The Second Lumbrical–Interosseous Latency Comparison in Carpal Tunnel Syndrome

Abstract

Carpal tunnel syndrome (CTS) is the most common nerve entrapment syndrome. Electromyogram (EMG) is beneficial in supporting the diagnosis of CTS. We compared standard nerve conduction studies of EMG with median and ulnar motor nerve conduction studies from recordings of second lumbrical and interosseal muscles in supporting the diagnosis of CTS. In this study, a total of 242 patients were included, and a total of 375 hands were involved. Electrophysiologic CTSs were diagnosed in 283 hands of 161 patients. A significant association between second lumbrical-interosseal distal motor latency difference (2LI-MDLD) and CTS was found in this study. Statistically, every 0.1 increment in the 2LI-MDLD value was observed to increase the risk of disease by 1.74. When a cut-off of ≥ 0.5 for 2LI-MDLD is taken for predicting CTS, the sensitivity of the test is found to be 89.4% and specificity 84.4%. When the cut-off value for motor distal latency of second lumbrical of the median nerve (2L-MDL) was taken as ≥ 3.15 milliseconds in the diagnosis of CTS, the sensitivity of the test was 87.3%, and specificity 70.7%. Previous reports and our findings suggest that in CTS diagnosis, not only 2LI-MDLD value but also 2L-MDL value are easy and rapidly obtainable and offer additional information in very severe cases where compound muscle action potentials (CMAP) cannot be recorded from the abductor pollicis brevis (APB) muscle.

Lumbrical-interosseous recording technique versus routine electrodiagnostic methods in the diagnosis of carpal tunnel syndrome

“…Furthermore, Ozben et al [26] found the sensitivity to be 89.4% and specificity to be 84.4% with a cut-off value of ≥0.5 in their study. However, based on a cutoff value of >0.5 for L-I latency difference, sensitivity and specificity were 86.9% and 91.3%, respectively.…”

Diagnosis of Severe Carpal Tunnel Syndrome Using Nerve Conduction Study and Ultrasonography

“…In these cases, clinicians perform a second lumbrical-interosseous latency comparison (2 L-INT) test (Kaul and Pagel 2002;Nobuta et al 2005;Sheean et al 1995). However, in the absence of 2 L-CMAPs (Inukai et al 2013;Ozben et al 2012), it is very difficult to quantitatively evaluate CTS severity using NCS. Some authors report that ulnar nerve distal motor latency (DML) and distal sensory latency can be significantly longer in patients with CTS than in controls (Chen and Tsai 2014;Kiylioglu et al 2011;Yemisci et al 2011).…”

A study to further develop and refine carpal tunnel syndrome (CTS) nerve conduction grading tool

“…Neurophysiological data was collected based on the extensive and complete description of previous study designs by Padua [4] and Bland [6] and which is understood to be followed by most of the clinical laboratories in the United Kingdom. In addition, Second Lumbrical-Interosseous Latency was also recorded to distinguish between ‘very severe’ and ‘complete absent’ response grading of CTS [10].…”

“…Amplitude was recorded from peak to peak for sensory responses, and base to peak for motor responses. If responses were not recordable from median sensory digit II, III and motor from APB muscles, then motor responses were elicited by placing recording electrodes on 2nd lumbricals by stimulating median and ulnar nerves at the wrist [7, 10–12].…”