Correction

Abstract

To the Editor: Rakocevic et al. 1 report 5 out of 38 consecutively studied patients with stiff person syndrome (SPS) and high-titer anti-GAD antibodies who also developed cerebellar disease. We would like to highlight the issue of eye movement abnormalities in those patients, and commend them on including that information.The authors reported that in Patient 1, hypometric saccades were prominent; Patient 2 had square-wave nystagmus; Patient 4 had nystagmus and hypometric saccades; and Patient 5 had impaired eye movements. They did not mention ocular motor abnormalities in Patient 3. They again introduced ocular motor abnormalities in the Discussion, stating that "Gait or focal limb ataxia, dysarthria, and visual disturbances were prominent in all patients. Slow and hypometric saccades and sustained lateral gaze-evoked nystagmus were common."Unfortunately, the documentation and discussion of eye movement disturbances in SPS and in cerebellar ataxia with GAD antibodies is rare and is usually based on vague, nonquantitative, clinical descriptions. 2 Economides and Horton 3 were the first to objectively report the presence of gaze-holding nystagmus, limited abduction, ocular misalignment, deficient smooth pursuit, and impaired saccadic initiation in a patient with SPS. They attributed these findings to a dysfunction of GABAergic pathways.Using the magnetic search coil technique, we recently reported a detailed quantitative documentation of a rare saccade velocity profile, downbeat nystagmus, and loss of downward smooth pursuit in a patient with SPS and cerebellar ataxia. 4 Additional studies using precise measurement of eye movements in SPS patients with and without cerebellar signs could be useful in clarifying the link between GAD antibodies and cerebellar dysfunction. The possibility of using quantitative eye measures as a biomarker of neurodegeneration has been discussed 5 regarding the assessment of eye movements in presymptomatic and symptomatic individuals with Huntington disease.We would like to encourage the authors and the neurologic community to quantitatively study eye movements in SPS patients with and without cerebellar signs and in cerebellar ataxia with GAD antibodies. C.R. Gordon, A.Z. Zivotofsky, T. Siman-Tov, N. Gadoth, Kfar Saba, Israel Disclosure: The authors report no conflicts of interest.Reply from the Author: Gordon et al. emphasize that abnormal eye movements can occur in patients with SPS and cerebellar ataxia. We agree. We have observed such abnormalities not only in patients with SPS and cerebellar ataxia reported in our present series, 1 but also in some SPS patients without ataxia. The association is highlighted even further by another patient we have recently seen who presented only with nystagmus and saccadic eye movement abnormalities and positive GAD antibodies, but without signs of SPS.These observations indicate that GABAergic pathways are involved in abnormal eye movements. We also agree with Gordon et al. that the eye movements need to be studied quantitatively and serially in...