An anatomically based imaging sign to detect adventitial cyst derived from the superior tibiofibular joint

Abstract

The origin for complex intraneural cysts remains controversial despite recent emerging evidence to support their articular origin. The coexistence of intraneural and adventitial cysts has been described due to the proximate neurovascular bundle, i.e., the articular (neural) branch and vessels at the joint capsule. To clarify the pathogenesis, anatomically based imaging patterns can be identified. This paper characterizes a common finding identified on MRI describing the adventitial component originating from the superior tibiofibular joint (STFJ). MRIs of patients with fibular (peroneal) (n = 24) and tibial (n = 7) intraneural ganglion cysts were reviewed. Eleven patients with fibular intraneural ganglion cysts were identified as having a coexisting adventitial component. In all cases, the adventitial cyst extended from the anterior portion of the STFJ, within the capsular vessels, and along the anterior tibial vessels. The reproducible anatomy permitted the identification of an imaging pattern: the "vascular U" sign, consisting of cystic anterior tibial vessels running through the interosseous membrane between the proximal tibia and fibula. This sign was seen on axial MR image(s) obtained at the level of the fibular neck in all cases. To generalize these findings, the rare tibial intraneural ganglion cysts (derived from the posterior aspect of the STFJ) were examined; two cases had coexisting adventitial cysts with visualization of the vascular U sign. This new imaging pattern can improve the identification of adventitial cysts at the level of the STFJ.

Intraneural ganglion cysts: a systematic review and reinterpretation of the world's literature

“…Finally, several cysts can form at the same time from the same joint, as demonstrated with a complex cyst from the STFJ or ulnohumeral joint leading to an intraneural, extraneural, and intraosseous cyst, 135,137 or combinations of intraneural and adventitial cysts from the STFJ. 54,142,149 The other 2 major theories that have been put forth we believe can be dismissed. The tumoral theory suggests that intraneural cysts are formed from the transformation of pre-existing tumors into cystic lesions.…”