AVMs will not dissapear like hemangioma, but grow 70 slowly or rapidly following a stimulus [6]. The color of the AVM does not change 71 [6].

72
AVMs were staged by Schobinger in the 1970s [8]. Stage I or quiescence, 73 corresponds to pink or purplish macules with the presence of an arteriovenous shunt 74 detected by Doppler ultrasound; this stage is asymptomatic and corresponds to the 75 patient from birth to puberty; Stage I may be accompanied by erythema and a 76 localized rise in temperature [6][7][8]. Stage II or expansion, consists of growth and

77
[ N e m e s i s ] T i t r e d e l ' a r t i c l e ( P U L -En-t ê t e p a i r e ) 4 infiltration of deep subcutaneous structures [8]. The lesion is associated with palpa-78 ble pulsations and audible noise. Tortuous vessels appear at puberty [7]. In stage III 79 or destruction appears dystrophic skin changes with skin ulceration, continuous pain, 80 bleeding, secondary infections and necrosis as well as lytic bone destruction [6][7][8].

89
Facial AVMs may present with the following symptoms: facial asymmetry, tooth 90 mobility, discoloration of the skin or oral mucosa, palpable pulsation, local increase 91 in temperature [11], spontaneous gingival bleeding, pain associated with thrombosis

Medical imaging
96 Doppler ultrasound is used as a first-line scan to distinguish between high-flow 97 AVMs and other low-flow vascular (venous, lymphatic) lesions [6]. The gold 98 standard is the angio-CT scan which identifies the vascular support and the selective 99 embolization of the collateral vessels before surgical resection [5,7].  [6,7,11].

103
The panoramic radiograph shows a poorly defined radiolucency with "soap bubble"

104
-type boxes, with displacement of the teeth, expansion of the cortices, without  118 reconstruction by flaps, and reserved for specialized centers [6,8,15]. Surgical 119 excision with healthy margins is extremely difficult to achieve on the face [6].

138
Complications from sclerosing agents cause acute or chronic paralysis, recurrence of 139 the lesion, skin ulceration associated with superficial lesions [6,7]. Embolization is performed between 24 hours and 72 hours before surgery to 145 reduce intraoperative blood loss [6,15,18,20]. AVMs are the most aggressive lesions of all types of vascular lesions [1] and are 150 at high risk of recurrence [1]. Diffuse AVMs have a recurrence rate of 93% [16].

151
AVMs who have bled once are 9 times more likely to bleed within a year [3].

152
Children with an exacerbation of AVM at a very young age will have a worse 153 prognosis, with more surgeries, greater morbidity and more sequelae than adult 154 patients [6].

156
We present a unique case of the use of cone beam computed tomography (CBCT) scientific articles and to CBCT reference images as a private dental practitioner [21].

165
One observer performed the search for the articles. We have chosen 2 languages: 166 English and French. We also chosen articles with abstracts, and free-access full text

187
For the Google Scholar database we used the keywords « pediatric », « facial »,

193
Finally we retained 20 articles for the literature review.

210
The CT scanner was too irradiating for the dental indication in pediatric patient.

211
We therefore chose to use the cone beam computed tomography (CBCT) with

287
Onyx embolization solution is known to present beam-hardening artifact on CT 288 scan [22,23]. Beam-hardening artifact related to Onyx solution is also present on 289 CBCT (Figures 2-6). In our clinical case the AVM was situated on the right side of 290 the face and the artifact was projected laterally toward the right side of the patient.

291
This situation allows sufficient visualisation of dental arches and of the position of 292 the right upper canine (Figures 3-7, 9).

293
CBCT allowed global three-dimensional visualisation of the AVM arterial and 294 venous network fixed by Onyx embolization process (Figures 8-10). Anatomical 295 extension of the embolized lesion can also be better understood (Figures 11-13).

296
However, three-dimensional CBCT reconstruction alone (Figure 7) was insufficient 297 to depict the arteriovenous embolized network. We needed to use more advanced

298
CBCT software visualization tools with superimposition of soft and hard tissues to 299 visualize the extension of the lesion (Figures 8-13). Structures close to the observer 300 were presented in yellow and structures far from observer were presented in blue to 301 enhance the perspective (Figures 8-10, 12,13).

302
In this clinical case the beam-hardening artifact was projected to the right from the 303 right-side embolized lesion (Figures 2-5, 7). It allowed to free the sight on the right

304
[ N e m e s i s ] T i t r e d e l ' a r t i c l e ( P U L -En-t ê t e i m p a i r e ) 17 dentoalveolar process. However, we don't know yet if a beam-hardening artifact 305 from left-side embolized lesion will be projected to the left or also to the right side 306 of the patient.

307
Finally, we advocate the use of CBCT as additional imaging tool in the follow-up of 308 pediatric dentomaxillofacial AVM, and for depiction of right dentoalveolar 309 structures that are inaccessible by conventional dental radiography.