200 Section - Gait Disturbance and Loss of Balance in Spinocerebellar Ataxia Type 8 Mimicking Parkinsonian Syndrome: A Case Report

The patient was initially diagnosed with Parkinson’s disease and paraneoplastic cerebellar syndrome. However, normal FP-CIT PET, no evidence of basal ganglia pathology on brain MRI, and genetic testing confirmed spinocerebellar ataxia type 8 (SCA8) with bilateral L5 radiculopathy.

Case Description:

A 59-year-old woman with a history of diffuse large B-cell lymphoma (DLBCL) and right breast cancer presented with progressive gait disturbance, balance loss, and left lower limb pain. Her gait unsteadiness, which began in September 2023, worsened after chemotherapy and autologous stem cell transplant for DLBCL in June 2024, eventually leading to wheelchair dependence. Parkinson’s disease was initially suspected but ruled out due to normal FP-CIT PET findings. Spine MRI in 2025 revealed lumbar pathology, and lumbar nerve root injections relieved coccygeal pain, but her gait remained impaired. Neurological examination showed impaired coordination and balance, but normal strength. Electrodiagnostic studies indicated bilateral L5 radiculopathy. Brain MRI showed mild cerebellar atrophy, and genetic testing confirmed SCA8 without a family history of similar diseases. The final diagnosis was SCA8 and bilateral L5 radiculopathy.

Discussions:

This case highlights diagnostic challenges in a patient with a complex oncologic history and progressive neurological symptoms. Parkinson’s disease was suspected due to gait slowness, rigidity, and functional decline. However, atypical features like truncal and limb ataxia, absence of rest tremor, preserved muscle strength, and poor response to levodopa raised doubts. FP-CIT PET confirmed preserved striatal uptake, ruling out Parkinson’s disease. Paraneoplastic cerebellar degeneration and chemotherapy-induced polyneuropathy were excluded through negative antibody tests and localized L5 radiculopathy. Genetic testing confirmed SCA8, explaining cerebellar ataxia and gait instability. Additionally, bilateral L5 radiculopathy contributed to her symptoms.

Conclusions:

This case emphasizes the importance of a comprehensive diagnostic approach, integrating clinical examination, imaging, electrophysiology, and genetic testing. Early genetic testing is crucial for accurate diagnosis, guiding management, and providing genetic counseling.