Nerve Entrapment Syndromes Workup

Updated: Jan 04, 2023
  • Author: Amgad Saddik Hanna, MD; Chief Editor: Brian H Kopell, MD  more...
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Imaging Studies

Magnetic resonance imaging (MRI) using the short inversion imaging recovery (STIR) technique displays high signal intensity in the affected nerve segment at the site of compression, probably due to edema in myelin sheath and perineurium. Magnetic resonance neurography is evolving as an important tool in sorting out various painful limb syndromes involving forearm and shoulder. This technique has been incorporated by some groups into treatment of patients with routine entrapment syndromes (eg, carpal and cubital tunnel syndrome). MRI and other imaging modalities are used with atypical presentations of common disorders or with recurrent symptoms after previous operation, as well as with suspected rare entrapment. For example, MRI is especially helpful in identifying a mass lesion in patients with a lesion compressing the suprascapular nerve, the ulnar nerve at the wrist, or the posterior interosseous nerve (PIN).


Diagnostic Procedures

The diagnosis of most entrapment neuropathies can usually be established on clinical grounds alone. For typical cases of carpal tunnel and ulnar cubital syndromes, electrodiagnostic tests (nerve conduction study and electromyography) are not always necessary. Still, they provide useful information: confirming the clinical diagnosis and localization, grading the lesion, identifying an underlying or superimposed peripheral neuropathy, and distinguishing other entities. Additionally, a baseline electrodiagnostic study may allow comparison with a postoperative study in patients with persistent symptoms.

In more unusual entrapment neuropathies such as those involving the suprascapular nerve, the ulnar nerve at the wrist, or the posterior interosseous nerve (PIN), electrodiagnostic tests may be invaluable. For PIN syndrome, electrodiagnostic studies combined with neuromuscular ultrasound can guide accurate electrode localization and can provide diagnostic information about lesion location. [27, 28]

Local nerve block with a local anesthetic agent is useful in confirming the diagnosis of certain entrapments such as meralgia paresthetica.