AN UNUSUAL BUMP ON THE HEAD: INTRAEXTRACRANIAL MENINGIOMA PRESENTING INCIDENTALLY

An 82–year–old gentleman presented to hospital following a fall. The patient had no recollection of the fall, and was found conscious sometime later on the floor by the neighbours. At the time of assessment, it was noted that the patient had a large swelling over the frontal area of his scalp, but the duration of this sign was unclear. Positive findings on examination included; brisk lower limb reflexes, an unsteady gait, and speech disinhibition. His cognition was more formally assessed; executive testing of frontal lobe function demonstrated good fluency with word and number–letter tasks but reduced design fluency. There was no evidence of frontal release signs, and no impulsivity. The patient displayed minimally impaired echopraxia, imitation behaviour and some counting task difficulties. CT head revealed a lesion in both frontal lobes with extracranial extension. MRI revealed a 10 cm mass with an intracranial and extracranial component that was composed of solid material which enhanced with contrast (figure 1). The skull itself was preserved but did show some lytic lesions. A chest X–ray revealed no focal lesions. Subgaleal biopsies showed two collagenous tissue fragments infi ltrated by solid synctial sheets of a cellular neoplasm that in places form perivascular aggregates. There was mild pleomorphism, with oval nuclei vesicular comprising a single prominent nucleolus. The mitotic activity in the small tumour fragments was inconspicuous and there was no necrosis. There was diffuse strong immunoreactivity for epithelial membrane antigen in keeping with a neoplasm of meningothelial origin. Overall this was an intracranial meningioma with extra cranial spread into the subcutaneous tissue of the scalp. Due to minimal symptomatology the patient was managed conservatively and was discharged home. Meningiomas are common intracranial neoplasms, accounting for 18% of all primary brain tumours.¹ Extracranial manifestations however, are rare with an incidence of 1% to 2%.² Analysis from a French neurosurgical unit between 1982 and 1993 revealed 11 cases of intra–extracranial vault meningiomas with six cases originating in the frontal areaas in our case.³ Cutaneous locations of extracranial meningiomas are the most common, followed in descending order by orbital, paranasal, temporal and oral presentations.¹ 10 years between onset of symptoms and diagnosis of meningioma is not uncommon.³ Hoye et al hypothesised four aetiological ways in which extracranial meningiomas may develop;⁴ 1. Primary intracranial meningioma with extracranial extension (secondary) 2. From arachnid cell rests, accompanying cranial nerve sheaths through a neural foramen (primary) 3. Ectopic, from extracranial embryonic arachnoid cell rests (primary) 4. Metastases from intracranial meningiomas (secondary). This is very rare with Teague et al reporting a metastatic meningioma within the lung.⁵ We conclude that our patient9s extracranial extension was probably due to trans diploic spread. The intracranial veins (including the diploic veins which communicate with the dural sinuses) and venous sinuses have no valves, therefore blood within them can flow in either direction.