Tuesday, January 23, 2018

Oculomotor and vestibular findings in Gaucher disease type 3

Bremova-Ertl T, Schiffmann R, Patterson MC, Belmatoug N, Billette de Villemeur T, Bardins S, Frenzel C, Malinová V, Naumann S, Arndt J, Mengel E, Reinke J, Strobl R and Strupp M (2018) Oculomotor and Vestibular Findings in Gaucher Disease Type 3 and Their Correlation with Neurological Findings. Front. Neurol. 8:711. doi: 10.3389/fneur.2017.00711

Objectives: To evaluate the function of the oculomotor and vestibular systems and to correlate these findings with the clinical status of patients with Gaucher disease type 3 (GD3). The goal of this cross-sectional and longitudinal study was to find oculomotor biomarkers for future clinical trials.

Methods: Twenty-six patients with GD3 were assessed for eligibility and 21 were able to perform at least one task. Horizontal and vertical reflexive saccades, smooth pursuit, gaze-holding, optokinetic nystagmus, and horizontal vestibulo-ocular reflex (VOR) were examined by video-oculography/video-head impulse test and compared concurrently with 33 healthy controls. The Scale for the Assessment and Rating of Ataxia (SARA), the modified Severity Scoring Tool (mSST), and Grooved Pegboard Test (GPT) were administered to assess overall neurological function. Eleven patients were also re-assessed after 1 year.

Results: Nine out of 17 patients exhibited gaze-holding deficits. One patient had upbeat nystagmus. Three patients presented with bilateral abducens palsy in combination with central oculomotor disorders, suggesting a bilateral involvement of the abducens nucleus. Horizontal angular VOR gain was reduced in all patients (0.66 ± 0.37) compared with controls (1.1 ± 0.11, p < 0.001). Most strongly correlated with clinical rating scales were peak velocity of downward saccades (SARA: ρ = −0.752, p < 0.0005; mSST: ρ = −0.611, p = 0.003; GPT: ρ = −0.649, p = 0.005) and duration of vertical saccades (SARA: ρ = 0.806, p < 0.001; mSST: ρ = 0.700, p < 0.0005; GPT: ρ = 0.558, p = 0.02) together with the VOR gain (SARA: ρ = −0.63, p = 0.016; mSST: ρ = −0.725, p = 0.003; GPT: ρ = −0.666, p = 0.004). Vertical smooth pursuit gain decreased significantly at follow-up.

Interpretation: This study shows neuronal degeneration of the brainstem and cerebellum with combined involvement of both supranuclear and nuclear oculomotor structures and the vestibular system in GD3. We also identified oculomotor parameters that correlate with the neurological status and can be used as biomarkers in future clinical trials.

From the article

This study evaluated the comprehensive ocular motor and vestibular function of a sizable international cohort of patients with GD3. It related this function to their overall clinical state in a systematic and standardized manner.

The major findings in this study are as follows:

First, gaze-holding function was compromised in some patients, which might indicate a cerebellar dysfunction, mainly of the flocculus, and/or dysfunction of the neuronal integrator (17).

Second, PV of downward saccades and duration of vertical saccades as well as gains in horizontal aVOR correlated significantly with the patients’ clinical status assessed by SARA, mSST, and the GPT. Therefore, these easily quantifiable oculomotor and vestibular parameters may be used as biomarkers for future studies.

Third, horizontal aVOR was impaired in all patients and showed consistent patterns over time in patients evaluated longitudinally.

Fourth, longitudinal analysis did not show significant changes over time, except for a deterioration of vertical smooth pursuit.

Topo-anatomical findings suggest that multiple areas in the brainstem and cerebellum are involved in patients with GD3: pontine paramedian reticular formation (PPRF), rostral interstitial nucleus of the medial longitudinal fascicle (riMLF), motoneurons of the abducens nucleus, cerebellum (mainly the flocculus), and the vestibular system. For typical clinical ocular motor findings in patients with GD3, see Video S1 in Supplementary Material of patient 9 on the webpage...

In conclusion, our findings suggest a widespread neuronal dysfunction, both at brainstem and cerebellar levels. The deficits seen in the oculomotor and vestibular examination, particularly those that progressed over time, can be used as biomarkers in future clinical trials. Future studies evaluating the voluntary saccades, including also absolute number of performed saccades or intersaccadic intervals, should be planned to assess the reliability of these biomarkers. The otolith function examined by VEMP holds promise as another vestibular biomarker, as was shown previously. Also, a compact binocular testing battery to minimize the effect of fatigue should be performed in clinical trials in the future. Our clinical experience also suggests performing the VOG as early as possible prior to the other clinical tests.

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