Slow vertical saccades in the frontotemporal dementia with motor neuron disease

Ocular motor abnormalities play an important role in differential diagnoses of Pick complex diseases.

We evaluated how frequently supranuclear vertical saccadic impairment was observed in patients with frontotemporal dementia with motor neuron disease (FTD-MND). In addition, we tried to characterize their vertical saccadic abnormalities.

Eleven patients with FTD-MND were recruited. Supranuclear vertical saccadic impairment on gross examination was defined as slow saccades with or without reduction in the final amplitude of the movement accompanied by intact oculocephalic reflex. We also recorded their saccades in 6 out of 11 patients using 2-dimensional videooculography (VOG). We measured the amplitude and peak velocity of each saccade.

On bedside examination, supranuclear vertical saccadic impairment was observed in 9 of 11 patients. One of the two remaining patients could not be evaluated due to poor cooperation and the other showed normal saccades. Five of nine patients with ocular abnormalities and one patient with normal saccade on gross examination underwent the VOG studies. The results showed that all the five patients with gross ocular abnormalities, compared with age-matched controls, had slowing of vertical saccades. Three out of five patients also showed slowing even in the large horizontal saccades.

Our results showed that slow vertical saccades are common in FTDMND. FTD-MND could be another disease that affects vertical gaze among Pick complex disease. Future pathologic studies are needed to confirm the involvement of the burst neurons in the dorsal midbrain in patients with FTDMND.