Keywords
Lhermitte–Duclos disease - dysplastic ganglioglioma of the cerebellum - magnetic resonance
spectroscopy - asymptomatic cases - cerebellum
Introduction
Intra-axial posterior fossa lesions constitute a common problem for the neurosurgeon.
The differential diagnosis differs between adults and children significantly. Metastatic
lesions to the cerebellum remain the most common diagnosis in adults.[1] Lungs, breasts in females, kidneys, and the gastrointestinal tract frequently harbor
the primary lesion.[2]
Alternatively, several other neoplasms may be encountered less frequently as intraparenchymal
lesions of the cerebellum. The differential diagnosis mainly includes hemangioblastomas,
pilocytic astrocytomas, medulloblastomas, and ependymomas.[3] Likewise, infections, such as cerebellitis[4] and cerebellar infarction,[5] may also present as space-occupying lesions of the cerebellum.
Depending on the diagnosis of the primary lesion, the radiological appearance, its
spread, and the patient's general performance, surgery provides the most effective
treatment option. Herein, we present the rare case with Lhermitte–Duclos disease (LDD)
and discuss our diagnostic approach and treatment challenges.
Case Report
A 57-year-old man presented at the outpatient department complaining about transient
difficulty in walking, dizziness, and a persistent occipital headache. Physical examination
identified cerebellar ataxia with positive cerebellar signs.
The T2-weighted magnetic resonance imagings (MRIs) demonstrated a high-intensity lesion
at the right cerebellar hemisphere without obstructive hydrocephalus ([Figs. 1], [2]). At the lesion's periphery, there were several indolent venous dilations. We initially
considered surgery to establish a histopathological diagnosis and decompress the posterior
fossa neural structures.
Awaiting surgery, the patient's symptomatology improved with minimal doses of steroids.
Based on the prominent striated folial pattern, an experienced neuroradiologist raised
the suspicion for a dysplastic ganglioglioma of the cerebellum. Hence, the patient
underwent a second MRI, including advanced imaging techniques. Cerebellar infarction
and cerebellitis were excluded due to the absence of abnormalities in the MR perfusion
and diffusion, respectively. Similarly, highly destructive lesions such as metastases
were rejected since the MRI spectroscopy showed a marginally increased choline to
creatinine ratio ([Fig. 3]). Of note, the levels of N-acetyl aspartate were at the lower average values compared
with the other hemisphere, and the lipid concentration was within normal values.
Finally, we preferred a more expectant approach since the patient's symptomatology
improved. There were no clinical manifestations or positive family history for Cowden's
disease. The chest and abdominal computed tomography findings were unremarkable. Therefore,
the patient is scheduled for follow-up every 6 months at the outpatient neurosurgery
department with regular MRIs.
Discussion
Dysplastic ganglioglioma of the cerebellum, also known as LDD, was initially described
in 1920.[6] It is characterized by enlarged cerebellar folia with abnormal ganglion cells in
the granular layers of circumscribed cerebellar regions. To date, less than 300 cases
have been described globally. It commonly affects males and females equally, particularly
in the third and fourth decades of life.
In rare cases, there is familial predisposition.[7] LDD is considered a member of the disease spectrum known as Cowden–Lhermitte–Duclos
syndrome, associated with PTEN (phosphatase and TENsin homolog deleted on chromosome
10) germline mutations.[8]
[9] The complete syndrome includes mucocutaneous lesions, thyroid diseases, and breast
and ovarian tumors.[10]
LLD commonly presents with posterior fossa clinical manifestations, such as ataxia,
hydrocephalus, and cranial nerve palsies. The MRI shows the typical tiger-striped
appearance. There is a regionally increased cerebral blood volume in perfusion images.
MR spectroscopy reveals an increased level of lactate and decreased level of myoinositol
and N-acetyl-aspartate, as observed in low-grade gliomas but with decreased choline
levels.[11] Undoubtedly, the definitive diagnosis is always set from the histopathology results.
However, all currently available evidence shows that MRI, including magnetic resonance
spectroscopy, could safely set the diagnosis.[12] Unfortunately, there is no diagnostic accuracy data on the performance of MRI in
LDD, since the available evidence originate from a limited number of case reports,
due to the rarity of the clinical entity under study. On top of that, an expectant
approach with a regular patient follow-up seems to be a more legally defensible strategy
than to proceed with an aggressive posterior fossa surgery, considering the potential
perioperative risk the patient's preference.
In symptomatic cases, surgical resection remains the treatment of choice. However,
the optimal treatment is under debate regarding asymptomatic cases due to the ill-defined
lesion's margins. Another indication for surgery is to establish a definite histological
diagnosis. The latter shows thickening and hypermyelination of the outer molecular
layer, loss of Purkinje cells and white matter, dysplastic ganglion cells with rounded
nuclei, and abundant mitochondria invading the inner granular layer.[5] The prognosis after surgery is encouraging, even though rare occasions of tumor
recurrence have been described.[13]
Fig. 1 The characteristic gyriform pattern with enlargement of cerebellar folia for Lhermitte-Duclos
disease shown in T1-weighted (A) axial and (B) sagittal magnetic resonance imaging scans.
Fig. 2 (A) Magnetic resonance imaging scan hypointense on T1-weighted images; (B) axial and (C) sagittal hyperintense on T2 (figure) weighted images, with parallel linear striations.
Fig. 3 The magnetic resonance spectroscopy demonstrates an elevated level of lactate and
decreased levels of choline and myoinositol.
Conclusion
The management of posterior fossa lesions requires a multidisciplinary approach, including
an experienced neuroradiologist. LDD should be considered in the differential diagnosis
of intra-axial posterior fossa lesions. Advanced MRI is priceless in asymptomatic
cases to avoid unnecessary surgical interventions.
