Evidence that atypical juxtafacet cysts are joint derived.
OBJECTIVE
Juxtafacet cysts (JFCs) in usual locations have recently been shown to have joint connections. The pathogenesis of JFCs in unusual locations has remained obscure. The authors hypothesize that all JFCs, including atypical ones, are joint derived.


METHODS
In this study the authors sought to explain the occurrence and formation of clinical outliers of spinal JFCs. In Part I, they performed an extensive literature search to identify case reports of spinal intraneural cysts that have been unappreciated despite the fact that they should occur. In Part II, they studied far-lateral (extraforaminal) cysts treated at their institution and reported in the literature. The presence of a joint connection was specifically looked for since this finding has not been widely appreciated.


RESULTS
In Part I, 3 isolated case reports of spinal intraneural JFCs without reported joint connections were identified: 2 involving L-5 and 1, C-8. In Part II, 6 cases involving patients with far-lateral JFCs treated at the authors' institution were reviewed and all 6 had joint connections. Two of these cases had been previously published, although their joint connections were not appreciated. In 2 of the newly reported cases, arthrography confirmed a communication between the facet and the cyst. Only 1 of 5 cases in the literature had a recognized joint connection.


CONCLUSIONS
The authors believe that all JFCs are joint derived. This explanation for intraneural and extraneural JFCs in typical locations would be consistent with the unified articular (synovial) theory and the pathogenesis for intraneural and extraneural ganglion cyst formation in the limbs. Facet joints appear no different from other synovial joints occurring elsewhere. Understanding the pathogenesis of these cysts will help target treatment to the joint, improve surgical outcomes, and decrease recurrences.
Spinner
Robert J
RJ
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota 55905, USA. spinner.robert@mayo.edu
Hébert-Blouin
Marie-Noëlle
MN
Maus
Timothy P
TP
Atkinson
John L D
JL
Desy
Nicholas M
NM
Amrami
Kimberly K
KK
D003937:Diagnosis, Differential; D045888:Ganglion Cysts / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging; D009192:Myelography; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D013122:Spinal Diseases / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D013126:Spinal Nerve Roots / Q000473:pathology; D013127:Spinal Nerves / Q000473:pathology*; D013581:Synovial Cyst / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D021801:Zygapophyseal Joint / Q000473:pathology* / Q000601:surgery