jahernandezpinzon@gmail.com

The diagnosis of Parsonage-Turner syndrome (PTS) is usually based on medical history, physical examination and electrodiagnostic tests. Recently ultrasound studies have identified reduced caliber in or terminal branches of the brachial plexus, this has been confirmed surgically in some cases with implication in prognosis and therapy.Our purpose is to analyze if this morphological change is correlated with the images of the neurography by MR (MRN).

We retrospectively reviewed clinical information and MRN images of 17 patients with confirmed diagnosis of PTS, who presented at our institution over a 5-year period. MRN were analyzed by two radiologists with experience in this technique. All brachial plexus images were obtained using 3T MR scanner (Discovery 750; GE Healthcare, Madison, WI, USA) with 16-channel neurovascular coil using 2D IDEAL coronal T2-WI, 3D IDEAL coronal T1-WI, 3D FIESTA axial and DWI axial sequences.Pathological nerve was defined as: hyperintense signal on T2-weighted images and changes in the nerve thickness.

17 patients met the inclusion criteria, media age was 42 years +/- 16.7 with 6 females and 11 males; the time between the symptoms and MRN was 90.5 +/- 78.9 days (range 8 to 240 days).61.5% patients presented clinical symptoms in the right arm, 23% in the left arm, and 15.3% in both arms, however we founded bilateral pathological nerve at MRN in all patients. All of our patients have multifocal nerve involvement.We founded 4 types of nerve constrictions in our cohort patients type I: incomplete focal constriction, type II: complete focal constriction (hourglass-like), type III [multifocal constrictions (string of pearls like)], type IV (segmental constriction) (fig 1); Inter-observer agreement was almost perfect (Cohen's kappa = 0.87) between MRN readers for this nerve findings.

In our patients we found bilateral and multifocal nerve affection of brachial plexus in all patients and identified different types of constrictions; this findings suggest that MRN may play a role in distinguish PTS from others polyneuropathies.Additional prospective studies to assess the prognostic and therapeutic value of these findings are necessary.

MRN may be used as a diagnostic aid in PTS, which was hitherto a clinical and electrophysiological diagnosis.Nerve constrictions in the MRN may be highly accurate in the diagnosis of PTS.