Detection of microbleeds in post-mortem brains of patients with frontotemporal lobar degeneration: a 7.0-Tesla magnetic resonance imaging study with neuropathological correlates

Background: Microbleeds (MBs) are frequently detected in brains of patients with Alzheimer dementia and rare in those with frontotemporal lobar degeneration (FTLD). This study investigates for the first time the topographic distribution of MBs on a T2*-weighted gradient-echo 7.0-T magnetic resonance imaging (MRI) in post-mortem FTLD brains.

Patients and methods: The neuropathological and MRI findings in 12 FTLD brains were compared with eight age-matched controls. The presence of cerebrovascular lesions was evaluated on a coronal section of a cerebral hemisphere at the level of the mamillary body and on a horizontal section through pons and cerebellum. On MRI, the distribution and the number of cortical focal signal intensity losses, representing MBs, were assessed on coronal sections at the frontal, the central and the occipital level of a cerebral hemisphere.

Results: Overall, cerebrovascular lesions were rare. Only white matter damage was significantly more severe in FTLD brains compared with controls (P = 0.03). On MRI, MBs were only significantly prevalent in the deep cortical layers (P < 0.01) and borderline increased in the middle cortical layers (P = 0.07) of the frontal section.

Conclusions: Cerebrovascular lesions are rare in FTLD. The white matter damage has to be considered as part of the neurodegenerative process. MBs prevail in the frontal regions with the most severe neuronal damage and probably represent associated disruption of the blood-brain barrier.