Infiltrating medulloblastoma in a child mimicking Lhermitte-Duclos disease.

Dear Sir,

We would like to present a unique case of a 3-year-old child who presented to our hospital with 15 days complaint of unsteadiness of gait and frequent falls, not associated with fever. On examination, there was gait ataxia otherwise no other significant clinical findings were present. All routine blood investigations were normal. MRI was done [Figure 1] which showed hyperintense right cerebellum with enlargement. Structural architecture of cerebellar folia were well preserved. Vermis was slightly more prominent with more hyperintense signal changes. Post contrast there was no contrast enhancement. Depending on these findings, possibility of Lhermitte–Duclos disease (LDD) was considered and patient was asked to come for follow-up after 1 month. After 1 month there was minimal worsening in gait associated with vomiting and headache. Repeat CT scan and MRI were done [Figure 2]. This time imaging findings showed increase in size of vermis with bright signal changes without significant contrast enhancement. There was mild development of hydrocephalus due to mass effect on 4th ventricle by the vermis. MR spectroscopy was done which showed elevated choline and reduced NAA from vermis. This time due to mild increase in size of vermis and spectroscopic findings, possibility of medulloblastoma was considered and patient was taken for decompressive surgery. Histopathological report showed medulloblastoma with infiltration into the cerebellum.

Figure 1

T2W axial images showing bright and enlarged right cerebellum with preserved cerebellar folia and prominent vermis

Figure 2

CT scan in (a) FLAIR in (b) T2W in (c) shows swollen and bright right side cerebellum with prominent hyperintense vermis. Post contrast T1W axial in (d) and MPR Coronal in (e) shows no significant contrast enhancement. Multivoxel 2D spectroscopy image from vermis in (f) shows elevated choline and significantly reduced NAA

LDD is a rare hamartomatous slow-growing benign cerebellar lesion associated with phakomatosis-like Cowden syndrome. It is usually asymptomatic and presents most commonly with headache and ataxia. It is a rare disease and reported cases are from birth to 74 years and becomes clinically evident in third or fourth decade due to obstructive hydrocephalus.[1]

Typical imaging findings of LDD on CT scan and MRI are described. On CT scan it shows swollen cerebellum with isodensity or hypodensity with mass effect on fourth ventricle. It can be associated with calcifications. MRI shows classical tiger-striped laminated pattern with swollen cerebellum and mass effect. Usually there is no contrast enhancement.[2] Similar findings can be present in unilateral pseudotumoral hemicerebellitis; however, it is usually associated with pial enhancement and should show regression on follow-up scans.[3]

Similar case report of medulloblastoma mimicking LDD has been described in adult. In their case there was mass effect with patchy contrast enhancement and restricted diffusion. As per the authors, restricted diffusion should suggest diagnosis of tumor rather then LDD.[4]

Our case is unique in few aspects. Medulloblastoma mimicking LDD in children is extremely rare. Medulloblastoma infiltrating hemicerebellum along with vermis without contrast enhancement and not showing restricted diffusion as in our case is also rare and not described. Only spectroscopy could suggest possibility of tumor in our case. Thus, we suggest that any case mimicking LDD should be studied with spectroscopy along with other imaging features and follow-up scans for early diagnosis and prompt treatment.