Untitled

Abstract

NTIL recently, descriptions of intraneural ganglia have centered on their static appearances. The unifying articular or "synovial" theory 33 we initially proposed was based on critical analyses of clinical, operative, and imaging observations as well as on assessments of reported cases. Using this theory, we sought to explain the most common form of intraneural cyst-that affecting the peroneal nerve. 32 More recently, the theory was validated with respect to the tibial nerve 31,35 and corroborated by other authors as well. 27 In short, we have shown that intraneural ganglia have characteristic, stereotypical appearances. 34,35 For example, peroneal and tibial intraneural ganglia arise from the anterior 8,32 and posterior 31,35 aspects of the superior tibiofibular joint, respectively, and extend intraepineurially via their own articular branches into the parent nerve, sometimes as far proximal as the buttock! Object. The pathogenesis of intraneural ganglia has been a controversial issue for longer than a century. Recently the authors identified a stereotypical pattern of occurrence of peroneal and tibial intraneural ganglia, and based on an understanding of their pathogenesis provided a unifying articular explanation. Atypical features, which occasionally are observed, have offered an opportunity to verify further and expand on the authors' proposed theory.Methods. Three unusual cases are presented to exemplify the dynamic features of peroneal and tibial intraneural ganglia formation.Results. Two patients with a predominant deep peroneal nerve deficit shared essential anatomical findings common to peroneal intraneural ganglia: namely, 1) joint connections to the anterior portion of the superior tibiofibular joint, and 2) dissection of the cyst along the articular branch of the peroneal nerve and proximally. Magnetic resonance (MR) images obtained in these patients demonstrated some unusual findings, including the presence of a cyst within the tibial and sural nerves in the popliteal fossa region, and spontaneous regression of the cysts, which was observed on serial images obtained weeks apart. The authors identified a clinical outlier, a case that could not be understood within the context of their previously reported theory of intraneural ganglion cyst formation. Described 32 years ago, this patient had a tibial neuropathy and was found at surgery to have tibial, peroneal, and sciatic intraneural cysts without a joint connection. The authors' hypothesis about this case, based on their unified theory, was twofold: 1) the lesion was a primary tibial intraneural ganglion with proximal extension followed by sciatic cross-over and distal descent; and 2) a joint connection to the posterior aspect of the superior tibiofibular joint with a remnant cyst within the articular branch would be present, a finding that would help explain the formation of different cysts by a single mechanism. The authors proved their hypothesis by careful inspection of a recently obtained postoperative MR image.Conclusions. These three cas...