The featured article is ‘Decline of cognition in multiple sclerosis: dissociable deficits’ by Jennekens-Schinkel and Sanders and freely available here. This is a case series from 1986. As this is a small case series, it is not sufficiently powered to produce generalisations about the cognitive decline in Multiple Sclerosis but instead offers a starting point for generation of hypotheses. The authors report 3 cases of multiple sclerosis with a pattern of cognitive decline.
In the first case, there is a description of optic neuritis followed by rapid cognitive decline, bradyphrenia, verbal IQ 65, Performance IQ 56 compared to premorbid IQ range 100-110, ‘slight anomia’ and marked cortical atrophy with ventricular enlargement.
In the second case, there is paraesthesia, ‘loss of memory for telephone numbers’, progressive gait instability and slurred speech and again there is a decline in IQ with estimated premorbid Full Scale IQ of 110 and measured IQ at time of entry into study of 69. There was also impaired word fluency and ‘slight naming impairment’. Again on CT head there was evidence of global cerebral atrophy.
In the third case, there is a description of frontal headaches, hypersomnia, ocular involvement and axial ataxia with performance IQ of 92 below the premorbid estimate of 120 although full scale IQ was still 108. There was also a decline in memory quotient compared to the estimated premorbid value. Simple and choice reaction times were increased. A CT scan of the head revealed oedema.
The authors emphasise the importance of different imaging techniques in identifying lesions in Multiple Sclerosis that wouldn’t necessarily be identified by CT. They then go on to discuss the distinction between subcortical and cortical dementia in this cases and the possible combination of these. The collection of these case descriptions offers a framework for thinking about the cognitive dysfunction that can occur in Multiple Sclerosis particularly the demarcation and conjunction of subcortical and cortical pathology although larger more rigorous studies offer further insights.
Here is a useful overview of genetic research in Multiple Sclerosis prepared by genetics students at the University of Missouri.
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