Coexistence of spinocerebellar ataxia type 3 and multiple sclerosis: a rare case report case presentation

Abstract

Case Presentation: A 56-year-old woman developed progressive imbalance, dysarthria and dysphagia since 2015. Over the following years, she experienced worsening of gait instability, leading to recurrent falls and the need for a walking aid. There was a family history of ataxia, with five affected siblings and a father with similar symptoms. Neurological examination showed scanning speech, wide-based ataxic gait, marked postural instability, horizontal and upbeat nystagmus, bilateral saccadic hypermetria, and limb dysmetria, more pronounced in the lower limbs. Strength and tone were preserved, with hyperreflexia and mild impairment of vibratory sensation in the lower extremities. Genetic testing confirmed Spinocerebellar Ataxia Type 3 (gene ATXN 3: 28/63 CAG repeats). Brain MRI demonstrated pontocerebellar atrophyy compatible with hereditary ataxia, but also multiple T2/FLAIR hyperintense lesions in the supratentorial white matter and spinal cord, including periventricular lesions perpendicular to the lateral ventricles, fulfilling criteria for dissemination in space suggestive of demyelinating disease. Cerebrospinal fluid analysis showed positive oligoclonal bands, while anti-aquaporin-4 antibodies and visual evoked potentials were normal- incluir o resultado do PESS que esta no prontuário-. Based on these findings, concomitant Multiple Sclerosis was considered. Discussion: Spinocerebellar ataxia type 3 (SCA3), or Machado-Joseph disease, is the most common autosomal dominant ataxia, marked by progressive cerebellar dysfunction with variable extracerebellar features such as pyramidal signs, oculomotor changes, peripheral neuropathy, and dysarthria. Its coexistence with multiple sclerosis (MS) is rare and may complicate evaluation, as both can cause cerebellar symptoms and gait impairment. In this case, family history and genetic testing confirmed SCA3. However, left-sided vibratory loss, along with MRI abnormalities and cerebrospinal fluid changes, suggested an associated demyelinating disease. Distinguishing neurodegenerative white matter changes from true demyelinating lesions is challenging, making longitudinal clinical and radiological follow-up essential. Final Comments: The coexistence of spinocerebellar ataxia type 3SCA 3 and multiple sclerosisMS is extremely rare and represents a diagnostic challenge, potentially influencing clinical follow-up and therapeutic decisions. We should consider the possibility of comorbidities when unusual signs Tappear in patients with SCA, as presented by our patient.his finding highlights the importance of careful evaluation of imaging and laboratory findings in patients with hereditary ataxias who present with white matter lesions suggestive of demyelination.