الفهرس 
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Abstract
Carpal Tunnel Syndrome (CTS) is the most common entrapment neuropathy, which is caused by median nerve entrapment over the wrist to palm segment (Lee et al., 2012).
Typical guidelines to diagnose CTS include the combination of clinical and electrodiagnostic findings. However, in early stages when clinical examination is nearly normal, history and topographic distribution of the symptoms is insufficient for CTS diagnosis. The most reliable method to confirm clinical diagnosis of CTS is electrodiagnostic testing (Lawrence et al., 2014).
In these early or suspected CTS cases, combined sensory index (CSI) which is the sum of median radial peak sensory latency difference (Thumb difference), median ulnar peak sensory latency difference (Ring difference) and median ulnar mid palmer peak sensory latency difference (Palm difference) believed to be more sensitive (Robinson et al., 1998).
However, this still leaves a small number of patients with the clinical symptoms of CTS and normal NCS (Taylor et al., 2010).
For this reason, High-resolution ultrasonography has been proposed as a useful tool for early detection of CTS and it can assess anatomical abnormalities that NCS do not evaluate. Moreover, the attraction of ultrasonography for diagnosis of CTS lies in its wide availability, lower cost, noninvasiveness, and shorter examination time (Visser et al., 2008).
The measurement of cross-sectional area (CSA) of the median nerve at the wrist is the most widely used ultrasonography method in CTS diagnosis. The ratio of median nerve cross sectional area at the carpal tunnel inlet as compared to the carpal tunnel outlet (IOR) recently used to compensate for the interindividual variability in the CSA of the median nerve and yield a more accurate diagnosis of CTS (Tengfei et al., 2015).
The aim of our study was to evaluate the diagnostic value of electrodiagnostic test (CSI) and diagnostic ultrasound (IOR) in early detection of CTS.
This study was conducted on twenty patients with symptoms and signs suggestive of carpal tunnel syndrome in one hand with duration 1 to 4 months and twenty hands of apparently healthy volunteers included as a control group. They were recruited from the outpatient clinic of Physical medicine, Rheumatology and Rehabilitation Department at Ain Shams University Hospitals.
Patient’s ages ranged from 25 to 45 with mean±SD (36.8±6.1) years. They were 3 males (15%) and 17 females (85%) and 20 apparently healthy volunteers served as control group. Their ages ranged from 25 to 45 with mean±SD (36.75±6.41) years. They were 9 males (45%) and 11 females (55%).
Our results revealed as regards comparison between patients and controls in electrodiagnostic tests that thumb difference test, Ring difference test and CSI had highly statistically significant difference between the two groups. While Palm difference test: revealed no statistically significant difference.
As regard sensitivity, specificity, and accuracy, we found that the most sensitive, specific and accurate test was the CSI with sensitivity 85%, specificity 100% and accuracy 97.5%.
Considering that, there is no “gold standard” for diagnosis of CTS as stated by (Werner and Andary, 2011).
Moreover, According to what proposed by Visser et al., 2008 that ultrasonography is a useful tool for early detection of CTS and it can assess anatomical abnormalities that NCS do not evaluate. In addition, According to what stated by (Cartwright et al., 2008) that the nerve cross-sectional area is the most reliable measurement for diagnosis of CTS.
In our work, we measure CSA of median nerve for diagnosis of early CTS. Moreover, on comparison between patients and control groups in ultrasonographic findings we found that CSA of median nerve at the tunnel inlet and Inlet to outlet ratio (IOR) both revealed highly statistically significant difference between the two groups. While CSA of median nerve at the tunnel outlet revealed no statistically significant difference between the two groups.
As regard sensitivity, specificity, and accuracy of ultrasonographic measures: Our results revealed that CSA inlet had the lowest sensitivity 55%, while the highest specificity 100% and accuracy 87.6%. Moreover, CSA outlet had the highest sensitivity 90% but the lowest specificity 35%, and accuracy 57.6% among the three measures. In addition, IOR sensitivity was 80%, specificity 70% and accuracy 85%.
Since, the use of ultrasonography (US) has changed the traditional concept of idiopathic carpal tunnel syndrome (CTS), caused by median nerve entrapment in the carpal tunnel (CT), as The US has the ability to show normal and pathologic median nerve morphology, abnormalities of the tunnel wall, as well as its contents (Klauser et al., 2010).
US has been compared to nerve conduction study and was recommended by many authors as a new alternative diagnostic modality for the evaluation of CTS (Roll et al., 2011).
Analysis of our results for comparison between CSI and IOR in early detection of CTS revealed that: CSI is more sensitive than IOR by 76.47% more specific by 60.87% and accuracy by 67.5 %.
However, according to what stated by other previous studies that there was a high degree of correlation between the conduction abnormalities of the median nerve as detected by electrodiagnostic tests and the measurement of the cross-sectional area of the nerve by US. Which give confident results for diagnosis, treatment planning and follow up of the patients with CTS.
In addition, many studies stated that US is not an alternative diagnostic tool to electrodiagnostic tests but they are complementary; US provides anatomic information of the nerve and its surrounding structures while the NCS provides information on the level of the lesion and the function of the nerve fibers with the largest diameters (Arnoldo et al., 2013)
In our study same result confirmed after combination of both electrodiagnostic test (CSI) and diagnostic ultrasound (IOR) in early detection of CTS, our results revealed that: sensitivity of both tests increased to 100%, specificity to 70%, and accuracy increased to 85% rather than the results obtained on comparison of both tests.
Consequently, we reached to a conclusion that US is not an alternative diagnostic tool to electrodiagnostic tests but they are complementary to each other in early detection of CTS.