Neil G Simon1, Cindy S-Y Lin2, Michael Lee3, James Howells4, Steve Vucic5, David Burke4, Matthew C Kiernan6. 1. Neuroscience Research Australia, Barker St, Randwick, NSW 2031, Australia; Prince of Wales Clinical School, University of New South Wales, Randwick, NSW 2031, Australia. 2. Prince of Wales Clinical School, University of New South Wales, Randwick, NSW 2031, Australia. 3. Neuroscience Research Australia, Barker St, Randwick, NSW 2031, Australia. 4. Sydney Medical School, K25 - Medical Foundation Building, The University of Sydney, NSW 2006, Australia. 5. Neuroscience Research Australia, Barker St, Randwick, NSW 2031, Australia; Westmead Clinical School, C24 Westmead Hospital, The University of Sydney, NSW 2006, Australia. 6. Neuroscience Research Australia, Barker St, Randwick, NSW 2031, Australia; Brain and Mind Research Institute, The University of Sydney, Mallett St, Camperdown, Australia. Electronic address: matthew.kiernan@sydney.edu.au.
Abstract
OBJECTIVES: There is accumulating evidence of dysfunction of spinal circuits in the pathogenesis of amyotrophic lateral sclerosis (ALS). METHODS: The present study was undertaken to characterise the pathophysiological changes in segmental motoneuronal excitability in 28 ALS patients, using recruitment curves of the soleus H-reflex and M-wave, compared with clinical assessments of upper motor neuron (UMN) and lower motor neuron dysfunction. RESULTS: H-reflex recruitment curves established that Hmax/Mmax and slope (Hθ/Mθ) ratios predicted clinical UMN dysfunction (p<0.001). Changes in Hθ/Mθ were driven by reduced Mθ. Assessment of Hmax/Mmax was similar in the ALS and control groups, and was affected by overlap of the H and M recruitment curves in ALS patients. CONCLUSION: Changes in the slope ratio (Hθ/Mθ) in ALS suggested that alterations in peripheral motor nerve excitability following UMN damage may affect the recorded H-reflex. Increased collision of reflex discharges with antidromically-conducted motor impulses may be exacerbated in ALS due to preferential loss of large-caliber α-motoneurones, which may explain the similarities in Hmax/Mmax between groups. SIGNIFICANCE: Findings from the present study provide further insight into the pathophysiology of ALS, specifically the relative contributions of premotoneuronal and segmental motoneuronal dysfunction.
OBJECTIVES: There is accumulating evidence of dysfunction of spinal circuits in the pathogenesis of amyotrophic lateral sclerosis (ALS). METHODS: The present study was undertaken to characterise the pathophysiological changes in segmental motoneuronal excitability in 28 ALSpatients, using recruitment curves of the soleus H-reflex and M-wave, compared with clinical assessments of upper motor neuron (UMN) and lower motor neuron dysfunction. RESULTS: H-reflex recruitment curves established that Hmax/Mmax and slope (Hθ/Mθ) ratios predicted clinical UMN dysfunction (p<0.001). Changes in Hθ/Mθ were driven by reduced Mθ. Assessment of Hmax/Mmax was similar in the ALS and control groups, and was affected by overlap of the H and M recruitment curves in ALSpatients. CONCLUSION: Changes in the slope ratio (Hθ/Mθ) in ALS suggested that alterations in peripheral motor nerve excitability following UMN damage may affect the recorded H-reflex. Increased collision of reflex discharges with antidromically-conducted motor impulses may be exacerbated in ALS due to preferential loss of large-caliber α-motoneurones, which may explain the similarities in Hmax/Mmax between groups. SIGNIFICANCE: Findings from the present study provide further insight into the pathophysiology of ALS, specifically the relative contributions of premotoneuronal and segmental motoneuronal dysfunction.
Authors: Neil G Simon; Michael Lee; Jong Seok Bae; Eneida Mioshi; Cindy S-Y Lin; Casey M Pfluger; Robert D Henderson; Steve Vucic; Michael Swash; David Burke; Matthew C Kiernan Journal: J Neurol Date: 2015-04-07 Impact factor: 4.849