Nerve sonography in the diagnostic evaluation of primary and secondary carpal tunnel syndrome in rheumatoid arthritis

BACKGROUND AND PURPOSE

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and extra-articular manifestation of rheumatoid arthritis (RA). However, in patients with RA, it is not always possible to clinically distinguish an actual CTS from other RA-based complaints.

METHODS

We evaluated the diagnostic role of nerve ultrasound (NUS) as supportive tool in the diagnostic process of CTS in patients with RA and tried to provide etiological clarification in cases of secondary CTS. Fifty-eight patients with RA and clinical suspicion of CTS were enrolled. All patients underwent a standardized clinical-neurological, electrophysiological (nerve conduction studies [NCS]), and NUS examination and completed the Boston CTS Questionnaire (BCTQ).

RESULTS

In 96 of 116 hands examined, a clinical suspicion of CTS was documented. In 43 of 96 (44.8%) CTS-positive hands, the diagnosis was primarily confirmed by NCS, whereas in another 16 of 96 (30.2%) hands, the diagnosis could only be verified by NUS, leading to a diagnosis of CTS in 59 of 116 (50.8%) hands. In 19 of 59 (32.3%) CTS-positive hands, tenosynovial hypertrophy was observed, and in 7 of 59 (11.8%), a cystic mass was identified as the underlying cause of secondary CTS. A good correlation between NCS and NUS findings was documented, but no significant correlation was found between NCS, NUS, and clinical findings/BCTQ.

CONCLUSIONS

In people with RA, a diagnosis of CTS purely on a clinical basis is nonspecific and should be supported by NCS and/or NUS. NUS markedly facilitates the diagnosis of CTS in these patients and enables differentiation between primary and secondary causes.

POS0584 ULTRASONOGRAPHY OF THE MEDIAN NERVE IN PATIENTS WITH RHEUMATOID ARTHRITIS UNDER SUSPICION OF CARPAL TUNNEL SYNDROME

Background:

Carpal tunnel syndrome (CTS) is the most common nerve compression syndrome and a common extra-articular manifestation of rheumatoid arthritis (RA). Different causes of CTS are known, among them inflammatory and non-inflammatory pathologies. Electroneurography (ENG) of the median nerve, the method of choice to diagnose CTS, measures impairment of nerve conduction velocity without explaining its underlying cause. However, because the electrical stimulation is often not well tolerated, ENG results may come out inconclusive. Using greyscale ultrasonography (GS-US) provides anatomic information including a structural representation of the carpal tunnel.

Objectives:

To investigate the performance of nerve GS-US in the diagnosis of CTS in patients with RA.

Methods:

Consecutive patients with active RA under suspicion of CTS presenting to a large rheumatologic center were included. Both hands were examined by an experienced neurologist including ENG and a GS-US (ML linear probe with 6-15 Hz) of the median nerve. An established grading system for ENG (1), and an established system for GS-US based on cut-offs for the nerve cross sectional area (CSA) [mild: 0,11-0,13cm2, moderate: 0,14-0,15 cm2, severe: > 0,15 cm2 CTS (2)] were used. In addition, the Boston Carpal Tunnel Syndrome Questionnaire (BCTSQ) was used to assess CTS symptoms (3).

Results:

Both hands of 58 patients with active RA (n=116) and clinical suspicion of CTS (in 38 cases bilaterally) were included. After clinical examination, CTS was suspicious in 96 hands (82.8%), and 59 of all hands had a final diagnosis of CTS (50.9%). Of the latter, 43 hands (72.9%) had a positive ENG and 16 (27.1%) a positive GS-US finding only, while 30 hands (50.8%) were positive in both examinations.

There was a good correlation of the cross-sectional area (CSA) as well as the CSA-ratio to the ENG findings: the larger the CSA, the more severe was the CTS as assessed by ENG (Spearman’s rho=0.554; p<0.001). The more severe the GS-US findings of CTS were, the more definite were the distal motor latency (Spearman’s rho=0.554; p<0.001) and sensible nerve conduction velocity of the median nerve (Spearman’s rho=-0.5411; p<0.001).

In the 46 hands positive in GS-US, tenosynovial hypertrophy of the flexor tendons was detected in 19 hands (41.3%), 7 of which (36.8%) also showed an additional cystic mass. In these 19 patients, clinical complains were more severely present than in patients with non-inflammatory CTS, as assessed by the BCTSQ with a total score of 68.8±13.4 vs. 59.3±13.7, respectively (p=0.007).

Conclusion:

In patients with active RA and clinical complains of CTS, ultrasound examinations provide additional information about inflammation which is helpful for a diagnosis of CTS. Thus, ENG and nerve GS-US should be used complementary for a diagnostic workup of CTS in RA patients with a suspicion of CTS. Power-Doppler may further improve the diagnostic performance of GS-US.

References:

[1]Padua L et al. Acta Neurol Scand 1997; 96:211–217

[2]El Miedany et al., Rheumatology (Oxford). 2004 Jul; 43(7):887-895

[3]Levine DW et al. J Bone Joint Surg Am 1993; 75: 1585-1592

Figure 1.

BCTSQ scores in patients with diagnosis of CTS and absence or presence of RA-related tenosynovial hypertrophy

Disclosure of Interests:

None declared