A 65 year old female participant , right handed, started with progressive bilateral visual loss in her temporal field, over 10 months, the participant underwent an MRI and it was found a sellar lesion that compressed the optic chiasm, an endoscopic endonasal transsphenoidal surgery was done for the resection of the lesion, using a novel bilaminar chitosan scaffold to assist the closure of the sellar floor. After a follow up of 2 years the participant returned to its normal visual function, without evidence of the sellar lesion on the postoperative MRI, and without complications.

Introduction This case describe the use of a novel bilaminar chitosan scaffold in the repair of the sellar floor after an endoscopic endonasal transsphenoidal surgery for a suspected hipofisary macroadenoma, the use of chitosan as a scaffold has been described in several preclinical studies and tested in tissue bioengineering of bone, neural tissue and soft tissue, in the case of bone tissue, several studies demonstrated its potential due to its biocompatibility, osteinductive and osteoconductive features, but there is a lack of clinical trials demonstrating this characteristics in the clinical setting. One of the most common complications for the neurosurgeons after an endoscopic endonasal transsphenoidal surgery is the CSF leak, depending on the technique and the reconstruction used for the sellar floor this complication could be presented from 5% to 75%of the cases, leading to complications such infections and pneumoencephalus, representing a great risk for comorbidities, longer recovery times and hospital costs, due to this challenges in the repair of the sellar floor,the investigators intent to approach the problematic with a chitosan scaffold for its characteristics in bone regeneration. The setting of a bioactive membrane in the defect of the surgery could be useful for a stronger and more suitable closure of the sellar floor.

Case description A 65 years old female participant, right handed, came to the neurosurgery consultation with progressive bilateral visual loss in her temporal fields, with predominance in the left eye over 10 months, two weeks before her admission the participant reported a sudden loss of consciousness, prompting her to go to the hospital. In her clinical examination, the participant was alert and oriented x3, normal cranial nerves examination except for decrease visual acuity by 20/200 in her left eye, 20/80 in her right eye, bitemporal hemianopia and mild primary athropy of the optic disc in the left eye, the gait and the motor and sensitive examination was normal. The laboratory studies showed a LH: 0.22 and prolactine: 53.7 .In the contrasted preoperative brain MRI, it was found a sellar lesion, hypointense in T1 but hyperintense in T2 signal with enhancing of the periphery after the infusion of gadolinium, the lesion presented extension to the sphenoid sinus, paraselar space without involvement of the carotids and supraselar with displacement of the optic chiasm. The participant underwent endoscopic endonasal transsphenoidal surgery for resection of the sellar lesion, under the direct visualization, the lesion appeared redish and soft with moderately bleeding, a sample was taken for pathology and the remaining is extracted without complications, then the scaffold is implanted in the site of the bone defect in the sphenoid sinus, due to its moldable nature, it was easily set, covering the entire extension of the defect, a fat graft was set in the sphenoid sinus covering the bilaminar chitosan membrane, then fibrin sealant was used for hemostatic control and a nasal packing was set in both nostrils for finalize the procedure. In the postoperative there was not complication and after a few days the participant was discharged with notable clinical improvement, after one month of follow up the participant recovered her visual acuity and the participant did not refer any symptom, the participant underwent a post operative brain MRI, where it is observed a gross total resection and good closure of the sellar floor, without signs of rejection or inflammation in the zone with the chitosan scaffold.

Materials and methods for the bilaminar chitosan scaffold The bilaminar implant is constitute by two types of different structures, one of the membranes presents a flat-smooth structure, the other membrane has a tridimensional-porous structure, each of the physical-chemical characteristics given to the membranes, was in function of the biological effect pretended in the effector tissue.

The two types of membranes, synthetized for the elaboration of the bilaminar implant, were elaborated with biomedical grade chitosan of medium molecular weight with 75-85% of deacetylation in powder presentation from the brand Sigma Aldrich®, U.S.A.

In the case of the membrane with flat-smooth structure, it was synthetized from a chitosan solution at 2%, the dissolution medium was diluted acetic acid (Sigma Aldrich®, U.S.A); In order to acquired a suitable solubilisation, the mix was set on a magnetic stirrer for 1 hour, posteriorly the solution was brought under the action of a sonicator at 28oc for 2 hours, until the air bubbles formed by the stirrer were completely eliminated.

For the membrane with the tridimensional-porous structure, it was synthetized from a chitosan solution at 4%, the dissolution medium was diluted acetic acid (Sigma Aldrich®, U.S.A); for a suitable solubilisation, the mix was set on a magnetic stirrer for 4 hours, afterward the solution was brought under the action of a sonicator at 28oc for 2 hours, until the air bubbles formed by the stirrer were completely eliminated.

Once the solutions were elaborated, for the synthesis of the two membranes (the flat-smooth and the tridimensional-porous) both were set in a constant quantity of ml/cm2 in a Petri dish, in the case of the flat-smooth membrane, it was brought under a procedure of drying with 98% of humidity loss and for the tridimensional-porous, a procedure of phase separating was termical induced.

When both membranes are already elaborated, it is proceed to synthetize the bilaminar implant, the membranes are combined using a solution of chitosan acetate at 2%, that was distributed uniformly between both membranes to create a sandwich structure, consecutively the ensemble was put in a Petri dish and the cover was set inverted in the superior aspect of petri dish. It was set for drying for 24 hours at room temperature and then it was precipitated in a solution of sodium hydroxide 1N, following the same indications used for each membrane separately.

Inclusion Criteria:

• male/female patient candidate for an endoscopic endonasal transphenoidal surgery, who need repair of the sellar floor as part of the surgical procedure.

Exclusion Criteria:

• Diabetes, heart diseases, immunological diseases, infectious diseases, bone diseases.

complete MRI sequences, laboratory studies, visual field tests, complete biomaterial patent registration , clinical reports.