Why do patients with PSP fall?

Abstract

Taken together, these results indicate that abnormal otolith-mediated reflexes may be at least partly responsible for frequent falls in progressive supranuclear palsy, and deserve further study.

Direction specific preserved limits of stability in early progressive supranuclear palsy: A dynamic posturographic study

“…In addition, Probst et al [22] reported presence of neurofibrillary fibers, neuropil threads throughout the basal ganglia and brainstem in PSP. In addition impairment of balance in PSP has been attributed to central vestibular dysfunction [9], deficits in motor programming [23], abnormal otolith-mediated reflexes [24], synergistic deterioration of brainstem and higher cortical functions [25] and involvement of cerebellum [26].…”

Head deviation in progressive supranuclear palsy: enhanced vestibulo-collic reflex or loss of resetting head movements?

“…The question is whether there is enhanced VCR activity per se (stabilising the head in space during body movements) or whether there is a loss of oppositely directed eye-head movements (which reset the eyes in the orbit and the head on the trunk). The former mechanism is unlikely because in PSP vestibular function is essentially normal [5,6], or even decreased according to the only study of PSP using VEMPs (although not in subjects specifically exhibiting torticollis) [7]. This is in sharp contrast to fast resetting eye and head movements, such as eye-head saccades and quick phases of nystagmus, notoriously reduced in PSP [3,5,8].…”

Disorders of vergence eye movements

“…When normal humans look through prisms to dissociate vergence angle from viewing distance, it is the latter that sets the magnitude of LVOR [3]. In some disorders with deficient or absent vergence responses, such as progressive supranuclear palsy (PSP), the magnitude of LVOR cannot be increased during near-viewing [20,21 ]. However, in other disorders such as cerebellar ataxias, the magnitude of LVOR is not increased even when the patient converges [22].…”