Functional correlates of vertical gaze palsy and other ocular motor deficits in PSP: an FDG-PET study

To determine the functional correlates of vertical gaze palsy and other ocular motor deficits in patients with progressive supranuclear palsy (PSP) using [(18)F]fluorodeoxyglucose (FDG-)PET.

Twenty-six patients with PSP underwent clinical examination of vertical gaze combined with FDG-PET scans to assess regional cerebral glucose metabolism as a marker of neuronal activity. Of these, eighteen PSP patients were also investigated by electrical nystagmography to determine horizontal ocular motor deficits. Statistical parametric mapping analyses were performed to correlate regional neuronal activity with ocular motor functions.

In categorical comparisons, patients with downward gaze palsy showed a significantly reduced glucose metabolism in bilateral anterior cingulate gyrus and right lingual gyrus compared to those without downward gaze palsy. Maximum velocity of horizontal saccades was positively correlated with glucose metabolism of the rostral vermis and lingual gyrus; regional metabolism of oculomotor vermis was associated with peak velocity of the optokinetic reflex. Analysis of smooth pursuit eye movement amplitude and peak velocity of corrective saccades showed positive correlation with metabolism in bilateral inferior parietal lobe and inferior part of the frontal eye field. All paradigms of smooth pursuit showed positive association with glucose metabolism in V5.

Ocular motor functions in PSP are correlated with neuronal activity in distinct anatomical regions. These include the anterior cingulate gyrus (downward gaze palsy), rostral cerebellum (saccades), oculomotor vermis (optokinetic reflex) and inferior parietal as well as temporal regions and frontal eye field (smooth pursuit). These findings provide a deeper insight into the pathophysiology of PSP-associated ocular motor abnormalities.