Air Embolus to Arachnoid Cyst as a Rare Delayed Complication of Intrathecal Medication Delivery

Abstract

Intrathecal (IT) medication delivery is a commonly used technique for the treatment of chronic intractable pain. Cerebrospinal fluid (CSF) loculation at the catheter tip has been described as a cause of progressive loss of drug effect that can often be difficult to diagnose. The clinical course of a 56-year-old woman was reviewed, including past imaging studies. The patient presented with acute lower extremity paresis secondary to air trapped within an arachnoid cyst thought to be due to long-term use of IT morphine and an undiagnosed CSF loculation. She rapidly recovered after surgical decompression. Symptomatic pneumorachis is rare. In this case, because of radiographically impressive compression and severe deficit, we felt that the trapped air was equivalent to a mass lesion and treated it aggressively. The arachnoid cyst was near the level of the catheter tip prior to revision, and we have retrospectively inferred a causal relationship.