Poster A53, Thursday, August 16, 10:15 am – 12:00 pm, Room 2000AB

Impaired Phoneme Discrimination and Word Comprehension Due to Acute Left Superior Temporal Gyrus Dysfunction

Luke Adams1, Kevin Kim1, Lynsey Keator1, Amy Wright1, Sadhvi Saxena1, Corianne Rogalsky2, Greg Hickok3, Argye Hillis1;1Johns Hopkins University School of Medicine, 2Arizona State University, 3University of California Irvine

Few studies have identified significant impairments in phoneme discrimination after unilateral stroke. One study found that deficits in phoneme discrimination were seen in 14 percent of left hemisphere stroke patients acutely, and were associated with word comprehension deficits. Lesion sites responsible for these deficits were not identified. We tested the hypotheses that acute deficits in phoneme discrimination are associated with infarct and/or hypoperfusion of left superior temporal gyrus (STG), and that deficits recover quickly due to reperfusion of STG or because right STG alone can become sufficient for phoneme discrimination. We evaluated patients with first-ever, unilateral left hemisphere stroke on a phoneme discrimination test within 48 hours of onset, and again 3, 6, and/or 12 months later. We tested phoneme discrimination by verbally presenting pairs of consonant-vowel syllables (real and non-words), to which the patient responded “same” or “different” (n=64). Word comprehension was tested with word-picture matching tests with mixed semantically and phonologically similar foils (n=20) or only phonologically similar foils (n=24). Participants were asked to indicate the picture matching auditory presented stimuli. Associations between phoneme discrimination deficits and tissue dysfunction (hypoperfusion and/or infarct) in 5 language network regions of interest (ROI: left STG; supramarginal gyrus, angular gyrus, arcuate fasciculus, and inferior frontal gyrus) were tested with Fisher’s exact tests. Results: Twelve patients with completed testing had both diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) available at onset, to identify areas of acute tissue dysfunction on MRI. Of these, 4 (33%) had significant impairment in phoneme discrimination at Day 1, in each case associated with both spoken word comprehension impairment and dysfunction of left STG. Two of four with initial phoneme discrimination deficits showed hypoperfusion (but no infarct) in left STG, and recovered to normal phoneme discrimination by 6-12 months. Two patients had infarct, but more extensive hypoperfusion in left STG, and showed improvement, but not recovery, of both phoneme discrimination and word comprehension by 6 months post-stroke. Seven patients had normal phoneme discrimination at all time points tested, and only one of these had hypoperfusion (but no infarct) in left STG. Impaired phoneme discrimination was significantly associated with dysfunction of left STG (p=0.010), but no other ROI. Conclusion: Results show that left STG dysfunction is associated with phoneme discrimination deficits and auditory word comprehension deficits acutely, often due to hypoperfusion; and these deficits recover by 6 months if there is no infarct in left STG. Results also confirm that impaired phoneme discrimination may underlie at least some cases of word comprehension deficits.

Topic Area: Language Disorders