TY - JOUR
T1 - Dissociated lower limb muscle involvement in amyotrophic lateral sclerosis
AU - Simon, Neil G.
AU - Lee, Michael
AU - Bae, Jong Seok
AU - Mioshi, Eneida
AU - Lin, Cindy S.Y.
AU - Pfluger, Casey M.
AU - Henderson, Robert D.
AU - Vucic, Steve
AU - Swash, Michael
AU - Burke, David
AU - Kiernan, Matthew C.
PY - 2015/6/17
Y1 - 2015/6/17
N2 - It has been suggested that corticomotoneuronal drive to ankle dorsiflexors is greater than to ankle plantar flexor muscles, despite the finding that plantar flexors are no less active than TA during walking and standing. The present study was undertaken to determine whether there was differential involvement of distal lower limb muscles in amyotrophic lateral sclerosis (ALS), to elucidate pathophysiological mechanisms of selective muscle involvement. Prospective studies were undertaken in 52 ALS patients, including clinical assessment, disease staging (revised ALS functional rating scale), Medical Research Council sum score, and a scale of upper motor neurone (UMN) dysfunction. Motor unit number estimates (MUNE) and compound muscle action potentials (CMAP) from ankle dorsiflexors and plantar flexors were used to provide objective measures. A novel ‘split leg index’ was calculated as follows: SLI = CMAPDF ÷ CMAPPF. In ALS, there was significantly greater reduction of MUNE and CMAP amplitude recorded from plantar flexors when compared to dorsiflexors, suggesting preferential involvement of plantar flexor muscles, underpinning a ‘split leg’ appearance. The SLI correlated with clinical plantar flexor strength (R= −0.56, p < 0.001). In no patient did the SLI suggest preferential dorsiflexor involvement. In subgroup analyses, mean SLI was greatest in lower limb-onset ALS. In conclusion, the present study has established dissociated involvement of muscles acting around the ankle in ALS. We suggest this reflects underlying differences in cortical, descending or local spinal modulation of these muscles.
AB - It has been suggested that corticomotoneuronal drive to ankle dorsiflexors is greater than to ankle plantar flexor muscles, despite the finding that plantar flexors are no less active than TA during walking and standing. The present study was undertaken to determine whether there was differential involvement of distal lower limb muscles in amyotrophic lateral sclerosis (ALS), to elucidate pathophysiological mechanisms of selective muscle involvement. Prospective studies were undertaken in 52 ALS patients, including clinical assessment, disease staging (revised ALS functional rating scale), Medical Research Council sum score, and a scale of upper motor neurone (UMN) dysfunction. Motor unit number estimates (MUNE) and compound muscle action potentials (CMAP) from ankle dorsiflexors and plantar flexors were used to provide objective measures. A novel ‘split leg index’ was calculated as follows: SLI = CMAPDF ÷ CMAPPF. In ALS, there was significantly greater reduction of MUNE and CMAP amplitude recorded from plantar flexors when compared to dorsiflexors, suggesting preferential involvement of plantar flexor muscles, underpinning a ‘split leg’ appearance. The SLI correlated with clinical plantar flexor strength (R= −0.56, p < 0.001). In no patient did the SLI suggest preferential dorsiflexor involvement. In subgroup analyses, mean SLI was greatest in lower limb-onset ALS. In conclusion, the present study has established dissociated involvement of muscles acting around the ankle in ALS. We suggest this reflects underlying differences in cortical, descending or local spinal modulation of these muscles.
KW - Amyotrophic lateral sclerosis
KW - Clinical phenotype
KW - Disease spread
KW - Pathophysiology
UR - http://www.scopus.com/inward/record.url?scp=84931007190&partnerID=8YFLogxK
U2 - 10.1007/s00415-015-7721-8
DO - 10.1007/s00415-015-7721-8
M3 - Article
C2 - 25845764
AN - SCOPUS:84931007190
SN - 0340-5354
VL - 262
SP - 1424
EP - 1432
JO - Journal of Neurology
JF - Journal of Neurology
IS - 6
ER -