"Disc cysts" and "posterior longitudinal ligament ganglion cysts": synonymous entities? Report of three cases and literature review.
OBJECTIVE AND IMPORTANCE: Extradural cysts intimately associated with relatively normal lumbar discs have rarely been reported. Histologically nonspecific, most have been designated posterior longitudinal ligament (PLL) or annulus fibrosus (AF) "ganglion cysts." Recently, "disc cysts" have been distinguished as a separate entity, mostly on the grounds of cyst-disc communication. CLINICAL PRESENTATION: Three young male patients presented with unilateral sciatica. In all cases, magnetic resonance imaging demonstrated rounded, cystic lesions (i.e., hypointense on T1- but hyperintense on T2-weighted scans) adjacent to minimally dehydrated, nonherniated disc spaces. INTERVENTION: At surgery, each cyst was found intimately related to either the AF (Case 3) or the PLL (Cases 1 and 2) of the adjacent disc; and direct disc-space communication was evident in Case 3. After cystectomy, with or without discectomy, all patients achieved complete and long-lasting resolution of their sciatic symptoms. Histological appearances were typical of ganglion cysts in all three cases, with evidence of prior hemorrhage in Cases 1 and 3. CONCLUSION: Our results and those of others suggest that all such cysts are ganglion cysts that derive from either the AF or the PLL at the disc level. Although disc cysts might be AF ganglion cysts exhibiting disc communication, their separate distinction is probably unnecessary. Cystectomy alone affords complete symptomatic remission; discectomy is usually unnecessary. Although anticipated with ganglia in general, neither spontaneous resolution nor postoperative recurrences have been witnessed. Unlike ganglia in general or juxtafacet ganglion cysts, such cysts seem to be unusually restricted to young men.