FRONTAL-LOBE DYSFUNCTION IN MULTIPLE-SCLEROSIS AS ASSESSED BY MEANS OF LURIAN TASKS - EFFECT OF AGE AT ONSET

We investigated frontal cognitive function in a group of 153 patients with multiple sclerosis and 100 healthy controls using a global scale composed by a set of items from the Luria-Nebraska Neuropsychological Battery (LNNB) which has been validated by Malloy and colleagues on fr ontally damaged patients. A second scale was built with LNNB items tap ping parietal lobes function. Patients who were specifically impaired on the frontal scale (12%) had a shorter disease duration and were les s physically disabled than those failing on the parietal tasks (8.5%) or those showing combined deficits (21.5%). Sixty-four patients were a lso tested on the Wisconsin Card Sorting Test (WCST). Twenty-seven (37 .5%) patients were found to be impaired on the WCST, but the latter co uld not predict reliably their performance on the LNNB frontal scale. We also examined whether age of onset and disease duration could have had any effect on the cognitive performance of selected groups of pati ents. We found that relative to normals, deficits on the frontal scale were more severe in patients with a clinical onset around age 20 than in patients with a later onset (i.e., around 35), the two groups bein g comparable for duration and degree of disability. Furthermore, patie nts with a longstanding illness (> 10 years) were more affected on vis uospatial processing and frontal control of language than those with a short duration (1.5 yrs). We propose that a greater disease activity interacting with contingent (developmental?) factors is responsible fo r the appearance of transient frontal deficits in several young MS pat ients. A differential involvement of long associative and connecting b undles is also proposed as a basis for understanding the pattern of co gnitive deficits encountered in selected patient groups.