[Spinal intradural arachnoid cyst associated with enlarged filum terminale].

This is a report of a spinal intradural arachnoid cyst associated with an enlarged filum terminale. A 9-year-old female was admitted to our hospital complaining of lumbosacral pain. Neurological examination revealed no abnormal findings. CT scan showed a round shaped mass lesion in the right dorsolateral side of the spinal canal between the level of L1 to S1/2. The mass lesion disclosed isodensity and was not enhanced. A small low density mass lesion was visualized in the dural sac at the same level. MRI showed the mass lesion with low signal intensity on the T1-weighted image, and high signal intensity on the T2. The small mass lesion in the dural sac was demonstrated with low signal intensity on the T1 and T2-weighted image. In addition to this finding, Chiari malformation type I was disclosed. It was suspected that this mass lesion was extradural arachnoid cyst associated with an enlarged filum terminale. Osteoplastic laminotomy between L3 to S1/2 was performed, and an arachnoid cyst was found in the intradural space. It compressed the cauda equina and enlarged tough filum terminale. The cyst was removed subtotally, and the filum terminale was cut off. Postoperative course was uneventful and the lumbosacral pain disappeared. It was thought that this pain might be derived from the intradural arachnoid cyst, or the enlarged filum terminale.(ABSTRACT TRUNCATED AT 250 WORDS)