Nerve Entrapment Syndromes Workup

Updated: Sep 21, 2017
  • 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 the compression, probably due to the presence of edema in the myelin sheath and perineurium. Magnetic resonance neurography is evolving as an important tool in sorting out various painful limb syndromes involving the forearm and shoulder. This technique has been incorporated by some groups into the management of patients with routine entrapment syndromes (eg, carpal and cubital tunnel syndrome). For many, MRI and other imaging modalities are used for patients with atypical presentations of common disorders, recurrent symptoms after previous operation, and in those suspected of having rare entrapments. For example, MRI is especially helpful in identifying a mass lesion in patients with a lesion compressing the suprascapular nerve, ulnar nerve at the wrist or 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 to a postoperative study in patients with persistent symptoms.

In more unusual entrapment neuropathies, such as those involving the suprascapular nerve, ulnar nerve at the wrist, or posterior interosseous nerve (PIN), electrodiagnostic tests may be invaluable. For PIN syndrome, electrodiagnostic studies combined with neuromuscular ultrasound can guide accurate electrode localization and provide diagnostic information about lesion location. [21, 22]

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