This may contribute to saccadic hypometria, as depicted in Figure 2, and slowed initiation of voluntary saccades [57] such as reduced number of rapid alternating self-paced saccades where subjects are asked to shift their gaze as fast and as accurately as possible between to stationary targets [45].
Saccadic hypometria in MSA can be observed, with mildly or moderately inaccurate saccade amplitudes.
Study of oculomotor dysfunctions both in PSP-RS and in PSP-P revealed a similar presentation comprising slowed vertical saccades, saccadic hypometria, prolonged latencies, and impaired pursuit eye movement [65].
In a recent study of oculomotor function in thirty patients with MSA, (8) excessive square-wave jerks were observed in 21 of the patients, a mild supranuclear gaze palsy in eight patients, a gaze-evoked nystagmus in 12 patients, a positioning down-beat nystagmus in 10 out of 25 patients, mild-moderate saccadic hypometria in 22 patients, impaired smooth pursuit movements in 28 patients, and reduced vestibulo-ocular reflex (VOR) suppression in 16 out of 24 patients.
(8) have recently published a list of 'red flag' criteria that are strongly suggestive of a diagnosis of MSA and include excessive square-wave jerks, mild to moderate hypometria of saccades, impaired VOR, and nystagmus.
Particularly useful in separating MSA from other Parkinsonian syndromes is the presence in the former of excessive square-wave jerks, mild to moderate hypometria of saccades, impaired VOR, and nystagmus.
The main abnormality consists of saccade
hypometria, although all types (predictive, anticipatory, and memory-guided) of saccade generation may be involved [24].
Hence, particularly useful in separating MSA from other Parkinsonian syndromes is the presence in the former of excessive square-wave jerks, mild to moderate
hypometria of saccades, impaired vestibule-ocular reflex (VOR), and nystagmus.