How to explain cystic adventitial disease coexisting in an adjacent artery and vein

Our group recently reviewed the literature to support the role of joint connections in cystic adventitial disease (CAD) (Desy and Spinner, 2014): cyst (joint) fluid would egress from a synovial joint and dissect along the adventitia of an articular (capsular) branch to a parent vessel. A recent meta-analysis of 503 reports (724 patients) revealed two patients, one involving the femoral (Ohta et al., 1984), and the other, the popliteal vessels (Alioti et al., 2005) with concurrent disease in adjacent arterial and venous adventitia at the time of operation. Neither case explained the location or the coexistence of the cysts. We believe there is an anatomical basis for both questions. Based on the evidence we have provided in previous publications (Spinner et al., 2013; Desy and Spinner, 2014), we feel that a joint connection was present but unrecognized in both cases (i.e., to the hip and knee, respectively). This is supported by the para-articular location of the cysts, similar to others in the literature including the popliteal and femoral vessels individually (Campbell and Millar, 1985; Hall et al., 1985; Chen et al., 2013; Spinner et al., 2013; Michaelides et al., 2014). Unfortunately, imaging data were not available for our retrospective review nor was postoperative follow-up provided in these two cases. Building on the articular theory that we have proposed, we supply three anatomic possibilities for the coexistence of arterial and venous cysts: (1) Simultaneous or sequential dissection along two separate articular branches from the artery and vein into the parent vessels; (2) Ascent toward the sheath surrounding parent vessels, via a common sheath encircling the capsular artery and vein; or (3) Ascent along a single capsular vessel with “cross-over” to the other vessel within a common (parental) sheath. The first option is supported by nine cases of CAD at the superior tibiofibular joint occurring together with peroneal intraneural ganglion cysts (Spinner et al., 2006). Extrapolating from this, we suggest that a cyst could also progress along capsular arterial and venous branches toward their parent artery and vein (Figs. 1A and 1B). The drawing in Ohta’s paper and the brief description by Alioti would support this mechanism as there appeared to be two separate cysts. The second option would necessitate a common sheath around the capsular vessels (Figs. 1C and 1D). Arteries and veins share a common adventitial layer in smaller mucosal vessels (Gray, 1918), retinal vessels (Jefferies et al., 1993), and the larger carotid vessels (Hayashi, 2007). It is possible that this also applies at the level of capsular vessels, providing a common conduit by which the cyst could ascend. At the bifurcation of this sheath, where the capsular artery and vein divide toward their parent vessels, cyst could progress via either route. If disease were to affect the artery first (Ohta et al., 1984), adventitial fibrosis might increase resistance within the cystic cavity, diverting cyst to the adjacent vein via the common capsular sheath (Fig. 1D); this could potentially explain the sequential development of two cysts from a single conduit. The third option demands the presence of a fibrous sheath investing both the parent artery and vein as is widely recognized in the popliteal and femoral vessels (Moore and Dalley, 2014). Cyst could either dissect circumferentially with the common sheath, or via a septum between the two vessels; explaining a cyst that surrounds the entire vascular bundle (Figs. 1E, 1F). We do not believe that the finding of coexisting artery/ vein cysts is coincidental, or that the two cases are outliers from the articular theory: these examples of CAD must have joint connections. We provide possible mechanisms to explain the concurrent disease, though we do not have proof to answer the question. We also recognize that compression of the adjacent vein by an arterial adventitial cyst (or vice versa) can happen and this must be carefully considered when reviewing images to determine whether in fact that cyst associated with the vein is within the adventitia. An understanding of these cases is essential to prevent recurrence of disease which can occur if the articular connection(s) is/are not addressed. High resolution MRI and MR or CT arthrography would best provide information to the surgeon about the cyst origin and even inter-cyst communication.