Paraneoplastic Downbeat Nystagmus and Cerebellar Ataxia Due to Small Cell Lung Carcinoma

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This is a 61-year-old woman (non-smoker) who developed a gait disorder, dizziness and oscillopsia that was progressive over 2 months. Exam demonstrated spontaneous downbeat nystagmus with side pocket nystagmus in lateral gaze (a combination of horizontal gaze-evoked and downbeat nystagmus, giving an oblique [down and out] appearance), in addition to hypermetric saccades, saccadic smooth pursuit and VOR suppression (not shown in this video). Mild limb dysmetria and gait ataxia were also present. MRI was normal, and there was a mild CSF pleocytosis. CT of the chest/abdomen/pelvis revealed a left hilar mass with extension into the bronchus, and biopsy revealed small cell carcinoma of the lung. It was thought that a paraneoplastic cerebellopathy was the most likely culprit despite a negative serum paraneoplastic panel. There was subjective improvement in vertical oscillopsia and objective improvement in her downbeat nystagmus with IVIG followed by chemotherapy. ; Paraneoplastic cerebellar disease typically develops over the course of days to weeks, and can be accompanied by other bulbar signs or symptoms. Most commonly, as in this case, presentation precedes cancer detection and recognition may allow for expedited diagnosis and treatment of the responsible malignancy. Work up may reveal inflammatory changes (e.g., pleocytosis) within the CSF, and autoantibodies may be detected. The most commonly found antibody-malignancy pairs are anti-Yo (ovarian and breast), anti-Hu (small cell lung carcinoma) and anti-Tr or anti-mGluR1 (both Hodgkins lymphoma). When an older patient presents with the subacute onset of a cerebellar syndrome, the clinician should have a high suspicion for a paraneoplastic disorder. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This patient experienced the subacute progression of imbalance and oscillopsia over weeks, due to a paraneoplastic cerebellar syndrome from lung cancer. Examination demonstrated spontaneous DBN and gaze-evoked nystagmus (causing a ‘side pocket' appearance), hypermetric saccades, saccadic smooth pursuit and vestibuloocular reflex suppression (not shown in this video). DBN improved significantly following intravenous immunoglobulin and treatment of the cancer. (Video and legend created with the assistance of Drs. Tony Brune and Kelly Sloane) https://collections. lib.utah.edu/ark:/87278/s6dn80mw