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Biomedical subjects

B E Pollock

Publications and source records attributed to B E Pollock.

At least 37 records · Page 2Linked to original sources
PubMed2000

Gamma knife radiosurgery as a primary treatment for prolactinomas.

OBJECT: The purpose of this study was to estimate the efficacy of gamma knife radiosurgery (GKS) in controlling tumor growth and endocrinopathy associated with prolactinomas. METHODS: Between 1993 and 1997, 164 of 469 patients with pituitary adenomas treated by GKS harbored prolactinomas. The dose to the tumor margin ranged from 9 to 35 Gy (mean 31.2 Gy), and the visual pathways were exposed to a dose of less than 10 Gy. The mean tumor diameter was 13.4 mm. The mean follow-up time for 128 cases was 33.2 months (range 6-72 months). Tumor control was observed in all but two patients who underwent surgery 18 and 36 months, respectively, after GKS. Clinical cure was achieved in 67 cases. Clinical improvement was noted with a decrease in the hyperprolactinemia after GKS. Nonetheless, in 31 (29%) of 108 patients who were followed for more than 2 years no improvement in serum prolactin levels was demonstrated, although this could be normalized by bromocriptine administration after treatment. Nine infertile women became pregnant 2 to 13 months after GKS and all gave birth to normal children. There was no visual deterioration related to GKS. Five women experienced premature menopause. In these patients there was subtotal disappearance of the tumor and an empty sella developed. CONCLUSIONS: Gamma knife radiosurgery as a primary treatment for prolactinomas can be safe and effective both for controlling tumor growth and for normalization of prolactin hypersecretion. A higher margin dose (> or = 30 Gy) seemed to be associated with a better clinical outcome. Gamma knife radiosurgery may make prolactinomas more sensitive to the bromocriptine.

Humans↗
PubMed2000

Gamma knife radiosurgery for skull base meningiomas.

Radiosurgery has been proven to be a safe and effective management strategy for skull base meningiomas either primarily or for tumor recurrence or progression after prior microsurgical resection. With its steep radiation falloff, radiosurgery provides long-term tumor growth control without the complications associated with conventional fractionated radiation therapy. Stereotactic MR imaging has allowed better definition of the tumor margin for precise multiisocenter conformal dose planning, and our current radiation dose prescription has decreased the incidence of new cranial nerve deficits after radiosurgery to less than 10%. Tumor growth control after radiosurgery remains greater than 90%; patients with subsequent growth typically have tumor outside the irradiated volume or a histologic diagnosis of atypical or malignant meningioma. Still, longer follow-up is needed to ensure that tumor growth control remains permanent after radiosurgery. For patients with large tumors of the skull base, radiosurgery can be part of a staged approach with microsurgery. Initially, the tumor is debulked without an attempt at resection involving the cranial nerves or basal vessels. Radiosurgery can then be performed for the small remaining tumor volume with little risk of cranial nerve deficits. Such multimodality treatment should result in reduced patient morbidity, with long-term tumor control.

Adult↗
PubMed1999

A multi-institutional analysis of complication outcomes after arteriovenous malformation radiosurgery.

PURPOSE: To better understand radiation complications of arteriovenous malformation (AVM) radiosurgery and factors affecting their resolution. METHODS AND MATERIALS: AVM patients (102/1255) who developed neurological sequelae after radiosurgery were studied. The median AVM marginal dose (Dmin) was 19 Gy (range: 10-35). The median volume was 5.7 cc (range: 0.26-143). Median follow-up was 34 months (range: 9-140). RESULTS: Complications consisted of 80/102 patients with evidence of radiation injury to the brain parenchyma (7 also with cranial nerve deficits, 12 also with seizures, 5 with cyst formation), 12/102 patients with isolated cranial neuropathies, and 10/102 patients with only new or worsened seizures. Severity was classified as minimal in 39 patients, mild in 40, disabling in 21, and fatal in 2 patients. Symptoms resolved completely in 42 patients for an actuarial resolution rate of 54% +/- 7% at 3 years post-onset. Multivariate analysis identified significantly greater symptom resolution in patients with no prior history of hemorrhage (p = 0.01, 66% vs. 41%), and in patients with symptoms of minimal severity: headache or seizure as the only sequelae of radiosurgery (p < 0.0001, 88% vs. 34%). CONCLUSION: Late sequelae of radiosurgery manifest in varied ways. Further long-term studies of these problems are needed that take into account symptom severity and prior hemorrhage history.

Adrenal Cortex Hormones↗
PubMed1999

Stereotactic radiosurgery and particulate embolization for cavernous sinus dural arteriovenous fistulae.

OBJECTIVE: To evaluate the safety and efficacy of stereotactic radiosurgery, either with or without transarterial embolization, in the treatment of patients with dural arteriovenous fistulae (DAVFs) of the cavernous sinus. METHODS: We reviewed the findings, from a prospectively established database, for 20 patients with cavernous sinus DAVFs who were treated with either radiosurgery alone (n = 7) or radiosurgery and transarterial embolization (n = 13) in a 7-year period. The median follow-up period after radiosurgery was 36 months (range, 4-59 mo). RESULTS: Nineteen of 20 patients (95%) experienced improvement of their clinical symptoms. Fourteen of 15 patients (93%) experienced either total (n = 13) or nearly total (n = 1) obliteration of their DAVFs, as documented by angiography performed a median of 12 months after radiosurgery. No patient experienced a recurrence of symptoms after angiography showed DAVF obliteration. Two patients developed new neurological deficits after embolization procedures. One patient exhibited temporary aphasia secondary to a venous infarction; another patient exhibited permanent VIth cranial nerve weakness related to acute cavernous sinus thrombosis. Two patients experienced recurrent symptoms and underwent repeat transarterial embolization at 7 and 12 months; both patients achieved clinical and angiographic cures (5 and 10 mo later, respectively). One patient experienced recurrent visual symptoms and underwent transvenous embolization 4 months after radiosurgery. CONCLUSION: Staged radiosurgery and transarterial embolization provided both rapid symptom relief and long-term cures for patients with cavernous sinus DAVFs. Radiosurgery alone was effective for patients with DAVFs whose arterial supply was not accessible via a transarterial approach, although the time course of symptom improvement was longer, compared with patients who also underwent embolization.

Adult↗
PubMed1999

Natural history of asymptomatic colloid cysts of the third ventricle.

OBJECT: To determine the natural history of colloid cysts of the third ventricle in patients in whom the cysts were incidentally discovered, the authors retrospectively reviewed cases observed during the modern neuroimaging era (1974-1998). METHODS: During this 25-year interval, 162 patients with colloid cysts were examined and cared for at our center. Sixty-eight patients (42%) were thought to be asymptomatic with regard to their colloid cyst and observation with serial neuroimaging was recommended. The mean patient age was 57 years at the time of diagnosis (range 7-88 years) and the mean cyst size was 8 mm (range 4-18 mm). Computerized tomography scanning revealed a hyperdense cyst in 49 (84%) of 58 patients. Three patients were excluded from the study because they died of unrelated causes within 6 months of scanning and seven patients were lost to follow-up review. Clinical follow-up evaluation was available at a mean of 79 months (range 7-268 months) in the remaining 58 patients. The numbers of patients who participated in follow-up review at 2, 5, and 10 years after diagnosis were 40, 28, and 14, respectively. The incidences of symptomatic progression related to the cyst were 0%, 0%, and 8% at 2, 5, and 10 years, respectively. No patient died suddenly during the follow-up interval. Two (6%) of 34 patients in whom follow-up imaging was performed either exhibited cyst growth (one patient) or experienced hydrocephalus (one patient) at a mean of 41 months after diagnosis (range 4-160 months). CONCLUSIONS: Patients in whom asymptomatic colloid cysts are diagnosed can be cared for safely with observation and serial neuroimaging. If a patient becomes symptomatic, the cyst enlarges, or hydrocephalus develops, prompt neurosurgical intervention is necessary to prevent the occurrence of neurological decline from these benign tumors.

Adolescent↗
PubMed1999

The Mayo Clinic gamma knife experience: indications and initial results.

OBJECTIVE: To review the results and expectations of contemporary stereotactic radiosurgery. MATERIAL AND METHODS: We conducted a retrospective analysis of 1,033 consecutive patients who underwent gamma knife radiosurgery at Mayo Clinic Rochester between January 1990 and January 1998. RESULTS: The number of patients undergoing radiosurgery increased from 57 in 1990 to 216 in 1997. Of 97 patients with arteriovenous malformations who underwent follow-up angiography 2 years or more after a single radiosurgical procedure, 72 (74%) had complete obliteration of the vascular malformation. Of 209 patients who underwent radiosurgery for benign tumors (schwannomas, meningiomas, or pituitary adenomas) and had radiologic studies after 2 years or more of follow-up, tumor growth control was noted in 200 (96%). Tumor growth was also controlled in 90% of brain metastatic lesions at a median of 7 months after radiosurgery. Of 20 patients with trigeminal neuralgia and follow-up for more than 2 months, 14 (70%) were free of pain after radiosurgery. CONCLUSION: Radiosurgery is a safe and effective management strategy for a wide variety of intracranial disorders. Use of radiosurgical treatment should continue to increase as more data become available on the long-term results of this procedure.

Arteriovenous Fistula↗
PubMed1999

Stereotactic radiosurgery for arteriovenous malformations.

Arteriovenous malformations (AVMs) were one of the first indications for radiosurgery. Radiosurgery has been shown to be an important management strategy for properly selected AVM patients. Radiosurgery is especially useful for patients with AVMs in deep brain locations and critical lobar areas. This article outlines the results and expectations of contemporary AVM radiosurgery and discusses the role of radiosurgery in the management of patients with AVMs.

Brain↗
PubMed1998

Factors associated with successful arteriovenous malformation radiosurgery.

OBJECTIVE: To analyze the clinical and angiographic variables that affect the results of arteriovenous malformation (AVM) radiosurgery and to propose a new method of reporting patient outcomes after AVM radiosurgery. This method incorporates both the obliteration status of the AVMs and the postoperative neurological condition of the patient. METHODS: Patient outcomes were defined as excellent (nidus obliteration and no new deficits), good (nidus obliteration with a new minor deficit), fair (nidus obliteration with a new major deficit), unchanged (incomplete nidus obliteration without a new deficit), poor (incomplete nidus obliteration with any new deficit), and dead. Two hundred twenty patients who underwent AVM radiosurgery at our center before 1992 were subjected to a multivariate analysis with patient outcomes as the dependent variable. RESULTS: Multivariate analysis determined four factors associated with successful AVM radiosurgery: smaller AVM volume (P=0.003), number of draining veins (P=0.001), younger patient age (P=0.0003), and hemispheric AVM location (P=0.002). Preradiosurgical embolization was a negative predictor of successful AVM radiosurgery (P=0.02). CONCLUSION: AVM obliteration without new neurological deficits can be achieved in at least 80% of patients with small volume, hemispheric AVMs after single-session AVM radiosurgery. Future studies on AVM radiosurgery should report patient outcomes in a fashion that incorporates all the factors involved in successful AVM radiosurgery.

Adult↗
PubMed1998

Vestibular schwannoma management in the next century: a radiosurgical perspective.

PURPOSE: To discuss how the evolution of vestibular schwannoma radiosurgery, changes in health care delivery, and patient accessibility to medical information will affect the management of vestibular schwannomas in the future. CONCEPT: In comparison with microsurgical resection of vestibular schwannomas, radiosurgery has a lower morbidity rate, a similar risk of requiring further surgery, and higher patient satisfaction. As this information becomes more widely available to patients and third-party payors, radiosurgery may replace surgical resection as the preferred management strategy for patients with small to medium sized vestibular schwannomas in the United States. RATIONALE: It is estimated that 2500 patients are diagnosed with vestibular schwannomas each year in the United States. Assuming that 80% undergo surgery, 2000 operations are performed annually for newly diagnosed vestibular schwannomas. Data available since 1987 regarding the number of cases for which gamma knife radiosurgery was performed were used to predict the number of patients who will undergo vestibular schwannoma radiosurgery in the future. If the current trend continues, an equal number of patients will undergo surgical resection and radiosurgery to treat their vestibular schwannomas (approximately 1000/yr) sometime between 2005 and 2010. Moreover, it is predicted that by 2020, two-thirds of the patients who are newly diagnosed with vestibular schwannomas will undergo radiosurgery, with surgical resection being reserved for patients with large tumors associated with symptomatic brain stem compression. DISCUSSION: Early data regarding vestibular schwannoma radiosurgery predicted an exponential growth curve. Although it is premature to assume that the current trend will continue, it is likely that an ever increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data are published regarding long-term tumor growth control rates. If the mathematical model proves to be accurate, then stereotactic radiosurgery will replace surgical resection as the preferred management strategy for the majority of patients with vestibular schwannomas.

Delivery of Health Care↗
PubMed1998

Vestibular schwannoma management. Part I. Failed microsurgery and the role of delayed stereotactic radiosurgery.

OBJECT: The purpose of this study was to analyze patient outcomes and to define the role of radiosurgery in patients who have undergone prior microsurgical resection of their vestibular schwannoma. METHODS: The authors evaluated the pre- and postoperative clinical and neuroimaging characteristics of 76 consecutive patients with 78 vestibular schwannomas who underwent radiosurgery after previous surgical resection. Twenty-nine patients (37% of tumors) had undergone more than one prior resection. Forty-three patients (55% of tumors) had significant impairment of facial nerve function (House-Brackmann Grades III-VI) after their microsurgical procedure; 50% had trigeminal sensory loss, and 96% had poor speech discrimination (< 50%). The median evaluation period following radiosurgery was 43 months (range 12-101 months). Tumor growth control after radiosurgery was achieved in 73 tumors (94%). Six patients underwent additional surgical resection despite radiosurgery (median of 32 months after radiosurgery), and one patient underwent repeated radiosurgery for tumor progression outside the irradiated volume. Eleven (23%) of 47 patients with Grades I to III facial function before radiosurgery developed increased facial weakness after radiosurgery. Eleven patients (14%) developed new trigeminal symptoms. CONCLUSIONS: Radiosurgery proved to be a safe and effective alternative to additional microsurgery in patients in whom the initial microsurgical removal failed. Stereotactic radiosurgery should be considered for all patients who have regrowth or progression of previously surgically treated vestibular schwannomas.

Adolescent↗
PubMed1998

Vestibular schwannoma management. Part II. Failed radiosurgery and the role of delayed microsurgery.

OBJECT: The indications, operative findings, and outcomes of vestibular schwannoma microsurgery are controversial when it is performed after stereotactic radiosurgery. To address these issues, the authors reviewed the experience at two academic medical centers. METHODS: During a 10-year interval, 452 patients with unilateral vestibular schwannomas underwent gamma knife radiosurgery. Thirteen patients (2.9%) underwent delayed microsurgery at a median of 27 months (range 7-72 months) after they had undergone radiosurgery. Six of the 13 patients had undergone one or more microsurgical procedures before they underwent radiosurgery. The indications for surgery were tumor enlargement with stable symptoms in five patients, tumor enlargement with new or increased symptoms in five patients, and increased symptoms without evidence of tumor growth in three patients. Gross-total resection was achieved in seven patients and near-gross-total resection in four patients. The surgery was described as more difficult than that typically performed for schwannoma in eight patients, no different in four patients, and easier in one patient. At the last follow-up evaluation, three patients had normal or near-normal facial function, three patients had moderate facial dysfunction, and seven had facial palsies. Three patients were incapable of caring for themselves, and one patient died of progression of a malignant triton tumor. CONCLUSIONS: Failed radiosurgery in cases of vestibular schwannoma was rare. No clear relationship was demonstrated between the use of radiosurgery and the subsequent ease or difficulty of delayed microsurgery. Because some patients have temporary enlargement of their tumor after radiosurgery, the need for surgical resection after radiosurgery should be reviewed with the neurosurgeon who performed the radiosurgery and should be delayed until sustained tumor growth is confirmed. A subtotal tumor resection should be considered for patients who require surgical resection of their tumor after vestibular schwannoma radiosurgery.

Aged↗
PubMed1998

Radiosurgical management of intracranial vascular malformations.

Stereotactic radiosurgery is an important treatment option for arteriovenous malformations (AVMs) and hemorrhagic cavernous malformations. Radiosurgery is effective in obliterating AVMs and preventing rebleeding of cavernous malformations with two or more hemorrhagic episodes. Outcome analyses of radiosurgery for these vascular malformations have provided important information to improve the safety and effectiveness of radiosurgical treatment.

Humans↗
PubMed1997

Complications from arteriovenous malformation radiosurgery: multivariate analysis and risk modeling.

PURPOSE/OBJECTIVE: To assess the relationships of radiosurgery treatment parameters to the development of complications from radiosurgery for arteriovenous malformations (AVM). METHODS AND MATERIALS: We evaluated follow-up imaging and clinical data in 307 AVM patients who received gamma knife radiosurgery at the University of Pittsburgh between 1987 and 1993. All patients had regular clinical or imaging follow up for a minimum of 2 years (range: 24-96 months, median = 44 months). RESULTS: Post-radiosurgical imaging (PRI) changes developed in 30.5% of patients with regular follow-up magnetic resonance imaging, and were symptomatic in 10.7% of all patients at 7 years. PRI changes resolved within 3 years developed significantly less often (p = 0.0274) in patients with symptoms (52.8%) compared to asymptomatic patients (94.8%). The 7-year actuarial rate for developing persistent symptomatic PRI changes was 5.05%. Multivariate logistic regression modeling found that the 12 Gy volume was the only independent variable that correlated significantly with PRI changes (p < 0.0001) while symptomatic PRI changes were correlated with both 12 Gy volume (p = 0.0013) and AVM location (p = 0.0066). CONCLUSION: Complications from AVM radiosurgery can be predicted with a statistical model relating the risks of developing symptomatic post-radiosurgical imaging changes to 12 Gy treatment volume and location.

Follow-Up Studies↗
PubMed1997

Stereotactic radiosurgical treatment of sphenopalatine neuralgia. Case report.

Sphenopalatine neuralgia is a rare craniofacial pain syndrome that is characterized by unilateral pain in the orbit, mouth, nose, and posterior mastoid process. During attacks of pain, vasomotor activity often results in ipsilateral nasal drainage, eye irritation, and lacrimation. The authors present a patient with a 15-year history of sphenopalatine neuralgia who underwent stereotactic radiosurgery targeted at the sphenopalatine ganglion, with initial pain relief, and repeated radiosurgery 17 months later for partial pain recurrence. Two years following radiosurgery, the patient is pain free, no longer suffering from nasal discharge and eye irritation.

Aged↗