The effect of cervical and vestibular reflexes on eye movements in Huntington's Chorea

Abstract

In 8 patients with manifest Huntington's Chorea vestibulo-ocular (VOR) and cervico-ocular (COR) reflexes were compared with eye movements during active head turnings. Seated patients were stimulated with their eyes closed by sinusoidal swings around the vertical axis at frequencies of 0.05, 0.1 and 0.2s-1 with amplitudes of 20, 40 and 60 degrees. 1) With all stimuli and in all patients a weak nystagmus was elicited in the direction of head movements, superimposed on larger slow eye deviations. 2) The averaged total saccadic amplitudes were smaller than in normals, increased with stimulus amplitudes and were smallest for COR, followed by VOR and active head movements. 3) The gain (peak velocity of slow phase of nystagmus to peak stimulus velocity) was only slightly below norm values and decreased with increasing stimulus frequency and amplitude. 4) The peak amplitudes of average slow eye deviations increased with stimulus amplitudes. In VOR they were comparable to norm values but were below them during COR and active head movements. 5) In normal subjects these slow eye deviations were compensatory to head movements in VOR but anticompensatory in COR and during active head movements. In choreic patients during COR and more often during active head movements these slow eye movements were compensatory for the head turning.

Complementary gain modifications of the cervico-ocular (COR) and angular vestibulo-ocular (aVOR) reflexes after canal plugging

“…There has been considerable controversy, however, whether there is adaptation of the COR following peripheral vestibular damage that compromises aVOR function (Atkin and Bender 1968; Gresty et al 1977; Kasai and Zee 1978; Barnes and Forbat 1979; Baker et al 1982; Böhmer et al 1982; Leopold et al 1982; Böhmer and Henn 1983a; Leopold et al 1983; Chambers et al 1985; Pettorossi et al 1987; Rioult-Pedotti and Dieringer 1988; Bronstein et al 1991, 1995; Heimbrand et al 1996; Schubert et al 2004; Sadeghi et al 2006; Yakushin et al 2009). A recent study of the COR in the rhesus monkey after unilateral neurectomy indicates that there was no increase in COR gain (Sadeghi et al 2008, 2009a, c).…”

“…One possible explanation is that there are two types of cervically induced, oculomotor responses during passive body oscillation relative to the head: a slow phase of eye rotation and eye position changes due to saccades that occur in the same direction as the slow COR phase (Schlagfeldverlagerung) (Frenzel 1928; Leopold et al 1982). Normal subjects utilize one or another behavior to a different extent.…”

“…This is opposite to the direction of relative head-re-body rotation and would add a compensatory component when combined with the response of the aVOR. Other studies found the COR action to be anticompensatory (Barlow and Freedman 1980; Fuller 1980; Leopold et al 1982; Chambers et al 1985; Jurgens and Mergner 1989). This variation in phase could be due to the low COR gain in normal subjects, which has little effect on combined COR/aVOR responses in the normal state.…”

The Neuropathology of Huntington’s Disease: Classical Findings, Recent Developments and Correlation to Functional Neuroanatomy

“…Initiation defi cits of vertical and horizontal saccades are very frequent disease signs of HD patients and may already be present in preclinical HD gene carriers and in the early clinical phase of HD. Some HD patients may also show an inability to converge , a reduced gain of the slow component of the vestibuloocular reaction , as well as impairments of the optokinetic nystagmus (i.e., reduced gain of the slow or rapid component, loss of the optokinetic nystagmus) ( Table 6.1 ) (Beenen et al 1986 ;Blekher et al 2004Blekher et al , 2006Fielding et al 2004 ;Golding et al 2006 ;Kennard and Lueck 1989 ;Kirkwood et al 2000 ;Lasker and Zee 1997 ;Leigh and 6.2 Oculomotor Dysfunctions in Huntington's Disease (HD) Zee 2006 ; Leigh et al 1983 ;Leopold et al 1982 ;Oepen et al , 1985Rüb et al 2009 ;Starr 1967 ). In addition, the vertical and horizontal saccades of HD patients can also be slowed, hypo-, or hypermetric, restricted in range, or completely lost.…”

Impaired modulation of the vestibulo‐ocular reflex in Huntington's disease

“…Conversely, the vestibulo‐ocular reflex (VOR), which stabilizes vision during head movement by generating equal and opposite smooth eye movements, has received relatively little attention. Although generally considered preserved even late in the disease,6–10 modulation of the reflex both on‐line and over time, has not been addressed.…”