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Changing concepts in the treatment of colloid cysts

An 11-year experience in the CT era

Walter A. Hall and L. Dade Lunsford

✓ Since computerized tomography (CT) scanning became available at the University Health Center of Pittsburgh in July, 1975, 17 patients have undergone removal of colloid cysts of the third ventricle by transfrontal, transcallosal, or stereotaxic surgery. All patients presented with symptoms and signs of increased intracranial pressure; CT scanning proved to be the best neurodiagnostic test to define the colloid cysts. Since the development of CT-guided stereotaxic surgery, the authors have preferentially performed stereotaxic aspiration in seven patients; three of these subsequently required craniotomies to remove residual cysts producing persistent symptoms. The viscosity of the intracystic colloid material and/or displacement of the cyst away from the aspiration needle were reasons for unsuccessful aspiration; the CT appearance did not correlate with the ability to aspirate the lesion by the stereotaxic technique. Postoperative patency of the ventricular system was documented by intraoperative CT ventriculography performed during stereotaxic surgery. Removal of the cyst wall was not necessary. Because of the low associated morbidity rate, percutaneous stereotaxic aspiration is recommended as the initial treatment of choice for colloid cysts of the third ventricle. If stereotaxic aspiration fails and symptoms persist, craniotomy should be performed.

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Douglas Kondziolka and L. Dade Lunsford

✓ Stereotactic aspiration is a valuable surgical alternative for colloid cysts when used alone or in conjunction with microsurgical resection. Since 1981, the authors have performed computerized tomography (CT)-guided stereotactic aspiration as the initial procedure in 22 patients with colloid cysts; stereotactic aspiration alone was successful in 11 patients (50%). Of the 11 patients in whom aspiration failed, stereotactic endoscopic resection was attempted in three and was successful in one. Seven patients required a craniotomy and microsurgical removal of the cyst performed via a transcortical approach.

The preoperative CT appearance in eight cases of a hypodense or isodense cyst correlated favorably with successful aspiration of the cyst in six patients. A hyperdense appearance on the preoperative CT scan in 14 cases was associated with subtotal aspiration in 13 patients; five required craniotomy for removal. Preoperative magnetic resonance (MR) imaging in eight patients provided excellent anatomical definition of the cyst and its relationship to other structures of the third ventricle, but it was not possible to correlate successful aspiration with cyst appearance on MR images with short or long relaxation time sequences. The authors' 9-year experience suggests that preoperative CT studies accurately determine size, predict viscosity, and help to define a group of colloid cyst patients for whom stereotactic cyst aspiration will likely be successful. Unsuccessful stereotactic aspiration was related to two features: the high viscosity of the intracystic colloid material (nine patients), or deviation of the cyst away from the aspiration needle due to small cyst volume (two patients). Because of its simplicity and low risk, stereotactic surgery can be offered to selected patients as the initial procedure of choice. Craniotomy can be reserved for those whose imaging studies predict failure or for those whose cyst cannot be aspirated.

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L. Dade Lunsford

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Travis Hamilton and L. Dade Lunsford

OBJECTIVE

The role of Gamma Knife radiosurgery (GKRS) has expanded worldwide during the past 3 decades. The authors sought to evaluate whether experienced users vary in their estimate of its potential use.

METHODS

Sixty-six current Gamma Knife users from 24 countries responded to an electronic survey. They estimated the potential role of GKRS for benign and malignant tumors, vascular malformations, and functional disorders. These estimates were compared with published disease epidemiological statistics and the 2014 use reports provided by the Leksell Gamma Knife Society (16,750 cases).

RESULTS

Respondents reported no significant variation in the estimated use in many conditions for which GKRS is performed: meningiomas, vestibular schwannomas, and arteriovenous malformations. Significant variance in the estimated use of GKRS was noted for pituitary tumors, craniopharyngiomas, and cavernous malformations. For many current indications, the authors found significant variance in GKRS users based in the Americas, Europe, and Asia. Experts estimated that GKRS was used in only 8.5% of the 196,000 eligible cases in 2014.

CONCLUSIONS

Although there was a general worldwide consensus regarding many major indications for GKRS, significant variability was noted for several more controversial roles. This expert opinion survey also suggested that GKRS is significantly underutilized for many current diagnoses, especially in the Americas. Future studies should be conducted to investigate health care barriers to GKRS for many patients.

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Katrina S. Firlik, A. Julio Martinez and L. Dade Lunsford

Object. The goals of this study were to analyze the accuracy of cytological techniques, consisting of touch and smear preparations, for the intraoperative diagnosis of stereotactically obtained brain biopsy samples, and to determine the prevalence of the use of these methods among neuropathologists.

Methods. A survey regarding preferred methods for intraoperative diagnosis of stereotactically obtained brain biopsy samples was completed by 92 (62%) of 148 neuropathologists. Twenty-three percent of respondents chose frozen-section examination alone; 13% chose one or more cytological methods alone; and the remainder (64%) chose a combination of frozen-section examination and cytology.

At the University of Pittsburgh, the neuropathology records for all stereotactic brain biopsies performed from May 1979 through May 1998 were retrospectively reviewed. Of the 946 stereotactic brain biopsies, 316 cases were excluded because the intraoperative neuropathological consultation was not recorded. Thirty-five cases were excluded because frozen-section examinations were performed. Therefore, a total of 595 cases were suitable for analysis.

Intraoperative cytological investigation correlated with the final diagnosis in 90% of cases (52% complete correlation and 38% partial correlation). In 11% of cases there was no correlation between the intraoperative and final diagnoses. Intraoperative diagnoses were most accurate in cases of abscess, germinoma, lymphoma, metastasis, and malignant glioma.

Overall, 91% of biopsy specimens were diagnostic when examined using the paraffin-embedded section technique. The sensitivity of cytological preparations in detecting a diagnostic specimen was 96% and the specificity in detecting a nondiagnostic specimen was 75%.

Conclusions. Intraoperative cytological preparations correlated with the final diagnoses in 90% of stereotactic biopsies and had a 96% sensitivity in detecting diagnostic specimens. The highest rate of correlation was noted in cases of abscess, germinoma, lymphoma, metastasis, and malignant glial tumor.

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L. Dade Lunsford, A. Julio Martinez and Richard E. Latchaw

✓ Modern stereotaxic surgery is dependent upon compatible advanced imaging tools, including computerized tomography (CT) scanning and magnetic resonance (MR) imaging. The authors describe three cases in which the patients underwent stereotaxic surgery for mass lesions identified by both MR imaging and CT scans. Identical target coordinates were defined by both techniques, and accuracy was confirmed by intraoperative CT. In comparison to stereotaxic CT, MR provided superior contrast resolution, allowed direct multiplanar imaging and target determination, and permitted accurate correlation of the image with histological features. The operative set-up and technique are described. Stereotaxic surgery with MR imaging may permit more accurate histopathological definition of tumor margins and ultimately lead to better dosimetry for therapeutic procedures such as interstitial brachytherapy.