Impact of collimator leaf width on stereotactic radiosurgery and 3D conformal radiotherapy treatment plans.

PURPOSE: The authors undertook a study to analyze the impact of collimator leaf width on stereotactic radiosurgery and 3D conformal radiotherapy treatment plans. METHODS AND MATERIALS: Twelve cases involving primary brain tumors, metastases, or arteriovenous malformations that had been planned with BrainLAB's conventional circular collimator-based radiosurgery system were re-planned using a beta-version of BrainLAB's treatment planning software that is compatible with MRC Systems' and BrainLAB's micro-multileaf collimators. These collimators have a minimum leaf width of 1.7 mm and 3.0 mm, respectively, at isocenter. The clinical target volumes ranged from 2.7-26.1 cc and the number of static fields ranged from 3-5. In addition, for 4 prostate cancer cases, 2 separate clinical target volumes were planned using MRC Systems' and BrainLAB's micro-multileaf collimators and Varian's multileaf collimator: the smaller clinical target volume consisted of the prostate gland and the larger clinical target volume consisted of the prostate and seminal vesicles. For the prostate cancer cases, treatment plans were generated using either 6 or 7 static fields. A "PITV ratio," which the Radiation Therapy Oncology Group defines as the volume encompassed by the prescription isodose surface divided by the clinical target volume, was used as a measure of the quality of treatment plans (a PITV ratio of 1.0-2.0 is desirable). Bladder and rectal volumes encompassed by the prescription isodose surface, isodose distributions and dose volume histograms were also analyzed for the prostate cancer patients. RESULTS: In 75% of the cases treated with radiosurgery, a PITV ratio between 1.0-2.0 could be achieved using a micro-multileaf collimator with a leaf width of 1.7-3.0 mm at isocenter and 3-5 static fields. When the clinical target volume consisted of the prostate gland, the micro-multileaf collimator with a minimum leaf width of 3.0 mm allowed one to decrease the median volume of bladder and rectum within the prescription isodose surface by 26% and 17%, respectively, compared to the multileaf collimator with a leaf width of 10 mm. Use of the 1.7 mm leaf width micro-multileaf collimator allowed one to decrease the median volume of bladder and rectum within the prescription isodose surface by 48% and 39%, respectively, compared to the multileaf collimator with a leaf width of 10 mm. CONCLUSIONS: For most lesions treated with radiosurgery, the use of a micro-multileaf collimator with a leaf width of 1.7-3.0 mm at isocenter and 3-5 static fields allows one to meet the Radiation Therapy Oncology Group guidelines for treatment planning. Both planning and treatment are relatively straightforward with a micro-multileaf collimator, allowing for efficient treatment of non-spherical targets with either stereotactic radiosurgery or fractionated stereotactic radiotherapy. When the clinical target volume consists of the prostate gland, micro-multileaf collimators with a minimum leaf width of 1.7-3.0 mm allow one to spare more bladder and rectum than one can with a multileaf collimator that has a 10-mm leaf width based on an analysis of PITV ratios, isodose distributions, and dose volume histograms.

Comparison of the effect of two and six week exposure to 80% and 100% oxygen on the lung of the newborn mouse: a quantitative SEM and TEM correlative study.

Prolonged inhalation of 80% oxygen, in contrast to 100% oxygen, has generally been assumed not to lead to significant pulmonary impairment. Two and six week old C57BL mice were systematically assessed by transmission and scanning electron microscopy for structural changes in the lung caused by inhalation of 80% and 100% oxygen from the first day of life, and the injury was quantitated morphometrically. Six weeks of continuous inhalation of 80% oxygen resulted in diffuse fibrosis of the gas exchanging parts of the lung superimposed on which were, in the 100% oxygen exposed mice, foci of coarse scarring. Lowering the inspired oxygen concentration from 100% to 80% appeared to reduce the mucosal injury more than the interstitial fibrotic response. This suggests that the most persistent alteration caused by chronic supplemental oxygen exposure below 80% will be interstitial fibrosis.

A comparison of arc-based and static mini-multileaf collimator-based radiosurgery treatment plans.

BACKGROUND: The purpose of this study is to compare arc-based and mini-multileaf collimator (mMLC)-based radiosurgery treatment plans using isodose distributions and dose-volume histograms. METHODS: Of 11 patients who underwent conventional arc-based radiosurgery for intracranial malignancies, four were treated with one isocenter, four were treated with two isocenters and three were treated with three isocenters. The same cases were re-planned using a test version of mMLC-based radiosurgery software for multiple static non-coplanar fields. RESULTS AND CONCLUSION: For non-spherical targets, treatment planning is relatively intuitive with mMLC-based radiosurgery, reducing the amount of time required for planning. Moreover, a lower dose of radiation is delivered to normal tissue with mMLC-based radiosurgery than with arc-based radiosurgery, which theoretically should lead to a reduced risk of complications.

Outcome analysis in 654 surgically treated lumbar disc herniations.

This article reports the outcomes of 654 consecutive patients treated during a 4.5-year period. Patients had a microdiscectomy, a laminectomy plus microdiscectomy, or a decompressive laminectomy with a microdiscectomy. The causes of ruptured discs were lifting (31.4%), falls (10.2%), and sports (10.0%). Almost all patients had complained of leg pain (99%), and 79% had radicular pain in a dermatomal distribution. Thirty-three percent of the patients had been involved in industrial accidents, and 6% had legal claims pending during the surgical period. Almost 11% of the patients had complications, and there was one death caused by abdominal arterial bleeding. Patients were also rated according to the Prolo Functional-Economic Outcome Rating Scale to improve the ability to compare series in the future. Almost 80% of the patients had good outcomes as defined by scores on this scale of 8 (16.2%), 9 (33.2%), and 10 (26.9%). Several conclusions can be drawn from the results of this series: 1) most patients had good outcomes; 2) patients with nonindustrial injuries had better outcomes than did patients with industrial injuries; 3) professionals with legal concerns and laborers with industrial insurance had good outcomes; and 4) the Functional-Economic Outcome Rating Scale appears to be a useful tool for comparing different procedures more objectively and for comparing the outcomes across series.

Extracerebral cavernous angiomas of the middle fossa.

Three cases of extracerebral cavernous angiomas of the cavernous sinus in the middle fossa are reported. These are rare lesions that primarily affect women and are usually associated with acute or subacute onset of visual symptoms: diplopia, exophthalmos, and decreased visual acuity. The growth of the lesion often erodes the bone in the area of the cavernous sinus. Angiography usually depicts a vascular mass. The lesions represent a formidable surgical problem because of their tendency to cause intraoperative life-threatening hemorrhages. Morbidity and mortality can be drastically reduced by not attempting to resect the lesion further after biopsy and by giving a course of radiation therapy before definitive surgical treatment.

Anatomical evaluation of the caudal regression syndrome (lumbosacral agenesis) with magnetic resonance imaging.

Caudal regression syndrome involves absence of the sacrococcygeal vertebrae with or without lumbar vertebral defects. Since the neurological condition of infants with this syndrome deteriorates, radiographic studies are important to rule out any surgically correctable lesion. A paraplegic male neonate with a vertebral canal ending at T11 is presented. This is the first report of using magnetic resonance imaging to evaluate the spinal cord and surrounding soft tissues involved in this syndrome. Magnetic resonance imaging provides more anatomical details than myelogram with computed tomography, which greatly aids in determining whether surgery is necessary.

Cervicomedullary junction decompression in a case of Marshall-Smith syndrome. Case report.

The case is reported of a 2-year-old boy born with Marshall-Smith syndrome who had difficulty in swallowing and who exhibited spasticity and quadriparesis due to compression of the medulla and cervical spine. This is the first child with this rare condition reported to have brain-stem compression from bone abnormalities at the craniovertebral junction and who has required surgery.

Decussation of hind-limb and fore-limb fibers in the monkey corticospinal tract: relevance to cruciate paralysis.

Cruciate paralysis is a clinical entity in which patients with trauma to the anterior cervicomedullary junction present with weakness of the upper extremity greater than that of the lower extremity. The underlying mechanism of this paralysis is commonly thought to be selective damage affecting the upper-extremity nerve fibers in the pyramidal decussation. The authors examined the anatomical basis of cruciate paralysis in six New World squirrel monkeys and two Old World cynomolgus monkeys. No evidence for a differential decussation of fore-limb and hind-limb fibers was found. Thus, there is no obvious anatomical explanation for cruciate palsy. The results do suggest two alternative explanations for cruciate paralysis: 1) selective damage to neural areas involving the internuncial cells, the central gray area, and the cuneate nucleus, or 2) injury to the ventral corticospinal tract.

Signet-ring cell lymphoma of the central nervous system. Case report.

Signet-ring cell lymphoma is a rare tumor described in the lymph nodes, skin, tonsils, thyroid, salivary gland, and ocular orbit. This is the first case report of a B-cell signet-ring cell lymphoma in the central nervous system with Dutcher and Russell bodies, signet-ring nuclei, intracisternal crystalline inclusions, and immunoglobulin M positivity. The patient is doing well 2 years after surgery and postoperative radiation therapy. No definitive prognostic characteristics have been elucidated. This disease entity can only be suspected on histological grounds and confirmed by immunocytochemical and ultrastructural studies.

Iatrogenic arteriovenous fistula presenting as a recurrent subdural hematoma. Case report.

An unusual case of an iatrogenic dural arteriovenous fistula is reported. The patient presented with a history of progressive generalized headache over a period of 3 to 4 weeks. Computerized tomography demonstrated a chronic subdural hematoma that was successfully evacuated by burr-hole drainage. The patient's postoperative course was complicated by recurrent acute subdural hematomas at the drainage site. Coagulation studies were unremarkable. Selective external carotid angiography demonstrated a small dural arteriovenous fistula adjacent to the burr hole used for the initial operative procedure. Extension of the bone flap and coagulation of the fistula resulted in a good outcome. In the patient with recurrent acute subdural hematoma, the possibility of a vascular malformation must be considered. Selective internal and external carotid angiography is key to the correct diagnosis.

The combined supra- and infratentorial approach for lesions of the petrous and clival regions: experience with 46 cases.

The combined supra- and infratentorial approach has been subdivided into three variations: the retrolabyrinthine technique (petrous bone resection with preservation of hearing); the translabyrinthine technique (greater petrous bone resection and sacrifice of hearing); and the transcochlear technique (maximum petrous drilling, sacrifice of hearing, and transposition of the facial nerve). These three variations maximize temporal bone drilling and therefore provide exquisite exposure of the clivus and petrous regions with minimal or no brain retraction. The superior petrosal sinus is always sacrificed and the tentorium completely cut. The sigmoid sinus can be transected or kept intact, depending on the venous drainage and the degree of exposure required. A series of 46 patients who underwent the combined approach is presented.

Cruciate paralysis: a clinical and radiographic analysis of injuries to the cervicomedullary junction.

Fourteen patients with superior cervical spinal cord injuries and the clinical signs and symptoms of cruciate paralysis are presented. This rare injury pattern is characterized by weakness of the upper extremities with little or no compromise of lower-extremity function following trauma to the superior spinal cord. Anatomically, cruciate paralysis is thought to represent selective injury to descending corticospinal tracts as they decussate at the cervicomedullary junction. The clinical and radiographic findings of each patient are outlined and the incidence and natural history of the injury syndrome, including a review of the literature, are presented.

Combined approach for lesions involving the cerebellopontine angle and skull base: experience with 20 cases--preliminary report.

Skull base tumors involving the clivus, petrous bone, and adjacent areas can be formidable lesions to successfully remove without causing significant neurologic deficits. At our institution in the last 5 years, twenty patients out of 103 patients with skull base tumors have undergone the supratentorial-infratentorial combined approach for removal of a neoplasm (nine schwannomas, six meningiomas, two epidermoids, one extensive basal cell carcinoma, one pontine cavernous malformation, and one basilar artery aneurysm). The average patient age was 43 years. The combined approaches in conjunction with the subtemporal exposure were retrosigmoid-retrolabyrinthine, retrosigmoid-translabyrinthine, or retrosigmoid-transcochlear. The choice depended upon the type and location of the lesion and the deficits noted preoperatively. Basically, the approach allowed communication of the middle fossa and posterior fossa by totally dividing the tentorium as much as necessary for effective surgical manipulations. Both sigmoid and superior petrosal sinuses are divided. There were no deaths. Postoperative neurologic deficits included temporary seventh nerve paralysis, sixth nerve weakness, fifth nerve sensory deficits, cerebrospinal fluid leaks, and hydrocephalus requiring a shunt. Overall, the results were very gratifying, considering the difficulties encountered in the surgical removal of these lesions.

Management of anterior skull base tumors.

A team approach is necessary to remove tumors involving cranial and facial structures. The combined talents of the appropriate specialists have allowed aggressive and successful removal of large and complicated tumors. Vascular reconstruction, free vascularized pedicle grafts, transfacial exposure combined with classic neurosurgical exposure have provided a new era for successful surgery of the frontal fossa of the cranium.

Surgical decisions regarding medically intractable epilepsy.

The neurosurgeon's primary intention in epilepsy care is to cure patients with medically intractable seizures. If cure cannot be achieved, reduction of the frequency and intensity of the seizures may be worthwhile. With these goals, work-up of the patients must be thoroughly carried out to localize the seizure focus and to demarcate surrounding functional brain. Once the seizure focus and pattern are well understood, the surgical decision can be based on a logical and flexible decision tree. Potential complications and past statistics must also enter into the decision process. With these factors combined, the routine and special needs for each patient can be accommodated. The advancing modalities of AVEEG monitoring and imaging, coupled with more sophisticated surgical techniques resulting in predictably good outcomes, have moved surgery for medically intractable epilepsy from a few dedicated centers to universal component of our health care. Increasing numbers of young patients afflicted with this chronic debilitating disease can expect freedom from social and employer ostracism, a chance to drive, and an opportunity for freedom from family or other caretaker dependence. Advancement in this will continue as neurosurgeons blend their knowledge of basic neurobiology and the clinical sciences.

Role of magnetic resonance imaging and three-dimensional computerized tomography in craniovertebral junction anomalies.

The surgical management of craniovertebral junction abnormalities depends on accurate radiological identification of the static and dynamic relationships. Four cases are presented to show the importance of flexion/extension magnetic resonance imaging and three-dimensional computerized tomography scanning in the evaluation of these relationships. With these techniques, anterior and/or posterior decompressive procedures can be appropriately planned to reduce and stabilize craniovertebral abnormalities. Long-term neural deficits can be reversed by these procedures.

Combined approach for lesions involving the cerebellopontine angle and skull base: experience with 30 cases.

This article presents a series of 30 patients who underwent a combination of the subtemporal and posterior fossa approaches for exposure of lesions in the clivus or medial petrous region. This combined supra- and infratentorial approach is divided into three variations with progressively greater petrous bone resection to increase exposure of the clivus and medial petrous region. The approach has been divided into petrous bone resection with preservation of hearing (retrolabyrinthine), greater petrous bone resection with sacrifice of hearing (translabyrinthine), and finally maximum petrous drilling with sacrifice of hearing along with transposition of the facial nerve (transcochlear). Ninety-three percent of the cases returned to their premorbid occupations.

Effect of prolonged exposure to 80% oxygen on the lung of the newborn mouse.

Continuous exposure of newborn C57BL mice to 80% oxygen at normal atmospheric pressure for as many as 6 weeks results in significant pulmonary injury. This injury is reflected morphometrically and morphologically primarily in an increase in the pulmonary interstitial compartment and in pulmonary fibrosis. The fibrotic response is both peribronchiolar and parenchymal. Lowering the oxygen concentration of continuous exposure from 100 to 80% appears to reduce the cellular response of the alveolar lining cells and the bronchiolar mucosa in the newborn lung more than the fibrotic response. This suggests that the most persistent response in the growing lung to supplemental oxygen concentrations at or below 80% will be peribronchiolar and parenchymal fibrosis. These findings would account for the clinically observed reduction of stage II bronchopulmonary dysplasia, yet persistence of chronic bronchopulmonary dysplasia in human infants treated with supplemental oxygen concentrations below 100%.