Magnetic resonance perfusion imaging in the study of language

Abstract

This paper provides a brief review of various uses of magnetic resonance perfusion imaging in the investigation of brain/language relationships. The reviewed studies illustrate how perfusion imaging can reveal areas of brain where dysfunction due to low blood flow is associated with specific language deficits, and where restoration of blood flow to improve the tissue function results in recovery of those deficits. This sort of evidence helps to reveal areas of the brain that are essential to a particular language task. Other studies have provided clues regarding the mechanisms of early language recovery, or have shown how perfusion imaging can identify patients with chronic hypoperfusion due to cerebrovascular stenosis in whom the BOLD effect in fMRI may be absent or reduced in areas of neural activation.

Fig. 1.

Probability of DWI abnormality in each voxel of diffusion-weighted images of a consecutive series of 11 patients who presented within 24 h of onset of any left hemisphere stroke symptoms and had a high resolution MRI that allowed registration of the scans to the MNI atlas.

Fig. 2.

DWI and PWI scans of three patients with hypoperfusion of left BA 37 (arrow) who had impaired oral and written naming but intact spoken and written word comprehension on Day 1. Relatively hypoperfused regions appear dark green or blue.

Fig. 3.

(A) DWI (top) done at Day 1 and PWI done at week 6 (bottom) of a patient with almost complete resolution of initial anomia and comprehension deficits, showing chronic hypoperfusion of left temporal cortex, including BA 37 (arrow). (B) fMRI study of word generation in six healthy control patients, showing significant BOLD effect in left BA 6 (dorsal posterior frontal; green circles), left BA 22, 37 (posterior temporal areas; blue circles), left BA 40 (supramarginal gyrus in the parietal lobe; black circles), and bilateral BA 44, 45 (posterior, inferior frontal) and 41/42 (auditory cortex), as well as right BA 21 (middle temporal gyrus). (C) fMRI study of word generation in the patient whose DWI and PWI are shown, demonstrating absence of the expected BOLD effect in the hypoperfused region (BA 37) and increased BOLD effect in the homologous region of the opposite hemisphere.

Fig. 4.

(A) DWI (top) and PWI (bottom) of a patient with hemispatial neglect and inattention, showing extensive hypoperfusion in right frontoparietal cortex. (B) fMRI study of word generation in six healthy control patients, showing significant BOLD effect in six healthy control patients in an extensive left dominant fronto-temporal-parietal network. (C) fMRI study of word generation (task minus rest) in the patient whose DWI and PWI are shown in (A), demonstrating absent of BOLD effect in the hypoperfused regions of the right frontoparietal cortex and relatively normal BOLD effect in the intact left hemisphere. (D) fMRI study of word generation (rest minus task) in the same patient, showing increased BOLD effect in the right, hypoperfused areas during rest relative to task in ROIs that showed right hemisphere BOLD signal in normal subjects in the opposite contrast (task relative to rest).