What is the role of electrodiagnostic studies in the workup of lumbosacral facet syndrome?

Updated: Nov 19, 2018
  • Author: Gerard A Malanga, MD; Chief Editor: Craig C Young, MD  more...
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Electrodiagnostic studies, such as nerve conduction studies and needle EMG, are not usually indicated for possible lumbosacral facet syndrome. However, these studies should be considered if the history and physical examination findings suggest nerve root impingement or if the diagnosis remains unclear.

Persons with Z-joint pathology typically present with normal sensory and motor examination findings; however, some patients describe the pain as radiating in nature and others report a positive straight leg – raise test result. Thus, electrodiagnostic testing may be helpful for excluding other causes of pain, such as radiculopathy.

RFA of the medial branch of the dorsal ramus affects the innervation of not only the Z-joint, but also the multifidus muscle. Normally, denervation potentials in the multifidus muscles in the setting of LBP are most commonly associated with lumbosacral radiculopathy. In the setting of a patient who has had previous RFA, however, the denervation potential is likely secondary to denervation from the procedure and not a radiculopathy.

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