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Arnaldo Neves Da Silva, Maria Beatriz Lopes and David Schiff

✓ Primary central nervous system lymphoma (PCNSL) is a rare form of primary brain neoplasm, accounting for less than 3% of all primary brain tumors. Ninety percent of cases involve a large B-cell lymphoma that presents as a homogeneously enhancing lesion or lesions, typically deep-seated in the brain parenchyma. The authors describe unusual pathological forms of PCNSLs, including low-grade, T-cell, and Burkitt types, and also rare presentations such as neurolymphomatosis and pituitary lymphomas.

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Björn P. Meij, Maria-Beatriz S. Lopes, Dilantha B. Ellegala, Tord D. Alden and Edward R. Laws Jr.

Object. Pituitary adenomas are considered benign tumors; however, they may infiltrate surrounding tissues including the dura mater. In this paper the authors analyze the clinical significance of microscopically confirmed dural invasion by comparing a range of variables (age and sex of patients, adenoma type, adenoma size on magnetic resonance [MR] images, remission, residual pituitary disease, recurrence, survival, and disease-free interval after surgery) between patients with noninvasive adenomas and those with invasive ones.

Methods. Between 1992 and 1997 dural specimens were obtained in 354 patients with pituitary adenomas who underwent transsphenoidal surgery performed by the senior author (E.R.L.). Dural specimens were examined using routine histological methods and assessed for invasion by pituitary adenoma tissue.

The dura was invaded by the pituitary adenoma in 161 patients (45.5%), and in 192 patients (54.5%) no evidence of dural invasion was found. Dural invasion was present significantly more frequently in the repeated surgery group (69%, 55 patients) than in the primary transsphenoidal surgery group (41%, 291 patients). The mean age of patients undergoing primary transsphenoidal surgery was significantly older in cases of invasive adenomas (50 years) compared with cases of noninvasive adenomas (43 years), and these age differences also correlated with adenoma size. Women tend to develop clinically evident, smaller adenomas at a younger age than men. Of the patients with pituitary adenomas that were 20 mm or smaller, 117 (76%) of 154 were women, whereas of the patients with adenomas that were larger than 20 mm, 74 (54%) of 137 were men. The frequency of dural invasion increased with increasing size of the pituitary adenoma as measured on MR images. In 291 patients who underwent primary pituitary surgery, the frequency of dural invasion according to adenoma size was 24% (≤ 10 mm), 35% (> 10 to ≤ 20 mm), 55% (> 20 to ≤ 40 mm), and 70% (> 40 mm). In patients who underwent primary transsphenoidal surgery, dural invasion was present in more than 50% of those with nonfunctioning adenomas and in 30 to 35% of patients with endocrinologically active adenomas. The mean diameter of the gonadotrophic adenomas and null-cell adenomas was significantly larger than that of each of the endocrinologically active adenomas.

In 58 (20%) of 291 patients who underwent primary pituitary surgery there was residual pituitary disease postsurgery, and 20% of this subset of patients showed clinical improvement to such an extent that no further management was recommended. After pituitary surgery, residual tumor tissue was demonstrable significantly more frequently in patients with invasive adenomas than in those with noninvasive adenomas.

Recurrences after initial remission (cure) of pituitary disease occurred in 18 (8.8%) of 205 patients between 2 and 79 months after primary pituitary surgery (median 25 months). The recurrence rate was not related to dural invasion in a consistent or significant fashion. Seven patients died between 14 and 79 months after pituitary surgery and all had invasive adenomas identified on gross observation at surgery and on microscopy. The survival rate was slightly but significantly decreased for patients with invasive adenomas (91%) compared with patients with noninvasive adenomas (100%) at 6 years postsurgery.

Conclusions. The principal significance of dural invasion by pituitary adenoma is the persistence of tumor tissue after transsphenoidal surgery (incomplete adenomectomy; 20% in primary pituitary tumor resections). The increase in adenoma size with time and the concurrent development of dural invasion are the major factors that determine an incomplete adenomectomy. When the adenoma remains restricted to the sellar compartment or shows only moderate suprasellar extension, dural invasion may not yet have developed and conditions for complete selective adenomectomy are improved.

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Gilberto K. K. Leung, Maria-Beatriz S. Lopes, Michael O. Thorner, Mary Lee Vance and Edward R. Laws Jr.

Object. The authors review their experience in the treatment of 16 patients with primary hypophysitis.

Methods. A retrospective study was undertaken to review cases of primary hypophysitis. The mean age of the patients was 47 years and there was an equal distribution of sexes. Recent pregnancy and underlying autoimmunity were noted in 50% of the patients. Two patients had undergone previous transsphenoidal operations at other centers, one for prolactinoma and another for hypophysitis. Headache, anterior pituitary deficiency, and suprasellar mass lesions were the most common presenting features. The initial presumptive diagnosis was pituitary adenoma in six patients (37.5%) and inflammatory hypophysitis in 10 (62.5%). Five patients received initial medical therapy for hypophysitis; although three (60%) responded satisfactorily, two (40%) did not and later underwent surgery.

Altogether 13 patients (81.2%) underwent transsphenoidal surgery. The histological diagnoses were lymphocytic hypophysitis in 10 (76.9%) and granulomatous hypophysitis in three (23.1%) of the surgically treated patients. A coexistent Rathke cleft cyst was noted in one patient. There was no death in this series. One patient experienced postoperative cerebrospinal fluid leakage and meningitis. One patient had bilateral internal carotid artery occlusion secondary to inflammatory involvement of the cavernous sinuses and arteritis. This patient recovered and is capable of independent functional activities.

Conclusions. All surgical patients experienced improvement in their headache and/or visual field defects and none had visual deterioration. None of the patients experienced any improvement in endocrine function and all required long-term hormone replacement. Transsphenoidal surgery was a safe and effective treatment especially for visual and pressure symptoms. A postoperative recurrence developed in two patients (15.4%) and the treatment modalities included steroid therapy, repeated surgery, and radiosurgery.

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W. Jeff Elias, Mohamad Khaled, Justin D. Hilliard, Jean-Francois Aubry, Robert C. Frysinger, Jason P. Sheehan, Max Wintermark and Maria Beatriz Lopes

Object

The purpose of this study was to use MRI and histology to compare stereotactic lesioning modalities in a large brain model of thalamotomy.

Methods

A unilateral thalamotomy was performed in piglets utilizing one of 3 stereotactic lesioning modalities: focused ultrasound (FUS), radiofrequency, and radiosurgery. Standard clinical lesioning parameters were used for each treatment; and clinical, MRI, and histological assessments were made at early (< 72 hours), subacute (1 week), and later (1–3 months) time intervals.

Results

Histological and MRI assessment showed similar development for FUS and radiofrequency lesions. T2-weighted MRI revealed 3 concentric lesional zones at 48 hours with resolution of perilesional edema by 1 week. Acute ischemic infarction with macrophage infiltration was most prominent at 72 hours, with subsequent resolution of the inflammatory reaction and coalescence of the necrotic zone. There was no apparent difference in ischemic penumbra or “sharpness” between FUS or radiofrequency lesions. The radiosurgery lesions presented differently, with latent effects, less circumscribed lesions at 3 months, and apparent histological changes seen in white matter beyond the thalamic target. Additionally, thermal and radiation lesioning gradients were compared with modeling by dose to examine the theoretical penumbra.

Conclusions

In swine thalamus, FUS and radiosurgery lesions evolve similarly as determined by MRI, histological examination, and theoretical modeling. Radiosurgery produces lesions with more delayed effects and seemed to result in changes in the white matter beyond the thalamic target.