Positron emission tomography in diagnosing brainstem vascular lesions that cause abnormal eye movements.

PURPOSE

To evaluate the efficacy of positron emission tomography (PET) in aiding in the diagnosis of brainstem infarctions that cause abnormal eye movements.

METHOD

Cerebral glucose metabolism was examined by PET with 18F-fluorodeoxyglucose as a tracer in five normal control subjects and six patients with abnormal eye movements. The PET images were registered to and superimposed on magnetic resonance images (MRIs).

RESULTS

All control subjects showed little asymmetry of glucose metabolism in the brainstem, whereas all six patients demonstrated areas of low glucose metabolism in the brainstem. Areas of low metabolism seen by PET were wider than they appeared to be by MRI; MRIs even appeared normal in some patients. Asymmetry index measurements at the level of the ischemic lesion ranged between 19% and 45%.

CONCLUSIONS

Positron emission tomography detected metabolic abnormality in patients with brainstem lesions that caused abnormal eye movements. Superimposing PET images on MRIs accurately localized abnormally low metabolism in the brainstem. Combined imaging with PET and MRI can be used to diagnose ischemic lesions in the brainstem from functional (PET) and morphologic (MRI) viewpoints.