Evaluation of Split Hand Syndrome in Early Diagnosis of Amyotrophic Lateral Sclerosis by Nerve Conduction Study as a Diagnostic Tool
Abstract
Background: Amyotrophic lateral sclerosis (ALS), a
degenerative disease of the motor neurons that can present
diversly. Needle electromyography (EMG) is the gold
standard investigation for the diagnosis of ALS. Split hand
syndrome (SHS) demonstrated by nerve conduction study
(NCS); a noninvasive tool could be useful in diagnosing
ALS. This study aimed to assess SHS by NCS in ALS.
Materials & Method: This diagnostic accuracy case-control
study included 37 cases of ALS and 37 age and gendermatched
controls. Compound muscle action potential
(CMAP) and distal motor latency (DML) of median and
ulnar nerves and the ratio of median and ulnar CMAP and
DML were compared between study groups. The diagnostic
validity testing of electrophysiological SHS was also done.
Results: The mean age of the ALS and control groups were
similar, 39.8±2.7 and 39.3±2.6 years, respectively. Sixteen
(43.2%) ALS patients were in 30-59 years age group. Malefemale
ratio was 5.2. In the ALS group, median-ulnar CMAP
ratio was lower and median-ulnar DML ratio was prolonged
than the control. The diagnostic efficacy of median-ulnar
CMAP ratio and DML ratio were calculated. A medianulnar
CMAP ratio cut-off value d”1 showed 70% sensitivity,
97% specificity, 96% positive predictive value and 77%
negative predictive value. A median-ulnar DML ratio cutoff
value e”1.5 showed 48% sensitivity, 89% specificity, 82%
positive predictive value and 65% negative predictive value.
Conclusion: NCS demonstrating SHS can be an important
tool in the early diagnosis of ALS.