Objectives: To study patients with crossed aphasia (aphasia secondary to lesions in the right hemisphere in right-handed patients) with functional brain imaging using positron emission tomography (PET) or single photon emission computed tomography (SPECT); to see whether left hemisphere structures were metabolically depressed during the acute phase and, in 1 patient, during recovery; and to review the modern literature on crossed aphasia, with special reference to left hemisphere involvement. Design: Case studies of 3 patients with crossed aphasia, including language testing, computed tomographic scanning, and functional imaging with PET or SPECT. Setting: Hospital case studies. Patients: Three-right-handed patients with crossed aphasia secondary to acute infarctions in the right hemisphere and left hemiparesis. Methods: All 3 patients were studied by means of bedside language testing, computed tomographic scanning, and functional brain imaging with PET or SPECT. Patient 1 also underwent serial testing with the Boston Diagnostic Aphasia Examination and follow-up PET scanning after 2 months of recovery. Outcome Measures: Clinical examination in all 3 patients and follow-up Boston Diagnostic Aphasia Examination and PET scanning in patient 1. Results: Two patients had severe global aphasia and 1 had Broca aphasia. In all cases, computed tomographic scans failed to reveal any left hemispheric lesions. Functional imaging with PET or SPECT showed extensive hypometabolism or hypoperfusion in the right hemisphere, with initial reductions in the left hemisphere as well. In patient 1, a follow-up PET image showed only persistent hypometabolism in the right hemisphere. Conclusions: These findings suggest that abnormal dominance for at least some language functions in the right hemisphere underlies the syndrome of crossed aphasia. Diaschisis, or functional depression of the anatomically normal left hemisphere, was seen in all 3 patients during the acute phase, but not in patient 1 after recovery had begun.
