How to manage cognitive issues in multiple sclerosis?

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The prevalence of cognitive impairment in MS (multiple sclerosis) is estimated to be between 40 and 65 percent. The cognitive abilities most often affected include episodic memory (recall of previously studied information, like a shopping list or story), working memory (temporary online maintenance and manipulation of information), divided attention (multitasking ability), and speed processing. Language, executive, and visuospatial functions are relatively spared. However, there is considerable variation in the neuropsychological presentation of MS patients. For example, one study identified six distinct cognitive profiles among patients with relapsing MS entering a trial of interferon-β1a. The largest subgroup, which included 34 percent of the sample, was cognitively intact. Only 2 percent showed global cognitive impairment across multiple cognitive domains. The remainder showed circumscribed deficits in two to three cognitive domains.

What are the factors considered when the patient states cognitive disorders?

Level of physical disability, as measured with the Expanded Disability Status Scale (EDSS), has at best a modest correlation with severity of cognition in MS. This is not surprising since the EDSS is heavily influenced by non-cognitive signs and symptoms, such as ambulation. Several studies have shown that cognitive dysfunction is greater in secondary progressive than in relapsing-remitting MS.

Cross-sectional studies have found only a modest relationship between the duration of the disease and the extent of cognitive impairment. As noted above, this is likely due to the inter-patient variability in the presentation of cognitive disorders. It is important to note that cognitive changes can occur early in the course of the disease and, in some patients, may never occur. Longitudinal neuropsychological studies of MS patients over an extended period suggest that approximately 5 to 10 percent of patients experience a discernible worsening of cognitive functioning for a year. Unlike patients with progressive dementias, MS patients with cognitive impairment can be stable for years.

In addition, recent case reports have noted cognitive impairment as a sole manifestation of relapse of MS, with cognitive declines correlating with new lesion formation on MRI (magnetic resonance imaging).

For the above reasons, we also do not assume that patients with physical disabilities are cognitively impaired, nor do we assume that those without physical impairment are cognitively intact.

Do MRI-detected abnormalities correlate with cognitive disorders?

Compared to demographic and disease variables, neuroimaging indices correlate relatively well with cognition in MS. Several studies have demonstrated an inverse relation between cognitive performance and the number of volume of lesions on conventional MRI, including T2-weighted or fluid-attenuated inversion recovery (FLAIR) imaging. Regionally specific relations between lesion volume and cognition have been reported. For example, one study showed specific relations between frontal lobe involvement and executive functions, like conceptual reasoning. Some studies have suggested that brain atrophy is a better predictor of cognitive impairment in MS than lesion volume. Longitudinal studies have shown a relationship between progressive brain atrophy and cognitive change patterns in MS. There are occasional patients with subacute cognitive changes that correlate with the presence of new lesions, so a new complaint of cognitive dysfunction may prompt further imaging to assess disease activity. Recent studies indicate that cortical lesions are not only present in early clinical MS but may be as common as white matter lesions. Such lesions and associated tract degeneration may underlie some component of the cognitive dysfunction in MS.

Note that in addition, there are patients with prominent cognitive symptoms with limited lesion burden or atrophy on brain imaging. In such patients, we would assess carefully for other factors such as medication, sleep disturbance, and depression masquerading as cognitive deficits.

Management

MDTA (multidisciplinary team advise) -

Consult a neuropsychiatric consultant for close follow-up and management.

I hope this has helped you. Please feel free to reach me again, in case of further queries.

Thank you.