Value of metrizamide CT in the demonstration of spinal arachnoid cysts.

Spinal arachnoid cyst presents a di agnosti c challenge to c linical neurologists as well as radiologists. Although not an infrequent cause of progress ive spasti c paraparesi s in the young and middle-aged , it is often overlooked in the differential diagnosis of progressive myelopathy. This is of concern in that early diagnosis and resection of these ben ign lesions could prevent progressive and irreversi ble damage to the spinal cord . Diagnostic evaluation of spinal arachnoid cysts has evolved with advent of newer technologies. Currently, watersoluble myelography is widely advocated , yielding less morbidity from arachnoidal scarring , which has often been associated with oily contrast mediaespec ially when trapped by or within the cyst [1 ]. Vonofakos et al. [2], however, argue in favor of oily contrast materi al , contending that metrizamide myelography could fail to demonstrate an arachnoid cyst owing to the homogeneous dilution of the contrast medium within the cyst and the subarachnoid space. Along with others, they emphasized the efficacy of oily contrast material with use of prone, supine, and erect positions [3, 4]. We report a case in whi ch both Pantopaque and metrizamide myelograms failed to demonstrate a spinal arachnoid cyst that was subsequently delineated by metrizamide computed tomography (CT). Metrizamide CT appears to be the most sensitive method for evaluating the spinal arachnoid cysts.