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A decade of pituitary microsurgery

The Herbert Olivecrona Lecture

Charles B. Wilson

✓ The author reviews his experience with surgical treatment of 1000 pituitary tumors, the majority of which were endocrine-active. The criteria of grading, the microsurgical technique used, and the postoperative results are presented. The mortality rate was 0.2% overall, with no deaths in the group of 774 patients with endocrine-active adenomas.

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Charles B. Wilson

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Charles B. Wilson

✓ The author reviews the molecular genetics, pathology, and cell kinetics of meningiomas and the role that regional multiplicity in the dura mater may play in their recurrence. Malignant and radiation-induced meningiomas are discussed, with summaries of series of 60 patients with frankly malignant lesions treated over a period of 22 years at the University of California, San Francisco, and of 10 patients with meningiomas induced by high-dose radiation therapy. Reviewing a 23-year series of 140 patients with subtotally removed meningiomas who were treated postoperatively with radiation, the author recommends that, with meticulous technique, irradiation is effective in preventing the regrowth of subtotally removed benign meningiomas and of all malignant meningiomas. Adoption of both the microscopical cytological grading system proposed by Jääskeläinen's group in Helsinki and the classification of operations proposed by Donald Simpson is also recommended. Wide removal of dura adjacent to meningioma reduces the risk of recurrence, and determination of the bromodeoxyuridine labeling index provides a valid basis for planning treatment and follow-up evaluations. Increased awareness is necessary for early recognition of radiation-induced meningiomas in patients at risk for developing such tumors. For meningiomas in such sites as the parasellar region and the posterior fossa, conservative removal of tumor followed by irradiation is advocated in preference to a radical operation that may cause neurological injury without being curative.

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Charles S. Cobbs and Charles B. Wilson

✓ The authors present a rare entity, an intrasellar cavernous hemangioma that on neuroimages mimicked a nonfunctioning pituitary macroadenoma in a patient with a known orbital hemangioma. Such lesions can grow extraaxially within the dural sinuses, particularly the cavernous sinus, and present like tumors. A better understanding of the neuroimaging, clinical, and anatomical features of these lesions may prevent difficulties in management.

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Joshua B. Bederson and Charles B. Wilson

✓ Outcome after 252 posterior fossa explorations for the treatment of trigeminal neuralgia was determined by a retrospective review. Patients with distortion of the fifth nerve root caused by extrinsic vascular compression underwent microvascular decompression, those with no compression underwent partial sensory rhizotomy, and those with vascular contact but no distortion of the nerve root underwent decompression and rhizotomy. The mean follow-up period was 5.1 years. An excellent (75%) or good (8%) clinical outcome was achieved in 208 patients; 13 patients (5%) experienced little or no pain relief. Thirty-one patients (12%) suffered recurrent trigeminal neuralgia an average of 1.9 pain-free years after operation; recurrence continued at a rate of approximately 2% per year thereafter. Reoperation for recurrent or persistent pain provided excellent or good results in 85% of reoperated patients, but partial sensory rhizotomy was required in most of these patients. Outcome was affected by previous surgical procedures. A previous percutaneous radiofrequency lesion was associated with a significantly greater incidence of fifth nerve complications and a worse outcome after posterior fossa exploration. Because of this finding, the authors recommend that percutaneous radiofrequency rhizolysis be reserved for patients who have failed posterior fossa exploration or who are not candidates for surgery. Patients with compressive nerve root distortion and a short duration of symptoms before surgery had a significantly better outcome than patients with a longer duration of symptoms. In contrast, there was no relationship between the duration of symptoms and outcome of patients without nerve root distortion. Vascular decompression may cause dysfunction of the trigeminal system in tic douloureux, but in patients who remain untreated for long periods an intrinsic abnormality develops that may perpetuate pain even after microvascular decompression. Posterior fossa exploration is recommended as the procedure of choice for patients with trigeminal neuralgia who are surgical candidates.

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Mitchel S. Berger and Charles B. Wilson

✓ Epidermoid cysts originating in the paramedian basal cisterns of the posterior fossa are congenital lesions that grow to a large size through slow accumulation of desquamated epithelium. These lesions grow between and ultimately displace cranial nerves, vascular structures, and the brain stem, causing a long course of progressive neurological deficits. The onset of symptoms usually occurs during the fourth decade of life. Epidermoid cysts are easily diagnosed with computerized tomography scans, which characteristically show a low-density extra-axial pattern. The primary surgical objective is to decompress the mass by evacuating the cyst contents and removing nonadherent portions of the tumor capsule; portions of the capsule adherent to vital structures should be left undisturbed. Aseptic meningitis is the most common cause of postoperative morbidity, and its incidence may be minimized by intraoperative irrigation with steroids followed by systemic therapy with dexamethasone. Symptomatic recurrences that occur many years after surgery should be managed with conservative reoperation.

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Intracranial dissecting aneurysms of the posterior circulation

Report of six cases and review of the literature

Mitchel S. Berger and Charles B. Wilson

✓ Dissecting aneurysms of the intracranial posterior circulation are unusual lesions that affect otherwise healthy young adults, are difficult to diagnose and manage, and carry a high morbidity and mortality rate. Headache in the suboccipital-posterior cervical region is the most common presenting symptom. The dissection usually occurs between the intima or internal elastic lamina and the media; subadventitial dissection does occur and accounts for the infrequent finding of subarachnoid hemorrhage. A deficit in the inner layers of the vessel is the proposed source of dissection. The angiographic features are inconsistent, although an irregularly narrowed arterial segment with proximal and/or distal dilatation are typical findings. Depending on the location of the dissection, the surgical options are: ligation, trapping, or reinforcement of exposed abnormal portions of the vessel. Anticoagulation therapy is not indicated in the management of this lesion.

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Brian T. Andrews and Charles B. Wilson

✓ The authors reviewed 38 cases of suprasellar meningioma to determine the correlation between tumor site and postoperative visual outcome. Progressive visual loss, the most frequent initial complaint (94.7%), occurred over a mean of 24½ months, was most often unilateral (18 patients) or bilateral but asymmetrical (14 patients), and was severe (20/200 vision or worse) in 23 patients; 24 patients had visual field abnormalities. Computerized tomography or magnetic resonance studies clearly delineated the lesions but did not appear to permit earlier diagnosis. Eleven patients had tumors limited to the tuberculum sellae; the tumor extended from the tuberculum sellae onto the planum sphenoidale in nine patients, into one optic canal in eight, onto the diaphragma sellae in seven, and onto the medial sphenoid wing in three. Patients with tumors affecting the optic canal had severe unilateral visual loss more often than those with tumors at other sites. Tumors limited to the tuberculum sellae were most often completely resected; postoperative recovery of vision was also most frequent in patients with tumors at this site. Tumors involving the diaphragma sellae or the medial sphenoid wing were least often completely removed and most likely to be associated with postoperative visual deterioration. Overall, 42% of patients had improved vision postoperatively, 30% remained unchanged, and 28% were worse. After a mean follow-up period of 38 months, 24 patients are doing well, four have significant visual disability, and three are blind or doing poorly. Two patients died of causes unrelated to their tumor. Three patients have had tumor recurrence.

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Epidermoid cysts of the brain stem

Report of three cases

William G. Obana and Charles B. Wilson

✓ The authors report the cases of three patients with epidermoid cysts which insinuated themselves into the brain stem. In all three patients, the tumor occupied the pons, although in one it was predominantly located in the medulla. The cyst contents and nonadherent tumor capsule were removed in all three patients, but no attempt was made to remove tumor densely adherent to the brain stem. One patient's cyst was removed in one operation, but maximal resection in the other two required two operations. After surgery, sixth nerve function completely returned in one patient; another patient had a stable pontine gaze palsy but developed new facial weakness; and the third patient had stable cranial nerve deficits with a diminished hemiparesis. The last patient developed a pseudomeningocele and communicating hydrocephalus, and required a lumboperitoneal shunt. In all three patients, computerized tomography scans demonstrated hypodense tumors not enhanced by contrast material. Magnetic resonance imaging was performed on two patients; in both, the tumors showed increased signal intensity relative to brain on T1-weighted images and decreased signal intensity relative to brain on T2-weighted studies. Magnetic resonance imaging, the most accurate modality for localizing these lesions and determining their extent, was also invaluable for postoperative monitoring and follow-up evaluation. Safe and adequate resection includes decompression of cyst contents and removal of nonadherent portions of the cyst capsule. Cyst wall adherent to the brain stem, however, should not be removed.

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Donald A. Ross and Charles B. Wilson

✓ Of 214 patients with acromegaly who underwent transsphenoidal microsurgical resection of a pituitary adenoma, 54% had growth hormone (GH) levels below 5 ng/ml and 74% had levels less than 10 ng/ml immediately after surgery. Among the 174 patients who could be contacted for long-term follow-up review (average duration 76 months), most recent GH determinations were available for 165. Of these 165 patients, 131 (79.4%) have a GH level less than 5 ng/ml and 153 (92.7%) have a level below 10 ng/ml; these represent 75.3% and 87.9%, respectively, of the total 174 patients reviewed. Fifty-two patients received postoperative radiation therapy. Nine patients underwent reoperation. There were five cases of tumor recurrence following an apparent surgical cure (4.3%), nine new instances of anterior pituitary hypofunction (5%), and five failures of multimodality therapy (2.3%). There were no perioperative deaths, five cases of cerebrospinal fluid leak requiring surgical repair (2.2%), and four cases of postoperative meningitis (1.8%). Permanent diabetes insipidus did not occur. Two of 52 patients who were irradiated postoperatively had severe complications; 23 (54.8%) of 42 patients who were available for follow-up evaluation had developed panhypopituitarism; and eight (19%) of 42 had normal pituitary function an average of 44 months postirradiation.