Enlarging Temporal Arachnoid Cyst Extending Inside the Sphenoid Sinus

BACKGROUND

Cerebral arachnoid cysts that eroded the skull base and extended into the paranasal sinus are very rare with only a few cases reported.

CASE DESCRIPTION

A 71-year-old woman with history of headache for 4 years was evaluated because of an enlarging right temporal cystic lesion with evidence of resorption of the greater wing of the sphenoid bone and a fluid-filled sphenoid sinus. For 3 years, the cerebral cyst remained stable and minimally symptomatic. On her last magnetic resonance imaging, the cyst enlarged and perilesional edema was identified. The patient was treated with an open intracranial approach to explore the cyst. An arachnoid cyst was found which extended into the sphenoid sinus through a defect in the temporal fossa floor. The skull base defect was repaired using a muscle plug and fibrin sealant to obliterate the dural and bony defect. The arachnoid cyst was fenestrated to the basal cisterns.

CONCLUSIONS

Cerebral arachnoid cysts extending into the paranasal sinuses are very rare presenting mostly with rhinorrhea and nasal symptoms. Patients with neurologic symptoms may need intracranial surgery to fenestrate the cyst. Obliteration of the fistula into the paranasal sinus is essential to prevent further complications.

Petrous and sphenoid arachnoid cysts: diagnosis and management

BACKGROUND

Intraosseous arachnoid cysts are rare and difficult to diagnose. The purpose of this study was to describe the clinical and radiological semiology of petrous and sphenoid arachnoid cysts and to propose a specific management strategy.

METHODS

This was a retrospective, descriptive study of patients with arachnoid cysts, which utilized CT, MRI, and the patients' medical histories.

RESULTS

Ten patients were included in this study. On CT, the lesions were lytic with bony delineation. On MRI, the lesions exhibited the same signals as cerebrospinal fluid and were not enhanced after contrast. On fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted sequences, the arachnoid cysts' signal disappeared, which is a key feature for eliminating the diagnosis of cholesteatoma. Two patients underwent surgery because of misdiagnosis, either with a meningocele or a cholesteatoma.

CONCLUSION

MRI FLAIR and diffusion-weighted sequences, together with osseous CT scans, help to distinguish arachnoid cysts from meningoceles and avoid unnecessary surgeries with potential complications.