Objective: Is chronic ocular motor dysfunction in syndrome of antiGAD antibody reversible with immune therapy?

Background: Increased serum titers of antiGAD antibody can be seen in patients with stiffness, ataxia, epilepsy, or encephalitis. Ocular motor deficits, such as downbeat nystagmus, gaze-evoked nystagmus and opsoclonus have been described. Despite rich literature on phenomenology, there is paucity of objective investigations of response to immune therapies. We utilized ocular motor function as an objective surrogate marker to examine the effects of immune therapies on two patients with syndrome of antiGAD antibody.

Methods: We used a high-resolution corneal curvature tracker (Ober, JazzNovo(R), Poland) to quantitatively measure horizontal and vertical eye positions in two patients who had increased titers of antiGAD antibody. The measurements were performed before and after a five day course of IVIG in one patient and PLEX in the other.

Results: Slow-phase velocity of downbeat nystagmus, gaze-evoked nystagmus were our outcome parameters in both patients. We quantified eye-in-orbit position dependence of downbeat and gaze-evoked nystagmus by measuring the slope of the regression function. There was no change in the eye-in-orbit position dependent slow phase eye velocity of nystagmus after treatment with IVIG or PLEX (ANCOVA, p>0.05). We measured the intercept of the fitted linear function with the axis depicting eye-in-orbit position to quantitatively determine the null. There was no change in the null position after immune therapy. The patient who received PLEX also had episodic opsoclonus. The amplitude of opsoclonus spontaneously fluctuated from time to time even at baseline; its frequency was in range of 10-20 Hz. PLEX did not affect the frequency of opsoclonus (ANOVA, p>0.05).

Conclusions: It is possible that permanent damage to the Purkinje neurons due to the autoimmune reaction is responsible for failure of immunotherapies in patients with chronic syndrome of antiGAD antibody. Nevertheless, immune therapy may have value in preventing worsening of progression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-chronic-ocular-motor-dysfunction-in-syndrome-of-antigad-antibody-reversible-with-immune-therapy/