Presentation
Right leg radicular symptoms in an S1 dermatome distribution.
Patient Data
A 22G gauge needles passes through the dorsal aspect of the right S1 foramen. The needle tip is adjacent to the right S1 nerve root. Gas can be seen extending from the needle tip to extend into the dorsal epidural space.
Case Discussion
Injections targeting nerve roots can be divided into selective nerve root blocks (SNRBs) and transforminal epidural steroid injections (TFESIs). SNRBs will have a higher diagnostic yield as the medication will predominantly be given around the targeted nerve root, as opposed to the nerve root and epidural space in TEFSI which could extend to other levels.
Gas was used in this case as a contrast agent to confirm the needle tip position. This is a useful technique is those patients with an allergy to iodine based contrast agents.
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