UNEXPECTED BILATERAL MIDDLE CEREBELLAR PEDUNCLE DEGENERATION FROM UNILATERAL PONTINE INFARCTION: A CASE STUDY

Background / Objective
Bilateral middle cerebellar peduncle (MCP) atrophy is a rare condition, making it challenging for radiologists to determine
the cause among many possible pathologies. Wallerian degeneration (WD) of the MCPs is one potential cause, which needs
to be taken into account especially in patients with a history of pontine infarction. WD is rarely detected due to the lack of
follow-up MRI scans after a stroke, often being discovered accidentally after a long time. This clinical case highlights the
importance of recognizing WD as a possible outcome of pontine infarction to avoid misdiagnosis.
Methods
We reported a case of unexpected bilateral degeneration in the MCP on T2-weighted images in a 62-year-old man who had
presented with a unilateral pontine stroke 8 months earlier.
Results
A 62-year-old man experienced a sudden onset of instability, dizziness, speech impairment, and left-side numbness in the
morning. The patient had cardiovascular risk factors such as hypertension, dyslipidemia, and type 2 diabetes. He was
admitted to a regional hospital for examinations due to the suspicion of cerebral infarction, with a time window of 4.5 hours
after symptom onset. The initial cranial CT and CTA scan revealed no pathological lesions of the brain; however, there was
left vertebral artery hypoplasia and suggested weaker vascularization of the left cerebellar lobe. The patient underwent
thrombolysis, and after the procedure, a control CT imaging showed no pathological findings. On the follow-up CT scan 9
days after the incident, there was a hypodense lesion in the right side of the pons, indicating a late subacute infarction. The
patient was discharged for further rehabilitation in a rehab facility. At the follow-up MR scan 8 months after the stroke, we
detected unexpected bilateral lesions in the MCP with atrophy, which is a rare finding in this area and suggested multiple
differential diagnoses. Based on the history of infarction, it is more likely that we should consider a rare condition: bilateral
MCP WD after unilateral pontine stroke. Bilateral atrophy following a unilateral pontine infarction occurs because the
pontocerebellar tracts (PT) cross the midline in the upper part of the pons. Additionally, the MCP are more vulnerable
because the majority of the PT are located there.
Conclusions
This case highlights the rarity of WD in both MCPs and the importance of further educating radiologists about this condition
and considering WD in patients after a pontine stroke.