title: Injectable corticosteroid preparations: an embolic risk assessment by static and dynamic microscopic analysis.
abstract: OBJECTIVE
  Transforaminal CS injections have been associated with severe adverse CNS events, including brain and spinal cord infarction. Our purpose was to describe the static and dynamic microscopic appearances of CS preparations, with an emphasis on their potential to cause adverse central nervous system events by embolic mechanisms during transforaminal injection.
  
  
  METHODS
  Pharmaceutical preparations of nondilute injectable CSs were used after appropriate mixing: MPA (40 mg/mL), TA (40 mg/mL), and DSP (8 mg/2 mL). For dynamic imaging, a novel methodology was devised to replicate the flow of crystals within spinal cord arterioles. In addition, CS preparations were mixed with plasma to assess for changes in crystal size, morphology, and tendency to aggregate.
  
  
  RESULTS
  The CS preparations MPA and TA are composed of crystals of varying sizes. MPA crystal size range was 0.4-26 μm (mean, 6.94 μm), TA crystal size range 0.5-110 μm (mean, 17.4 μm), and DSP did not contain any significant crystals or particles. There was no change in the crystal morphology or propensity to aggregate after mixing with local anesthetic. After mixing with plasma, the crystals also were unchanged; however, there was a significant reduction in the size of aggregates. On dynamic imaging, these aggregates were proved to maintain their integrity and to act as potential embolization agents.
  
  
  CONCLUSIONS
  MPA and TA have a substantial risk of causing infarction by embolization if inadvertently injected intra-arterially at the time of TFESI. DSP is completely soluble and microscopically has no potential to obstruct arterioles. When performing cervical TFESI procedures, the administration of insoluble CSs should be avoided.
authors.affiliation: Department of Radiology, Mater Misericordiae University Hospital, Dublin, Ireland. petermacmahon@yahoo.com
authors.forename: P J
authors.initials: PJ
authors.lastname: MacMahon
authors.forename: M J
authors.initials: MJ
authors.lastname: Shelly
authors.forename: D
authors.initials: D
authors.lastname: Scholz
authors.forename: S J
authors.initials: SJ
authors.lastname: Eustace
authors.forename: E C
authors.initials: EC
authors.lastname: Kavanagh
mesh_terms: D000305:Adrenal Cortex Hormones / Q000008:administration & dosage* / Q000009:adverse effects*; D006801:Humans; D015552:Injections, Intralesional / Q000009:adverse effects; D020766:Intracranial Embolism / Q000139:chemically induced* / Q000473:pathology*; D008853:Microscopy; D019047:Phantoms, Imaging; D018570:Risk Assessment
chemical_list: D000305:Adrenal Cortex Hormones