A 63 year old white man presented to the accident and emergency department with a 24 hour history of gradual onset of mild weakness of his left upper limb, which progressed to involve his left lower limb. There was no history of any other CNS symptoms. He also stated that the paresis varied with posture—being worse on standing and sitting, while it was relieved by lying down; it was also associated with a noticeably diminished short-term memory over the past few weeks. Clinical examination confirmed a mild left hemiparesis (grade 4/5), with brisk reflexes and an “equivocal” plantar response on the left. The rest of the examination was unremarkable: he was normotensive, no carotid bruits were auscultated and the fundi were normal. Haematological and biochemical investigations were normal. A diagnosis of a progressive cerebrovascular accident (CVA) was made and he was admitted to hospital for further observation.

Over the next few days, his hemiparesis slightly worsened, and routine computed tomography was carried out four days later. Routine axial sections (fig 1) revealed a 5 cm diameter pneumocephalus, and a mass with irregular calcification was noted arising from the base of skull in the right ethmoid sinuses (fig 2), encroaching on to the orbit. He was transferred to the regional ENT/neurosurgical centre, where a surgical intervention was decided upon. He underwent a simultaneous lateral rhinotomy and bilateral frontal craniotomy with an osteoplastic flap. A complete excision of his osteoma was performed, apart from a small area near the orbital apex. Some 40 ml of air were found trapped intracranially, and the osteoma was associated with multiple mucoceles, which was responsible for the irregular appearance on computed tomography. His skull base defect was repaired with a fascia lata graft from his thigh. He made an uneventful recovery and his paresis improved immediately. His only persistent neurological deficit is anosmia. Subsequent histopathological examination confirmed the diagnosis of an osteoma, with dense trabeculae and little evidence of osteoblastic activity.

Primary osteomas of the ethmoid sinuses are rare tumours, and spontaneous pneumocephalus is an unusual complication. They have been known to present acutely with fits, headaches, dementia,¹ cerebral abscesses,² and acute cerebral hypertension.³ In this case the striking postural hemiparesis was presumably attributable to the tension pneumocephalus compressing the cerebral cortex. Interestingly, it is probable that the pneumocephalus would have been apparent from initial presentation on a plain skull radiograph.

In conclusion, spontaneous pneumocephalus is one of the rare conditions that should be considered in the differential diagnosis of raised intracranial pressure and atypical neurological symptoms including “change with posture”.

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Figure 1

Coronal CT scan showing the osteoma with associated mucocele.

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Figure 2

Axial CT scan showing the frontal location of the pneumocephalus. Patient supine.