Morphological analysis of brainstem and cerebellar vermis on magnetic resonance imaging in the Indian population: A retrospective observational study

Background: The interpretation of brainstem and cerebellar vermian sizes as normal or pathological in routine magnetic resonance imaging (MRI) is made on subjective norms. Since the morphologic discrepancies in their size happen throughout life, subjective methods might not be suitable to distinguish between their normal and abnormal biometry of brainstem and cerebellar vermis (CV). Aims and Objectives: The aim of this study was to assess age- and sex-related variations in brainstem and CV morphometry and derive normal reference values on MRI in the Indian population. Materials and Methods: A retrospective observational study was conducted in 200 subjects in a teaching institute in Madhya Pradesh, from June 2021 to May 2024. All the measurements were done manually on T2-weighted image MRI images. Results: The mean age of study cohort was 22.1±20.7 years (range: 3 days–85 years). All the dimensions except antero-posterior-CV value showed significant growth in first 12 years. The study revealed differential age related shrinkage in midbrain size after 50 years. There was slow growth pattern of pons and medulla till third decade with plateau phase thereafter. The study showed selective regional age-related decline in size of CV. All these dimensions showed similar values and age-related trends in males and females. Conclusion: The present study demonstrated differential age-associated shrinkage in size of midbrain and CV in adults without substantial decline in pontine and medullary sizes. The age-wise normative reference values of brainstem and CV were estimated in routine MRI for the Indian population using simple, quick, and replicable methods.