Objective. To determine the value of investigations for nonspecific ne
urogenic thoracic outlet syndrome (NNTOS) and formulate a rational dia
gnostic approach. Design. Retrospective review. Setting. Thoracic surg
ery clinic. Patients. Fifty-six patients referred with a presumptive d
iagnosis of NNTOS. Patients with arterial, venous, or true (classic) n
eurogenic TOS were excluded. interventions, All patients underwent car
eful history and examination. Fifty-three had cervical spine radiograp
hs, 45 had electrophysiologic testing, and 30 patients had arterial do
ppler studies. Main outcome measures. The value of investigations that
documented a diagnosis other than NNTOS could be assessed but objecti
ve evaluation of investigations that appeared to support a diagnosis o
f NNTOS was not possible. No standard diagnostic criteria exist for NN
TOS. Results. Forty (71%) patients were female. Thirty-four (61%) pati
ents had a pulse deficit with provocative maneuvers. Cervical spine ra
diographs showed cervical ribs in 10 patients and degenerative disease
in 11 patients. Electrophysiologic testing demonstrated carpal tunnel
syndrome in II patients. Arterial Doppler studies were strongly posit
ive for TOS in 10 patients. Thirty-six (64%) patients were diagnosed w
ith conditions other than NNTOS. The diagnosis of NNTOS was accepted i
n 20 (36%) patients. All 20 patients were initially treated conservati
vely but 3 (5%) eventually underwent surgery. Conclusions. NNTOS is a
diagnosis of exclusion. Two thirds of patients referred to a thoracic
surgery clinic were eventually diagnosed with conditions other than NN
TOS. Objective evaluation of investigations that may support a diagnos
is of NNTOS is not currently possible.