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LETTER TO EDITOR
Year : 2014  |  Volume : 62  |  Issue : 2  |  Page : 230-232

Primary ventral foramen magnum meningeal melanocytoma


1 Department of Neurosurgery, PGIMER, Chandigarh, India
2 Department of Histopathology, PGIMER, Chandigarh, India
3 Department of Radiotherapy, PGIMER, Chandigarh, India

Date of Submission10-Jan-2014
Date of Decision02-Feb-2014
Date of Acceptance19-Apr-2014
Date of Web Publication14-May-2014

Correspondence Address:
Pravin Salunke
Department of Neurosurgery, PGIMER, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.132452

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How to cite this article:
Sodhi HB, Salunke P, Sahoo SK, Radotra BD, Kumar N. Primary ventral foramen magnum meningeal melanocytoma. Neurol India 2014;62:230-2

How to cite this URL:
Sodhi HB, Salunke P, Sahoo SK, Radotra BD, Kumar N. Primary ventral foramen magnum meningeal melanocytoma. Neurol India [serial online] 2014 [cited 2021 Mar 4];62:230-2. Available from: https://www.neurologyindia.com/text.asp?2014/62/2/230/132452


Sir,

Primary meningeal melanocytomas are intriguing because of their rarity and unusual radiological appearance. [1] They are usually located around the cervicomedullary junction and upper cervical spine. [2] Of interest, melanocytoma at the ventral foramen magnum has never been reported. We report one such case.

A 22-year-old male presented with headache, intermittent diplopia on left lateral gaze, and correctable neck tilt to the right of 3 months duration. Examination revealed mild papilledema. Magnetic resonance imaging (MRI) revealed dural based lesion at ventral foramen magnum, isointense on T1 and T2 with brilliant enhancement suggesting a meningioma. Both vertebral arteries (VA) (right more than left) appeared to be encased within the lesion. Interestingly, a T1 hyper and T2 hypointense intralesional nodule (suspicious of blood or melanin) was seen abutting one of the VA [Figure 1]. He was operated through right far lateral approach , by the senior author PS. The arachnoid was opened, and a moderately vascular, reddish-black friable lesion was encountered that was apparently infiltrating the cranial nerves and encasing VAs. However, patient dissection revealed an arachnoid layer making peeling of the tumor from each cranial nerve and VA (engulfment and not encasement) possible. The lesion was attached to the dura ventrally up to C2 level [Figure 2]. The area corresponding to the nodule was fleshy and firm. Total excision could be achieved. Histopathology and immunohistochemistry confirmed melanocytoma [Figure 3]. Following surgery, the diplopia and neck tilt improved. The positron emission tomography-computed tomography (CT) ruled out lesions at other sites. He received 45 Grays of radiation and is doing well at 6 months follow-up. Radiology at 6 months follow-up ruled out recurrence or residual lesion [Figure 4].
Figure 1: The top row shows ventrally located lesion at the foramen magnum. The lesion is iso-hyper-dense on computed tomography, isointense on T1 and T2. The vertebral arteries (VA) appear to be encases. There is nodule close to the left vertebral artery, hyper on T1 and hypointense on T2. The middle row shows no attenuation on FLAIR, sagittal T2 showing the extent and the MR angio showing the VA. The bottom row shows the extent and Brilliant enhancement of lesion on contrast

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Figure 2: Intraoperative images showing sequential excision of the tumor from lower cranial nerves and both vertebral arteries. The arachnoid plane is well-maintained. A - arachnoid, T - tumor, VA - Vertebral artery, PICA - Posterior inferior cerebellar artery, 12th N - hypoglossal nerve, 11th N - spinal accessory nerve, 9 to 10th N - Glossopharyngeal and vagus nerve, BS - Brain stem

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Figure 3: (a) It shows loose nests of oval to spindle cells containing variable melanin pigment H and E, ×20. There are no mitoses. The tumor is well-circumscribed and shows extensive pigment and spindle cells in other areas (b) immunohistochemistry showing negative staining for epithelial membrane antigen and (c) strong melan A positivity (×40)

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Figure 4: Contrast-enhanced magnetic resonance imaging, at 6 months follow-up showing no recurrence or residual lesion

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Melanocytes are neural crest derivatives and their abnormal differentiation in the central nervous system can give rise to diffuse leptomeningeal melanocytosis, meningeal melanocytoma or primary melanoma. [1] Melanocytes occur in the highest concentration ventrolateral to the medulla oblongata and making this a common site for intracranial meningeal melanocytomas. Extensive review by Fan et al. showed various locations of melanocytoma. [2] However, a ventrally located foramen magnum melanocytoma has not been described yet. These lesions have a propensity to arise in proximity to nerves as they exit the brainstem and spinal cord. [1] Meningeal melanocytoma may present with raised intracranial pressure, neuropsychiatric symptoms, seizures, or rarely spinal cord compression. Commonly, the tumor appears hyper- or iso-dense on CT scan with contrast enhancement. It is usually hyperintense on T1-weighted and Fluid Attenuated Inversion Recovery (FLAIR), and hypointense on T2-weighted MRI with contrast enhancement. [1] However, these radiological features are not definitive and may mimic a meningioma.

Grossly, the lesion appears black, mimicking bleed. It is firmly attached to the underlying meninges at some point and is vascular. These lesions have a propensity to invade along the cranial and spinal nerves, which makes their gross total excision difficult. [1],[3] Contrary to this, we found a well-maintained arachnoid plane and with patience, the tumor could be dissected from each nerve and the vessel. Microscopy shows melanin granules. Immunohistochemically, the lesion shows S-100 protein, antimelanoma antibodies (HMB-45) and vimentin positivity, and stains negative for keratin, epithelial membrane antigen and glial fibrillary acidic protein. [1],[3]

Gross total resection (GTR) is the most important predictor of good long-term outcome. [4] The 5-year survival rates are 100% after GTR with or without radiotherapy (RT). Adjuvant RT improves the survival in cases of incomplete resection (IR) to 100% as compared with 46% without RT. [4] Though appearing benign, melanocytoma may follow an aggressive course. Local recurrences are common even after GTR and may occur earlier with malignant transformation. Therefore, surveillance MRI should be obtained at regular 6 monthly intervals. In addition, metastasizing meningeal melanocytomas do occur. The 5-year local control rate was 80% after GTR alone, 100% after GTR-RT, and 72% after IR-RT versus 18% after IR alone. RT doses of 45-55 Gray have shown to achieve better control than 35-40 Gray. [4] Gamma knife radiosurgery has shown to reduce the tumor size and improve clinical outcome. Intrathecal methotrexate or interleukins too have been tried in few cases. Currently, GTR with adjuvant RT provides the best local control and survival. [1]

Apart from the unusual location, this report highlights the importance of patient dissection following a good surgical planning to achieve total excision, which is desirable in such lesions as it bears a good long-term outcome.

 
 » References Top

1.Liubinas SV, Maartens N, Drummond KJ. Primary melanocytic neoplasms of the central nervous system. J Clin Neurosci 2010;17:1227-32.  Back to cited text no. 1
    
2.Fan MC, Wang JF, Fu WW, Liu K, Li LD, Sun P. Primary meningeal melanocytoma located in foramen magnum: A case report and review of the literatures. Chin Med Sci J 2012;27:115-20.  Back to cited text no. 2
    
3.Jaiswal S, Vij M, Tungria A, Jaiswal AK, Srivastava AK, Behari S. Primary melanocytic tumors of the central nervous system: A neuroradiological and clinicopathological study of five cases and brief review of literature. Neurol India 2011;59:413-9.  Back to cited text no. 3
[PUBMED]  Medknow Journal  
4.Rades D, Schild SE, Tatagiba M, Molina HA, Alberti W. Therapy of meningeal melanocytomas. Cancer 2004;100:2442-7.  Back to cited text no. 4
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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