Spinal excitability changes do not influence the mechanisms of split-hand syndrome in amyotrophic lateral sclerosis.

INTRODUCTION: We studied spinal excitability and its relation to motor unit action potential (MUAP) changes in the thenar and hypothenar muscles in patients with amyotrophic lateral sclerosis (ALS). METHODS: Quantitative MUAP and peak ratio interference analyses were performed, and cutaneous silent period (CutSP) was measured in the abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles of patients with ALS and controls. RESULTS: Patients with ALS revealed more prominently increased duration (P = 0.002), number of phases (P = 0.02), size index (P = 0.02), and thickness (P = 0.02) in ADM than in FDI. The number of small segments was significantly decreased in ADM (P = 0.036) compared with controls. CutSP latency was prolonged in both ADM and FDI in ALS (P < 0.05). DISCUSSION: Although the reinnervation capacity was notably higher in the ADM of patients with ALS, the lack of a significant difference in CutSP measurements between ADM and FDI argues against spinal excitability changes in the development of split-hand syndrome. Muscle Nerve 58: 503-508, 2018.

Electrophysiological characteristics of the split hand syndrome in amyotrophic lateral sclerosis and the variant / 中华神经科杂志

Objective To study the electrophysiological characteristics of hands muscle of upper limb onset amyotrophic lateral sclerosis (UL-ALS), and the variant-flail arm syndrome (FAS) for diagnosis and differential diagnosis. Methods We chose 55 UL-ALS and 12 FAS patients as the cases, 20 cervical spondylotic amyotrophy (CSA) patients as the case controls, and 20 healthy volunteers as the normal controls from January 2013 to March 2018 in the Third Central Hospital of Tianjin. Conventional nerve conduction studies of the median nerve and ulnar nerve were performed in all the patients. The main analysis was done in the compound muscle action potential (CMAP) recorded on the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) and the ratio of the two. Results The ratio of CMAPAPB/CMAPADM of ALS was 0.59 (0.25, 0.79), which was depressed obviously compared with FAS (1.02 (0.92, 1.18), Z=-4.440, P=0.000), CSA (1.88 (1.42, 3.19), Z=-5.902,P=0.000) and the normal controls (0.96 (0.88, 1.15), Z=-5.416, P=0.000). The low ratio of CMAPAPB/CMAPADM (<0.6) was encountered in 40％(23/55) ALS patients, 0 CSA patient and 1/12 FAS patients. An absent APB CMAP and an abnormally low APB/ADM CMAP amplitude ratio (<0.25) were observed only in 25.4％ (14/55) ALS patients. The area under receiver operating characteristic curve in patients of UL-ALS was 0.911 (P=0.000), and in FAS was 0.518 (P=0.559). Using a cut-off value of CMAPAPB/CMAPADM=0.7 for diagnosing ALS yielded 85.5％sensitivity and 95.0％specificity. Conclusion The split hand syndrome is not specific for ALS; however, the low APB/ADM CMAP amplitude ratio may help predict prognosis and can be the diagnostic marker for ALS.

Terminal latency abnormality in amyotrophic lateral sclerosis without split hand syndrome.

Amyotrophic lateral sclerosis (ALS) has a peculiar involvement pattern; clinically it is known as split hand syndrome and electrophysiologically shows abnormalities in the abductor pollicis brevis (APB)/abductor digiti minimi (ADM) ratio. The aim of this study was to find a significant electrophysiological parameter in upper limb onset ALS patients with normal APB/ADM ratio when compared to cervical spondylotic amyotrophy (CSA) and healthy controls. We retrospectively reviewed the electrophysiological results of 47 upper limb onset ALS and 42 CSA cases; 20 healthy individuals were included as controls. We included ALS and CSA patients with normal ADM/APB ratio (≥0.6, and ≤1.7), and the parameters of electrophysiological study were compared. The electrophysiological parameters of statistical significance among ALS, CSA and normal controls were: amplitude of median and ulnar nerves, the terminal latency of median nerve, F-wave latency of median and ulnar nerves, terminal latency ratio of ulnar/median nerves, and F-wave latency ratio of ulnar/median nerves (p < 0.05). Among these parameters, the terminal latency ratio of ulnar/median nerve and terminal latency of median nerve in ALS were significantly different with both of CSA and normal control (p < 0.006). The abnormality in the terminal latency of the median nerve can be partly explained by the distal motor axonal dysfunction due to sodium and potassium channel abnormalities. The hypothesis of distal axonopathy is known to play an important role in the pathogenesis of ALS causing a significant prolongation of the terminal latency in the median nerve and the ulnar/median nerve ratio.

Reverse split hand syndrome: Dissociated intrinsic hand muscle atrophy pattern in Hirayama disease/brachial monomelic amyotrophy.

Preferential involvement of C7, C8, T1 level anterior horn cells is a typical feature in Hirayama disease/brachial monomelic amyotrophy (BMMA). There are no clinico-electrophysiological studies to substantiate the peculiar pattern of muscle involvement. Thirty subjects, 10 in each group of BMMA, amyotrophic lateral sclerosis (ALS) and age-matched normal healthy subjects underwent detailed clinical and electrophysiological testing. Results showed that the mean age at evaluation for BMMA and ALS patients was 25.8 ± 3.8 and 51.8 ± 9.5 years, respectively; illness duration was 8.1 ± 5.7 years and 11.14 ± 2.85 months, respectively. Clinically, all BMMA patients had reverse of split hand (RSH) syndrome [abductor digiti minimi (ADM) affected more than abductor pollicis brevis (APB)], while 7/10 ALS patients had classical split hand syndrome (APB affected more than ADM). In BMMA, the compound muscle action potential (CMAP) of APB was preserved but reduced/absent in ADM compared to the ALS group which demonstrated reverse findings. APB/ADM ratio was >0.8 in the BMMA group (>1.4 in 80%), around 1.0 in normal controls (none had >1.4) and <0.8 in ALS (70% having values <0.6). In conclusion, RSH syndrome may provide valuable diagnostic clues to differentiate this relatively self-restricted disease from progressive degenerative disease like ALS.