Pneumosinus Dilatans: An exploration into the association between Arachnoid Cyst, Meningioma and the pathogenesis of Pneumosinus Dilatans.

OBJECTIVES

To investigate the association between certain intracranial masses (meningioma and arachnoid cyst) and the incidence of Pneumosinus Dilatans (PSD) - including whether the size of the mass correlates with severity of the condition.

PATIENTS AND

METHODS

A review of the available case reports on PSD was performed. Clinical data was extracted from 111 case reports for analysis. A further case-control study was performed using CT Head datasets to investigate the aetiological relationship between intracranial masses and PSD. Cases included patients with confirmed arachnoid cyst or meningioma. Controls included patients with no intracranial masses.

RESULTS

PSD is most common in the frontal (48%) and sphenoid sinuses (43%). Men are twice as likely to be affected as women. 58% of cases occur in patients aged 35 or under. The most common symptoms reported are facial deformities (39%), headache (24%) and visual loss (15%). Unexplained visual changes (e.g. diplopia, reduced visual acuity) are strongly correlated with sphenoid sinus involvement. PSD is more common in patients with skull-base meningioma (OR 5.67) and middle cranial fossa arachnoid cysts (OR 10.00). Mean sinus volume in patients with PSD can increase by up to 4 times.

CONCLUSION

We present the first direct investigation into the relationship between meningioma, arachnoid cyst and Pneumosinus Dilatans. There is a statistical correlation between skull-base meningioma and middle cranial fossa arachnoid cysts and the incidence of PSD. This specific anatomical relation suggests that local factors contribute to the pathogenesis of the condition. Alterations in intracranial pressure due to mass effect or vascular occlusion, in addition to the localised release of bone growth factors (IGF-1, IGF-2, PDGF), are possible mechanisms for this. The first peak in incidence of PSD coincides with the completion of normal sinus pneumatisation, which raises the further possibility that predisposing genetic factors also contribute.