Abstract
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. 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. 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. 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.
Highlights
AND PURPOSE: Transforaminal CS injections have been associated with severe adverse CNS events, including brain and spinal cord infarction
There has been considerable controversy with regard to the severity of adverse effects associated with transforaminal steroid injections, especially those performed at the level of the cervical spine
These procedures are routinely performed to treat radicular symptoms by administering CS and LA into the region of the neural foramen. This injection technique has been associated with severe adverse CNS events, with brain and spinal cord infarction being the most frequent of these uncommon sequelae.[2,3,4,5,6,7]
Summary
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). We used the -Slide I Luer flow kit (Ibidi, Munich, Germany) to perform dynamic microscopic analysis. This allows microscopic images to be obtained as CS preparations flow through a 200-m-depth channel (Fig 1). A single drop of prepared sample was placed on a microscope slide via a standard 25-gauge needle, and a coverslip was applied. High resolution (2080 ϫ 1542) color RGB digital images were obtained at ϫ100, ϫ200, and ϫ400 magnification after calibration had been performed. The prepared samples were manually injected via a short low-pressure tube attached to the -Slide device (Fig 1).
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