Clinical and Radiological Features of Aphasia Caused by Brainstem Infarction: Two Case Reports.

Cognitive impairment resulting from cerebellar damage, known as cerebellar cognitive affective syndrome (CCAS), can cause language impairment and aphasia. The disruption of the cerebro-cerebellar pathway is a possible mechanism for CCAS. Consequently, aphasia may also arise from brainstem lesions. However, the precise mechanisms of brainstem-induced aphasia are not fully understood owing to the scarcity of published reports describing this condition. Herein, we investigated characteristics of patients with aphasia attributed to the brainstem infarction. We retrospectively analyzed medical records of 24 patients with brainstem infarction, two of whom presented with aphasia. The first patient was a 64-year-old, right-handed Japanese man who developed word-finding difficulties and verbal paraphasia. The second patient was an 85-year-old, right-handed Japanese woman who developed auditory verbal comprehension impairment, word-finding difficulties, and verbal paraphasia. Both patients had an infarction of the left ventral part of the upper pons on magnetic resonance imaging scans. Next, we illustrated language-related cerebellar afferent and efferent fibers using HCP-1065 Young Adult Fiber Template. The afferent pathway, which projected from the Broca area to the right Crus I and II through the cortico-ponto-cerebellar pathway, descended to the pons and decussated contralaterally at the ventral part of the upper pons, the area affected by the lesions common to our two cases. The efferent pathway (dentate-rubro-thalamic tract) was located away from these lesions. An infarction of the left ventral part of the upper pons may disrupt the language-related cerebellar afferent pathway, which likely caused word-finding impairments in our two patients.