Intraneural pseudocyst (so-called ganglion) in an unusual retroperitoneal periadnexal location?

Obturator Intraneural Ganglion Cysts: Joint Connected and Underdiagnosed

BACKGROUND

Intraneural ganglion cysts of the obturator nerve are rare. Our aim is to review cases of obturator intraneural ganglion cysts at our institution and those reported in the literature.

METHODS

We reviewed all cases evaluated by the senior author. A literature search was performed using the PubMed database and Google Scholar with the following terms: "obturator cyst," "obturator intraneural ganglion cyst," and "obturator intraneural ganglia." All cases underwent a retrospective review. Patient demographic data, including age, sex, and presenting signs and symptoms were recorded. Imaging studies were re-evaluated by 2 musculoskeletal radiologists experienced in the diagnosis of intraneural ganglion cysts.

RESULTS

We identified 2 cases of obturator intraneural ganglia at our institution; both were connected to the hip joint. We found 4 cases that were clearly diagnosed as intraneural ganglia in the literature, of which only 1 was recognized by the original authors as being joint connected, but based on our reinterpretation, 3 of 4 were joint connected. An additional 9 cases identified in the literature did not definitely report the nerve-cyst relationship, but based on our reinterpretation, were believed to be intraneural; 8 were joint connected.

CONCLUSIONS

We believe that obturator intraneural ganglion cysts adhere to the principles of the unifying articular theory. They arise from the anteromedial hip joint and extend into an articular branch and can reach the parent obturator nerve. Surgery should address the hip disease and/or the articular branch connection. Not appreciating the pathoanatomy of these cysts can lead to persistent or recurrent cysts.

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

OBJECTIVE The etiology of intraneural ganglion cysts has been controversial. In recent years, substantial evidence has been presented to support the articular (synovial) theory for their pathogenesis. The authors sought to 1) perform a systematic review of the world's literature on intraneural cysts, and 2) reinterpret available published MR images in articles by other authors to identify unrecognized joint connections. METHODS In Part 1, all cases were analyzed for demographic data, duration of symptoms, the presence of a history of trauma, whether electromyography or nerve conduction studies were performed, the type of imaging, surgical treatment, presence of a joint connection, intraneural cyst recurrence, and postoperative imaging. Two univariate analyses were completed: 1) to compare the proportion of intraneural ganglion cyst publications per decade and 2) to assess the number of recurrences from 1914 to 2003 compared with the years 2004-2015. Three multivariate regression models were used to identify risk factors for intraneural cyst recurrence. In Part 2, the authors analyzed all available published MR images and obtained MR images from selected cases in which joint connections were not identified by the original authors, specifically looking for unrecognized joint connections. Two univariate analyses were done: 1) to determine a possible association between the identification of a joint connection and obtaining an MRI and 2) to assess the number of joint connections reported from 1914 to 2003 compared with 2004 to 2015. RESULTS In Part 1, 417 articles (645 patients) were selected for analysis. Joint connections were identified in 313 intraneural cysts (48%). Both intraneural ganglion cyst cases and cyst recurrences were more frequently reported since 2004 (statistically significant difference for both). There was a statistically significant association between cyst recurrence and percutaneous aspiration as well as failure to disconnect the articular branch or address the joint. In Part 2, the authors identified 43 examples of joint connections that initially went unrecognized: 27 based on their retrospective MR image reinterpretation of published cases and 16 of 16 cases from their sampling of original MR images from published cases. Overall, joint connections were more commonly found in patients who received an MRI examination and were more frequently reported during the years 2004 to 2015 (statistically significant difference for both). CONCLUSIONS This comprehensive review of the world's literature and the MR images further supports the articular (synovial) theory and provides baseline data for future investigators.