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|Year : 2019 | Volume
| Issue : 6 | Page : 1456-1458
Extracapsular Resection of Noninvasive Functional Pituitary Adenomas
Chandrashekhar Deopujari, Aniruddha Bhagwat
Department of Neurosurgery, BHIMS, Mumbai, Maharashtra, India
|Date of Web Publication||20-Dec-2019|
Dr. Chandrashekhar Deopujari
Department of Neurosurgery, BHIMS, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Deopujari C, Bhagwat A. Extracapsular Resection of Noninvasive Functional Pituitary Adenomas. Neurol India 2019;67:1456-8
The series by QingXin et al. in this issue very well describes the logically possible benefits expected from extracapsular resection of functional noninvasive pituitary adenoma. The foundation of modern pituitary surgery for functioning tumors was laid by Jules Hardy from Montreal, who used magnification and illumination provided by an operating microscope for the first time to facilitate the selective radical resection of pituitary microadenomas. This served the purpose of differentiating the surrounding normal parenchyma from the adenomatous tissue and thus preserving normal hormonal function. Over the years, neurosurgeons have worked on these very lines, and various new techniques have been designed keeping in mind the same goals viz. maximal safe resection, normalization of hormonal function, and avoidance of recurrence. The endoscopic endonasal approach has now become the standard of care for pituitary surgery. The rapid improvements in endoscope technology have led to a remarkable rise in its popularity, as also an attendant revolutionary change in the concepts of pituitary surgery.
The concept of a tumor pseudocapsule has been well established through the work of Oldfield and Vortmeyer. The techniques of intracapsular and extracapsular resection have been designed with respect to this pseudocapsule [Figure 1] and [Figure 2]. There are numerous pros and cons to both of these techniques. Extracapsular excision allows a more complete excision of the adenoma, with superior functional hormonal normalisation, although at the cost of higher rates of the injury to the cavernous sinus, normal parenchyma, and infundibulum, as also higher cerebrospinal fluid (CSF) leak rates. For this reason, extracapsular approaches went out of favour for a long time. It may be useful to note that in cases with MRI negative microadenomas that are lateralized on bilateral inferior petrosal sinus sampling (BIPSS), the success rate of hemi-hypophysectomy may be higher than that of extracapsular resection.,, This is especially true while reoperating patients with microadenoma due to the lack of normalization of hormonal levels.
The series by Li et al. from China  is a fairly large series of both endoscopic and microscopic techniques for pituitary adenoma surgery. It, however, avoids any comparison between endoscopy and microscopy group outcomes and thus does not emphasise the well-known benefits of modern high-definition endoscopic visualisation.
The technique of extracapsular excision follows a generally established pattern. The endonasal component of the procedure is usually performed with the help of an ENT colleague in our setup. Wide drilling of the sellar floor is performed between the cavernous sinuses laterally and the intercavernous sinuses anteroposteriorly. A semicircular durotomy is made, preserving the pituitary capsule. For macroadenomas, internal debulking of the tumor is then begun, followed by tumor clearance in the following zones in sequential order—anterior, inferior, lateral, and superior. This does not allow premature descent of the diaphragm sellae obscuring tumor behind. This is followed by appropriate closure and repair techniques as per the size of arachnoid defect or the magnitude of intraoperative CSF leak. Recent use of fibrin glue and vascularized nasoseptal (Haddad) flap have decreased the incidence of adverse events. In microadenomas, we follow the same sequence of separation, but after complete excision of the sellar floor, we proceed to explore the appropriate side and site of microadenoma.
The paper by Li et al. recommends limited sellar floor drilling, which may not serve the purpose of total tumor clearance. The excision of the tumor en masse with the intact capsule as described by the authors may be difficult especially with soft/semi-liquid adenomas, which tend to ooze out as soon as the dura is opened.
The concept of extracapsular excision presumes gross excision of the tumor, but cannot rule out a microscopic functional remnant, which may be to the tune of 70–85% [Figure 2]A and [Figure 2]B. This has been well-established by numerous papers on the subject by Laws et al. and others.,,,, This effect tends to offset the process of hormonal normalization even in the absence of gross/MRI detectable residual lesions, especially in somatotroph and corticotroph adenomas. The removal of disease close to the cavernous sinus (which is the most common location in Cushing's, that is, corticotroph microadenoma) is especially difficult since the pseudocapsule is less well-developed in this area [Figure 3]A and [Figure 3]B.
The series by Li et al. reports an unusually high incidence of post-op diabetes insipidus (DI) (73%), given that the routinely observed rate by us as well as many others is to the tune of 18% for temporary and 2% for permanent DI.,, This high rate of DI may be attributed to a greater than usual handling of the stalk/neurohypophysis during extracapsular resection.
There is also a very high proportion of microprolactinomas among the total number of operated cases (70%) in this series. This is in contradiction to our experience as well as those of others, due to a generally followed practice of medically managing microprolactinomas.,, The definite indications of the surgical treatment of microprolactinomas need to be restated and better defined. The authors have inexplicably excluded patients with tumor recurrence from the series, which would be an important indicator of the success of extracapsular excision and may have an impact on their conclusions.
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[Figure 1], [Figure 2], [Figure 3]