Atypical Posterior Reversible Syndrome Simulating Medulloblastoma Recurrence: a Potential Pitfall in the Radiological Interpretation

A 12-year-old male patient, diagnosed with group 4 desmoplastic medulloblastoma, previously submitted to surgery and radiotherapy of the skull and neuraxis, classified as high risk of recurrence. He was in adjuvant chemotherapy with cyclophosphamide, cisplatin, and vincristine when presented with seizures. Imaging studies were requested for evaluation.

Initial non-enhanced CT demonstrated hypodensity in the left parieto-occipital white matter.

MRI demonstrated diffuse dural thickening as well as leptomeningeal enhancement in the frontal and parietal lobes.

There were also areas of white matter hyper signal in T2 / FLAIR in both frontal lobes and left occipital and parietal lobes, with no restricted diffusion and no increased perfusion.

The residual neoplastic lesion centred on the IV ventricle was unchanged compared to the previous exam.

These findings may suggest leptomeningeal/ cerebrospinal fluid (CSF) spread along with post-ictal changes. It was decided to continue the supportive treatment after the child was stable.

After 28 days, MRI showed regression of the findings and stable neoplastic lesion in the fourth ventricle.

Medulloblastoma is an embryonal neoplasm tumour of childhood with four molecular subtypes: SHH, WNT, Group 3, and Group 4 [1].

The worst prognosis comes from group 3 and group 4, with a greater chance of recurrence and post-treatment cerebrospinal fluid dissemination [2].

The patient clinically presented seizures during treatment with chemotherapy, and imaging evaluation was indicated.

The presence of areas of leptomeningeal impregnation in the context of group 4 medulloblastoma under treatment should raise the suspicion of CSF spread.

However, clinically the patient was stable with supportive treatment and CSF analysis was normal.

The presence of leptomeningeal impregnation and parenchymal oedema with frontoparietal distribution can be seen in atypical presentations of reversible posterior encephalopathy syndrome (PRES) [3].

Chemotherapy treatment may be associated with PRES, particularly with cyclophosphamide [4].

Normal magnetic resonance imaging after 28 days confirmed the diagnosis of drug-induced atypical PRES, not CSF spread of the disease.

Teaching Points

Medulloblastoma has four molecular subtypes: SHH, WNT, Group 3, and Group 4, and the worst prognosis comes from group 3 and group 4.

Leptomeningeal impregnation in the context of group 4 medulloblastoma should raise the suspicion of CSF spread.

Leptomeningeal impregnation and parenchymal oedema with frontoparietal distribution can be seen in atypical presentations of reversible posterior encephalopathy syndrome.

Chemotherapy treatment may be associated with PRES, particularly with cyclophosphamide.

‘Written informed patient consent for publication has been obtained.’