PAG gray matter volume in relation to the duration of asthma in the patient group.

A) Statistical parametric map demonstrating a significant increase of gray matter volume in the brainstem PAG with increasing duration of asthma (shown at p<0.005, uncorrected). Gray matter changes are superimposed onto the asthma groups' mean structural T1 weighted MRI image. B) Mean PAG gray matter volumes of each patient in relation to the individual duration of asthma.