Letter to the Editor Regarding "Spontaneous Regression of a Hypoglossal Neurinoma: Case Report and Review of the Literature"

Does complete regression of intraneural ganglion cysts occur without surgery?

PURPOSE

The dynamic nature of intraneural ganglion cysts, including spontaneous expansion and regression, has been described. However, whether these cysts can regress completely in the absence of surgical management has important therapeutic implications. Therefore, we aim to review the literature for cyst regression without surgical intervention.

METHODS

We reviewed our database of 970 intraneural ganglion cysts in the literature to search for evidence of complete regression based on strict radiologic confirmation, either spontaneously, or after percutaneous cyst aspiration or steroid injection.

RESULTS

We did not find any examples of complete regression without surgical treatment that met inclusion criteria. Spontaneous regression was reported in four cases; however, only two cases had follow-up imaging, both of which demonstrated residual cysts. Nineteen cases of percutaneous intervention were found in the literature, 13 of which reported clinical improvement following aspiration/steroid injection; however, only seven cases had available imaging. Only two cases reported complete resolution of cyst on MR imaging at follow-up, but reinterpretation found residual intraneural cyst in both cases.

CONCLUSION

We believe that pathology (structural abnormalities and/or increased joint fluid) always exists at the joint origin of intraneural ganglion cysts which persist even with regression of the cyst. The persistence of a capsular abnormality or defect can lead to recurrence of the cyst in the future, and while imaging may show dramatic decreases in cyst size, truly focused assessment of images will show a tiny focus of persistent intraneural cyst at the joint origin. Thus, expectant management or percutaneous intervention may lead to regression, but not complete resolution, of intraneural ganglion cysts.

Totally Cystic Schwannoma: A Misnomer

BACKGROUND

Although partial cystic degeneration is commonly observed in schwannoma, cases of totally cystic forms have also been reported. A literature review of cases describing totally cystic schwannoma was performed to assess their imaging characteristics.

METHODS

PubMed was queried with the phrases "totally cystic schwannoma," "purely cystic schwannoma," and "completely cystic schwannoma." A total of 19 papers encompassing 22 cases of reported totally cystic schwannoma were included. Patient characteristics, clinical presentation, and reported imaging characteristics were recorded. Computed tomography and magnetic resonance images from the papers were collected and reviewed by a senior musculoskeletal radiologist.

RESULTS

The most frequent presenting location of these lesions was in spinal nerve roots. The interpretations of imaging reported in the papers described a homogeneous lesion that was isointense to slightly hyperintense to cerebrospinal fluid (CSF) on T1-weighted images. On contrast administration, the studies described a thin rim of "ring-like" enhancement around the lesion. Our reinterpretation of the imaging revealed heterogeneous lesions that were hyperintense to CSF on T1-weighted images. Post-contrast images typically demonstrated an irregularly thickened enhancing rim. Most images showed evidence of solid components in the lesion, with many containing enhancing soft tissue elements. The observed imaging features were not consistent with simple cystic lesions.

CONCLUSIONS

Review of the imaging studies of the reported cases of completely cystic schwannoma did not produce any convincing examples of purely cystic lesions. The description of these lesions as "totally cystic" appears to be a misnomer and has diagnostic and therapeutic implications.