Cognitive-linguistic deficit and speech intelligibility in chronic progressive multiple sclerosis

Multiple sclerosis is a disabling neurological disease with varied symptoms, including dysarthria and cognitive and linguistic impairments. Association between dysarthria and cognitive-linguistic deficit has not been explored in clinical multiple sclerosis studies.

In patients with chronic progressive multiple sclerosis, the study aimed to investigate the presence and nature of cognitive-linguistic deficit, the association between levels of cognitive-linguistic ability and speech intelligibility, and of both of these with functional disability and time since onset of multiple sclerosis symptoms.

The Arizona Battery for Communication Disorders of Dementia (ABCD) (Bayles and Tomoeda 1993 ), The Assessment of Intelligibility of Dysarthric Speech (AIDS) Sentence Intelligibility Task (Yorkston and Beukelman 1984 ), and the Modified Barthel Activities of Daily Living Index (MBADLI) (Shah 1998 ) were administered to 24 chronic progressive multiple sclerosis participants with dysarthria. A total of 24 non-neurologically impaired participants, matched for gender, age and education, formed a control group.

For multiple sclerosis participants, linear regression analysis showed a strong association between ABCD and AIDS (beta = 0.89, p = 0.005), no association between ABCD and either MBADLI or time since onset, a strong association between AIDS and MBADLI (beta = 0.60, p = 0.001), and a trend towards an association between AIDS and time since onset (beta = -0.29, p = 0.08). Correlations between the four included ABCD construct scores and between these and the total ABCD score were significant (r>0.60, p<0.01). For each of the 15 included ABCD measures and for the four construct scores and the overall ABCD score, multiple sclerosis and control group performances were significantly different (p<0.01) and effect sizes were large (d>0.80).

The results revealed a strong association between dysarthria, as measured by connected speech intelligibility testing, and cognitive-linguistic deficit, in people with chronic progressive-type multiple sclerosis. While some of the impairments that are associated with multiple sclerosis, including motor speech disorder, may influence performance on the ABCD, the data support the conclusion that marked cognitive-linguistic deficit is present in chronic progressive-type multiple sclerosis patients with dysarthria. Deterioration was global, rather than being indicative of a construct specific deficit, and encompassed language, both expression and comprehension. Episodic memory and linguistic expression were especially affected. Speech and language therapists who work with dysarthric patients with chronic progressive multiple sclerosis should monitor cognitive-linguistic impairment. An awareness of this might influence assessment, intervention and management, including the information and advice given to patients and their relatives.