Functional magnetic resonance imaging in homonymous hemianopsia.

PURPOSE: We performed functional magnetic resonance imaging associated with brain activity to evaluate the abnormality of the visual pathway in hemianoptic patients.

METHODS

We studied five patients with homonymous hemianopsia caused by retrochiasmal lesions and five control subjects. On the basis of a blood oxygenation level-dependent contrast mechanism, magnetic resonance imaging was performed with a standard clinical 1.5-tesla system. We evaluated the asymmetrically increased signal intensities in the calcarine cortex during visual stimulation and compared them with the findings of Goldmann perimetry.

RESULTS

Cortical activations with a marked interhemispheric contrast of the primary visual cortex consistent with the visual field defects were observed in three of the five patients. In two of the patients without macular field preservation in the defective hemifield, functional magnetic resonance imaging showed an absence of response in the primary visual cortex of the affected side. In the patient with superior quadrantanopsia, we could detect clear laterality by selecting the imaging plane inferior to the calcarine fissure. The other two hemianoptic patients with macular sparing showed symmetric responses.

CONCLUSIONS

These findings suggest that functional magnetic resonance imaging is valuable in assessing local brain function in patients with visual deficits; therefore, it is a promising method for the objective detection of abnormalities in the afferent visual system.