Objective: Report a case of Fragile X associated Tremor/Ataxia Syndrome (FXTAS) with acute middle cerebellar peduncle (MCP) infarction, and highlight the potential susceptibility of the MCP for ischemia in patients with FXTAS and poorly controlled vascular risk factors.

Background: FXTAS is caused by expansion in the trinucleotide CGG repeat in the fragile X mental retardation 1 (FMR1) gene. It usually occurs in individuals over age fifty who carry between 55-200 CGG repeats, also known as “premutation” carriers. Cases of FXTAS have also been identified in carriers of “gray zone” alleles (45-54 CGG repeats). Clinically, FXTAS is characterized by kinetic tremor, cerebellar ataxia, cognitive decline, psychiatric symptoms, parkinsonism, neuropathy, and dysautonomia. More than half of males with FXTAS have a hyperintensity on T2-weighted MRI in the MCP, or “MCP sign”.

Methods: A 61 year-old man presented to the outpatient clinic with numbness, tingling, imbalance, anxiety, depression, and poor memory. His grandson has Fragile X syndrome (FXS) and his two daughters are premutation carriers. Genetic testing revealed 54 CGG FMR1 repeats and MRI of his brain showed extensive scattered subcortical T2 hyperintensities, but no “MCP sign”. This combination of physical exam findings, genetic testing, and MRI findings supported a diagnosis of definite FXTAS. Six months later he presented to the emergency department with acutely worsening gait imbalance and vomiting which began after a visit to his chiropractor for neck “re-alignment”. Examination now revealed new gaze-evoked nystagmus, dysmetria, and worsening balance.

Results: MRI/MRA of his brain revealed an acute infarct in the left MCP and atherosclerotic narrowing of the left V4 segment (Figure 1A – FLAIR Image, Figure 1B – Diffusion Weighted Image, Figure 1C – Apparent Diffusion Coefficient Image) . His LDL was 127.

Conclusions: This is the first reported case of an acute MCP infarct in a patient with FXTAS. Isolated MCP infarcts are rare (<0.15% of all strokes) and are typically associated with transient hypoperfusion in the setting of vertebral artery disease and neck manipulation. We suspect that his underlying neurodegenerative process may have put the MCP fibers at risk for further damage. The combination of poorly controlled vascular risk factors and a narrow left V4 segment may have caused transient hypo-perfusion during neck manipulation resulting in preferential damage to vulnerable cerebellar Purkinje cells. This case suggests that aggressive stroke risk factor management is important in patients with FXTAS and that acute worsening of cerebellar signs in these patients should be evaluated emergently.

References: 1. Hall DA, Robertson E, Shelton AL, Losh MC, Mila M, Moreno EG, et al. Update on the Clinical, Radiographic, and Neurobehavioral Manifestations in FXTAS and FMR1 Premutation Carriers. Cerebellum. 2016;15(5):578-86. doi: 10.1007/s12311-016-0799-4. PubMed PMID: 27287737. 2. John S, Hegazy M, Cheng Ching E, Katzan I. Isolated bilateral middle cerebellar peduncle infarcts. J Stroke Cerebrovasc Dis. 2013;22(8):e645-6. doi: 10.1016/j.jstrokecerebrovasdis.2013.03.035. PubMed PMID: 23635919.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/acute-stroke-in-middle-cerebellar-peduncle-in-a-patient-with-fxtas/