The Gait Disorder in Downbeat Nystagmus Syndrome

Abstract

BackgroundDownbeat nystagmus (DBN) is a common form of acquired fixation nystagmus with key symptoms of oscillopsia and gait disturbance. Gait disturbance could be a result of impaired visual feedback due to the involuntary ocular oscillations. Alternatively, a malfunction of cerebellar locomotor control might be involved, since DBN is considered a vestibulocerebellar disorder.MethodsInvestigation of walking in 50 DBN patients (age 72±11 years, 23 females) and 50 healthy controls (HS) (age 70±11 years, 23 females) using a pressure sensitive carpet (GAITRite). The patient cohort comprised subjects with only ocular motor signs (DBN) and subjects with an additional limb ataxia (DBNCA). Gait investigation comprised different walking speeds and walking with eyes closed.ResultsIn DBN, gait velocity was reduced (p<0.001) with a reduced stride length (p<0.001), increased base of support (p<0.050), and increased double support (p<0.001). Walking with eyes closed led to significant gait changes in both HS and DBN. These changes were more pronounced in DBN patients (p<0.001). Speed-dependency of gait variability revealed significant differences between the subgroups of DBN and DBNCA (p<0.050).Conclusions(I) Impaired visual control caused by involuntary ocular oscillations cannot sufficiently explain the gait disorder. (II) The gait of patients with DBN is impaired in a speed dependent manner. (III) Analysis of gait variability allows distinguishing DBN from DBNCA: Patients with pure DBN show a speed dependency of gait variability similar to that of patients with afferent vestibular deficits. In DBNCA, gait variability resembles the pattern found in cerebellar ataxia.

Postural Ataxia in Cerebellar Downbeat Nystagmus: Its Relation to Visual, Proprioceptive and Vestibular Signals and Cerebellar Atrophy

“…Despite DBN-related oscillopsia, patients can use visual signals to stabilize posture in the same way as healthy persons do. This is in line with related studies showing that gait impairments of DBN patients deteriorate during absent visual control [7]. In line with our current posturographic data, DBN patients even utilize visual information better than healthy controls.…”

“…From a clinical point of view, the strong visual dependency of postural control resembles proprioceptive ataxia of stance in patients with polyneuropathy rather than patients with cerebellar ataxia. This in line with ataxia of gait in DBN patients which clearly differ from cerebellar patients with additional limb involvement [7]. …”

“…Moreover, gait disturbances in DBN have been found not to be purely related to impaired visual control since walking in darkness (eyes closed) was significantly worse than in age-matched controls [7]. …”

Cerebellar Dizziness and Vertigo: Etiologies, Diagnostic Assessment, and Treatment

“…50 The characteristic pattern of gait variability in cerebellar patients indicates disturbed integration of sensory feedback (during slow walking) and abnormal function of cerebellar pacemakers and feedforward coordination of multijoint movements (mostly during fast walking). Cerebellar pathologies that predominantly affect the flocculonodular lobe (such as DBN) show more prominent gait variability during slow versus fast walking, which highlights the importance of the vestibulocerebellum for sensory feedback mostly during slow walking 51,52 (►Fig. 2).…”

Stand- und Ganganalyse bei Schwindel

“…Insbesondere bei Patienten mit vestibulären oder zerebellären Erkrankungen zeigt sich, dass Untersuchungsbedingungen, die außerhalb des selbstgewählten, "normalen" Gehens getestet werden, besonders sensitiv und damit relevant sind. Hierbei sind vor allem das langsame Gehen und das Gehen mit geschlossenen Augen zu nennen, während dessen sich die typische Gangunsicherheit der Patienten regelhaft deutlich verstärkt [27,[34][35][36]. Patienten mit einer Kleinhirnataxie zeigen zudem eine Zunahme der Gangstörung auch beim schnellen Gehen, mutmaßlich aufgrund gestörter zerebellärer Lokomotionsfunktionen, welche beim schnellen Gehen besonders relevant werden [27,37,38].…”