gms | German Medical Science

Objectives/Interrogation: MRI has been gradually spreading for diagnosis of carpal tunnel syndrome. Most reports have been used axial images for the diagnosis, however, we focused on sagittal view of T2 fat suppression because pathology of the entrapment point can be well-described. The purpose of this study is to clarify the usefulness of sagittal view of MRI on diagnosis of carpal tunnel syndrome, and to compare with clinical or electrophysiological severity.

Methods: Sixty-three hands of 55 patients with carpal tunnel syndrome (19 males, 44 females, average age: 62.3 years) were included. All patients' wrist underwent simple MRI, and pseudo-neuroma was high signal on the sagittal image of T2 fat suppression. The maximum anteroposterior diameter (AP-D) and the distance between the proximal end of the high signal area and the wrist joint (LT-D) were measured. We also evaluated clinical severity according to Hamada's classification (Stage I: positive sensory disturbance without thenar muscle atrophy; Stage II: with thenar muscle atrophy; Stage III: impossible for thumb opponens). Motor nerve conduction study was performed and distal latency (DL) was measured, and more than 6.5 msec. was considered as severe group. We compared the AP-D and the LT-D and Hamada's classification and DL.

Results and Conclusions: There was significant positive correlation coefficient between the LT-D and DL (r=0.52, p<0.05), but not significance between the AP-D and DL. There was no significant correlation between the AP-D or LT-D and Hamada's classification. The cut-off value of the AP-D obtained using the ROC curve was 2.9 mm, which was significantly associated with Hamada stage II and III (p = 0.01). Similarly, the LT-D cutoff value was 8.9 mm, which was significantly related to severe group of DL (p = 0.04). Although high reliability of diagnosis for patients with carpal tunnel syndrome has been reported using axial view of MRI, we focused on sagittal view of MRI because constriction and/or pseudo-neuroma can be described. This study revealed that patients with more than 2.9 mm of AP-D and more than 8.9mm of LT-D could be diagnosed as severe group on clinical and electro-physiological studies. We believe carpal tunnel syndrome should be diagnosed using MRI without electro-physiological studies.