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• Focal onset of ALS
  Andrew Eisen
  Published on: 15 November 2011

• Published on: 15 November 2011

  Focal onset of ALS

  • Andrew Eisen, Neurologist

  Focal onset of ALS is attractive; it superficially mirrors what is encountered clinically, initial weakness in an arm, leg or bulbar muscles and is an explanation for phenotypic variation in terms of site of onset and rate of progression (Ravits and La Spada 2009). I congratulate Fujimura-Kimono and colleagues in their efforts to define patterns of spread through the ALS motor system and finding that the interval between...

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  Focal onset of ALS is attractive; it superficially mirrors what is encountered clinically, initial weakness in an arm, leg or bulbar muscles and is an explanation for phenotypic variation in terms of site of onset and rate of progression (Ravits and La Spada 2009). I congratulate Fujimura-Kimono and colleagues in their efforts to define patterns of spread through the ALS motor system and finding that the interval between the onset and subsequent region is an important prognostic indicator is of considerable value.

  However, there are at least two issues that should raise concern and question the focal onset of ALS. Firstly even though onset may appear to arise rather focally, for example one limb or bulbar, this does not necessarily reflect reality. Even when weakness and wasting appears to be restricted to a limb or the bulbar region, fasciculation which, is an essential feature of ALS is frequently quite diffuse. This may not be evident clinically and often requires needle electromyography to confirm (Eisen 2009). For ALS specialist who is also an electromyographer, it is clear that acute and/or chronic denervation (fibrillation and/or complex unstable motor units) are seen much more diffusely than suggested by the "focal" clinical onset deficit. This was the underlying philosophy of the new Awaji criteria (Carvalho and Swash 2009). Fujimura-Kimo et al do recognize that absence of electrophysiology is a limitation of their study. In addition subtle but diffuse upper motor neuron signs frequently accompany focal muscle weakness and wasting.

  The second issue relates to the time of onset of ALS. If ALS is similar to other neurodegenerative disorders (Alzheimer's and Parkinson's) which is currently accepted, there is a lengthy, albeit, underdetermined pre-clinical period during which complex, poorly understood, dysfunction of the motor system occurs which is insufficient to translate into clinical deficit. It is this that eventually results in relative focal failure of motor function involving different neuronal populations and non -neuronal cells. So the important question is what is it that triggers a diffuse propensity of non-clinical neuronal dysfunction into one with a focal neurological deficit?

  Fujimura-Kiyono, C, Kimura, F, Ishida, S et al (2011). "Onset and spreading patterns of lower motor neuron involvements predict survival in sporadic amyotrophic lateral sclerosis" J Neurol Neurosurg Psychiatry 82(10) Carvalho, M. D. and M. Swash (2009). "Awaji diagnostic algorithm increases sensitivity of El Escorial criteria for ALS diagnosis." Amyotrophic lateral sclerosis : official publication of the World Federation of Neurology Research Group on Motor Neuron Diseases 10(1): 53-57. Eisen, A. (2009). "Amyotrophic lateral sclerosis: A 40-year personal perspective." Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 16(4): 505-512. Ravits, J. M. and A. R. La Spada (2009). "ALS motor phenotype heterogeneity, focality, and spread: deconstructing motor neuron degeneration." Neurology 73(10): 805-811.

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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