Cortical degeneration associated with phonologic and semantic language impairments in AD

Objective: To compare the pattern of cortical degeneration associated with different language deficits in cases of AD.,Methods: Cases for detailed neu ropathologic analysis (Patients 1 and 2) were selected because of their det ailed clinical and neuropsychological assessments of language dysfunction i n ED. Patient 1 had severe phonologic impairment with relatively preserved semantic aspects of language. Patient 2 had severe semantic language impair ment with relatively preserved phonologic skills. The tissue volume of cort ical regions associated with speech and language function was measured usin g standardized three-dimensional techniques. Neuronal areal fraction was al so measured from histologic tissue samples. The degree of volume atrophy an d neuronal loss was calculated in comparison to control measures (n = 10 me n and II women). Measurements more than 2 SD from controls were considered abnormal. Results: Both AD cases had significant degeneration of the superi or temporal gyrus and area 37, Cortical language regions affected only in P atient 1 included the anterior and posterior insula and part of Broca's are a. In contrast, Patient 2 had a greater degree of degeneration in the tempo ral gyri and their white matter connections with the hippocampal/entorhinal complex. Conclusions: Variable patterns of neurodegeneration underlie the clinical differences observed in patients with AD. Disconnection within the temporal lobe appears associated with semantic language difficulties, wher eas disconnection of the anterior and posterior language areas appears asso ciated with phonologic and grammatical impairment.