The present case corresponds to a 30-year-old woman with no relevant personal history, who consulted for an initial picture of a pulsating right hemicranial headache of two months' duration which progressed to become holocranial. The headache had organic features and was resistant to conventional treatment (non-steroidal anti-inflammatory drugs and triptans). In addition, it was accompanied by blurred vision, more pronounced in the left eye, two episodes of self-limited diplopia and occasional episodes of left eyelid ptosis. The neurological examination revealed an afferent pupillary defect in the left eye with a decrease in visual acuity of 0.1 and 0.25 in the right eye. The rest of the cranial nerves showed no alterations on examination. The hormonal study did not reveal any functional alterations. Cranial computed tomography (CT) scan showed a non-calcified cystic lesion eroding the sphenoid sinus and the lateral walls of the sella turcica. Magnetic resonance imaging (MRI) of the brain confirmed the existence of a 4 x 3 x 3 cm tumour in the region of the sphenoid sinus, which was destroying, eroding and expanding the walls of the sinus and the clivus itself. The lesion caused compression and cranial displacement of the pituitary gland and the chiasm. It was isointense on T1-weighted sequences and hyperintense on T2-weighted sequences, with fluid-liquid levels inside, septate appearance and peripheral enhancement on post-contrast sequences. In addition, there was sclerosis of the surrounding sphenoid bone.

Under general anaesthesia, a transsphenoidal sublabial approach was performed, partially resecting the lesion in its central part, with the intention of decompressing the optic chiasm.
The anatomopathological analysis confirmed the presence of a benign tissue with a partially mineralised appearance, with the presence of osteoblasts and irregular trabeculae forming large venous lakes, compatible with an aneurysmal bone cyst.
Post-surgical control MRI showed adequate decompression of the optic chiasm with residual lesion in both lateral regions and ethmoidal cells.
The neuro-ophthalmological examination performed at three months confirmed that the patient's visual acuity was practically normal (O.D.: 1 and O.I.: 0.9).