Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 4, 2011, pp. 608-611

Neurology India, Vol. 59, No. 4, July-August, 2011, pp. 608-611

Case Report

Gamma knife treatment of an endolymphatic sac tumor: Unique features of a case and review of the literature

Xing Cheng, Shu Qin, Xing Wang, Peng Li, Balkrishna Shrestha, Wei Wang

Department of Neurosurgery of the West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
Correspondence Address: Wei Wang, Department of Neurosurgery of the West China Hospital, Sichuan University, Guoxue Street 37, Chengdu, Sichuan Province, 610041, China, co_60@126.com

Date of Submission: 14-Nov-2010
Date of Decision: 07-Dec-2010
Date of Acceptance: 16-Jan-2011

Code Number: ni11181

PMID: 21891944

DOI: 10.4103/0028-3886.84348

Abstract

Keywords: Cerebellopontine angle, endolymphatic sac tumor, gamma knife radiosurgery

Introduction

Endolymphatic sac tumor (ELST), first described in 1984, by Hassard et al., ^[1] is a rare, histologically non-aggressive lesion, but often becomes locally invasive and leads to erosion of the petrous bone. Most often ELST are solitary, bilateral lesions, mostly seen in patients with von Hippel-Lindau (VHL) disease and only 1% of the bilateral lesions occur in other patients. ^[2] We report a patient with multiple ELSTs treated with gamma knife radiotherapy, and review the relevant literature review.

Case Report

A 44-year-old male presented with progressive hearing loss on the left side, of two months' duration and left facial weakness and hypoacusis on the right side, since few weeks. A neurological examination revealed left side sensorineural deafness and moderate hearing loss on the right side, and also a left lower motor neuron type of facial palsy. Magnetic resonance imaging (MRI) revealed three homogeneously enhancing lesions located in both the cerebellopontine angles and the vermis of the cerebellum [Figure - 1]. Diagnosis of metastatic disease was considered and a work-up was conducted for the primary focus: computed tomography (CT) scan of the chest and abdomen, serum tumor markers (CEA, SCC, CA-125, CA-19-9, CYFRA21-1, and T-PSA), colonoscopy, and 99mTc-methylene diphosphonate bone scanning, which were all normal.

He was taken up for exploratory surgery. He underwent a left retromastoid suboccipital craniectomy. Intraoperatively the tumor was grayish-red, soft, and fragile (0.6 cm×0.2 cm×0.1 cm) and was close to the facial and vestibulocochlear nerves. The tumor was carefully isolated from the cranial nerves and radical resection of the lesion was done. The pathology of the tumor showed a papillary-glandular appearance, with soft tissue invasion and bony erosion. The lesion showed a clear cell predominance resembling prostate carcinoma and renal cell carcinoma. On immunohistochemical evaluation, the tumor was positive for epithelial membrane antigen (EMA), pan-cytokeratin (PCK), cytokeratin 7 (CK7), neuron specific endolase (NSE), and CDX 2. The tumor was negative for cytokeratin 20 (CK20), CD31, CD34, CD57, Nestin, D2-40, Vimentin (Vim), S100, glial fibrillary acid protein (GFAP), prostate specific antigen (PSA), and thyroid transcription factor-1 (TTF1) [Figure - 2].

As the patient refused a second surgery to resect the right side lesion, stereotactic radiosurgery, gamma knife radiosurgery was performed, two months after the first surgery, with a prescription dose of 17.0 Gy and a prescription isodose of 50.0% [Figure - 3]a. A follow-up scan five months after surgery, showed metastases to the brainstem. Brainstem metastases were treated with gamma knife radiosurgery with a prescription dose of 11.0 Gy and a prescription isodose of 50.0% [Figure - 3]b. After 18 months of the first surgery, the tumor in the right cerebellopontine angle regressed in size and the lesions in the vermis of cerebellum and brainstem disappeared. He had recurrence of a left-side tumor resulting in vertigo and cerebellar ataxia, and the recurrent tumor was treated with gamma knife radiosurgery with a prescription dose of 16.0 Gy and a prescription isodose of 50.0% [Figure - 3]c. At a follow-up, 27 months after the first gamma knife radiosurgery, the tumor in the right cerebellopontine angle had recurred and the recurrent tumor was treated with a prescription dose of 12.0 Gy and a prescription isodose of 45.0% [Figure - 3]d. In the follow-up six months after the last gamma knife radiosurgery, an MRI showed no remnants of the tumor in both the cerebellopontine angles, vermis of the cerebellum or brainstem [Figure - 3]e. The patient is free of the disease and is under regular follow-up.

Discussion

Endolymphatic sac tumors are locally aggressive papillary adenocarcinomas originating from the endolymphatic sac. ^[3] The gene mutation for ELSTs and other neoplasms associated with VHL disease is the same. ^[4] About 28% of ELSTs are bilateral and mostly seen in patients with VHL disease, whereas, only 1% of bilateral ELSTs occur in other patients. ^[2] Metastasis of ELST is extremely rare and only one case has been reported to date. ^[5] The common presentation is progressive or sudden, and the clinical features are sensorineural hypoacusis with ipsilateral facial paralysis. Other clinical features include headache, dizziness, tinnitus, vertigo, cranial nerve paralysis, Vernet's syndrome, and cerebellopontine angle syndrome. ^[6],[7] The differential diagnosis include other lesions in the cerebellopontine angle, such as, schwannoma, meningioma, jugular paraganglioma, metastatic adenocarcinoma, and choroid plexus papilloma. Early diagnosis and treatment is important in order to preserve hearing and facial nerve function. ^[8] The diagnostic imaging modalities include computed tomography (CT), including high resolution CT (HRCT), MRI, and digital subtraction angiography (DSA). The CT findings in ELST include lytic lesions at the endolymphatic sac in the petrous bone, central calcific spiculation, and posterior rim calcification. ^[9],[10] Skull base high-resolution computed tomography (HRCT) can clearly demonstrate the borders of the tumor and the extent of bone erosion. A T1-weighted (non-contrast) MRI sequence often shows hyperintense foci. T1-weighted post-gadolinium scans show variable enhancement, based on the degree of tumor vascularity. T2-weighted sequences show heterogeneous signals. ^[10] DSA shows the hypervascularity of the mass and the arterial supply of the lesion. ^[11],[12] Grossly, ELSTs are highly vascular red masses. Microscopically, ELSTs show two main patterns: ^[13] well-formed papillary fronds and thyroid follicle-like glandular structures. Hemorrhages, calcifications, siderophages, cholesterol clefts, and inflammatory cells can be frequent observations. Immunohistochemistry usually reveals positive staining for S100, cytokeratin, EMA, NSE, GFAP, and vimentin. ^[14]

Given that the ELSTs are low-grade papillary adenocarcinomas and metastasis is rare, complete surgical resection is the first treatment of choice. However, hypervascularity and encasement of the cranial nerves often make successful resection very difficult. This is probably the reason for very high recurrence rates. For complete resection preoperative angiography and embolization, interoperative electrophysiological monitoring, and microsurgery are suggested. ^[15],[16] Surgical approaches include the transmastoid, retromastoid or retrolabyrinthine-transdural approaches, which are selected on the basis of the location and extent of the tumor and the patient's preoperative functional deficits. ^[6],[8] The role of radiotherapy or gamma knife radiosurgery is controversial, and the published series are too few to provide a definite conclusion. Most studies reported an uncertain effect of radiotherapy or gamma knife radiosurgery. ^{[6],[7],[9],[12],[17]} Two cases treated with gamma knife radiotherapy, with long-term follow-up, and with no recurrence, have been reported. ^[5],[18]

In our case, the patient had only sensorineural hypoacusis and facial paresis at the time of the first admission. The lesion in the left cerebellopontine angle was pathologically ELST. The lesions in the right cerebellopontine angle and vermis of the cerebellum were also considered to be ELSTs, based on the image characteristics on the MRI. Probably this is the first report of multiple ELSTs in a patient without VHL disease. The other unique feature of our case is metastases. The literature review reveals a report of only one case of metastatic ELST, distant from the original site of surgery. ^[5] Our patients had two sites of metastases (vermis of the cerebellum and brainstem). gamma knife radiosurgery showed a good effect on tumor remission. Thus, with an appropriate prescription dose and isodose gamma knife radiosurgery may have an important role in curing the recurrence or metastasis of ELSTs.

References

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