Mild Cognitive Impairment: Cognitive Screening or Neuropsychological Assessment?

The featured paper is ‘Mild Cognitive Impairment: Cognitive Screening or Neuropsychological Assessment?’ by Diniz and colleagues and freely available here. The authors begin by focusing in the introduction on the definition of Mild Cognitive Impairment (MCI) and the 10% progression to dementia. The expansion of the term MCI to include non-amnestic types together with the relationship to dementia subtypes was then discussed. The authors then discuss some of the difficulties inherent in the diagnosis including the heterogeneity of the group (this might result from the focus on a restricted group of symptoms in contrast with dementia). There is an interesting point about the specificity of combining the MMSE and Clock Drawing test in multidomain MCI which increases diagnostic specificity to 75%. The authors state a number of aims

1. To characterise MCI subtypes with neuropsychological tests in comparison with controls and people with Alzheimer’s Disease

2. To examine the discriminatory properties of the MMSE and CAMCOG for the subtypes of MCI

There are potentially important benefits for practice in answering these questions.

The researchers recruited 249 people, 3/4 of them being female, with a mean age of 71.2 and a mean of 10.5 years in education. The researchers used an interesting method for recruiting which included not only volunteers but also ‘acquaintances of patients’. The study gained approval from the local Ethics Committee. The CAMDEX was used as well as the Hamilton Depression Scale. Blood tests were completed for all patients and imaging studies where appropriate. Consensus at multidisciplinary meetings was used for diagnostic purposes. As a Kolmogorov-Smirnov test had revealed distributions on test results to be normally distributed, the researchers undertook parametrical testing of mean differences utilising ANOVA.

The results showed that there was no significant difference between genders on the distribution of diagnoses. The group with Alzheimer’s Disease (AD) had greater age and higher scores on the Hachinski Ischaemic Index than the other groups. The AD group performed significantly worse than the other groups on all of the cognitive tests.

With regards to the MCI groups, there were similar performances to the control group on the Clock Drawing Test and MMSE. The MCI groups excluding multiple-domain MCI performed similarly to the controls on the CAMCOG. The non-amnestic MCI group  performed worse on the Trail B Test (a test of executive functioning). The multiple domain MCI group had impairment in praxis, memory and executive functioning. The MMSE didn’t discriminate between MCI and controls while the CAMCOG was better in this regards. With multi-domain MCI, the CAMCOG had a sensitivity of 85% and specificity of 75% in distinguishing from controls.

In their discussion the authors mention the Montreal Cognitive Assessment which has been designed specifically for assessing people with MCI. The authors also comment on the significance of multi-domain MCI in terms of progression to Alzheimer’s Disease – suggesting that when multiple domains are involved the global performance threshold is more likely to be crossed. They also consider the significance of conversion from amnestic MCI to multi-domain MCI which may become an important pathway although further research will be needed in this area.

Steps To Treatment – 3 (Further replication of results needed, if validated incorporated into screening program, then considered for local policy).

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