Matos, A

Negrão, L

Pereira da Silva, JA

Rovisco, J

Santiago, T

Name not available

Median nerve ultrasound: A screening tool in the diagnosis of carpal tunnel syndrome?

Repositório Institucional dos Hospitais da Universidade de Coimbra

1 Background Ultrasound studies in carpal tunnel syndrome (CTS) have demonstrated increased median nerve cross-sectional area (CSA) at the carpal tunnel inlet. Thus, ultrasound of the median nerve may be useful in screening for CTS. The objective of this study was to assess the diagnostic utility of ultrasound for the diagnosis of CTS and to evaluate the reproducibility of median nerve CSA measurements. 2 Methods Ø  Participants    Individuals with symptoms compatible with classic/probable CTS were consecutively recruited among patients referred to the electromyography laboratory.     Asymptomatic healthy volunteers were recruited among hospital staff.  Ø  Boston Carpal tunnel syndrome Questionnaire (Portuguese version)    Symptom severity (11 items) and functional status (8 items). Multiple choice format scored from 1 point (mildest) to 5 points (most severe). Ø  Nerve conduction studies (NCS)    NCS were considered diagnostic of CTS if 1. sensory nerve action potential (SNAP) distal latency <3ms and/or 2.  median-ulnar latency difference >0.4ms. Additional abnormalities,      including compound muscle action potential onset latency >4ms and absence of median SNAP were used to determine the severity of CTS.    The severity of electrophysiological CTS impairment was assessed by a previously reported neurophysiological classification: Normal, Mild, Moderate, Severe and Very severe [Padua L et al, 1997]. Ø  Ultrasound evaluation    Median nerve cross-sectional area and intraneural power Doppler at the proximal inlet of the carpal tunnel were  measured three times, and the mean values were used for analysis. Ø  Inter- and intra-reader reliability     Two rheumatologists with different levels of experience performed the clinical and US measurements independently and blinded to the clinic and electrophysiological findings. Ø  Statistical analysis    Two-tailed Student t-test was used to evaluate the significance of the differences between the CTS and control group, in SPSS software.     Receiver operating characteristic analysis was used to assess the sensitivity and specificity of the CSA in predicting electrophysiological findings. MEDIAN NERVE ULTRASOUND:  A SCREENING TOOL IN THE DIAGNOSIS OF CARPAL TUNNEL SYNDROME? Santiago T1, Rovisco J1, Matos A2, Negrão L2, Da Silva JAP1 1 Rheumatology Unit, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal; 2 Neurology Unit, Centro Hospitalar e Universitário de Coimbra 3 Results Ø  Sixty symptomatic wrists and twenty-six asymptomatic control wrists were examined (see Table 1).                     5 Conclusions a)  Median nerve ultrasound is a highly sensitive screening tool providing an excellent discrimination between CTS patients and controls.  b)   Our results suggest that US measurement of the median nerve CSA is an easy-to-perform and reproducible technique when a standardized ultrasound examination protocol is used.  c)  Further studies are needed to define the diagnostic threefold to ensure the best possible diagnostic performance of US examination. 4 Discussion We found that the median nerve ultrasound is a highly sensitive screening tool for NCS abnormality. Possible implications of median nerve ultrasound screening:  Ø Fast, inexpensive and confortable for patients Ø Short learning curve allowing the use of ultrasound in CTS routine evaluation Ø May cost-effectively reduce the number of NCS in patients with suspected CTS Expand the study to a larger population would be necessary to determine how US and NCS testing can be used together to improve the diagnosis and treatment of CTS. Table 1 Distribution of patients´ demographic and clinical data according to symptomatic-NCS positive, symptomatic-NCS negative and asymptomatic NCS negative groups. Fig. 2 Distribution of cross-sectional areas of median nerves. Optimal screening cut-off values for CSA is 8.8mm2 (93% sensitivity, 40% specificity, 78% positive predictive value, 77% negative predictive value). The area under ROC is 0.914. Ø CSA was statistically different between the severity groups according to NCS (p<0.05) (see Fig. 2). Ø The inter- and intra-reader reliability for CSA were 0.94 and 0.91, respectively.  Fig. 1- ROC curve for median nerve. Values are labeled as mean (SD). BMI body mass index, VAS visual analog scale for pain, BQ-sympt BQ symptoms scale, BQ-funct BQ function scale. #Statistically significant difference between symptomatic EMG positive and EMG negative group (p<0.05).  tStatistically significant difference between EMG positive and control group (p<0.05).  N=           36           12                 17                   10                  11                Normal                          Mild                      Moderate                    Severe                   Very severe 

Median nerve ultrasound: A screening tool in the diagnosis of carpal tunnel syndrome?

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Repositório Institucional dos Hospitais da Universidade de Coimbra