THE PATHOGENESIS OF intraneural ganglia has been an issue of curiosity, controversy, and contention for 200 years. Three major theories have been proposed to explain their existence, namely, 1) degenerative, 2) synovial (articular), and 3) tumoral theories, each of which only partially explains the observations made by a number of investigators. As a result, differing operative strategies have been described; these generally meet with incomplete neurological recoveries and high rates of recurrence. Recent advances in magnetic resonance imaging and critical analysis of the literature have clarified the mechanisms underlying the formation and propagation of these cysts, thereby confirming the unifying articular (synovial) theory. By identifying the shared features of the typical cases and explaining atypical examples or clinical outliers, several fundamental principles have been described. These include: 1) a joint origin; 2) dissection of fluid from that joint along an articular nerve branch, extension occurring via a path of least resistance; and 3) cyst size, extent, and directionality being influenced by pressures and pressure fluxes. We believe that understanding the pathogenesis of these cysts will be reflected in optimal surgical approaches, improved outcomes, and decreased frequency, if not elimination, of recurrences. This article describes the ongoing process of critically analyzing and challenging previous observations and evidence in an effort to prove a concept and a theory.
Departments of Neurologic Surgery, Orthopedics, and Anatomy, Mayo Clinic, Rochester, Minnesota (Spinner)
Department of Laboratory Medicine, Mayo Clinic, Rochester, Minnesota (Scheithauer)
Departments of Neurologic Surgery and Radiology, Mayo Clinic, Rochester, Minnesota (Amrami)
Reprint requests: Robert J. Spinner, M.D., Mayo Clinic, Department of Neurological Surgery, Gonda 8S-214, Rochester, MN 55905. Email: email@example.com
Received, April 19, 2008.
Accepted, January 29, 2009.