Issues with normative data of hippocampal volumetry in Indian population.

Sir,

We read the paper entitled, “Hippocampal volumetry: Normative data in Indian population[1]” with great interest. The paper has attempted to give the normative data of hippocampal volumes in Indian population.

The paper, though written well, could have been better if it clarified some of the issues:

Paper mixes two issues of medial temporal sclerosis with hippocampal atrophy of Alzheimer's disease and other dementias. Both however are different issues. Only a very small number of Alzheimer's disease patients have hippocampal sclerosis. How could the paper extrapolate the data from the adults to elderly?

Present study has taken adults, and given the normative data using 200 adults. The sample size calculations for the same have not been mentioned. How did the authors arrive at the figure of 200? Sampling method could have been mentioned.

Implications of volumetry in medial temporal sclerosis (MTS) could have been mentioned apart from lateralization.

Authors could have discussed more about the difference in the findings of hippocampal volumes e.g. Western data, Asian and their own data. Why is this difference? What do they hypothesize?

Means of hippocampal volumes have been given, but the paper does not mention standard deviation of the same. Means without standard deviation would not make much sense? How could one deduce limits of “ abnormal hippocampal volume/s” when standard deviations have not been given.

Why was paired t-test used to know intra-rater variability and which 20 patients were chosen for the same? And why only 20? What decided the sample size calculations for the same? Intra-rater reliability coefficient could have been mentioned.

Authors could specify which protocol of the review paper they have used and how was the calculation of area and volume was done as described by Konard et al.[2]

Authors somehow attempt to extrapolate the data they obtained in young adults to older adults. This does not seem appropriate as hippocampus is a plastic and vulnerable structure[3] affected by several stimuli and moreover, medial temporal lobe gets affected by a variety of factors in patients with Dementias.[4]