Clinical Correlation Between Vertical Gaze Palsy and Midbrain Volume in Progressive Supranuclear Palsy

Supranuclear vertical gaze palsies and slowed vertical saccades are characteristic clinic features of progressive supranuclear palsy (PSP). The "hummingbird sign," reflective of midbrain atrophy, is a classic radiographic sign of PSP. Correlation between eye movement abnormalities and radiographic findings in PSP has been reported previously. However, due to the use of clinical criteria not commonly employed in neuro-ophthalmic practice and neuroimaging techniques that are not widely available, it remains unclear whether correlation between midbrain structure and characteristic ocular-motor disturbances can be helpful to neuro-ophthalmologists seeking to adjudicate difficult or unusual diagnostic cases.

Patients with a diagnosis of probable PSP according to Movement Disorders Society criteria were studied retrospectively. A neuroradiologist calculated brainstem volumes in enrolled participants and normal controls. Spearman correlations were used to correlate the extent of eye movement limitation as assessed by 2 neuro-ophthalmologists with brainstem volumes.

Fourteen participants with PSP and 15 healthy controls with similar age and gender distribution were enrolled and evaluated retrospectively. All 14 participants with PSP had undergone MRIs. Midbrain atrophy significantly correlated with the PSP rating scale (P < 0.001). PSP patients had significantly reduced volumes in the midbrain (P -0.0026), tegmentum (0.0001), tectum (0.0001), and medulla (P = 0.0024) compared with normal controls. Notes documenting quantified ocular motor function were available in 7 of 14 participants with PSP. Midbrain atrophy significantly correlated with in the extent of upward gaze limitation (P = 0.03).

The severity of upward gaze limitation correlates with the severity of midbrain atrophy in patients with PSP. Recognition of this correlation may help to adjudicate diagnostic dilemmas and guide further evaluation.