Thinking and behaviour in motor neurone disease : a clinical neuropsychological investigation

Abstract

Traditionally Motor Neurone Disease (MND) has been thought of as a syndrome exclusively affecting the motor regions of the cortex only. However, recent research has found evidence of extra-motor involvement in patients with the classical form of MND predominately on tests of executive dysfunction. This selective cognitive dysfunction found in classical MND patients, namely on tests of executive function and to a lesser extent on memory and language functions, has led to the hypothesis that MND is a spectrum disorder. It follows, that if ALS and MND-D are part of a continuum then evidence of subtle behavioural change characteristic of MND-D and FTD consistent with orbitofrontal dysfunction should be observed in the nondemented ALS patient group. The research aims of this study were therefore to investigate whether patients with non-demented ALS do in fact display subtle behavioural change associated with orbitofrontal dysfunction characteristic of frontotemporal dementia. A neuropsychological battery including tests of behavioural dysfunction was administered to 10 ALS patients and 10 healthy controls. The cares of each patient were also asked to complete three informant-based questionnaires in order to assess patients’ behavioural profile. Evidence was presented of subtle behavioural change in this patient group in the domains of apathy, disinhibition and executive dysfunction as well as evidence of behavioural features associated with the FTD diagnostic criteria set out by Neary and colleagues (1998). This evidence adds further weight to the hypothesis that ALS, MND-D and FTD form variants of a clinical pathological continuum. Further investigations are necessary to confirm theses findings, with the possible use of imaging techniques to provide evidence of cerebral abnormality in a similar patient group.