[Coccygodynia disclosing Tarlov's cysts].

In a 63-year old male patient coccygodynia, initially isolated then complicated by incomplete cauda equina syndrome, could be attributed to large perineurel meningeal cysts on the sacral nerve roots. The diagnosis was suspected at computerized tomography and nuclear magnetic resonance and confirmed by sacculoradiculography. Intradural injections of corticosteroids provided lasting pain relief. Arachnoid cysts are often asymptomatic, by they may be responsible for coccygodynia and/or incomplete cauda equina syndrome. Their presence is suggested by the characteristics of the symptoms which are paroxysmal, exacerbated in standing position, relieved in dorsal position and revived by percussing the sacrum. Treatment is medical in most cases. The decision to operate depends on the persistence and intensity of pain and on whether signs of neurological defecit are present.