Journal of neurology · 2026
Electrophysiological assessment of motor unit loss in adult spinal muscular atrophy types III and IV: a multicenter national study comparing MUNIX, CMAP, and MUSIX.
Клиническое исследованиеСравнительное исследованиеСтатьяМногоцентровое исследованиеНазвание и аннотация: Перевод в очереди
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Sole-Cruz Eva, Salort-Campana Emmanuelle, Lenglet Timothee, Fortanier Etienne, Pereon Yann, Berling Edouard, Beloribi-Djefaflia Sadia, Bouhour Françoise, Cintas Pascal, Delmont Emilien, Cavalli Michelle, Ezaru Andra, De La Cruz Elisa, Fernandes Sara, Kaminsky Anne-Laure, Kouton Ludivine, Magot Armelle, Nadaj-Pakleza Aleksandra, Tard Céline, Pegat Antoine, Nicolas Guillaume, Stojkovic Tanya, Hogrel Jean-Yves, Attarian Shahram
Аннотация
BACKGROUND: Spinal muscular atrophy (SMA) types III and IV are the most common late-onset forms, and they progress slowly, making the identification of sensitive biomarkers critical. The Motor Unit Number Index (MUNIX) estimates motor unit loss and may complement traditional electrophysiological measurements such as Compound Muscle Action Potential amplitudes (CMAP). However, their respective performances have never been directly compared in adult SMA.
METHODS: In a French multicenter study (NCT04690998), 71 adult patients with SMA and 24 healthy controls underwent clinical and electrophysiological evaluation. MUNIX, CMAP, and Motor Unit Size Index (MUSIX) were recorded in four muscles, and sum scores (SumMUNIX, SumCMAP, SumMUSIX) were calculated. Reliability was assessed using intraclass correlation coefficients (ICCs), and associations with functional outcomes were explored.
RESULTS: MUNIX and CMAP effectively distinguished SMA patients from controls, showing strong test - retest reliability. MUNIX showed the highest discriminative performance (AUC = 0.92), while CMAP demonstrated the strongest and most consistent associations with clinical severity. In multivariate analyses, only CMAP remained independently associated with all functional and strength measures, whereas MUNIX and MUSIX lost significance.
CONCLUSION: MUNIX demonstrated the highest discriminative performance among biomarkers for differentiating SMA from controls, indicating early motor unit loss even when CMAP values were within normal limits. However, disease burden and functional impairment were better reflected by CMAP, probably due to it integrating both motor unit loss and reinnervation. The complementary nature of these profiles supports their combined use (concurrent application), and longitudinal studies are warranted to assess their responsiveness in adult SMA as well as their appropriateness for clinical trial settings.
METHODS: In a French multicenter study (NCT04690998), 71 adult patients with SMA and 24 healthy controls underwent clinical and electrophysiological evaluation. MUNIX, CMAP, and Motor Unit Size Index (MUSIX) were recorded in four muscles, and sum scores (SumMUNIX, SumCMAP, SumMUSIX) were calculated. Reliability was assessed using intraclass correlation coefficients (ICCs), and associations with functional outcomes were explored.
RESULTS: MUNIX and CMAP effectively distinguished SMA patients from controls, showing strong test - retest reliability. MUNIX showed the highest discriminative performance (AUC = 0.92), while CMAP demonstrated the strongest and most consistent associations with clinical severity. In multivariate analyses, only CMAP remained independently associated with all functional and strength measures, whereas MUNIX and MUSIX lost significance.
CONCLUSION: MUNIX demonstrated the highest discriminative performance among biomarkers for differentiating SMA from controls, indicating early motor unit loss even when CMAP values were within normal limits. However, disease burden and functional impairment were better reflected by CMAP, probably due to it integrating both motor unit loss and reinnervation. The complementary nature of these profiles supports their combined use (concurrent application), and longitudinal studies are warranted to assess their responsiveness in adult SMA as well as their appropriateness for clinical trial settings.