Davis G. Taylor and John A. Jane Jr.
Davis G. Taylor, John A. Jane Jr. and Edward H. Oldfield
Extracapsular resection of pituitary microadenomas improves remission rates, but the application of pseudocapsular techniques for macroadenomas has not been well described. In larger tumors, the extremely thin, compressed normal gland or its complete absence along the tumor’s anterior surface limits the application of the traditional pseudocapsular technique that can be used for microadenomas. However, in the authors’ experience, the interface between the pseudocapsule at the posterior margin of the adenoma and the compressed normal gland behind it is universally present, providing a surgical dissection plane. In mid-2010, the authors began using a new surgical technique to identify and use this interface for the resection of larger macroadenomas, a technique that can be used with the microscope or the endoscope.
The authors performed a cohort study using prospectively collected preoperative imaging reports and operative details and retrospectively reviewed postoperative images and clinical follow-up of patients with a pituitary macroadenoma 20–40 mm in maximum diameter undergoing microscopic transsphenoidal resection. Since dissection of the tumor capsule only pertains to encapsulated tumor within the sella and not to tumor invading the cavernous sinus, assessment of tumor removal of noninvasive tumors emphasized the entire tumor, while that of invasive tumors emphasized the intrasellar component only. The incidence of residual tumor on postoperative imaging, new-onset endocrinopathy, and recovery of preoperative pituitary deficits was compared between patients who underwent surgery before (Group A) and after (Group B) implementation of the new technique.
There were 34 consecutive patients in Group A and 74 consecutive patients in Group B. Tumors in 18 (53%) Group A and 40 (54%) Group B patients had no evidence of cavernous sinus invasion on MRI. Use of the posterior pseudocapsule technique reduced the incidence of intrasellar residual tumor on postoperative MRI for tumors without cavernous sinus invasion (39% [Group A] vs 10%, p < 0.05) and in all tumors regardless of invasion (50% vs 18%, p < 0.005). The incidence of new endocrinopathy was less likely (25% vs 12%, p = 0.098) and the recovery of prior deficits more likely (13% vs 27%, p = 0.199) among patients treated using the pseudocapsule approach, although the differences are not statistically significant.
Use of the posterior pseudocapsule dissection plane can enhance the resection of pituitary macroadenomas.
Davis G. Taylor, Panagiotis Mastorakos, John A. Jane Jr. and Edward H. Oldfield
A subset of patients with Chiari I malformation demonstrate patent subarachnoid spaces around the cerebellum, indicating that reduced posterior fossa volume alone does not account for tonsillar descent. The authors distinguish two subsets of Chiari I malformation patients based on the degree of “posterior fossa crowdedness” on MRI.
Two of the coauthors independently reviewed the preoperative MR images of 49 patients with Chiari I malformation and categorized the posterior fossa as “spacious” or “crowded.” Volumetric analysis of posterior fossa structures was then performed using open-source DICOM software. The preoperative clinical and imaging features of the two groups were compared.
The posterior fossae of 25 patients were classified as spacious and 20 as crowded by both readers; 4 were incongruent. The volumes of the posterior fossa compartment, posterior fossa tissue, and hindbrain (posterior fossa tissue including herniated tonsils) were statistically similar between the patients with spacious and crowed subtypes (p = 0.33, p = 0.17, p = 0.20, respectively). However, patients in the spacious and crowded subtypes demonstrated significant differences in the ratios of posterior fossa tissue to compartment volumes as well as hindbrain to compartment volumes (p = 0.001 and p = 0.0004, respectively). The average age at surgery was 29.2 ± 19.3 years (mean ± SD) and 21.9 ± 14.9 years for spacious and crowded subtypes, respectively (p = 0.08). Syringomyelia was more prevalent in the crowded subtype (50% vs 28%, p = 0.11).
The authors' study identifies two subtypes of Chiari I malformation, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation.
Toshihiro Ogiwara, Alhusain Nagm and Kazuhiro Hongo
Panagiotis Mastorakos, Davis G. Taylor, Ching-Jen Chen, Thomas Buell, Joseph H. Donahue and John A. Jane Jr.
Cavernous sinus invasion (CSI) in Cushing’s disease (CD) negatively affects the probability of complete resection, biochemical cure, and need for adjuvant therapy. However, the prediction of CSI based on MRI findings has been inconsistent and variable. Among macroadenomas, the Knosp classification is the most widely utilized radiographic predictor of CSI, but its accuracy in predicting CSI and the probability of gross-total resection is limited in the setting of microadenomas or Knosp grade 0–2 macroadenomas. The authors noticed that the presence of a triangular shape of adenomas adjacent to the cavernous sinus on coronal MR images is frequently associated with CSI. The authors aimed to determine the correlation of this radiographic finding (“sail sign” [SS]) with CSI.
The authors performed a retrospective review of all patients with a pituitary lesion < 20 mm and a biochemical diagnosis of CD treated with endoscopic or microscopic transsphenoidal resection from November 2007 to May 2017. Overall 185 patients with CD were identified: 27 were excluded for negative preoperative imaging, 32 for lacking tumors adjacent to the sinus, 7 for Knosp grade 3 or higher, and 4 for inadequate intraoperative assessment of the CSI. Following application of inclusion and exclusion criteria, 115 cases were available for statistical analysis. Intraoperative CSI was prospectively evaluated at the time of surgery by one of two neurosurgical attending surgeons, and MRI data were evaluated retrospectively by a neurosurgical resident and attending neuroradiologist blinded to the intraoperative results.
A positive SS was identified in 23 patients (20%). Among patients with positive SS, 91% demonstrated CSI compared to 10% without an SS (p < 0.001). Using the SS as a predictor of CSI provided a sensitivity of 0.7 and a specificity of 0.98, with a positive predictive value (PPV) of 0.91 and a negative predictive value of 0.9. Among patients with positive SS, 30% did not achieve immediate postoperative remission, compared to 3.3% of patients without an SS (p < 0.001).
The presence of a positive SS among Cushing’s adenomas adjacent to the CS provides strong PPV, specificity, and positive likelihood ratio for the prediction of CSI. This can be a useful tool for preoperative planning and for predicting the likelihood of long-term biochemical remission and the need for adjuvant radiosurgery.