Progressive supranuclear palsy presenting with dynamic aphasia

Progressive supranuclear palsy (PSP) is an akinetic-rigid syndrome of unknown aetiology which usually presents with a combination of unsteadiness, bradykinesia, and disordered eye movement. Speech often becomes dysarthric but language disorders are not well recognised.

Three patients with PSP (pathologically confirmed in two) are reported in which the presenting symptoms were those of difficulty with language output.

Neuropsychological testing showed considerable impairment on a range of single word tasks which require active initiation and search strategies (letter and category fluency, sentence completion), and on tests of narrative language production. By contrast, naming from pictures and from verbal descriptions, and word and sentence comprehension were largely intact. The degree of semantic memory impairment was also slight.

Relatively selective involvement of cognitive processes critical for planning and initiating language output may occur in some patients with PSP. This presentation resembles the phenomenon of "verbal adynamia" or "dynamic aphasia" seen in patients with frontal lobe damage. Although definite cortical changes were present at postmortem examination, it is likely that the neuropsychological deficits reflect functional frontal deafferentation secondary to interruption of frontostriatal feedback loops.