Zinc finger protein 4 (Zic4) antibodies occur as paraneoplastic cerebellar syndrome (PCS) in subjects with small cell lung carcinoma (SCLC).1Oscillopsia as presenting feature of Zic4 antibody associated paraneoplastic neurological syndrome (PNS) has not been reported. A 50-year-old lady presented with severe disabling oscillopsia, of 8 weeks duration, to the extent that she felt more disabled with eyes open and was subjectively better when walking with eyes closed. She also had frequent bouts of vertigo which subsided with vestibular sedatives. There were no systemic symptoms such as weight loss, anorexia or night sweats. Examination showed normal saccades with broken pursuits and impaired inhibition of vestibulo-ocular reflex (abnormal pursuit to either side as the subject's eye and head track a moving target), bilateral gaze-evoked nystagmus, subtle left upper limb dysmetria, mild gait ataxia, with leftward swaying while walking, and no dysarthria (Video 1). There was no nystagmus in the neutral position. Rest of the neurological examination was normal. Clinical localization was to the cerebellum and vestibulo-cerebellar connections. An immune mediated (eg, anti GAD-65, neuromyelitis optica spectrum disorder), paraneoplastic or infratentorial metastatic lesions were considered. Her magnetic resonance imaging (MRI) of brain showed mild cerebellar atrophy (Fig. 1A–D). Chest X-ray showed a mass lesion in the right lung which was confirmed by computed tomography (CT). Positron emission tomography (PET) CT showed hypermetabolic heterogeneously enhancing lesion in the upper lobe of right lung with ipsilateral mediastinal adenopathy and right adrenal metastasis (Fig. 1E–H). CT guided biopsy of lung mass diagnosed SCLC. Serum paraneoplastic panel was strongly positive (3+) for anti-Zic4 antibodies and negative for antibodies to Hu, Ma2, Yo, Ri, CAR, CV2, VGKC, amphiphysin, and GAD-65 (immunoblot technique). Our patient fulfilled the criteria for a definite paraneoplastic syndrome as she had a classic PNS with a well characterized antibody and an identifiable tumor as etiology. She was treated with pulse dose intravenous methylprednisolone for 5 days, followed by a tapering schedule of oral steroids and is undergoing chemotherapy. PCS, often associated with anti-Yo, anti-Hu, anti- CV2, anti-Tr, anti Zic4 and anti KLHL11 antibodies, manifests with symmetric limb ataxia, gait ataxia, dysarthria, and nystagmus.2 The Zic family includes five genes that encode zinc finger proteins that are expressed during the maturation of central nervous system and have critical roles in the development of cerebellum. Patients with PCS expressing Zic4 antibodies can also have other paraneoplastic antibodies like anti-Hu1 and hence work up for the entire panel, as done here, is needed before nailing the culprit. Oscillopsia has been described in PNS caused by anti DPPX, anti NMDAR, anti GAD65, mGluR1 and anti KLHL11 antibodies though not as the initial feature3 as in our unique case. Pursuit eye movements checked in the same direction (Video segment 1) of head movements (ie, following a head-fixed target) require inhibition of the vestibulo-ocular reflex (VOR), mediated by a class of vestibular neurons namely floccular-target neurons (FTN) which have substantial input from the floccular complex of the cerebellum.4 FTN neurons constitute the flocculo nodular pathway that is responsible for VOR motor learning and adaptation to modulate an accurate VOR response.4 Anti-Zic4 antibody mediated damage of flocculo nodular lobe can affect suppression of the VOR required for retaining visual gaze upon the target during combined eye-head orienting movement complex. Oscillopsia is thus caused by impaired ocular stability, due to a deficit in VOR cancellation during gaze shift along with head motion.5 Symptoms of anti-Zic4 associated PNS can precede tumor diagnosis in 50% to 60% of patients1 as seen in our subject. This highlights the importance of comprehensive tumor screening, even with atypical presentations. Table S1 (supplementary data) shows cases of isolated Zic4 antibody mediated PNS reported till date. Mutations of different Zic genes have yielded various anomalies, including cerebellar malformation, holoprosencephaly and spina bifida.6 The preponderant cerebellar phenotype in Zic gene mutations and the detection of intrathecal Zic4 antibodies in PCS subjects, demonstrate that autoimmunity to Zic proteins, chiefly manifests as cerebellar degeneration. Zic4 immune reactivity corresponds to the granule cell layer of the cerebellum.1 Whereas, lymphoma associated anti-Tr [also known as delta and notch-like epidermal growth factor-related receptor (DNER)] antibodies, anti-Yo antibodies and those against protein RGS8 are against Purkinje cells.7 The use of combination checkpoint inhibitor therapy with nivolumab and ipilimumab in metastatic head and neck squamous cell carcinoma can rarely cause anti-Zic4 antibody associated ataxia.8 Our patient had a response to immunotherapy. Anti-Hu, anti-Yo, anti-Ri, anti-CV2, anti-Ma2, and anti-Zic4 belong to the classical PNS associated autoantibodies that bind to intracellular target antigens where damage is predominantly mediated by cytotoxic T-cells and is often irreversible, explaining their incomplete response.9 Nevertheless, immunomodulatory treatment can improve outcomes in some patients compared to the natural course of illness.9 (1) A. Conception, B. Organization, C. Execution; (2) Manuscript Preparation: A. Writing of the first draft, B. Review and Critique. A.V.: 1A, 1B, 1C, 2A A.C.: 1A, 1B, 1C, 2A D.K.P.: 1A, 1B, 1C, 2B S.K.: 1A, 1B, 2B H.P.: 1B, 1C, 2B Written informed consent was obtained per institute guidelines for videotaping the subject and publishing his video and history. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. The authors report no sources of funding and no conflicts of interest. The authors declare that there are no additional disclosures to report. Table S1. Isolated Zic4-Antibody related Paraneoplastic neurological syndromes Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.