MRI ASYMMETRIES AND LANGUAGE DOMINANCE

Objective: To examine the relationship between language dominance, as measured by Wada testing, and hemispheric asymmetries on MR brain imag es. Background: A previous report that did not include verification of language dominance compared the length of the planum temporale with h emispheric asymmetries seen on CT and inferred that occipital lobe asy mmetry is related to language dominance. Methods: Language dominance w as identified by the Wada test in 57 patients evaluated for surgical t reatment of epilepsy. Fifty-five had an MRI scan that allowed accurate measurement. In a blinded fashion, two examiners independently measur ed bilateral frontal, parietal, and occipital lobe lengths on MR scan for each patient. Measurements of asymmetries were compared with langu age dominance established by the Wada test. Results: Reliability of me asurement between the examiners was 97%. Asymmetry of the occipital lo be length on MR scan 10 mm above the tentorium was the only measuremen t significantly related to language dominance (p < 0.01). Occipital lo be length was longer on the left in 19 (40%) and on the right in 10 (2 1%) patients with left dominance. The right lobe was longer in six of seven (86%) patients with bilateral dominance. One patient with right hemisphere dominance had a longer left lobe. None of the measurements significantly related to handedness. Conclusion: Asymmetries of occipi tal lobe length relate to language dominance, but such dominance canno t be reliably identified by MR in an individual patient.