PP1501 - Paraneoplastic Cerebellar Degeneration: Clinical Factors and Vestibular Test Findings

Introduction

Paraneoplastic cerebellar degeneration (PCD) is a rare condition in which the presence of cancerous tumors causes aberrant mechanisms of autoimmunity. It is hypothesized that tumor-mediated antibodies are produced in response to cancer, which compromises the function of Purkinje cells within the cerebellum. As a result, patients with PCD can experience vertigo, imbalance, and gait instability. This case presentation will examine the symptoms and vestibular findings of a patient with PCG, and the journey to receiving a diagnosis.

Clinical Presentation

A 67-year-old female presented for a vestibular evaluation for concerns of dizziness, gradual imbalance, and lower extremity weakness characterized as a “heaviness” sensation. Symptoms began approximately one month before the evaluation. At the time of the vestibular evaluation, she denied any associated symptoms or history of migraines/headaches or cervicalgia. Significant medical history included a history of left breast cancer status post mastectomy in 2013, hypothyroidism, and right hip replacement. There was no known family history of neurological or gait disorders.

 All portions of videonystagmography (VNG) testing were unremarkable apart from continuous, pure down-beating nystagmus observed upon both right and left Dix-Hallpike. Another noteworthy finding was the presence of bilaterally reduced VOR gain of the posterior semi-circular canals (SCCs) with bilateral corrective saccades observed upon video head impulse testing (vHIT), with all other SCCs spared. The patient was referred to neurology for further evaluation.

The patient had an outpatient neurology consultation one month following vestibular testing and a subsequent evaluation a month later. In addition to continued gait imbalance, she developed difficulties with left handwriting and an inability to control movement of her left leg. Significant examination findings included truncal ataxia, rotary lateral gaze nystagmus of left eye, and positive Babinski. The managing neurologist’s differential included paraneoplastic syndrome; confirmatory tests were ordered but were not completed. With a continued progression of symptoms, she was seen in the emergency department (ED) three times over two months. While in the ED, laboratory tests confirmed present Anti-yo antibodies consistent with PCD; this was corroborated with cerebellar degeneration observed upon MRI.

Conclusion

PCG results in direct dysfunction of Purkinje cells of the cerebellum (Mendes et al., 2022). Purkinje cells have projections to the vestibular nuclei; therefore, the presence of downbeating nystagmus observed is possibly due to dysfunction of flocculonodular lobe. While downbeating nystagmus was not observed during visual fixation, bilateral posterior canal dysfunction upon vHIT could be due to superimposed nystagmus, central dysfunction, or due to other ocular abnormalities caused by cerebellar degeneration. Patients with PCD can be seen in the vestibular clinic given symptoms of vertigo, dizziness, and gait instability, which can often precede other central signs and symptoms (Mendes et al., 2022). Given the rapid disease progression documented within medical literature, it is prudent for audiologists to gather cancer history when central vestibular findings are observed, and promptly refer patients to neurology for medical management.