Motor unit number index (MUNIX) versus motor unit number estimation (MUNE): a direct comparison in a longitudinal study of ALS patients.
OBJECTIVE
To evaluate how the motor unit number index (MUNIX) is related to high-density motor unit number estimation (HD-MUNE) in healthy controls and patients with amyotrophic lateral sclerosis (ALS).


METHODS
Both MUNIX and HD-MUNE were performed on the thenar muscles in 18 ALS patients and 24 healthy controls. Patients were measured at baseline, within 2 weeks, and after 4 and 8 months. Clinical evaluation included Medical Research Council (MRC) scale and the ALS functional rating scale (ALSFRS).


RESULTS
There was a significant positive correlation between MUNE and MUNIX values in ALS patients (r=0.49 at baseline; r=0.56 at 4 months; r=0.56 at 8 months, all p<0.05), but not in healthy controls. After 8 months, both MUNE and MUNIX values of the ALS patients decreased significantly more compared to MRC scale, ALS functional rating scale (ALSFRS) and compound muscle action potential (CMAP) (p<0.05). There was no significant difference in relative decline of MUNIX and HD-MUNE values.


CONCLUSIONS
In ALS patients, MUNIX and HD-MUNE are significantly correlated. MUNIX has an almost equivalent potential in detecting motor neuron loss compared to HD-MUNE.


CONCLUSIONS
MUNIX could serve as a reliable and sensitive marker for monitoring disease progression in ALS.
Donders Institute for Brain, Cognition and Behavior, Department of Neurology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
Werner A
WA
Boekestein
Helenius J
HJ
Schelhaas
Michel J A M
MJ
van Putten
Dick F
DF
Stegeman
Machiel J
MJ
Zwarts
Johannes P
JP
van Dijk
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000473:pathology / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D009410:Nerve Degeneration / Q000473:pathology / Q000503:physiopathology