Spinal Syrinx Due to Lipiodol-Induced Arachnoiditis.

We present a case of a progressive symptomatic intramedullary cyst, diagnosed decades after Lipiodol injection. Lipiodol was originally administered intrathecally for the radiologic diagnosis of spinal masses. A link between the lesion and the history of Lipiodol injection was never suspected. Surgical exploration revealed a membrane above the lesion, separating the intradural space in a cranial and caudal compartment. On the level of the cyst, we identified glassy pearls containing a fatty liquid, compatible with Lipiodol deposits. We hypothesize that the syrinx is secondary to the impact of cerebrospinal fluid pulsations on the reactive membrane and that this membrane originated from an arachnoiditis caused by Lipiodol deposits. Lipiodol was indeed abandoned after it was found to cause arachnoiditis and neurologic sequelae. Despite the cessation of its usage, the causal role of Lipiodol in arachnoiditis and spinal cyst formation should still be considered, as symptoms may arise many years after Lipiodol administration.