title: Air embolus to arachnoid cyst as a rare delayed complication of intrathecal medication delivery.
abstract: BACKGROUND
  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.
  
  
  METHODS
  The clinical course of a 56-year-old woman was reviewed, including past imaging studies.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: LSU Health Sciences Center, New Orleans, Louisiana, USA.
authors.forename: Daniela C
authors.initials: DC
authors.lastname: Atencio
authors.forename: John M
authors.initials: JM
authors.lastname: Gachiani
authors.forename: Erich O
authors.initials: EO
authors.lastname: Richter
mesh_terms: D016080:Arachnoid Cysts / Q000209:etiology* / Q000473:pathology / Q000601:surgery; D001416:Back Pain / Q000188:drug therapy; D019299:Decompression, Surgical / Q000379:methods; D016503:Drug Delivery Systems; D004618:Embolism, Air / Q000209:etiology*; D005260:Female; D006801:Humans; D015918:Infusion Pumps, Implantable / Q000009:adverse effects*; D007278:Injections, Spinal / Q000009:adverse effects*; D008875:Middle Aged; D013904:Thoracic Vertebrae