Neuropsychological assessment in different King's clinical stages of amyotrophic lateral sclerosis.

Emerging evidence shows that cognitive deficits associated with frontal lobe dysfunction occur from early stages of amyotrophic lateral sclerosis (ALS). We aimed to assess neuropsychological functioning at different stages of ALS to further delineate the occurrence of cognitive impairment alongside the trajectory of ALS as defined by standard assessment procedures. We investigated several cognitive domains in 74 ALS patients classified into four different clinical stages of disease, according to a recently validated staging system for ALS (known as 'King's' system), and evaluated and compared the corresponding cognitive profiles. We found that data derived from global cognitive assessment and several executive (i.e. Frontal Assessment Battery and Trail Making Test B-A) and long-term memory (i.e. memory prose) tests were significantly different among the subsets of ALS patients, showing poorer performances with increasing clinical disability. In conclusion, our preliminary results support the notion that mainly frontotemporal abilities may be impaired during the ALS course and suggest that neuropsychological information could supplement the current clinical staging of patients. However, ALS-specific multi-domain screening instruments, which allow to correct neuropsychological scores for physical disability, should be validated in larger populations worldwide and routinely introduced in clinical practice.