Giant Extra-Axial Cerebellopontine Angle Ependymoma with Sub-Axial Cervical Extension: A Unique Subtype of Infratentorial Ependymoma
Year: 2024
Type: article
Study design: Case Report
Abstract: Sir, Ependymomas are glial tumors that typically arise from the ependymal lining of the ventricles and central canal. About two-thirds of intracranial ependymomas occur infratentorially. It is very uncommon for an infratentorial ependymoma to arise away from the fourth ventricle.[1] Only seven such cases of pure extra-axial infratentorial ependymomas have been reported in literature to date and all of them originated in the cerebellopontine (CP) angle. We report findings of a giant extra-axial ependymoma with epicenter in the right CP angle, that had grown incessantly, extending from basal cisterns superiorly to the spinal compartment, almost reaching the upper body of C4. Such a giant extra-axial CP angle ependymoma with extensive sub-axial cervical extension has not been hitherto described. We review the literature regarding similarities and differences between typical fourth ventricle and these atypical extra-axial ependymomas. Thirty-seven-year-old gentleman with occipital headache and pain at the back of the neck for four months and features of raised intracranial pressure (ICP) due to obstructive hydrocephalus underwent ventriculoperitoneal (VP) shunt at an outside hospital. The patient presented thereafter to our institute for the management of the tumor. His vomiting had resolved after VP shunt but the occipital headache was persistent. Neurological examination revealed papilloedema, but no cranial nerve, motor, or sensory deficits. There was no hearing loss. He had cerebellar nystagmus in both eyes, truncal ataxia, and signs of bilateral appendicular ataxia (right more than left). Magnetic resonance imaging (MRI) showed a single, well-defined, extra-axial mass lesion in the posterior fossa and cervical spine. Epicenter was in CP angle, extending from tentorium superiorly to upper body of C4 vertebrae inferiorly. Lesion was crossing to the opposite side across the brainstem and occupying perimesencephalic, prepontine, and cerebellomedullary cisterns. It was compressing the cerebellum, brainstem and pushing the fourth ventricle to the opposite side. Tumour encased both the vertebral arteries and basilar artery. It was hypointense on T1, hyperintense on T2 relative to grey matter with heterogeneous ill-defined contrast enhancement. There was no diffusion restriction [Figure 1 a-d]. There were no spinal metastases. A working diagnosis of lower cranial nerve schwannoma was made based on pre-operative radiological features.Figure 1: (a) Pre-operative T2 sagittal MR: giant extraaxial heterointense tumor in CP angle extending from tentorium superiorly to upper body of C4 body inferiorly. (b) T2 axial MR: Extraaxial mass in right CP angle with compression and shifting of fourth ventricle towards opposite side. Note that the lesion is distinct from the fourth ventricle. The lesion is crossing across brainstem towards opposite side and is encasing the basilar artery. No extension into IAC is seen. (c and d) axial and sagittal T1 contrast MR: ill-defined heterogenous contrast enhancement. (e) and (f) Intra-operative microscopic image showing the cervical extension of the tumor with well-defined plane from the cord parenchyma and the accessory nerve adherent to the tumor (black arrow)The patient underwent a right suboccipital craniotomy with C1-C3 laminectomy and near-total tumor excision. Tumour was yellowish, soft-to-firm, moderately vascular, extra-axial, and had a well-defined plane from cord parenchyma and cerebellum, except for a small lateral part of the brainstem to which it was densely adherent. Intraoperatively, there was no connection of lesion to the fourth ventricle. Spinal accessory nerve on the right side was adherent to the tumor [Figure 1e and f]. A near-total decompression of tumor was done, leaving behind a thin rim close to the brainstem [Figure 2a and b]. As per operative findings, we suspected the tumor to be a schwannoma, possibly arising from the accessory nerve.Figure 2: (a and b) Post-operative T1 contrast axial and sagittal MR showing gross total excision of the tumor. (c) H and E at 10×: tumor cells with round to oval nuclei, evenly dispersed granular chromatin in fibrillary background. Few perivascular pseudo rosettes seen. (d) Immunohistochemistry (IHC) for EMA at 40× magnification with dot and ring-like positivity. (e) IHC for S100 at 10×: positive. (f) Microscopic image at 10× showing pseudorosettes marked with an arrowPostoperative course was uneventful with no new neurological deficits. Histopathological examination showed a cellular tumor with extensive fibrillary background, microcystic spaces, vague fascicles, and occasional cells with pleomorphic nuclei. Tumour showed immunopositivity for S100, vimentin, and para nuclear dot-like positivity for EMA [Figure 2 c-f]. Blepharoplasts were not seen on routine staining and microscopic examination; however, they are not an essential diagnostic feature.[2] These findings were consistent with a diagnosis of ependymoma. He was planned for adjuvant radiotherapy as per the current treatment protocols but the patient did not give consent for any adjuvant therapy. At 9 months follow-up, the patient has remained asymptomatic. Follow-up MRI at 6 months post-surgery showed a small 2 × 1 cm residual in the cerebellomedullary cistern and linear enhancement along the upper cervical cord. Further follow-up is required. Fourth ventricle ependymomas arise from its floor, roof, or the lateral recess. They usually remain confined within the ventricle or extend to CP angle cistern or cisterna magna via foramina of Luschka and Magendie respectively, to become extra-axial.[3,4] Such ependymomas with a tongue like protrusion from the fourth ventricle to the cisterns/subarachnoid space have been termed “Plastic Ependymomas” by Courville and Broussalian.[5] They can grow to have a large extension by following the contours of the cistern due to their plastic nature. On the other hand, pure extra-axial CP angle ependymomas are extremely rare and have no connection whatsoever to the ventricle/ependymal surface. As discussed previously, these extra-ventricular ependymomas are more common in a supratentorial location rather than infratentorially due to reasons unknown.[1] These extra-axial extra-ventricular ependymomas have been reported earlier in CP angle,[3,4,6–10] interhemispheric fissure,[11] cervicothoracic junction,[12,13] pituitary fossa[14] and spinal cord.[15] Furthermore, ependymomas of soft tissues are also known to occur in the ovary, lung, mediastinum, and pelvis apart from the neuraxis.[16–19] These extra-axial ependymomas are believed to arise from embryological ependymal cell rests present in extra-ventricular regions like CP angle, falx, and other intra/extracranial sites. The imaging characteristics of ependymomas are nonspecific and hence an accurate preoperative diagnosis is difficult to make.[1,9] However, the presence of a CP angle mass in a middle-aged patient with no hearing loss, and in the absence of typical radiological features of meningioma/epidermoid should raise the suspicion of ependymoma. A literature review revealed seven previously reported cases of extra-axial ependymomas in or originating from the CP angle [Table 1]. These reported extra-axial CP angle ependymomas were either confined to CP angle or extended to the cavernous sinus, IAC, and pineal region,[3,4,6–10] interhemispheric fissure,[11] cervicothoracic junction.[12,13] However, our case is unique in that it was a giant (9.4 × 6.0 × 5.5 cm), purely extra-axial CP angle ependymoma, extending from tentorium superiorly to the upper border of C4 body inferiorly.Table 1: Summary of eight cases of pure extra-axial CPA ependymomas till dateInterestingly, despite their propensity to attain the colossal size and extensive involvement of CP angle cistern, most of the extra-axial CP angle ependymomas did not present with features of typical CP angle syndrome. It is interesting to note that none of the reported extra-axial CP angle ependymomas (including our case), despite extensive involvement of the CP angle cistern and even IAC in one case, presented with hearing loss. Only two of the eight cases of CP angle ependymoma had a preoperative facial weakness. Instead, they presented like typical fourth ventricle ependymomas, that is, with features of raised ICP (headache, vomiting) with cerebellar sign/symptoms. Unlike typical fourth ventricle ependymomas which present at a younger age (mean age = 23 years),[1] the mean age of presentation in extra-axial CP angle ependymomas is 46.25 years which is almost double. Male and female incidence of fourth ventricle ependymomas is approximately equal,[1] whereas it is 3:1 in the case of extra-axial CP angle ependymomas [Table 2].Table 2: Differentiating clinical features of two types of infratentorial ependymomasEpendymomas are WHO grade II or grade III tumors. All reported extra-axial CP angle ependymomas have been reported as low grade (grade II) ependymomas. None of them have been described as grade III (anaplastic). Prognosis in ependymomas is determined by age of patient, the pathological grade of tumor and the extent of surgical resection.[1,7,20] Although long-term follow-up is not available (longest follow-up of 3 years),[3] patients with extra-axial ependymomas seem to have a better prognosis than typical fourth ventricle ependymomas as they have age in their favor, they are low grade (grade II) and it is possible to safely resect them completely [Table 2]. Patients with sub-total or near-total resection require radiotherapy as per current treatment guidelines. Ependymoma should be suspected in the presence of a CP angle mass in a middle-aged patient with no hearing loss in the absence of typical radiological features of meningioma/epidermoid. Due to its plastic nature, it can attain a massive size at presentation and can extend to many other areas, including the cervical spine. Prognosis is better due to its low-grade nature. Gross total resection can be achieved with present-day microsurgical techniques and different operative corridors. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Source: Neurology India
Authors: Jigish Ruparelia, Jaskaran Singh Gosal, Mayank Garg, Suryanarayanan Bhaskar, Deepak Kumar Jha, Poonam Elhence
Language: English
Subfield: Genetics
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
OpenAlex ID: W4409130834