By Dr. Fatima Mahmood
Abstract:
We report the case of a 14-year-old boy diagnosed with a
posterior fossa medulloblastoma who exhibited progressive
neurological symptoms. Preoperative MRI revealed a large,
well-defined lesion centered at the fourth ventricle with both
superior and inferior extensions. Surgical resection confirmed
WHO Grade IV medulloblastoma on histopathology.
Postoperatively, the patient developed complications, and
follow-up imaging revealed a residual lesion as well as a new,
incidental optic chiasmal mass consistent with an optic
pathway glioma. The patient was planned for craniospinal
irradiation (CSI) using 36 Gy in 20 fractions with concurrent
vincristine chemotherapy, and a 10-fraction boost (18 Gy) to
both medulloblastoma and optic glioma. This case highlights
the importance of vigilant postoperative imaging, recognition
of secondary pathologies, and a multidisciplinary treatment
approach in pediatric neuro-oncology.
Introduction
Central nervous system (CNS) tumors have the second-highest
frequency of pathogenic germline mutations among pediatric
cancers. Among CNS tumors, medulloblastomas show the
second highest mutation rate, with pathogenic variants
identified in 13.5% of cases [1]. Medulloblastoma is the most
common malignant pediatric brain tumor, typically presenting
at a median age of 7 years, with a male predominance \[2].
These tumors often obstruct cerebrospinal fluid (CSF) flow,
resulting in increased intracranial pressure and symptoms such
as morning headaches, vomiting, and ataxia \[3].
Optic pathway gliomas (OPGs) are low-grade tumors
involving the precortical visual pathways and account for
2–5% of pediatric CNS tumors \[4]. They may occur
sporadically or in association with neurofibromatosis type 1
(NF1) \[5]. OPGs display variable growth patterns, making
management complex and typically guided by the degree and
progression of visual impairment rather than size alone \[6].
Discussion:
The co-occurrence of medulloblastoma and optic nerve glioma
in a pediatric patient represents an exceptionally rare clinical
scenario, with few cases reported in the literature (7). Both of
these central nervous system (CNS) tumors are
well-characterized individually in pediatric oncology;
however, their synchronous or metachronous presentation in
the same patient raises important considerations regarding
diagnosis, treatment planning, and long-term outcomes.
Medulloblastoma (MB) is the most common malignant CNS
tumor in children, comprising 15–20% of all pediatric CNS
neoplasms and 64% of pediatric embryonal tumors (8,9).
Clinical symptoms typically include intracranial hypertension
and posterior fossa mass effect, manifesting as headache,
nausea, ataxia, and visual disturbances (10). Histologically,
MB is classified into four subtypes: classic (68–80%),
desmoplastic/nodular (7%), MB with extensive nodularity
(3%), and large cell/anaplastic (10–22%), the latter associated
with a more aggressive course (11). In this case, the patient
presented with classic symptoms of a posterior fossa tumor,
including gait instability, left-sided weakness, dysarthria, and
headaches. MRI revealed a large lesion centered in the fourth
ventricle with superior and inferior extension, consistent with
typical medulloblastoma radiological patterns.
In contrast, optic pathway gliomas are typically low-grade
astrocytomas, often pilocytic, and frequently associated with
neurofibromatosis type 1 (NF1) (12). However, this patient did
not exhibit clinical stigmata of NF1, suggesting a sporadic
optic glioma. A new optic chiasmal lesion identified on
follow-up imaging coincided with the patient’s progressive
visual decline. While optic gliomas have been sporadically
reported as secondary CNS neoplasms, the timing in this case
suggests a coincidental, rather than treatment-induced,
etiology.
In 1977, G. R. Bhangui reported the case of multiple primary
brain tumors in a 12-year-old girl, including medulloblastoma,
optic nerve glioma, ganglioglioma, and pilocytic astrocytoma
(7). Another case describes the synchronous occurrence of
glioblastoma and medulloblastoma in a 5-year-old boy with
suspected cancer predisposition syndrome (13). To our
knowledge, this is the second documented case of both
medulloblastoma and optic nerve glioma occurring
simultaneously in the pediatric population.
While no direct causal relationship between optic nerve
gliomas and medulloblastomas has been definitively
established, recent studies suggest that aberrant Sonic
Hedgehog (Shh) signaling may be implicated in both entities
(14, 15). The SHH signaling pathway plays a critical role in
neural development, acting as a mitogen for precursor cell
populations in the brain, retina, optic stalk, and cerebellum
(16). Dysregulation of this pathway, particularly in cerebellar
granule neuron precursors, is known to drive the development
of the Shh-subtype of medulloblastoma (17). Growing
evidence also implicates this pathway in the pathogenesis of
other CNS tumors, including gliomas (18,19). MDT and
vigilant approach is warranted.