Skull Base Reconstruction After Endonasal Cranio-endoscopic Resection Using Autologus Grafts

Endonasal endoscopic approach to the skull base has been expanded in the last several years owing to advances in the radiological aspect that provided a better evaluation of the lesions and the surrounding structures, technological advances that include angled endoscope, development of high-resolution cameras, high definition monitors and navigation systems and better anatomical experience. The endoscopic endonasal approach now provides access to frontal sinus to the second cervical vertebra in the sagittal plane and from the sella to the jugular foramen in the coronal plane. Endoscopic resection of large skull base tumors results in large defect for which repair is a challenge. Several factors besides the size of the defect should be considered during skull base repair as CSF leak, CSF pressure, history or need for future radiotherapy, lack of support and local tissue vascularity. The aim of this study is to Provide an algorithmic approach for skull base reconstruction after endonasal cranio-endoscopic resection using autologous grafts according to the extent of resection, skull base defect size, the presence of CSF leak, CSF pressure and local tissue vascular

Type of the study:

A prospective clinical study will be conducted in the period between January 2018 and January 2020.

Study Setting:

Otolaryngology Department, Alexandria University Hospital. Otolaryngology Department, Assiut University Hospital.

Study tools :

Preoperative evaluation:

1. Personal history: age, sex, marital status, occupation, number of children, and endocrinal history in case pituitary tumors.
2. Presentation: endocrine, visual, oculomotor and/or a headache.
3. Therapeutic history.
4. Past history: trans-sphenoidal surgery, trauma and nasal diseases and/or surgery.
5. General examination: including gross features of Cushing's disease or acromegaly.
6. Full ENT examination including assessment of the nasal cavity, nasal septum for deviation, perforation and/or adhesions) and nasal turbinates; including nasal endoscopic examination and dental assessment.
7. Neurosurgical consultation.
8. Ophthalmological assessment: visual acuity, visual field, fundus examination and color vision.
9. Radiological assessment:

   1. MRI of the brain: A complete protocol including at least, T1- and T2-weighted images and T1-weighted post-contrast (gadolinium) images, in the three orthogonal planes at max 3 mm sections: for assessment of tumor site, size and extension, and involvement of large blood vessels and nerves.
   2. Multi-slice CT scan of the nose and paranasal sinuses (bone window, high resolution, with intravenous contrast, in the three orthogonal planes, with three-dimensional reconstruction and at maximum 3 mm sections): for assessment of nasal cavity abnormalities including the nasal septum, sinus pathology, type of sphenoid sinus pneumatization, etc.
10. Assessment of the general condition of the patient:

    1. Complete blood count: to assess for anemia or other hematological abnormalities.
    2. Serum electrolytes: mainly sodium and potassium.
    3. Fasting and postprandial blood glucose level.
    4. ECG and echocardiography.

Operative techniques:

After cranio-endoscopic resection and complete removal of the lesion skull base defect will be repaired according to the following scheme (modified from Sigler et al) No leak →No repair or single layer Low-flow leak → Multilayer repair Autograft (fascia Lata, fat, bone, mucosa) High-flow leak →Multilayer repair Autograft (fascia Lata, fat, bone, mucosa)+ Intranasal vascularized flap.

Modifying factors (factors that indicate the need for a vascularized flap regardless of leak type): Cushing disease, morbid obesity, craniopharyngioma, meningioma, extended skull base approach, large defect, revision surgery, history of or future need for radiation treatment.

So repair technique after extensive dural and bony resection or high flow leak will include multiple layers of fascia lata with pieces of fatty tissue in between. After that, a nasoseptal flap (or other vascularized flap, e.g., posterior pedicled inferior turbinate, posterior pedicled middle turbinate, bipedicled anterior septal, anterior inferior turbinate) will be harvested and applied according to local vascularity.

Then a separator will be applied; to prevent future accidental dislodgement of grafts during Merocel® removal, followed by placement of a moderately inflated Foley balloon catheter; to support the reconstruction.

At the end of the procedure, when hemostasis will be achieved, irrigation will be performed to remove any bone residuals or blood clots from the choanae and the nasopharynx. Then, the middle turbinates will be gently repositioned medially. At last, nasal Merocel® (polyvinyl alcohol) sponges will be placed in the nasal cavity on either side and hydrated with saline to expand.

Repair of low flow leak will be the same as the previous technique with the replacement of the vascularized flap with free mucosal graft and no need for Foley catheter.

Early postoperative management:

For the next twenty-four hours, the patient will be monitored in the intensive care unit, particularly for diabetes insipidus (after pituitary surgery), visual deterioration, any CSF leak, manifestations of meningitis or any hemorrhage.

Inspection for CSF leak will be a part of the routine evaluation of every patient, both in the recovery room and in the days after surgery. If persistent CSF leak became evident, a lumbar drainage was tried before re-exploration under general anesthesia. Analgesics will be routinely prescribed. Prophylaxis against postoperative nausea and vomiting will be achieved by an intraoperative intravenous administration of a single dose of an antiemetic, ondansetron 4 mg, as well as a throat pack to prevent intraoperative bleeding from draining into the stomach.

An intravenous third-generation cephalosporin will be started with anesthesia induction and continued until removal of the nasal packing. Then, patients will be kept on a five days course of an oral antibiotic; for safety.

Nasal packs will be removed on the third or fifth postoperative day. Then, the patient will be examined under endoscopic guidance.

Follow up:

I. Otorhinolaryngologic assessment: The first office visit will be scheduled after a week following the surgery. After application of topical anesthesia (lidocaine 10%), any blood clots will be endoscopically removed and any synechiae will be released. The examination will be for any bleeding or CSF leakage. The patient will be seen on a weekly basis for the first three weeks and then every three weeks for the next two appointments. Healing usually occurs three to six weeks. Further appointments will be scheduled as necessary II. Neuro-radiological assessment: Early MRI will be obtained on the first or second postoperative day to assess the extent of resection, the location of the fat graft if one is present, and the presence of any hematoma. Serial imaging was done after six months and then annually.

III. Endocrinal assessment: in case of hypophysectomy. IV. Ophthalmological assessment: serial visual field, visual acuity, and fundus examinations will be done for every patient, especially those with a pre-operative visual loss.

Eligibility Criteria:
Inclusion Criteria:

* All patients undergoing endonasal cranio-endoscopic resection

Exclusion Criteria:

* Unfit patient for surgery.
* Patient refusal to participate in this study.