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Updated: Oct 26, 2026
In Vivo Electrophysiological Measurement of Compound Muscle Action Potential from the Forelimbs in Mouse Models of Motor Neuron Degeneration
Published on: June 15, 2018
CMAP as an electrophysiological biomarker in spinal muscular atrophy: A systematic review
Carlo Alberto Cesaroni1, Giulia Pisanò2, Susanna Rizzi2
1Child Neurology and Psychiatry Unit, Mother and Child Department, Santa Maria Nuova Hospital, AUSL-IRCCS di Reggio Emilia, Reggio Emilia, 42123, Italy; Pediatric Neurophysiology Laboratory, Mother and Child Department, AUSL-IRCCS di Reggio Emilia, Reggio Emilia, 42123, Italy.
Objectives:
To appraise the evidence on compound muscle action potential (CMAP) as a biomarker in spinal muscular atrophy (SMA): responsiveness to therapy, correlation with motor function, diagnosis and prognostic value, and patterns across SMA types.
Methods:
Conducted per PRISMA 2020 (PROSPERO CRD420261476823). PubMed and Embase were searched to August 15, 2026 for studies reporting CMAP in genetically confirmed SMA. Findings were synthesized narratively across four pre-specified domains using a Synthesis Without Meta-analysis approach. Two reviewers independently assessed risk of bias with Joanna Briggs Institute tools.
Results:
Sixty-two studies (2513 participants across reports) were included. Following disease-modifying therapy, CMAP increased in 22 of 33 contributing studies (66.7%), was stable in 9 (27.3%), and showed a mixed pattern in 2 (6.1%); none reported a net decrease. All three disease-modifying therapies were associated with CMAP increase. CMAP correlated moderately to strongly with motor function scales and discriminated diagnostic or severity categories in 6 of the 11 studies that formally tested this. Risk of bias was low or low-moderate in 27 studies; small sample size and absence of a concurrent control group were the most frequent limitations.
Discussion:
CMAP rises in roughly two-thirds of treated cohorts and reflects disease severity, but floor, ceiling, and site-dependent effects limit its use as a standalone surrogate endpoint. Selecting the recording site by severity, adding a second site chosen on the same basis, and agreeing standardized acquisition and normative values would strengthen its role as a prognostic stratifier and a component of multimodal models.
