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Subacute Supranuclear Palsy in anti-Hu Paraneoplastic Encephalitis

Anti-Hu-associated paraneoplastic syndrome, which is commonly characterized by encephalitis and sensory neuronopathy, usually precedes the diagnosis of an underlying tumour— overwhelmingly a small-cell lung cancer (SCLC). One area frequently affected by encephalitis is the brainstem, predominantly in the pons and medulla. In the rare case in which the mesencephalon is affected, distinctive eye movement disorders such as supranuclear vertical gaze palsy may result. Herein we report an unusual case of anti-Hu-associated paraneoplastic encephalitis presenting with supranuclear vertical gaze palsy preceding the identification of SCLC. Anti-Hu antibodies are formed against intraneuronal antigens; thus, their detection implies neuronal damage. Early recognition of neurological signs compatible with an underlying paraneoplastic neurological syndrome may provide the opportunity to intervene early on in the disease course. Early diagnosis and treatment have the potential to limit neuronal damage, and to detect (and treat) an underlying tumour when present. A 57-year-old right-handed man presented with gradual progression of vertical gaze limitation for three weeks, followed two weeks later by impaired cognition. That made it difficult for him to remember his customers’ orders in his own restaurant and handle a noodle-making machine or a cash register well. He had a history of insulin-treated type two diabetes mellitus and heavy smoking, but no family history of neurological disorders. On admission, he was afebrile. A neurological examination revealed normal horizontal eye movement but severely abnormal vertical pursuit and saccadic eye movements as well as incomplete convergence (Figure 1). His pupillary reflex, Bell’s phenomenon and the vestibulo-ocular reflex were preserved, compatible with supranuclear vertical gaze palsy. Cranial nerve examination results were otherwise normal. His short-term memory and recall were mildly impaired on objective testing, and his MMSE (Mini-Mental State Examination) score was 27 out of 30 points, losing 1 point for recall and 2 points for calculation. Extensive laboratory testing revealed that, whereas anti-Hu antibodies were present in the serum, anti-Ma1 and anti-Ma2 antibodies—occasionally positive in paraneoplastic encephalitis characterized by eye movement abnormalities such as vertical gaze palsy—were not. Cerebrospinal fluid analysis showed mild elevation of total protein concentration (62mg/dL) and IgG index (0.81, normal limit= below 0.7) without pleocytosis and oligoclonal bands. Culture and a search for the 14.3.3 protein were negative. Magnetic resonance imaging (MRI) of the brain showed hyperintense lesions on fluid-attenuated inversion recovery images at the right extreme capsule and surrounding the third ventricle, and no abnormalities in the brainstem (Figure 2a,b). Chest computed tomography revealed a mass in the right middle lobe of the lung and mediastinal lymphadenopathy (Figure 2e,f), and F-fluorodeoxyglucose (FDG)-positron emission tomography scans showed marked uptake of FDG, respectively (Figure 2g,h). A transbronchial biopsy of the lymph node confirmed the presence of SCLC. Therefore, the patient was diagnosed with anti-Hu-associated paraneoplastic encephalitis and SCLC in the right middle lobe of the lung reaching the mediastinal lymph node. Four cycles of chemotherapy with cisplatin and etoposide, concurrently with hyperfractionated thoracic irradiation, achieved a complete response in tumour size. Intravenous immunoglobulin (400mg/kg for 5 days) was administered to treat paraneoplastic encephalitis; however, the patient’s supranuclear vertical gaze palsy and memory function remained impaired for 3 years as far as we could observe. On the other hand, the hyperintense lesions at the extreme capsule and surrounding the third ventricle on brain MRI were nearly disappeared (Figure 2c,d).