Eye Movements in Parkinson’s Disease and Inherited Parkinsonian Syndromes

Abstract

Despite extensive research, the functions of the basal ganglia (BG) in movement control have not been fully understood. Eye movements, particularly saccades, are convenient indicators of BG function. Here, we review the main oculomotor findings reported in Parkinson’s disease (PD) and genetic parkinsonian syndromes. PD is a progressive, neurodegenerative disorder caused by dopaminergic cell loss within the substantia nigra pars compacta, resulting in depletion of striatal dopamine and subsequent increased inhibitory BG output from the internal globus pallidus and the substantia nigra pars reticulata. Eye movement abnormalities are common in PD: anomalies are more evident in voluntary than reflexive saccades in the initial stages, but visually guided saccades may also be involved at later stages. Saccadic hypometria (including abnormally fragmented saccades), reduced accuracy, and increased latency are among the most prominent deficits. PD patients show also unusually frequent and large square wave jerks and impaired inhibition of reflexive saccades when voluntary mirror saccades are required. Poor convergence ability and altered pursuit are common. Inherited parkinsonisms are a heterogeneous group of rare syndromes due to gene mutations causing symptoms resembling those of PD. Eye movement characteristics of some parkinsonisms have been studied. While sharing some PD features, each syndrome has a distinctive profile that could contribute to better define the clinical phenotype of parkinsonian disorders. Moreover, because the pathogenesis and the underlying neural circuit failure of inherited parkinsonisms are often well defined, they might offer a better prospect than idiopathic PD to understand the BG function.

EEG Microstates Change in Response to Increase in Dopaminergic Stimulation in Typical Parkinson’s Disease Patients

“…Therefore, this justifies the presence of microstate E in patients before dopaminergic stimulation and its disappearance after they took levodopa ( Lou, 2009 , 2015 ). Finally, the cuneus is also related with oculomotor control ( Darby et al, 1996 ), which is well-known to also be a function specifically regulated by the basal ganglia, whose function is altered in PD ( Pretegiani and Optican, 2017 ).…”

Hypomania and saccadic changes in Parkinson’s disease: influence of D2 and D3 dopaminergic signalling

“…Saccadic intrusions are involuntary, conjugate movements, which take the form of an initial fast movement away from the desired eye position and followed after a short duration, by either a return secondary saccade or a drift. 60 Square wave jerks (usually 0.5-5°) are one subtype of saccadic intrusions, which are a typical feature in PD, that moves the eye from and back to the fixation point with an intersaccadic interval of about 200 ms. 61 In addition, changes in PD can be found in the smooth pursuit. 62 Unfortunately, we did not specifically control for saccadic intrusions in our experiment, though we conducted an outlier detection step.…”

Saccadic Direction Errors are Associated with Impulsive Compulsive Behaviours in Parkinson’s Disease Patients

“…1 PD-related dopaminergic depletion in the dorsolateral prefrontal cortex coupled with deficits in cortical inhibitory circuits in PD+ICB 20 may explain the failure to suppress an automatic saccade. 21 An important caveat is that PD+ICB had higher UPDRS scores, which could contribute to increased anti-saccadic error rate; both anti-saccadic error rate and reaction time increase as PD progresses. 22,23 However, there are important differences between our study and previous reports of saccadic abnormalities in advanced PD.…”