Chondroma of cerebellopontine angle
Intracranial chondromas usually arise at the skull base from embryonic chondrocytic cell remnants or from meninges from metaplastic meningeal fibroblasts [1,2]. Less commonly they originate from the cerebral parenchyma [3-5]. Only a few reports describe a chondroma at the CP angle [4,5]. Histogenesis of these lesions at the CP angle or within the brain parenchyma is not clear. Possible theories include cartilaginous metaplasia of mesenchymal perivascular cells, heterotopic chondrocytes, and cartilaginous displacement by trauma [1,6]. Intracranial chondromas may be solitary or multiple, as a component of Ollier's disease and Maffucci's syndrome .
The present case is illustrative of a chondroma arising in the area of the petrous bone and involving the cerebellopontine angle by direct extension. Chondromas can be quite extensive [7-9] and may grow a considerable distance from their site of origin likewise in the present case the tumor was involving CP angle, bone and cranial nerves.
Clinically they present according to their site of involvement. Tumors of the hemispheres produce seizures, hemiparesis and language dysfunction whereas tumors at the base are most likely to produce visual symptoms .
Neuroimaging reveals typical, but not characteristic features. In many cases calcification within the tumor is demonstrable. However calcification is rarely seen in cerebellopontine angle chondromas . Erosion and destruction of surrounding bone, hyperostosis of the inner table of the skull, cystic change, variable tumor density and patchy, delayed contrast enhancement are other features [7,10,11]. The main differential diagnosis for an intracranial chondroma is meningioma and especially at CP angle is schwannoma.
Although the differential diagnosis between chondrosarcoma and benign chondromas can be difficult on a histological basis, insufficient evidence of anaplasia was present to consider this lesion to be a chondrosarcoma. Chordoma of the skull is usually differentiated by distinctive physaliphorous cells and cytokeratin immunostaining. The other differential diagnoses include schwannoma or meningioma with extensive chondroid metaplasia. But there were no areas where nonchondroid elements could be recognized.
The only effective treatment appears to be surgical removal. Mostly subtotal removal only is possible due to the encroachment of the tumor on contiguous structures . In the present case tumor was not completely excised due to widespread involvement.
Contributed by Deepali Jain, MD, DNB, Sunita Bhalla, MD, Veer Singh Mehta, MS, Mch