Objective: To present a case of paraneoplastic cerebellar degeneration whose first sign was ataxia.

Background: Paraneoplastic cerebellar degeneration (PCD) is a rare autoimmune syndrome that presents with rapid progressive ataxia and dysarthria. Often presents before an underlying malignancy is diagnosed such as ovarian, breast, or small-cell lung cancer, where the immune system attacks Purkinje cells in the cerebellum. This report describes the case of a patient with paraneoplastic cerebellar degeneration diagnosed with hepatic adenocarcinoma who began experiencing symptoms of ataxia and dysarthria that progressed rapidly until becoming bedridden.

Method: A 65-year-old male patient, history of alcohol use, presented with mild imbalance and slight dysarthria at age 63 in 2023. In 2024, he developed progression of dysarthria with difficulty pronouncing some words. Neurological examination revealed mild dysarthria with scanning speech, mild bilateral dysmetria, and mild ataxic gait. He underwent physical therapy and used levodopa without improvement. In 2025, there was rapid progression with moderate dysarthria, mild rigidity in the lower limbs, ataxia and tandem gait with deviations, and increased abdominal volume.

Results: Brain MRI showed moderate cerebellar atrophy. Genetic testing for spinocerebellar ataxias was negative. Immunological and infectious causes were negative. CT scan revealed hepatic cirrhosis and a mass on the right with splenomegaly; biopsy was consistent with hepatic adenocarcinoma. Paraneoplastic cerebellar degeneration was diagnosed. Currently, the patient requires support for all basic activities and has significant speech limitations.

Conclusion: PCD is a disease with a poor prognosis, patients experience a rapid progression of symptoms that quickly leads to bed restlessness. Detection of the underlying malignancy can be delayed in a large proportion of these patients, which worsens the prognosis. This case illustrates a rare cause of rapidly progressing ataxia associated with underlying neoplasia, highlighting the importance of considering paraneoplastic syndromes in the differential diagnosis. 

Case submitted to the Brazilian Congress of Movement Disorders, April 2026, not yet accepted, no intention of publication.

CT axial Hepatic adenocarcinoma

CT sagittal Hepatic adenocarcinoma

MRI sagittal Cerebellar atrophy

MRI coronal Cerebellar atrophy

References: Graus F, Dalmau J. Paraneoplastic neurological syndromes. Current Opinion Neurol. December 2012; 25 (6):795-801

Fanous I, Dillon P. Paraneoplastic neurological complications of breast cancer. Exp Hematol Oncol. 2015; 5:29

Pelosof LC, Gerber DE. Paraneoplastic syndromes: an approach to diagnosis and treatment. Mayo Clin Proc. 2010 Sep; 85(9):838-54

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