Cognitive Problems in Multiple Sclerosis Part II
Thinking about one's own thinking is worthwhile. Before he recently died, the great scientist and DNA co-discoverer, Sir Francis Crick, was fascinated by the whole issue of consciousness and whether it had a seat in the brain. I just wonder if the small region he identified deep in the brain, http://en.wikipedia.org/wiki/Claustrum, will ever explain all we need to know about our self-awareness.
To me, there are levels of self-awareness, just as there are levels of cognition or general thinking. I've always been struck by the fact that patients with Multiple Sclerosis have great self-awareness. They are often quite attuned to their own neurological problems. Perhaps I'm describing an "intelligence for one's disease" that deserves special consideration in so many of you who have this quality despite fighting a disease that is often so challenging.
Gorerover and colleagues (Multiple Sclerosis 2005) have noted that overall cognitive abilities, which include memory, speed of thinking and perception, are better the more MS patients are aware of problems in their own abilities in the cognitive spheres of planning, organizing, maintaining focus/attitude and the control of inhibitions.
They also note that if MS patients are depressed or anxious, there was a reduction in the accuracy of their self-reporting about their own cognitive difficulties.
Many implications derive from this.
One relates to the information of my last column, Cognitive Problems in Multiple Sclerosis Part I. which pointed to the importance of stress in the unfolding of inflammation of brain tissue in MS. Stress is often related to free floating fear characterizing anxiety. As a consequence, one's ability to monitor oneself can be sidetracked; thus, difficulties in appreciating thinking problems can be impaired. At the same time, since stress can feed into inflammation in the brain via what I described as part of the basic neuro-immunological problem of MS, more deficits in thinking can show themselves because a depressed, stressed out patient may indeed have a more active disease. Very recent research has shown that one of the SSRI drugs for depression (fluoxetine) can decrease immunology related problems in the brains of MS patients. For some patients, treating the depression may not only help the mood problem but also decrease white matter damaging MS disease activity.
One of the biggest cognitive problems in MS, which relates to the damage or demyelination of the white matter tracts (the axons) connecting neurons, is a loss of processing speed. Some call this reaction time. Lazeron and associates in Amsterdam last year (Multiple Sclerosis 2006) showed that the slower your thinking speed scores, the more lesions are in your brain. Accuracy of thinking was often very good, but if your thinking slows down too much, there can be both inflammation in specific sites and overall loss of brain volume.
Interestingly, another type of white matter thinking problem in MS is alexia, which is a severe reading impairment. Also, there can be a certain type of language problem characterized by difficulty in repeating words called "conduction aphasia".
Balsimelli et al in Brazil (Arq Neuropsiquiatr 2007) found that poor attention span in Relapsing and Remitting MS patients was related to slow thought processing. But Geurts and others in the Netherlands (J Neuropathol Exp Neurol 2007) found that memory too is a problem in MS (often short term and new learning ability) based upon problems in the brain called the hippocampus. Whereas "the wires being frayed" (white matter demyelination) can explain slow thinking and some forms of memory impairment, the hippocampal damage goes along with the fact that MS also affects gray matter
The frontal and pre-frontal cortex in the front of the brain is the orchestra leader, the region where we vary focus, strategize and decide to decide, and then decide. This executive function center can be struck in MS causing problems in these realms while also triggering some inappropriate joking around. Drew et al (Arch Clin Neuropsychol 2007) studied 95 of the 4000 people in New Zealand with MS. He found that most showed mild executive dysfunction of some type, but there was no typical MS deficit.
In the back of the brain are the occipital lobes. Connections to neurons within and across the hemispheres can cause the reading problem noted earlier. Nagy and associates in Hungary (Cogn Behav Neurol 2007) also found visual perception of fleeting faintly colored objects and target focus in the visual field can be abnormal in MS patients who might have both frontal and occipital lesions.