The medial temporal lobe atrophy (MTA) score, also known as Scheltens' scale, is useful in distinguishing patients with mild cognitive impairment and Alzheimer disease from those without impairment 2 is helpful in the assessment of patients with possible dementia (see neurodegenerative MRI brain - an approach).
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Usage
The MTA score has a sensitivity of ~75% and specificity of ~85% to discriminate Alzheimer disease from healthy controls 10.
Although the MTA score has been widely used, it does not capture entorhinal cortex atrophy, which has been shown to occur early in the development of Alzheimer disease. An additional scoring system entorhinal cortical atrophy (ERICA) has been developed which is reported as having better diagnostic accuracy in distinguishing healthy controls from those with Alzheimer disease 7.
Classification
The MTA score is a visual score performed on MRI of the brain using coronal T1 weighted images in a plane parallel to the brainstem axis and through the hippocampus at the level of the anterior pons 5. The score is also validated for assessment on CT brain 6. Both sides are evaluated and the higher or the average score have been both used for for further grading by various authors 6,9.
It is based on three features 1,3:
width of the choroid fissure
width of the temporal horn of the lateral ventricle
height of the hippocampus
These result in a score of 0 to 4:
0: no CSF is visible around the hippocampus
1: choroid fissure is slightly widened
2: moderate widening of the choroid fissure, mild enlargement of the temporal horn and mild loss of hippocampal height
3: marked widening of the choroid fissure, moderate enlargement of the temporal horn, and moderate loss of hippocampal height
4: marked widening of the choroid fissure, marked enlargement of the temporal horn, and the hippocampus is markedly atrophied and internal structure is lost
Interpretation
The score is interpreted in relation to age:
<75 years: ≥2 is abnormal
≥75 years: ≥3 is abnormal
A more detailed cut-off for an abnormal average score has been proposed 6:
<65 years: ≥1 is abnormal
65-74 years: ≥1.5 is abnormal
75-84 years: ≥2 is abnormal
>85 years: ≥2 is abnormal
It has been also noted that the exact cut-off has limited value above the age of 85 due to the substantial decrease in sensitivity 6. Additionally, both gender, age and education were found to be confounders of the score 9,10.
High scores have been shown to be present in Alzheimer disease and frontotemporal dementia, although parietal atrophy will be seen in the former 10.
Atrophy has been shown to correlate with likelihood of progression from mild cognitive impairment (MCI) to dementia 4.
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