Large chondroma of the dural convexity in a patient with Noonan's syndrome. Case report and review of the literature.

INTRODUCTION Intracranial chondromas are extremely rare intracranial tumours that usually arise from the skull base synchondrosis. Exceptionally, they may grow from cartilage rests within the dura mater of the convexity or the falx. They may be part of Ollier's multiple enchondromatosis or Maffuci's syndrome. We describe the case of a young male diagnosed of Noonan's syndrome that underwent resection of a large intracranial chondroma arising from the dural convexity. To our best knowledge this is the first report of such association. CASE REPORT An 18-year-old male presented with a single generalized seizure. The patient was previously diagnosed of Noonan's syndrome on the basis of his special phenotype (Turner-like), low stature, cardiac malformation, retarded sexual and bone development and normal karyotype. He harboured mild psychomotor retardation. Physical and neurological examinations were unremarkable. Brain Magnetic Resonance image showed a large well-circumscribed intracranial mass in the dural convexity of the left frontal-parietal lobes, with heterogeneous contrast enhancement and no peritumoural oedema. The patient was initiated on valproic acid and underwent craniotomy and complete excision of the tumour. The tumour was firm, white-greyish, avascular and could be finely dissected away from the cortex. Postoperative seizures required additional anticonvulsant therapy. He was discharged uneventfully. The pathological study revealed a mature chondroma. Subsequent brain MRI studies have shown no evidence of recurrence after 33 months of follow up. DISCUSSION Chondromas comprise less than 0.3% of intracranial tumours. Only twenty-five cases of intracranial dural convexity chondromas are reported in the literature. Several hystopathogenetic theories have been proposed: metaplasia of meningeal fibroblasts and perivascular meningeal tissue, traumatic or inflammatory cartilaginous activation of fibroblasts and growth of aberrant embryonal cartilaginous rests in the dura mater. Chondromas present clinical features similar to meningiomas. CT scan imaging shows a mass of variable density due to different degrees of calcification with minimum to moderate contrast enhancement. MRI studies show a well-circumscribed lesion without surrounding tissue oedema, that exhibit heterogeneous signal with intermediate to low intensity on T1-weighted images and mixed intensity on T2-weighted images with minimum enhancement. Angiogram is clue to differentiate from meningiomas since chondromas are completely avascular. Complete tumour resection including its dural attachment is the treatment of choice. Long-term prognosis is favourable. Radiation therapy is currently not recommended for residual tumours or inoperable patients due to risk of malignization. Noonan's syndrome (also known as pseudo-Turner syndrome) is a complex familial genetic disorder with a phenotype that resembles that of Turner's syndrome but exhibits no chromosomal defect. No predisposition of Noonan's syndrome for tumoural development is reported in the literature. Association of a dural convexity chondroma with Noonan's syndrome is unique as far as the literature is concerned.