Introduction/Aims Neurogenic thoracic outlet syndrome (NTOS) is a heterogeneous and often disputed entity. An electrodiagnostic pattern of T1 > C8 axon involvement is considered characteristic for the diagnosis of NTOS. However, since the advent of high‐resolution nerve ultrasound (US) imaging, we have encountered several patients with a proven entrapment of the lower brachial plexus who showed a different, variable electrodiagnostic pattern. Methods In this retrospective case series, 14 patients with an NTOS diagnosis with a verified source of compression of the lower brachial plexus and abnormal findings on their electrodiagnostic testing were included. Their medical records were reviewed to obtain clinical, imaging, and electrodiagnostic data. Results Seven patients showed results consistent with the “classic” T1 axon  > C8 pattern of involvement. Less typical findings included equally severe involvement of T1 and C8 axons, more severe C8 involvement, pure motor abnormalities, neurogenic changes on needle electromyography in the flexor carpi radialis and biceps brachii muscles, and one patient with an abnormal sensory nerve action potential (SNAP) amplitude for the median sensory response recorded from the third digit. Patients with atypical findings on electrodiagnostic testing underwent nerve imaging more often compared to patients with classic findings (seven of seven patients vs. five of seven respectively), especially nerve ultrasound. Discussion When there is a clinical suspicion of NTOS, an electrodiagnostic finding other than the classic T1 > C8 pattern of involvement does not rule out the diagnosis. High resolution nerve imaging is valuable to diagnose additional patients with this treatable condition.

Value of Ultrasound in the Diagnosis of Neurogenic Thoracic Outlet Syndrome Diagnostic imaging techniques for neurogenic thoracic outlet syndrome (NTOS) are lacking. However, a potential valuable diagnostic imaging technique for NTOS is high resolution ultrasound (HRUS) of the brachial plexus. 1 The aim of this prospective study was to determine the diagnostic value of HRUS in NTOS patients.All patients referred to the Catharina Hospital in Eindhoven, The Netherlands, with suspected NTOS were examined following the diagnostic standards for NTOS as described in the SVS TOS Reporting Standards. 2 Medical history, complaints, physical examination, disability of the arm shoulder and hand (DASH), and Cervical Brachial Symptom Questionnaire (CBSQ) score, colour Doppler of the subclavian artery, and Xray of the superior thoracic

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