T2-Signal of Ulnar Nerve Branches at the Wrist in Guyon’s Canal Syndrome

Abstract

ObjectiveTo evaluate T2-signal of high-resolution MRI in distal ulnar nerve branches at the wrist as diagnostic sign of guyon’s-canal-syndrome (GCS).Materials and Methods11 GCS patients confirmed by clinical/electrophysiological findings, and 20 wrists from 11 asymptomatic volunteers were prospectively included to undergo the following protocol: axial T2-weighted-fat-suppressed and T1-weighted-turbo-spin-echo-sequences (3T-MR-scanner, Magnetom/Verio/Siemens). Patients were examined in prone position with the arm extended and wrist placed in an 8-channel surface-array-coil. Nerve T2-signal was evaluated as contrast-to-noise-ratios (CNR) from proximal-to-distal in ulnar nerve trunk, its superficial/sensory and deep/motor branch. Distal motor-nerve-conduction (distal-motor-latency (dml)) to first dorsal-interosseus (IOD I) and abductor digiti minimi muscles was correlated with T2-signal. Approval by the institutional review-board and written informed consent was given by all participants.ResultsIn GCS, mean nerve T2-signal was strongly increased within the deep/motor branch (11.7±4.8 vs.controls:−5.3±2.4;p = 0.001) but clearly less and not significantly increased in ulnar nerve trunk (6.8±6.4vs.−7.4±2.5;p = 0.07) and superficial/sensory branch (−2.1±4.9vs.−9.7±2.9;p = 0.08). Median nerve T2-signal did not differ between patients and controls (−9.8±2.5vs.−6.7±4.2;p = 0.45). T2-signal of deep/motor branch correlated strongly with motor-conduction-velocity to IOD I in non-linear fashion (R2 = −0.8;p<0.001). ROC-analysis revealed increased nerve T2-signal of the deep/motor branch to be a sign of excellent diagnostic performance (area-under-the-curve 0.94, 95% CI: 0.85–1.00; specificity 90%, sensitivity 89.5%).ConclusionsNerve T2-signal increase of distal ulnar nerve branches and in particular of the deep/motor branch is highly accurate for the diagnostic determination of GCS. Furthermore, for the first time it was found in nerve entrapment injury that T2-signal strongly correlates with electrical-conduction-velocity.

MR Neurography: Diagnostic Imaging in the PNS

“…2). More than that, results of the study demonstrated that it is possible to directly correlate the increased nerve T2w signal as most valuable MR neurographic marker with the DML as the current gold-standard NCS parameter, which underlines that the detected changes in nerve T2w signal express true and functionally relevant nerve lesions [20].…”

“…In Guyon's canal syndrome (GCS), the most distal entrapment neuropathy of the ulnar nerve, patients typically present with motor and sometimes also sensory deficits in the distribution of the distal ulnar nerve branches, the deep motor and the superficial sensory branch. Even at this distal anatomical level at the wrist, where nerve structures are at the limit of current structural resolution, high-resolution MRN has been proven to reliably determine clinically relevant nerve branch injury with high diagnostic accuracy (AUC of 0.94; 95 % CI, 0.85-1.00, specificity 90 %, sensitivity 89.9 %) [20]. In accordance with clinical symptoms, the distal motor branch was predominantly affected.…”

“…Even in 2006, Andreisek et al [27] found that the sensitivity and specificity of MR signs in CTS are low, and stated PNS disorders [16][17][18][19][20][21]. To achieve high structural resolution and visualization of nerve fascicles, high magnetic field strength of 3 T and fat-saturated 2D T2w sequences with an in-plane resolution of 0.1-0.4 × 0.1-0.4 mm and a slice thickness of 2-3.5 mm are required [21].…”

“…Results of this study have proven that high-resolution MRN can reliably determine a neuropathy with high diagnostic accuracy even at wrist level, where nerve structures are at the limit of current structural resolution. From Kollmer et al [20] under the Creative Commons Attribution license type 1 and 2 DPN. Results of this pilot study in a relatively small group, revealed findings similar to those in TTR-FAP with multifocal fascicular, symmetric lesions in proximal sciatic nerve trunks [42].…”

Magnetic Resonance Imaging of the Skeletal Musculature

“…As the ulnar nerve passes the intramuscular medial septum and the medial head of the triceps muscle it may be compressed by a locally thickened ligament (sometimes also referred to as the Struther 0 s arcade) (Wehrli and Oberlin 2005). Recent MRI data at 3 T could impressively demonstrate the high sensitivity of MRI in detecting signal changes of the deep motor branch of the ulnar nerve in Guyon's-canal-syndrome (Kollmer et al 2012). Then it is defined by the course of the nerve underneath a retinaculum proximally and further distally underneath the arcuate ligament of Osborne and finally it is covered by the deep aponeurosis of forearm flexor muscles (Assmus et al 2009).…”