Background: Split hand syndrome (SHS) is a hand atrophy pattern characterized by predominant wasting in the thenar muscles (abductor pollicis brevis-APB, first dorsal interosseous-FDI), with relative sparing of the hypothenar (abductor digiti minimi-ADM). SHS was also reported in CMTX1, but eventually attributed to median–ulnar dissociated involvement. We investigated the presence and specificity of SHS in CMTX1. Methods: We gathered clinical/neurophysiological/radiological information in CMTX1 and non-CMTX1 patients, including disease severity (CMT Examination Score-CMTES) and compound muscle amplitude potential (CMAP) of APB/FDI/ADM. We obtained ADM/APB ratio (ADM/APBr) = CMAPADM/CMAPAPB and split-hand index (SHI) = (CMAPAPB × CMAPFDI)/CMAPADM. Eight patients underwent 3T MRI of the hand muscles. We defined SHS based on three criteria: clinical, neurophysiological, and radiological, with at least one criterion required for SHS diagnosis. Through ADM/APBr > 1.7, we assessed the specificity of SHS for CMTX1 among the Italian CMT Registry cohort, encompassing 750 clinically well-characterized patients. Results: We evaluated 22 CMTX1 (age 41.3 ± 12.2) and 40 non-CMTX1 (49.2 ± 14.9). 50% (vs. 3% of non-CMTX1, p < 0.001) and 64% (vs. 0%, p < 0.001) of CMTX1 had clinical and neurophysiological SHS, respectively. In CMTX1, SHS was independent from gender and hand dominance. Both ADM/APBr and SHI correlated with disease duration (rs = 0.77, p < 0.001; rs = −0.65, p = 0.022, respectively), and CMTES (rs = 0.56, p = 0.006; rs = −0.62, p < 0.001, respectively). 3/8 CMTX1 had radiological SHS. Within the Italian CMT Registry cohort, ADM/APBr > 1.7 yielded a specificity of 74% for CMTX1 females among I-CMT/CMT2, and 85% for CMTX1 males among CMT1/I-CMT. Discussion: Up to 59% of CMTX1 patients develop thenar-hypothenar (rather than median-ulnar) SHS. MRI is a novel approach to detect this dissociated denervation pattern. ADM/APBr > 1.7 may be useful to address GJB1 testing in males.
Split Hand Syndrome in Charcot–Marie–Tooth Disease Type X1 (CMTX1): A Clinical, Neurophysiological, and Radiological Study / Alessandro, B., Marco, M., Claudia, C., Mattia, V., Eleonora, C., Luca Maria, S., Marina, G., Paola, L., Davide, P., Chiara, P., Cmt Network, I., Manganelli, F., Maria Fabrizi, G., Schenone, A., Tozza, S., Cavallaro, T., Taioli, F., Ferrarini, M., Grandis, M., Bellone, E., et al.. - In: EUROPEAN JOURNAL OF NEUROLOGY. - ISSN 1351-5101. - 32:5(2025). [10.1111/ene.70188]
Split Hand Syndrome in Charcot–Marie–Tooth Disease Type X1 (CMTX1): A Clinical, Neurophysiological, and Radiological Study
Fiore Manganelli;Stefano Tozza;Lucio Santoro;
2025
Abstract
Background: Split hand syndrome (SHS) is a hand atrophy pattern characterized by predominant wasting in the thenar muscles (abductor pollicis brevis-APB, first dorsal interosseous-FDI), with relative sparing of the hypothenar (abductor digiti minimi-ADM). SHS was also reported in CMTX1, but eventually attributed to median–ulnar dissociated involvement. We investigated the presence and specificity of SHS in CMTX1. Methods: We gathered clinical/neurophysiological/radiological information in CMTX1 and non-CMTX1 patients, including disease severity (CMT Examination Score-CMTES) and compound muscle amplitude potential (CMAP) of APB/FDI/ADM. We obtained ADM/APB ratio (ADM/APBr) = CMAPADM/CMAPAPB and split-hand index (SHI) = (CMAPAPB × CMAPFDI)/CMAPADM. Eight patients underwent 3T MRI of the hand muscles. We defined SHS based on three criteria: clinical, neurophysiological, and radiological, with at least one criterion required for SHS diagnosis. Through ADM/APBr > 1.7, we assessed the specificity of SHS for CMTX1 among the Italian CMT Registry cohort, encompassing 750 clinically well-characterized patients. Results: We evaluated 22 CMTX1 (age 41.3 ± 12.2) and 40 non-CMTX1 (49.2 ± 14.9). 50% (vs. 3% of non-CMTX1, p < 0.001) and 64% (vs. 0%, p < 0.001) of CMTX1 had clinical and neurophysiological SHS, respectively. In CMTX1, SHS was independent from gender and hand dominance. Both ADM/APBr and SHI correlated with disease duration (rs = 0.77, p < 0.001; rs = −0.65, p = 0.022, respectively), and CMTES (rs = 0.56, p = 0.006; rs = −0.62, p < 0.001, respectively). 3/8 CMTX1 had radiological SHS. Within the Italian CMT Registry cohort, ADM/APBr > 1.7 yielded a specificity of 74% for CMTX1 females among I-CMT/CMT2, and 85% for CMTX1 males among CMT1/I-CMT. Discussion: Up to 59% of CMTX1 patients develop thenar-hypothenar (rather than median-ulnar) SHS. MRI is a novel approach to detect this dissociated denervation pattern. ADM/APBr > 1.7 may be useful to address GJB1 testing in males.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
