Hypothalamic Atrophy, Expanded CAG Repeat, and Low Body Mass Index in Spinocerebellar Ataxia Type 3.

Background: Spinocerebellar ataxia type 3 (SCA3) is an inherited motor disorder that is characterized by low body mass index (BMI). Considering the role of the hypothalamus in regulating appetitive behaviors and metabolism, low BMI may result from hypothalamic degeneration.

Objectives: To examine hypothalamic volume changes in SCA3 by comparing patients and matched healthy controls and to identify potential mediating effects of hypothalamic pathology on CAG repeats for BMI.

Methods: Magnetic resonance imaging datasets of hypothalamic volumes from 41 SCA3 patients and 49 matched controls were analyzed. Relationships among CAG repeat number, hypothalamic volumes, and BMI were assessed using correlation and mediation analyses.

Results: SCA3 patients exhibited significant hypothalamic atrophy. Tubular hypothalamic volume was significantly associated with BMI. Mediation analysis revealed an indirect effect of CAG repeat number on BMI via tubular hypothalamic atrophy.

Conclusions: Low BMI in SCA3 is related to neurodegeneration within the tubular hypothalamus, providing a potential target for energy-based treatment. © 2022 International Parkinson and Movement Disorder Society.