Nerve ultrasound for diagnosing chronic inflammatory neuropathy: a multicenter validation study

Objective To validate the diagnostic accuracy of a previously described
short sonographic protocol to identify chronic inflammatory neuropathy
(CIN), including chronic inflammatory demyelinating polyneuropathy (CIDP),
Lewis Sumner syndrome (LSS) and multifocal motor neuropathy (MMN) and to
determine the added value of nerve ultrasound to detect
treatment-responsive patients compared to nerve conduction studies (NCS)
in a prospective multicenter study. Methods We included 100 consecutive
patients clinically suspected of CIN in three centers. The study protocol
consisted of neurological examination, laboratory tests, NCS and nerve
ultrasound. We validated a short sonographic protocol (median nerve at
forearm, upper arm, and C5 nerve root) and determined its diagnostic
accuracy using the EFNS/PNS criteria of CIDP/MMN (reference standard). In
addition, to determine the added value of nerve ultrasound in detecting
treatment-responsive patients, we used previously published diagnostic
criteria based on clinical, NCS, sonographic findings and treatment
response (alternative reference standard). Results Sensitivity and
specificity of the sonographic protocol for CIN according to the reference
standard were 87.4% and 67.3%, respectively. Sensitivity and specificity
of this protocol according to the alternative reference standard were
84.6% and 72.8%, respectively, and of NCS 76.1% and 93.4%. With addition
of nerve ultrasound 44 diagnoses of CIN were established compared to 33
diagnoses with NCS alone. Conclusions A short sonographic protocol shows
high diagnostic accuracy for detecting CIN. Nerve ultrasound is able to
detect up to 25% more patients who respond to treatment. Classification of
evidence This multicenter study provides Class IV evidence that nerve
ultrasound improves diagnosing of CIN.