Case Report: Radiological diagnosis of atypical meningioma

Introduction

Meningiomas originate from arachnoid cells on the dura’s inner surface and the latter originate from mesodermal and neuronal crest-derived meningeal progenitor cells. Grade I Benign meningioma is seen in 90% of cases, Grade II atypical meningioma is seen in 5-7% of cases, and Grade III malignant meningioma is seen in 1-3% of cases.¹ When compared to WHO grade I meningiomas, grade II meningiomas have a higher re- occurrence and mortality rate. Atypical meningioma has two histological variants:- clear cell meningioma, and choroid meningioma, which is a more aggressive form of meningioma and signals a WHO grade 2 tumor. The risk of brain tumors increases with age, overweight, hormones, obesity, any previous radiotherapy treatments and in certain syndromes such as Li–Fraumeni, Gorlin, Cowden and von Hippel–Lindau syndromes, multiple endocrine neoplasia type 1 and neurofibromatosis type 2 (NF2) can determine the development of meningiomas. The tumors associated with these conditions are often multiple and occur mostly in children. Patients with atypical meningiomas have a survival rate of 63.8% which is 5-year survival. It is difficult to differentiate between grade I and II meningiomas based on radiological criteria; therefore histopathology is required. The Histopathologic features, such as mitoses between 4 and 19 per high-power field, brain invasion, or three of five particular histologies, including spontaneous necrosis, sheeting conspicuous nucleoli, high cellularity, and small cells, are used to make the diagnosis.¹ The Ki-67 proliferation index is inversely proportional to the apparent diffusion coefficient (ADC) value, which helps distinguish low-grade and aggressive meningiomas. Histologically, mitotic activity, necrosis, increased nucleus-to-cytoplasm ratio and tumor cells of atypical meningiomas result in decreased water diffusion rates, thus leading to lower ADC values.² Therefore, early detection of atypical meningioma helps in determining the location, size, and structures that are affected by the growing tumor and helps in early surgical excision of the tumor. Complete surgical resection is frequently curative, reduces peritumoral edema and improves neurological symptoms. However, radiotherapy may be used in cases of incompletely resected or recurring cancers that have not previously received radiation. There are different ways of delivering radiotherapy, including traditional external beam irradiation, Lekshell gamma knife, linear accelerator, and Cyberknife radiosurgery.^1,3,4 Radiotherapy for aggressive cancers can prevent re-occurrence. Immunochemotherapy may be considered if the meningioma is incurable or when all previous treatments (surgery or radiation) fail. While cyclophosphamide, adriamycin, vincristine, ifosfamide/mesna, and adriamycin/dacarbazine have been used to treat patients with aggressive or malignant meningiomas, hydroxyurea, interferon-alpha, tamoxifen, and mifepristone have only modest success in treating patients with recurrent meningiomas.¹

Methods

Diagnostic assessment

Investigations:

CBC investigation: Hb – 10.2 grams/deciliter (g/dl); total Red Blood Cell count – 4.4 million cells, total WBC count – 10,200 cells/cubic millimeter, total platelet count – 2.5. All values were within the normal ranges.

Cerebrospinal fluid examination (CSF) was – clear and colorless in nature, PH – 7.2, protein content – 10 g/L, lactate dehydrogenase (LDH) – 62 units/liter, Glucose – 79 milligram/deciliter (mg/dl), no RBC, no pus cells, no organism seen, and negative for acid – fast bacilli.

Histopathological examination: Excisional biopsy of the tumor showed a grade II atypical meningioma (WHO classification).

4) Radiological investigation – The patient complained of dizziness and headache. A magnetic resonance imaging (MRI) was performed in which atypical meningioma was diagnosed, which showed a well-defined lesion that was arose from the left tentorial leaflet appearing heterogeneously iso to hypointense on T1 image shown in Figure 1 causing a mass effect in the form of effacement of adjacent sulcogyral spaces and compression of the 4th ventricle shown by the lower arrow in Figure 2 with mild dilatation of the 3rd ventricle as shown by the upper arrow in Figure 2, heterogeneously iso to hyperintense with surrounding vasogenic edema on T2 Image as shown in Figures 3 and 4, heterogeneously enhancing with few non enhancing necrotic areas within the tumor on T1 contrast images as shown in Figures 5 and 6. The lesion shows restriction on the diffusion-weighted image (DWI), shown by the arrow in Figure 7 and the apparent diffusion coefficient (ADC) shows low signal intensity, as shown by the arrow in Figure 8.

Figure 1. T1 WI Sagittal section.

A well defined lesion that arose from the left tentorial leaflet appearing heterogeneously iso to hypointense on T1 image.

Figure 2. T1 WI Axial section.

A well-defined lesion that was arose from the left tentorial leaflet causing mass effect in the form of effacement of adjacent sulcogyral spaces and compression of the 4th ventricle shown by the white arrow with mild dilatation of the 3rd ventricle as shown by the white arrow.

Figure 3. T2 WI Coronal section.

A well-defined lesion that was arose from the left tentorial leaflet is a well-defined lesion that was arising from the left tentorial heterogeneously iso to hyperintense with surrounding vasogenic edema causing mass effect in the form of effacement of adjacent sulco-gyral spaces shown by the white arrow.

Figure 4. T2 WI Axial section.

A well-defined lesion that was arising from the left tentorial heterogeneously iso to hyperintense with surrounding vasogenic edema causing mass effect in the form of effacement of adjacent sulco-gyral spaces shown by the white arrow.

Figure 5. T1 With contrast axial section.

A well defined heterogeneously enhancing mass lesion with few non enhancing necrotic areas within the tumor shown by the white arrow.

Figure 6. T1 With contrast coronalsection.

A well defined heterogeneously enhancing mass lesion with few non enhancing necrotic areas within the tumor shown by the white arrow.

Figure 7. Diffusion weighted imaging.

The lesion shows restriction on the diffusion-weighted image shown by the white arrow.

Figure 8. Apparent diffusion coefficient.

The lesion shows low signal intensity on apparent diffusion coefficient (ADC)as shown by the white arrow.

There is dilatation of the bilateral lateral ventricles are shown by the arrow in Figure 9.

Figure 9. T1 WI Axial section.

There is dilation of the bilateral lateral ventricles shown by the white arrow.

MR spectroscopy showed increased choline values and reduced N-acetyl aspartate values, indicating showing increased choline/NAA ratio suggesting that the lesion was malignant in Figure 10.

Figure 10. MR Spectroscopy.

The lesion shows increased choline values and reduced N-acetyl aspartate values, indicating increased choline/NAA ration suggesting that the lesion was malignant.

Therapeutic intervention

Medical management

The patient was managed conservatively and was administered ibuprofen 200 mg tablet once a day for headache, betahistine 16 mg twice daily (histamine agonists) for dizziness, and ondansetron 8 mg sos-if required for nausea and vomiting.

Surgical management

A basal brain tumor sub-total excision of atypical meningioma was performed along with ventriculo-peritoneal shunting for non-communicating hydrocephalus. Post operative adjuvant radiotherapy was started to reduce the size of the tumor and to prevent reoccurrence. A Post operative contrast-enhanced CT scan was performed which showed a lesion that was heterogeneously enhanced on post contrast with surrounding perilesional edema few areas of calcific foci and a central area of hypodensity mostly due to necrosis noted arising from the left tentorial leaflet suggestive of the residual lesion shown in Figure 11A with right-sided ventriculoperitoneal shunt shown by the arrow in Figure 11B.

Figure 11. Contrast enhanced CT axial sections.

There is a heterogeneously enhancing mass lesion on post contrast with surrounding perilesional edema few areas of calcific foci and a central area of hypodensity mostly due to necrosis noted arising from the left tentorial leaflet suggestive of the residual lesion shown by the white arrow in (A) with a right-sided ventriculoperitoneal shunt traversing througfh the right parietal lobe with its tip into the body of right lateral ventricle shown by the white arrow in (B).

Discussion

Meningiomas are common intracranial tumors that can be identified based on their radiological and histological characteristics. However, meningiomas can also mimic other brain tumors. Females are more likely to have meningiomas, and the incidence rate increases with age. Meningioma development has been linked to specific molecular changes and ionizing radiation. Meningiomas are divided into 15 subtypes and are categorized into three classes, with survival and re-occurrence rates getting worse as the grade rises.⁵ Atypical meningioma (WHO Grade II) is a more aggressive form of meningioma with a higher five-year re-occurrence rate (41%), than grade I (benign) meningiomas (12%), and the diagnosis is mainly on histopathologic findings on biopsy as it is difficult to differentiate between grade I and II meningioma based on radiologic criteria. The Symptoms include headache, seizures, change in personality or behavior, development of a localized neurologic impairment, drowsiness, confusion, loss of hearing or tinnitus, fatigue on exertion, projectile vomiting and visual disturbances. If a meningioma is left untreated, it can cause problems such as loss of neurological function, weakness/numbness, hearing or vision loss, and balance problems. Sometimes there is worsening of the signs of persistent headache, the origin of new episodes of seizures, or increased intracranial pressure (e.g., vomiting, swelling of the 2nd cranial nerve), initially a neurological evaluation should be performed followed by radiological studies if necessary initial diagnoses are made using contrast-enhanced CT or MRI. A wait-and-see strategy is used for tiny, asymptomatic tumors, but total surgical removal is the best course of action for symptomatic meningiomas.⁵ Intraoperative MRI helps to obtain tissue samples and remove the tumor during surgery. The biochemical profile and nature of the tumor can be better visualized using on MR spectroscopy. In adults, prognosis is mostly age-dependent. In general, early diagnosis has a better prognosis. If the entire tumor is operable, the outcome is better. Tumor removal is the main goal of surgery, however the patient’s neurological capabilities must be preserved or improved first.⁶ Preoperative embolization of the tumor is widely performed for patient safety throughout the surgical process. In patients when the total tumor is removed, there is a comorbidity risk (any side effect that can cause deterioration in the quality of life) and it may be preferable to leave some of the tumors in place and monitor future growth with routine imaging examinations.⁷ In the case of a GRADE II atypical meningioma, an MRI scan should be performed every 6-12 months. After 5 years, MRI is performed every 2 years.⁸

Conclusion

Sophisticated imaging techniques can be used to diagnose meningioma. The main radiological investigations performed for diagnostic purposes are magnetic resonance imaging (MRI) and computed tomography. Intraoperative magnetic resonance imaging (MRI) was performed to guide tissue samples and tumor removal during surgery. Magnetic resonance spectroscopy (MRS) can be used to investigate the biochemical profile of a tumor and determine the nature of the lesions observed on the MRI. An atypical meningioma was diagnosed in this case, which appeared as a well-defined lesion arising from the left tentorial leaflet with surrounding perilesional vasogenic edema appearing heterogeneously isointense to hypointense on T1 Weighted Image and heterogeneously isointense to hyperintense on T2 Weighted Image and showing heterogeneous enhancement with few areas of necrosis within the contrast images. No evidence of calvarial destruction or intra-osseous enhancement was observed. The combination of necrosis and invasion of the brain is generally associated with an increased risk of re-occurrence of tumor and such a combination shows a radio-resistance nature. MR spectroscopy showed increased choline values and reduced N-acetylaspartate values, thereby showing an increased choline/NAA ratio suggesting a malignant lesion in the case of atypical meningioma. A basal brain tumor excision of atypical meningioma was done along with ventriculoperitoneal shunting for non-communicating hydrocephalus was the surgical management carried out in this case. Post operative adjuvant radiotherapy was started to reduce the size of the remaining tumor as there was incomplete resection due to involvement of crucial structures of the brain and to prevent chances of reoccurrence. Follow-up was advised every 6 months to determine the prognosis of the surgery and re-occurrence of the tumor.