T2-signal of ulnar nerve branches at the wrist in guyon's canal syndrome.
OBJECTIVE
To evaluate T2-signal of high-resolution MRI in distal ulnar nerve branches at the wrist as diagnostic sign of guyon's-canal-syndrome (GCS).


METHODS
11 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.


RESULTS
In 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 (R(2) = -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%).


CONCLUSIONS
Nerve 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.
Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany. jennifer.kollmer@med.uni-heidelberg.de
Jennifer
J
Kollmer
Philipp
P
Bäumer
David
D
Milford
Thomas
T
Dombert
Frank
F
Staub
Martin
M
Bendszus
Mirko
M
Pham
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014459:Ulnar Nerve / Q000473:pathology*; D017769:Ulnar Nerve Compression Syndromes / Q000175:diagnosis / Q000473:pathology*; D014953:Wrist / Q000473:pathology*