Keywords
low-grade astrocytoma - dural destruction - calvarial destruction - magnetic resonance
imaging - surgical excision
Introduction
Most of the literature on intra-axial lesions causing calvarial and dural destruction
comes from case reports for glioblastoma, lymphoma, metastasis, and aggressive meningioma,[1] extremely uncommon with low-grade gliomas[2] cases reported so far have been mostly oligodendrogliomas.[3] To our knowledge, only one case of calvarial and dural erosion with low-grade astrocytoma
has been well documented. This article describes the unusual case of a 23-year-old
male patient with a left-sided intra- and extracranial frontal low-grade astrocytoma
spontaneously destroying the overlying dura and calvaria, who underwent maximal safe
resection.
Case Presentation
A 23-year-old man, previously healthy, presented to us in the emergency room with
generalized convulsions. This was his second episode; there was a history of headaches
and occasional vomiting 1 month before admission. On examination, he was fully conscious,
orientated, and without neurological deficits. A soft tissue through bony round defect
(2 cm in diameter) was palpable in the left frontal area.
A computed tomographic (CT) brain scan revealed a mass of low density with isodensity
component in the left frontal region as well as an area of destruction of the ipsilateral
frontal bone; a bone window revealed an overlying destruction of the calvaria ([Fig. 1A–C]). Brain magnetic resonance imaging (MRI) showed a 3.5-cm intra-axial lesion in the
left frontal area that was hypointense on T1 and hyperintense on T2 with enhancement of superficial component on gadolinium causing motheaten, permeative
destruction of calvaria. It also showed inward displacement of the hypointense dura,
suggesting extra-axial extension ([Fig. 1D–F]).
Fig. 1 (A–C) Computed tomography scan showing hypodense lesion with isodensity component in the
left frontal region with overlying calvarial destruction, slightly enhanced after
contrast. (D–F) Brain magnetic resonance imaging showing a 3.5-cm intra-axial lesion in the left
frontal area that was hypointense on T1 with enhancement of superficial component on gadolinium causing motheaten, permeative
destruction of calvaria. It also showed inward displacement of the hypointense dura
(arrow), suggesting extra-axial extension of the lesion, well seen in fluid-attenuated inversion
recovery sequence.
Left hemicoronal skin incision over the tumor was made. After the scalp was opened,
the erosions of the calvaria were immediately visible. The tumor mass was seen and
had not infiltrated the soft tissue of the overlying scalp. Craniectomy was performed
by using wide margins around the destroyed calvaria. After the bone flap was removed,
a tumor mass was found in the epidural space; the dura under this mass has a ring-shaped
perforation. Both the epidural and subdural part of the tumor mass was easily separate
off the dura mater. The dura was then open in a star-shape manner and attention was
focused on the intraparenchymal part of this lesion. The bulk of the tumor was gray
and soft without clearly identifiable margins between tumor and surrounding normal
brain tissue in the depth. Near-total resection was achieved, the dura was repaired
with dural substitute, the bone flap was then inspected, the rest tumor resected,
and acrylique cement was used to repair the defect ([Fig. 2A–C]).
Fig. 2 Tumor eroding through the bone before the bone flap was created (arrow) (A). The bone flap with the rest tumor involved both tables and the diploe of the skull
(B). Epidural tumor leaving the dura that has a ring-shaped perforation; dotted circle
indicates the tumor (C).
Table 1
Summary of clinical characteristics of five cases of astrocytoma with calvarial erosion
reported in English literature up to date including our case
|
First author, year of publication
|
Journal
|
Age year/sex
|
Clinical presentation
|
Location and type of overlying erosion bone (CT)
|
Radiological findings of the mass (CT / MRI)
|
Surgical finding
|
Histology
|
Outcome/follow-up
|
|
Osborn and Ley (1986)[5]
|
American Journal of Neuroradiology
|
26/F
|
Tinnitus, visual field defects, headaches, seizure
|
Left frontal bone, 5 cm bony erosion of the inner table and thinning of the diploe
|
Large left frontal mass with edema and contralateral shift
|
Total resection
|
Low-grade astrocytoma
|
Good
|
|
Khan and Hashmi (2007)[2]
|
Pediatric Neurosurgery
|
15/M
|
Generalized convulsions, palpation of the bony swelling in the right parietal area
|
Right anterior parietal region, remodeling and scalloping of the internal table of
the skull
|
2-cm lesion in the right parietal area, hypointense on T1, hyperintense on T2, cystic
component superficially located
|
Total resection (no invasion of the bone; the dura was bulging locally)
|
Low-grade astrocytoma
|
Good without recurrence or seizures / 4 months
|
|
Handzhiev et al (2017)[6]
|
Clinical Neuroscience
|
64/M
|
Headaches, right hemianopsia, right hemiparesis, palpation of the firm tissue mass
with bony consistence over the left parietal area
|
Left parietal region, erosion
of the inner table and the
diploe with the intact external table
|
Heterogeneous left parietal mass
|
Total resection (the dura has a ring-shaped perforation)
|
Low-grade astrocytoma
|
Good without recurrence or seizures /4 months
|
|
Lee et al (2017)[7]
|
Brain Tumor Research and Treatment
|
28/F
|
Symptoms
due to increased intracranial pressure
|
Bony thinning on the right frontal bone
|
Cystic and enhancing mass on the right frontal lobe, dural enhancement suspected to
be the dural tail sign
|
Total resection (the dura was intact and there were no abnormal findings at the craniotomy
eroded bone site)
|
Pilocytic astrocytoma
|
Recurrence at 9 months follow-up, second surgery (anaplastic astrocytoma).
Postoperative radiation therapy, no tumor recurrence/ 3 years
|
|
Our case
|
_
|
23/M
|
Generalized convulsions, headaches, vomiting, palpation of the soft tissue through
bony round defect in the left frontal area
|
Left frontal bone, destruction of both tables and diploe of the skull
|
3,5-cm intra-axial lesion in the left frontal area, hypointense on T1, hyperintense
on T2, enhancement of superficial component, inward displacement of the hypointense
dura suggesting extra-axial extension
|
Total resection (tumor eroding through the bone, the dura has a ring-shaped perforation)
|
Low-grade astrocytoma
|
Good without recurrence or seizures / 6 months
|
Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging.
Postoperatively, the patient's clinical symptoms were improved. The histopathologic
specimens showed a fibrillar background of a glial tumor proliferation of low cell
density composed of cells with nucleus showing mild cytonuclear atypia without mitosis,
necrosis, or endovascular proliferation, tumor cells are positive for glial fibrillary
acidic protein, negative for isocitrate dehydrogenase 1 and low proliferative index
(Ki67) ([Fig. 3A–D]). No pathological difference existed between intra and outer dura part; the diagnosis
of low-grade astrocytoma without bone or dural infiltration was confirmed. A 6 months'
follow-up brain MRI post-surgery showed postoperative changes without evidence of
recurrent. The patient was kept on anticonvulsants for 12 months and has also had
no seizures since discontinuation.
Fig. 3 Microscopic image showing on a fibrillar background a glial tumor proliferation of
low cell density composed of cells with nucleus demonstrating mild cytonuclear atypia
without mitosis, necrosis, or endovascular proliferation (A: ×10) hematoxylin and eosin staining. Photomicrograph showing tumor cells positive
for glial fibrillary acidic protein (B: ×100), negative for isocitrate dehydrogenase1(C: ×100) and low proliferative index (D: Ki67 × 100).
Discussion
Intracranial masses that may produce calvarial erosion include meningioma, lymphoma,
intracranial cysts, dural metastases, chronic juvenile subdural hematomas, and anomalous
development of the cisterna magna.[1]
[3]
Calvarial erosion caused by a superficially located glioma is rare; most of the literature
comes from case reports for glioblastoma.[3] Destruction of dura and calvaria by low-grade gliomas is extremely uncommon[2] cases reported so far have been mostly oligodendrogliomas.[3]
These superficially located gliomas usually present with seizures. Brain CT will show
a hypodense lesion located superficially and without enhancement on contrast. It will
have irregular margins. Calcification is absent in astrocytomas, and bone windows
will show the erosion above. The erosion is presumed to be a pressure erosion caused
by the peripheral location and slow-growing nature of this lesion.[4] Brain MRI will show a hypodense lesion on T1 and hyperdense lesion on T2; the lesion does not show any enhancement on contrast injection. Our case is unusual,
which showed an enhancement area in and under the bone destruction.
To the best of our knowledge, four case reports about low-grade astrocytoma with bone
erosion have been made, of which three are representative and well documented.[2]
[5]
[6]
[7] The clinical characteristics (demographics, clinical presentation, calvarial erosion
and tumor localization, surgical findings and outcomes) of five cases including our
case were gathered on a summarized table ([Table 1]). Handzhiev et al described a case of parietal low-grade glioma with destruction
of the dura and calvaria in the absence of prior surgery or radiation; in his case
the tumor mass was found beneath the intact external table in the diploe and the dura
under this mass had a ring-shaped perforation.[6] Khan and Hashmi reported a case of a low-grade astrocytoma causing calvarial scalloping
in the right anterior parietal region with intact dura.[2] In the context of the reviewed cases, there are some peculiarities in our patient;
our case is analogous to the case of Handzhiev et al, however, with involved both
tables of the skull that not have been described before in low-grade astrocytoma.
The calvarial thinning or remodeling caused by low-grade gliomas is thought to result
from their chronic mass effect, by displacing the overlying layer of cerebrospinal
fluid and transmitting brain pulsations directly to the inner table of the skull.
Pressure thinning of the inner table of the skull may be caused by Pacchionian granulations
close to the midline.[1]
Conclusion
Superficially located low-grade astrocytoma can exceptionally cause calvarial and
dural destruction. Although this is extremely uncommon, MRI may include low-grade
astrocytoma in the differential diagnosis in such cases.
