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Wallerian degeneration of the bilateral middle cerebellar peduncles

Published:January 03, 2015DOI:https://doi.org/10.1016/j.jns.2014.12.044
      A 61 year old male presented with right sided weakness and was diagnosed with acute left paramedian pontine infarction (Fig. 1 A, B ) secondary to occlusion of the perforating pontine branches of the basilar artery, and was started on antiplatelet therapy and high dose of statin. Follow-up brain Magnetic Resonance Imaging (MRI) after 6 weeks demonstrated bilateral symmetrical hyperintensity in middle cerebellar peduncles on T2-weighted image (Fig. 1 C). Development of symmetrical hyperintensity in the middle cerebellar peduncles following basis pontis infarction or hemorrhage is consistent with Wallerian degeneration of pontocerebellar fibers, and should not be confused with additional infarctions. As these fibers cross the midline at the basis pontis, this phenomenon develops bilaterally, even if the initial pontine lesion is unilateral [
      • Uchino A.
      • Sawada A.
      • Takase Y.
      • Kudo S.
      Symmetrical lesions of the middle cerebellar peduncle: MR imaging and differential diagnosis.
      ]. Wallerian degeneration of pontocerebellar tracts can also occur after pontine hemorrhage and central pontine myelinolysis. Bilateral symmetric involvement of cerebellar peduncles is not limited to Wallerian degeneration and has been reported in several other neurological disorders, including Wilson's disease, hepatic encephalopathy, extrapontine myelinolysis and toluene abuse. Mild diffuse abnormal signal intensity in bilateral middle cerebellar peduncles has been also reported in neurodegenerative diseases such as multiple system atrophy and spinocerebellar degeneration. Bilateral middle cerebellar peduncle lesions are also found in bilateral anterior inferior cerebellar territory infarction, encephalitis and gliomas of the brainstem; however, the involvement is usually asymmetric in these entities [
      • De Simone T.
      • Regna-Gladin C.
      • Carriero M.R.
      • Farina L.
      • Savoiardo M.
      Wallerian degeneration of the pontocerebellar fibers.
      ]. Male carriers of the fragile X premutation who develop progressive intention tremor and ataxia accompanied by progressive cognitive and behavioral difficulties can also demonstrate bilateral symmetric signal abnormality in cerebellar peduncles [
      • Brunberg J.A.
      • Jacquemont S.
      • Hagerman R.J.
      • Berry-Kravis E.M.
      • Grigsby J.
      • Leehey M.A.
      • et al.
      Fragile X premutation carriers: characteristic MR imaging findings of adult male patients with progressive cerebellar and cognitive dysfunction.
      ]; however there is usually additional signal abnormality in the cerebellum, inferior and lateral to cerebellar nuclei, in this condition.
      Figure thumbnail gr1
      Fig. 1Initial brain MRI demonstrates T2 prolongation (A) and restricted diffusion (B) in left paramedian pons consistent with acute infarction. Follow up MRI after 6 weeks demonstrates symmetric axial T2 hyperintensity in bilateral middle cerebellar peduncles (C).

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      References

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        Symmetrical lesions of the middle cerebellar peduncle: MR imaging and differential diagnosis.
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        Fragile X premutation carriers: characteristic MR imaging findings of adult male patients with progressive cerebellar and cognitive dysfunction.
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