Spontaneous cerebrospinal fluid fistula secondary to hyper-pneumatized paranasal sinuses and skull base: two case reports

Background Spontaneous cerebrospinal fluid (CSF) fistulas occur due to various reasons other than well-identified causes such as trauma, neoplasia or infection. Various contributory factors are attributed to formation of spontaneous CSF leaks such as idiopathic intracranial hypertension leading to prominent arachnoid granulations. Further, presence of hyper-pneumatized paranasal sinuses or the skull base weakens the bone and predisposes to development of spontaneous defects and further fistulas. This case report highlights two cases of spontaneous CSF leaks associated with hyper-pneumatized petrous bone and sphenoid sinus. Case presentation A 26-year-old female patient with history of right rhinorrhea with imaging evidence of bilateral hyper-pneumatized petrous bones and a bony defect in the right petrous bone on computed tomography (CT). Subsequent CT cisternography demonstrated CSF leak extending into the right pneumatized petrous apex cells, Eustachian tube, middle ear cavity, aditus, antrum and mastoid air cells. Pooling of contrast in the right nasal cavity and ethmoid cells was also seen. A 49-year-old female patient with history of right rhinorrhea with features of hyper-pneumatization of sphenoid bone involving right greater wing of sphenoid bone and bilateral pterygoid process with a bony defect in the right greater wing of sphenoid was demonstrated on CT. Corroborative magnetic resonance imaging (MRI) brain Constructive interference in steady state (CISS) sequence revealed a meningoencephalocele. Additionally, a suspicious focal dehiscence was observed in the right cribriform plate CSF pockets herniating into right ethmoid sinus. Conclusion Hyper-pneumatized petrous bone and paranasal sinuses can be attributed as a risk factor for formation of spontaneous CSF leaks.