The differential diagnostic value of video-oculography in the early differentiation of PSP-P and IPD

Objectives: Recent studies have suggested a further differentiation of PSP in Richardson's Syndrome (RS) and PSP-Parkinsonism (PSP-P). On clinical grounds, early PSP-P is hard to distinguish from Idiopathic Parkinson's disease (IPD). Although vertical gaze palsy is one of the core features in the diagnosis of progressive supranuclear palsy (PSP), it is reported to occur later if at all in PSP-P compared to RS. The aim of this study was to search for possibly early oculomotor abnormalities in the PSP-P subset out of a sample of PSP patients via video-oculography (VOG) and to compare these findings with those of RS and IPD patients and a control group.

Materials and Methods: Twelve cases of RS, 5 cases of PSP-P and 27 cases of IPD were examined by use of VOGand compared to 39 healthy controls. In order to elicit possible correlations between the clinical data and the oculomotor parameters, a clinical data sheet was designed for all patients including the core symptoms of Parkinsonian syndromes as well as the Hoehn & Yahr scale. For statistical analysis, all VOG parameters were subjected to an ANOVA analysis and suspected differences between the groups were analyzed with the Mann-Whitney-U test.

Results: VOG showed statistically significant differences of RS and PSP-P patients in comparison with both IPD patients and normal controls. Thus, a clear-cut separation of both PSP syndromes and IPD could be achieved based upon VOG. The oculomotor dysfunction, however, did not differ between RS and PSP-P since PSP-P patients exhibited similar oculomotor alterations as RS patients although they were still in an early stage of the disease. A correlation of VOG data and clinical data could not be observed.

Conclusion: Via VOG, it was possible to measure a statistically significant slowing of reactive saccades in PSP-P compared with patients and controls. Remarkably, these alterations occured already in the early course of disease, when the clinical hallmarks of PSP-P like lateralisation of rigidity and akinesia as well as levodopa responsivity were still apparent. This finding can be considered as an early specific sign of gaze palsy in PSP-P. Hence, in view of the difficulties in the early differentiation of PSP-P and IPD on clinical grounds, VOG might play an important role in the diagnostics of these entities. Further studies in larger samples will be necessary to analyse if the observed early affection of eye movement in PSP-P is more common than yet expected.