|Ahead of print
En plaque tuberculoma of the dura with extracranial extension in an adolescent mimicking an aggressive en plaque meningioma
Prasad Krishnan1, Nabanita Ghosh2, Sugat Sanyal3
1 Department of Neurosurgery, National Neurosciences Centre, Kolkata, India
2 Department of Neuroanesthesiology, National Neurosciences Centre, Kolkata, India
3 Department of Pathology, Peerless Hospital, Kolkata, India
|Date of Submission||08-Apr-2021|
|Date of Decision||05-Jul-2021|
|Date of Acceptance||03-Aug-2021|
|Date of Web Publication||07-Jan-2022|
Department of Neurosurgery, National Neurosciences Centre, 2nd Floor, Peerless Hospital Campus, 360, Panchasayar, Garia 700094, Kolkata, West Bengal.
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Tuberculosis has been called the “great mimic.” We present an uncommon case of an en plaque dural tuberculoma in an adolescent that was both causing mass effect intracranially and eroding the skull and extending extracranially mimicking an aggressive meningioma and discuss the theories about the origin of dural tuberculomas, enumerate common radiological differential diagnosis and mention ways that may help to identify the disease without recourse to surgery.
Keywords: Dural tuberculoma, en plaque tuberculoma, meningioma, spectroscopy, tuberculosis
| Introduction|| |
Tuberculosis of the central nervous system (CNS) is said to account for 1% of all cases of tuberculosis and 10–15% of extrapulmonary tuberculosis., While the infection usually presents as meningitis, tubercular abscesses and tuberculomas are other commonly encountered pathologies in CNS tuberculosis., Most of the intracranial tuberculomas are intraparenchymal in location, whereas dural-based en plaque tuberculoma is a rarely encountered pathology.,,,
| Case Report|| |
A 17-year-old right-handed boy complained of progressively worsening headache for 6 months, a frontal scalp swelling for 4 months, and occasional blurring of vision and nausea for 1 month. On examination, he had no deficits. Computed tomography (CT) scan of brain showed an ill-defined lesion in the left frontal lobe with perilesional edema compressing the ipsilateral frontal horn. Subgaleal soft tissue was also seen. Bone windows and three-dimensional (3-D) reconstruction of the skull showed a small erosion of the frontal bone on the left side above the frontal air sinus [Figure 1]A–D. Magnetic resonance imaging (MRI) scans showed a T1 and T2 isointense mass with perilesional edema in the left frontal region anterior to the frontal pole with some extra-calvarial scalp tissue. The mass had an arachnoidal plane separating it from the brain at some places, whereas at other places it was difficult to identify any plane of cleavage. Contrast studies showed that it was enhancing on contrast, whereas MR spectroscopy showed elevation of both creatine and lipid lactate peaks [Figure 2]A–F.
|Figure 1: CT scans of the brain showing an ill-defined mass in the left frontal region (A and B) with perilesional edema and mass effect on the ipsilateral frontal horn. A small extracalvarial soft tissue component (green arrows) is also seen. Bone window (C) and 3-D reconstruction (D) show patchy erosion of the frontal bone on the left side|
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|Figure 2: MRI shows the mass is isointense on T1 (A) and T2 (B) sequences and is compressing the brain with perilesional edema. Extracalvarial soft tissue component (green arrows) is also seen. Contrast-enhanced MRI in axial (C), sagittal (D), and coronal (E) planes shows uniform intense enhancement of the mass and the extracranial component as well. MR spectroscopy (F) shows elevated lipid lactate (green arrow) and creatine peaks|
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Our clinical suspicion was of an aggressive en plaque meningioma, and our patient underwent left frontal craniotomy and gross total removal of the lesion with reconstruction of the basal dura with temporalis fascial graft and exteriorization of the frontal air sinus. Intraoperatively, the lesion was essentially thickened dura that was reddish gray, moderately vascular with a poor plane separating it from the brain at places. It was getting its blood supply both from the basal dura and from the pial vessels. The extracranial part of the lesion was subgaleal and had been curetted out while the frontal bone itself was not punched out but was patchily eroded over a small area. Histopathological examination showed multiple granulomas with caseation and Langhans type giant cells, epitheloid cells, histiocytes, and lymphocytes within the dura with finger-like projections into the glial matrix of the brain [Figure 3]A–D. The patient had prompt relief of his headache, nausea, and visual symptoms and once the biopsy report was available, he was put on conventional antitubercular medications—initially, a four-drug regimen (rifampicin, isoniazid, ethambutol, and pyrazinamide) for 3 months and then a three-drug regimen (rifampicin, isoniazid, and ethambutol) for 9 months and finally a two-drug regimen (rifampicin and isoniazid) for 6 months—a total of 18 months. Repeat MRI done after this showed complete disappearance of the lesion, and there was no residual dural enhancement [Figure 4]A–E.
|Figure 3: Hematoxylin and eosin stains at low magnification show (A) multiple granulomas (green arrows) in the background of fibrocollagenous dural substrate (blue rhombus) and (B) the granulomas (green) are seen with finger-like projections in the glial substrate (yellow arrows). At high magnification (C) caseating granulomas with Langhans type giant cells (blue arrows) containing peripherally arranged nuclei in horseshoe pattern are seen and (D) granulomas with epitheloid histiocytes, mature plasma cells, and lymphocytes (green arrows) seen in a background of dural tissue (blue rhombus)|
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|Figure 4: MRI of brain in T1 (A) and T2 (B) sequences shows no residual lesion or mass effect on the brain. Area of peripheral gliosis at the operated site is seen. Contrast-enhanced MR images in axial (C), sagittal (D), and coronal (E) planes show no residual mass or abnormal dural enhancement|
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| Discussion|| |
En plaque tuberculomas are formed either by (a) inflammation following hematogenous seeding directly of the dura by TB bacilli from elsewhere in the body or (b) subpial seeding of the bacilli (rich foci) with subsequent inflammation that then form granulomas, coalesce, and adhere to the dura without breaching into the subarachnoid space., Macroscopically, the presentation is of a solid plaque-like dural-based mass without caseation.,, They commonly involve the frontal and parietal convexity dura, although involvement of the falx and tentorium has also been described., Unlike intraparenchymal tuberculomas that are commoner in younger age groups, most of the few case reports of dural en plaque meningiomas have been described in adults. Kumar et al. describe the average age at presentation as 40.5 years while in the only series of en plaque tuberculomas in literature by Srikanteswara et al.,, no patient was below the age of 20. In all these cases, however, there was no extracranial extension of the lesion.
En plaque tuberculomas present with features of raised intracranial pressure, seizures, or focal neurological deficits. As in our case, the lesions are isodense to hyperdense on CT scans, whereas on MRI they are isointense on T1-weighted sequences and iso- to hypointense on T2-weighted sequences with significant perilesional edema and usually enhance uniformly and avidly in contrast. In the absence of specific radiological features, the disease mimics other pathologies such as meningiomas, dural-based metastases, solitary fibrous tumors, hemangiopericytomas, and gliosarcomas,, and is a diagnostic dilemma. Calvarial tuberculosis too may mimic and en plaque dural tuberculomas erode through the skull but in the former the pathology originates in the skull bones; although there may be reactive changes in the dura, there is usually no brain invasion as the dura is a resilient barrier preventing inward spread. MR spectroscopy may be a useful guide in these cases if a significant decrease in n-acetyl-aspartate to creatine (NAA/Cr) and elevation of lipid-lactate peaks can be demonstrated and may help to avoid unnecessary surgery. One study has stressed the role of cerebrospinal fluid (CSF) analysis and CSF polymerase chain reaction to clinch the diagnosis and institute treatment. Both these tools (CSF analysis and MR spectroscopy) should be employed where feasible as they may aid to clinch a preoperative diagnosis in such atypical lesions.
Our case was peculiar in that the age of the patient was younger than previous cases (we had not found any case in literature below the age of 20), and the lesion was not only growing inwards and compressing the brain but, like an aggressive tumor, was also eroding through the skull and becoming extracalvarial (in contrast to most cases documented in literatures in which the location had been intradural only). While in retrospect the MR spectroscopy should have raised a suspicion of en plaque dural tuberculosis; due to significant edema, no CSF study had been done. Inflammatory lesions often present with disproportionate edema and this along with involvement of frontal sinus should have alerted us to possibilities such as fungal lesions; because of the transcalvarial erosion, we had presumed the lesion to be a meningioma and had not considered any other possibility preoperatively. Surgical excision helped us to both clinch the diagnosis and decrease raised intracranial pressure.
| Conclusion|| |
Isolated en plaque dural tuberculomas are rare pathologies more so in children, and an awareness of this entity with a high index of suspicion and investigations such as MR spectroscopy and CSF analysis (in patients without raised intracranial pressure) may help in early diagnosis and initiation of treatment and avoid surgery.
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Conflicts of interest
There are no conflicts of interest.
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