Endoscopic endonasal approach (EEA)
History
The history of the endoscope in skull base surgery is de facto the history of pituitary surgery. The first pituitary operation was likely performed by Sir Victor Horsley in 1889 via a transfrontal approach though he did not publish his results 1).
His compatriots, Caton and Paul, were the first to publish the results of this operation in 1893 2) in which they reported that their patient was cured of his headaches for the three months he survived post operatively.
But, it is Schloffer who is widely regarded as the father of modern pituitary surgery. In 1906 he published a seminal paper discussing the possibility of pituitary surgery via a transsphenoidal approach 3) and performed this operation on March 16, 1907. The operation was performed via nasal translocation and lasted about 75 min. Though there were no intraoperative complications, the patient died two months later and on autopsy was found to have hydrocephalus as a result of residual tumor blocking the foramen of Monro 4)
Then in 1910, Oskar Hirsh, an otolaryngologist, introduced a transseptal, transsphenoidal approach to the pituitary gland 5) an operation which is still in use today. Cushing performed his first pituitary operation in 1909 6) using Schloffer's method but then rapidly adopted Hirsh's approach adding a sublabial incision and a headlamp to improve visualization of the sella. Using this approach he performed 231 operations with a 5.6% mortality rate 7) 8).
Hirsch continued to perform transphenoidal hypophysectomy and by 1937 had performed the operation on 277 patients with a mortality rate of 5.4% 9). After being displaced from Austria by the Nazis shortly thereafter, he emigrated to the US and continued to operate at Massachusetts General Hospital in collaboration with a neurosurgeon, Hannibal Hamlin. The other surgeon who kept the technique alive was Norman Dott, a British neurosurgeon who learned the approach in 1923 from Cushing and by 1956 had performed 80 procedures with no deaths 10).
The modern advent of the transsphenoidal approach as the preferred approach to the pituitary began in 1956 when a French neurosurgeon, Gerard Guiot, learned the technique from Dott and brought it back to Paris and reintroduced it to skeptical colleagues. He ultimately performed over 1,000 transsphenoidal hypophysectomies and also introduced the use of intraoperative fluoroscopy 11) 12) 13).
A student of Giuot, Jules Hardy revolutionized the transsphenoidal pituitary approach when he introduced the use of the operating microscope and microsurgical instrumentation in 1967. The microscope with increased illumination and magnification permitted a more thorough and safer resection without deaths or major morbidities 14) 15).
Indeed, Hardy's contributions led to a paradigm shift in pituitary tumor surgery. Previously, the operation was performed to debulk large tumors off the optic apparatus, but now microsurgical techniques were introduced allowing for surgical cure of hormonal disease in microadenomas.
Although the procedure described by Hardy underwent numerous modifications (including extended approaches to other skull base sites: clival and suprasellar tumors as well as cavernous sinus lesions), it was the main procedure performed by neurosurgeons for removal of pituitary tumors from the 1960's through the early 1990's 16).
Although Griffith and Veerapen reported a case of endonasal approach to the sellar region in 1987, the transsphenoidal endonasal approach did not gain popularity. 17).
There has been a paradigm shift linked to developing endoscopic technologies with the introduction of completely endoscopic endonasal approaches to the ventral skull base.
Endoscopic endonasal skull base surgery has dramatically changed and expanded over recent years due to significant advancements in instrumentation, techniques, and neuroanatomy understanding. With these advances, the need for more robust skull base reconstructive techniques was vital 18)
Since 1995 there is a remarkable advancement in endonasal approach by endoscope. Refinements in camera definition, neurosurgical instruments, neuronavigation, and surgical technique.
Since 2000s, Endoscopic endonasal approach has become the most popular choice of neurosurgeons and otolaryngologists to treat lesions of the skull base, with minimal invasiveness, lower incidence of complications, and lower morbidity and mortality rates compared with traditional approaches.
The dual surgeon team, have facilitated purely endonasal endoscopic approaches to the majority of the midline skull base that were previously difficult to access through the transsphenoidal approach via microscope.
Types
Endoscopic transsphenoidal approach.
Extended endoscopic transsphenoidal approach.
Indications
Endoscopic Endonasal Approach Indications.
Advantages
see Endoscopic skull base surgery advantages. The major potential advantage of the endoscopic endonasal approach to the skull base is that it provides a direct anatomical route to the lesion without traversing any major neurovascular structures, obviating brain retraction. Many tumors grow in a medial-to-lateral direction, displacing structures laterally as they expand, creating natural corridors for their resection via an anteromedial approach.
Refinements in approach and closure techniques have reduced the risk of Cerebrospinal fluid fistula and infection. This has allowed surgeons to more aggressively treat a variety of pathologies. Now its a safe and effective procedure for various parasellar lesions. Selection of patients who are unlikely to develop complications seems to be an important factor for procedure efficacy and good outcome 19).
Disadvantages
Potential disadvantages of this procedure include the relatively restricted working space and the danger of an inadequate dural repair with Cerebrospinal fluid fistula and potential for meningitis resulting. These approaches often require a large opening of the dura mater over the tuberculum sellae and posterior planum sphenoidale, or retroclival space. In addition, they typically involve large intraoperative Cerebrospinal fluid fistulas, which necessitate precise and effective dural closure 20).
Sinus opacity is still present after one year of advance endoscopic skull base surgery but symptoms seems to return to basal after 12months of follow-up 21).
Requirements
Endoscopic skull base surgery requirements.
Technique
Supine position with the trunk raised 10º and the head in neutral position rotated 10º towards the surgeon. The head is secured in a Horseshoe Headrest without rigid three-pin fixation. The nose is prepared by placing pledgets soaked with 0.02% of Oxymetazoline into each nostril, followed by Povidone Iodine solution applied over the nose and upper lip as well as into the nares with cotton tip applicators.
Pediatric population
Endonasal endoscopic skull base approaches are viable in the pediatric population, they are not impeded by sphenoid sinus aeration, and they have minimal risk of Cerebrospinal fluid fistula and meningitis. Outcomes and complications can be predicted based on specific radio anatomical skull base measurements rather than age 22).
Challenges
One challenge performing endoscopic endonasal approaches is the surgical conflict that occurs between the surgical instruments and endoscope in the crowded nasal corridor. This conflict decreases surgical freedom, increases surgeon frustration, and lengthens the learning curve for trainees.
The application of a malleable endoscope to transsphenoidal approaches to the parasellar region decreases instrument-endoscope conflict and improves surgical freedom 23).
Endoscopic endonasal surgery (EES) of the skull base often requires extensive bone work in proximity to critical neurovascular structures.
In selected EES, the ultrasonic bone curette was successfully used to remove loose pieces of bone in narrow corridors, adjacent to neurovascular structures, and it has advantages to high-speed drills in these specific situations 24).
Complications
see Endoscopic endonasal approach complications.
Outcome
Quality-of-life instruments
see Shukla A, Ahmed OG, Orlov CP, Price C, Mukherjee D, Choby G, Rowan NR. Quality-of-life instruments in endoscopic endonasal skull base surgery-A practical systematic review. Int Forum Allergy Rhinol. 2021 Feb 21. doi: 10.1002/alr.22783. Epub ahead of print. PMID: 33611853.
The Endoscopic Endonasal Sinus and Skull Base Surgery Questionnaire (EES-Q), is a comprehensive, multidimensional, disease-specific instrument. A distinguishing characteristic is that, apart from the physical and psychological domains, the EES-Q also encompasses a social domain. Understanding different HRQoL aspects in patients undergoing EES may help caregivers restore, improve, or preserve the patient's health through individualized care, which depends on identifying their specific needs 25).
Case series
Endoscopic endonasal approach case series.