Endoscopic Pituitary and Suprasellar Surgery
Aldo C. Stamm
Eduardo Vellutini
INTRODUCTION
The first successful removal of a pituitary tumor, via the transcranial approach, is credited to Victor Horsley in 1889. In 1907, Schloffer was the first to report resection using transsphenoidal access. Soon afterward, in 1910, Cushing developed the sublabial transseptal-transsphenoidal technique, which was employed over two decades in more than 400 patients with a mortality rate of 5.2%. Simultaneously, Oskar Hirsh, an otolaryngologist, introduced a transseptal-transsphenoidal approach to the pituitary gland in 1910. Kanavel and Halstead had previously suggested intranasal access as an initial step, followed by sublabial access to the sellar region. The use of the microscope with fluoroscopy was introduced in 1965 by Hardy.
From 1951 to 1956, Hopkins was responsible for many contributions to the development and improvement of endoscopes; however, it was only after the studies published by Messerklinger in 1969, and later ones by Draf, Stammberger, and Kennedy, that endoscopy became known worldwide. Today, it is used widely in the surgical treatment of lesions of the anterior skull base and sellar and parasellar regions.
Jankowski et al. first described endoscopic endonasal resection of pituitary adenomas in 1992, while Sethi et al. described the application of the transnasal endoscopic surgical technique to treatment of pituitary adenomas in 1995. A 1997 paper by Jho and Carrau then marked the beginning of modern endoscopic pituitary surgery.
Surgery of the sellar and parasellar tumors has undergone significant evolution in recent decades. The introduction of microsurgery and, more recently, endoscopy was the determining factor. The current philosophy for the treatment of sellar and parasellar lesions relies on a multidisciplinary team (otolaryngologist, neurosurgeon, endocrinologist, anesthesiologist, and critical care specialist) working together on preoperative, intraoperative, and postoperative care.
The endoscope provides an excellent range of mobility, angled view, and superior image resolution for documentation, learning, and teaching, making sellar and parasellar surgery safer and more dynamic. This is an extremely helpful advance, especially for surgery of the sphenoid sinus, which is a deep structure and has a lateral relationship with important structures such as the optic nerves and internal carotid arteries, where an angled view is essential. Many studies have shown that endoscopically assisted surgery decreases postoperative discomfort and hospital stay, providing faster recovery as compared with patients undergoing surgery by the traditional microscopic approach. Operative time and blood loss have also been shown to be lower with use of the endoscope. For all these reasons, many authors believe that the endoscope has replaced the surgical microscope for surgery of pituitary adenomas and other sellar lesions. Another great contribution to sellar and skull base surgery was the development of techniques for closure of dural defects by harvesting vascularized nasoseptal flaps, significantly reducing the rate of postoperative cerebrospinal fluid (CSF) leak.
HISTORY
There are two typical complaints of a patient with a pituitary tumor, namely symptoms arising from endocrine dysfunction and visual complaints arising from deterioration of the visual fields. The majority of the tumors are nonendocrine secreting, and narrowing of the visual field is the main symptom, especially the lateral (temporal) view. Some of the patients with non-endocrine-secreting tumors may have symptoms of hypopituitarism or a secondary elevation of prolactin levels due to compression of the pituitary stalk. Women complain of galactorrhea and menstrual disturbances; men may complain of lowered libido.
The most common secreting tumor is the prolactinoma that causes the same symptoms of compression of the pituitary stalk as is seen in nonsecreting tumors; the only difference is that there is a higher serum prolactin level. Patients with growth hormone (GH)-secreting tumors and corticotropic tumors frequently present with diabetes mellitus and elevated blood pressure. The first group has acromegalic features, while the second has a typical type of obesity most prominent in the face and trunk.
The patient should also be questioned with regard to the presence of acute or chronic sinusitis, nasal and sinus symptoms, and a history of prior nasal or sinus surgery. Although the presence of chronic sinusitis is not a contraindication to transnasal surgical intervention, the presence of an acute exacerbation in elective cases typically would result in postponement of surgical intervention until the acute exacerbation had resolved.
All patients with a pituitary tumor should be evaluated by a neuroendocrinologist, who will define the most appropriate therapy in each case. Besides endocrinologic evaluation, all patients with suprasellar extension of their tumors should undergo neuroophthalmic examination with visual acuity, intrinsic and extrinsic ocular motility, and visual field testing.
PHYSICAL EXAMINATION
The physical examination should include endoscopic assessment of the nasal cavity in order to visualize any nasal lesions and document the integrity of the septum, septal deviations, and other abnormal anatomical findings. This procedure is performed with the patient in a semisitting position. The nasal cavity is prepared with a topical anesthetic solution containing a vasoconstrictor. The examination is performed with rigid 4.0-mm 0-degree, 30-degree, and 70-degree endoscopes. In children, the flexible 3.2-mm endoscope is preferable, and occasionally, a straight 2.7-mm endoscope may be used.
For lesions of the sellar and parasellar regions, the physical examination includes a gross neurologic assessment with special focus on cranial nerve function. An examination by an ophthalmologist is suggested if optic nerve or orbital integrity is compromised. A visual field examination is also recommended.
INDICATIONS
Surgical removal is considered first-line therapy for nonfunctioning pituitary macroadenomas and for Cushing disease (both for micro- and macroadenomas). Patients with GH-producing adenomas are surgical candidates when microadenomas and macroadenomas cause visual disturbance. Medical therapy is indicated as first-line treatment for invasive tumors.
Debulking surgery, even when noncurative, may improve the response to somatostatin analogues in primary cases resistant to these drugs, prolactinomas in drug-resistant or drug-intolerant patients, pituitary apoplexy, cystic tumors, and presence of CSF fistula after medical treatment.
CONTRAINDICATIONS
Nonsecreting microadenomas
Prolactinomas, even large ones with visual impairment, are treated medically unless drug resistant
PREOPERATIVE PLANNING
MRI imaging not only defines the diagnosis of pituitary tumor, but provides extremely valuable information for the intraoperative period, as it demonstrates the relationship of the tumor to the normal gland, pituitary stalk, optic structures, and internal carotid arteries. Prediction of the consistency of pituitary tumors on diffusion-weighted MRI has recently been reported. CT images provide information about the dimensions of the sphenoid sinus, the position of the inter- and intrasinus septum, and the anatomy of the nose and paranasal sinuses. At the time of surgical intervention, perioperative prophylactic antibiotics are routinely administered.
SURGICAL TECHNIQUE
Surgery is performed under general anesthesia with endotracheal intubation. To keep blood pressure and heart rate at lower levels, which helps in maintaining hemostasis, the use of total intravenous anesthesia with propofol and fentanyl is preferred.
The patient is positioned on the operating table with the back elevated 30 degrees and the head slightly extended and rotated toward the surgeon. Fixation of the head is not necessary, unless neuronavigation without head tracking is used.
The lateral thigh is prepped, draped, and kept aseptic and may be used as a donor site for adipose tissue and fascia lata grafts if reconstruction and closure of dural defects becomes necessary.
Combined Endoscopic Transnasal/Transseptal Binostril Approach
This has been the approach of choice for our patients with pituitary tumors. It enables work by two surgeons and four hands without causing perforation of the nasal septum and causes less injury to the nasal mucosa when compared with the direct bilateral transnasal technique.
The first step in the transnasal/transseptal is an incision in the caudal septum followed by subperichondrial dissection and removal of the cartilaginous and bony septum, keeping an “L” shape of the cartilage of the septum to prevent nasal deformity. Secondly, a pedicled nasoseptal flap is harvested contralateral to the septal incision and placed in the nasopharynx (Fig. 27.1). Then, the sphenoid rostrum is exposed, and a very wide sphenoidotomy is performed to allow a good visualization of the bony impression of the structures in the posterior wall of the sphenoid sinus, such as the optic chiasm, internal carotid arteries, sella, and clivus.
