Agnès Pérez-Millan*, Sergi Borrego-Écija*, John C van Swieten, Lize Jiskoot, Fermin Moreno, Robert Laforce, Caroline Graff, Mario Masellis, Maria Carmela Tartaglia, James B Rowe, Barbara Borroni, Elizabeth Finger, Matthis Synofzik, Daniela Galimberti, Rik Vandenberghe, Alexandre de Mendonça, Chris R Butler, Alexander Gerhard, Simon Ducharme, Isabelle Le Ber, Isabel Santana, Florence Pasquier, Johannes Levin, Markus Otto, Sandro Sorbi, Pietro Tiraboschi, Harro Seelaar, Tobias Langheinrich, Jonathan D Rohrer, Roser Sala-Llonch, Raquel Sánchez-Valle & The Genetic FTD Initiative, GENFI (* equivalent contribution). Journal of Neurology.
ABSTRACT
Background and objectives: The C9orf72 expansion is the most common genetic cause of frontotemporal dementia (FTD) and/or motor neuron disease (MND). Corticospinal degeneration has been described in post-mortem neuropathological studies in these patients, especially in those with MND. We used MRI to analyze white matter (WM) volumes in presymptomatic and symptomatic C9orf72 expansion carriers and investigated whether its measure may be helpful in predicting the onset of symptoms.
Methods: We studied 102 presymptomatic C9orf72 mutation carriers, 52 symptomatic carriers: 42 suffering from FTD and 11 from MND, and 75 non-carriers from the Genetic Frontotemporal dementia Initiative (GENFI). All subjects underwent T1-MRI acquisition. We used FreeSurfer to estimate the volume proportion of WM in the brainstem regions (midbrain, pons, and medulla oblongata). We calculated group differences with ANOVA tests and performed linear and non-linear regressions to assess group-by-age interactions.
Results: A reduced WM ratio was found in all brainstem subregions in symptomatic carriers compared to both noncarriers and pre-symptomatic carriers. Within symptomatic carriers, MND patients presented a lower ratio in pons and medulla oblongata compared with FTD patients. No differences were found between presymptomatic carriers and non-carriers. Clinical severity was negatively associated with the WM ratio. C9orf72 carriers presented greater age-related WM loss than non-carriers, with MND patients showing significantly more atrophy in pons and medulla oblongata.
Discussion: We find consistent brainstem WM loss in C9orf72 symptomatic carriers with differences related to the clinical phenotype supporting the use of brainstem measures as neuroimaging biomarkers for disease tracking.