Amyotrophic lateral sclerosis and cognitive disorders: review and analysis of the literature.

In the last ten years, the syndromic nature of amyotrophic lateral sclerosis (ALS) has become more accepted. Together with upper and lower motor neuron signs, sensory or cognitive impairment are not uncommon. The frequency of a multidegenerative profile in ALS with SOD1 mutations is also an argument for this. We reviewed the literature about: I) cases where ALS and dementia coexist; 2) the neuropsychological and neurofunctional profile of ALS patients. Dementia and ALS coexist in 3 to 6p. 100 of the ALS patients. In familial ALS the frequency of such an association is twice that of sporadic cases. Most often the dementia is of the fronto-temporal type (FTLD) with an onset either before or after the motor neuron involvement Neuropsychological abnormalities have been largely described in ALS with a predominant frontal impairment correlated most often with cerebral blood flow (SPECT) or metabolic (PET) alterations. Both the non exceptional association of FTLD with ALS and the frequent frontal involvement in ALS early after onset raise nosological problems all the more as motor neuron involvement is one of the criteria for the diagnosis of FTLD. It then appears that the question of a continuum between ALS and FTLD should be addressed. It could hypothesized that according to the localization and the spreading of neuronal degeneration those disorders are phenotypic variants.