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Joseph C. T. Chen, Darlene M. Bugoci, Michael R. Girvigian, Michael J. Miller, Alonso Arellano, and Javad Rahimian

Object

Radiosurgery is an important and well-accepted method in the management of brain metastases. Using conventional frame-based techniques, high lesional control rates are expected. The introduction of image-guided techniques allows for improved patient comfort and workflow. Some controversy exists as to the accuracy of imageguided techniques and consequently the impact they might have on control of brain metastases (as opposed to the level of control achieved with frame-based methods). The authors describe their initial 15-month experience with image-guided radiosurgery (IGRS) using Novalis with ExacTrac for management of brain metastases.

Methods

The authors reviewed the cases of brain metastasis treated by means of IGRS in their tertiary regional radiation oncology service over a 15-month period. During the study period 54 patients (median age 57.9 years) harboring 108 metastases were treated with IGRS. The median time from cancer diagnosis to development of brain metastasis was 12 months (range 0–144 months). The median tumor volume was 0.98 cm3 (range 0.03–19.07 cm3). The median prescribed dose was 18 Gy to the 80% isodose line (range 14–20 Gy). Lesions were followed with postradiosurgery MR imaging every 2–3 months following treatment.

Results

The median follow-up period was 9 months (range 0–20 months). Median actuarial survival was 8.6 months following IGRS. Eight patients with 18 lesions died within the first 2 months after the procedure, before scheduled follow-up imaging. Thus 90 lesions (in 46 patients) were followed up with imaging studies. Lesions that were unchanged or reduced in size were considered to be under control. The 6-month actuarial lesion control rate was 88%. Smaller lesions (< 1 cm3) had a statistically improved likelihood of complete imaging response (loss of all contrast-enhancement p = 0.01).

Conclusions

Image-guided radiosurgical treatment of brain metastases resulted in high rates of tumor control comparable to control rates reported for frame-based methods. High control rates were seen for small lesions in which spatial precision in dose delivery is critical. These data suggests that in regard to lesion control, IGRS using Novalis with ExacTrac is equivalent to frame-based radiosurgery methods.

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Joseph C. T. Chen, Javad Rahimian, Michael R. Girvigian, and Michael J. Miller

✓ Radiosurgery has emerged as an indispensable component of the multidisciplinary approach to neoplastic, functional, and vascular diseases of the central nervous system. In recent years, a number of newly developed integrated systems have been introduced for radiosurgery and fractionated stereotactic radiotherapy treatments. These modern systems extend the flexibility of radiosurgical treatment in allowing the use of frameless image-guided radiation delivery as well as high-precision fractionated treatments. The Novalis linear accelerator system demonstrates adequate precision and reliability for cranial and extracranial radiosurgery, including functional treatments utilizing either frame-based or frameless image-guided methods.

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Joseph C. T. Chen, Michael Girvigian, Hugh Greathouse, Michael Miller, and Javad Rahimian

Object. Radiosurgery has emerged as an important treatment of trigeminal neuralgia. Substantial advantages have been demonstrated in safety and comfort over other modalities. Radiosurgical treatment of trigeminal neuralgia has been well investigated with gamma knife devices involving fixed cobalt sources. Few reports exist concerning trigeminal neuralgia treated using linear accelerator (LINAC)—based devices. In recent years these devices have reached the level of mechanical precision that is required for such functional treatments. The authors describe their initial experience with radiosurgical treatment of trigeminal neuralgia when using a BrainLAB Novalis LINAC device equipped with the commercially available 4-mm collimator.

Methods. A total of 32 patients were treated in a 12-month period between November 2002 and November 2003. The median patient age was 67 years (range 38–84 years). Facial pain was graded using the Barrow Neurological Institute (BNI) scoring system. All patients' pain was BNI Grade IV or V prior to treatment. Of these patients, 22 were undergoing initial treatment, and 10 were undergoing retreatment for recurrent pain following various treatments including percutaneous procedures, gamma knife surgery (GKS), or microvascular decompression. Two patients had multiple sclerosis. In patients undergoing initial radiosurgery, the most proximal segment of the cisternal portion of the trigeminal nerve received 85 to 90 Gy administered in a 5— or 7—noncoplanar arc single-isocenter plan with a 4-mm circular collimator. In patients undergoing repeated radiosurgery, the target received 60 Gy.

Overall good and excellent results (BNI Grade I, II, or III) were achieved in 25 (78%) of 32 patients. The median time to pain relief was 6 weeks. Fair results (improvement in pain with BNI Grade IV) were achieved in three patients (9%), and poor results (no improvement in pain and BNI Grade IV or V) were seen in four (13%). Two patients demonstrated new trigeminal dysfunction following treatment. No other complications occurred.

Conclusions. High-precision imaging and LINAC instrumentation have allowed for treatment of trigeminal neuralgia with results and safety comparable to those achieved using GKS. Linear accelerator—based radiosurgery with the Novalis device is a safe and effective method of managing trigeminal neuralgia and may become the preferred means at centers where the technology is available.

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Edward H. Oldfield

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Joseph C. T. Chen, Arun P. Amar, SooHo Choi, Peter Singer, William T. Couldwell, and Martin H. Weiss

Object. Transsphenoidal adenomectomy with resection of a defined pituitary adenoma has been the treatment of choice for CD for the last 30 years. Surgical resection, however, may not always result in long-term remission of CD. This is particularly important in light of the high risk of morbidity and mortality in patients in the unsuccessfully treated cushingoid state. As such, it is interesting to identify prognostic factors that may predict the likelihood of long-term remission.

Methods. The authors review their series of 174 patients who have undergone transsphenoidal procedures for CD over a period of 20 years with minimum follow-up periods of 5 years. Selection of these patients was based on clinical, imaging, and laboratory criteria that included serum cortisol levels, loss of diurnal variation in serum cortisol levels, urinary free cortisol concentration, and results of a dexamethasone suppression test, petrosal sinus sampling, and corticotroph-releasing hormone stimulation tests as indicated. All patients who met the biochemical criteria underwent transsphenoidal microsurgery.

The authors found an overall rate of remission of 74% at 5 years postoperatively. Patients in whom morning serum cortisol concentrations were lower than 3 µg/dl (83 nmol/L) on postoperative Day 3, following an overnight dexamethasone suppression test, had a 93% chance of remission at the 5-year follow-up examination. Patients with cortisol concentrations higher than this level uniformly failed to achieve long-term remission.

Conclusions. Transsphenoidal microsurgery is an effective means of control for patients with adrenocorticotrophic hormone—producing microadenomas. Clinical outcome correlated well with the size of the tumor, as measured on preoperative imaging studies, and with postoperative morning cortisol levels following an overnight dexamethasone suppression test. Postoperative cortisol levels can be used as a useful prognostic indicator of the likelihood of future recurrence following transsphenoidal adenomectomy in CD.

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Arun P. Amar, William T. Couldwell, Joseph C. T. Chen, and Martin H. Weiss

Object. Prolactin-secreting pituitary adenomas may be managed by surgery, medication, radiotherapy, or observation. The authors reviewed a consecutive series of patients who were followed for at least 5 years after surgery to assess the prognostic significance of preoperative factors (tumor size and prolactin level) and an immediate postoperative factor (prolactin level obtained the morning after surgery) on long-term hormonal outcome, thereby clarifying the indications for surgical removal of tumor, the definition of successful treatment outcomes, and the nature of “recurrent” tumors.

Methods. Between 1979 and 1991, 241 patients with prolactinomas underwent transsphenoidal resection. Nineteen patients were lost to follow-up review, whereas the remaining 222 patients underwent measurement of their prolactin levels on postoperative Day 1 (POD 1), at 6 and 12 weeks, and every 6 months thereafter for a minimum of 5 years. On POD 1, prolactin levels in 133 patients (Group 1) were lower than 10 ng/ml, in 43 patients (Group 2) between 10 and 20 ng/ml, and in 46 patients (Group 3) higher than 20 ng/ml. At 6 and 12 weeks, normal prolactin levels (≤ 20 ng/ml) were measured in 132 (99%) of the 133 patients in Group 1 but only in 32 (74%) of the 43 patients in Group 2. By 5 years postoperatively, normal levels of prolactin were still measured in 130 patients (98%) in Group 1 compared with only five patients (12%) in Group 2. No patient with a prolactin level lower than 3 ng/ml on POD 1 was found to have an elevated hormone level at 5 years. The likelihood of a long-term chemical cure was greater for patients with microadenomas (91% cure rate) than for those with macroadenomas (33%). Preoperative prolactin levels also correlated with hormonal outcome.

Conclusions. Prolactin levels lower than 10 ng/ml on POD 1 predict a long-term chemical cure in patients with microadenomas (100% cure rate) and those with macroadenomas (93% cure rate). In contrast, a cure is not likely to be obtained in patients with normal levels ranging between 10 and 20 ng/ml on POD 1 if they harbor macroadenomas (0% cure rate). A recurrence reported several years after surgery probably represents the presence of persistent tumor that was not originally removed. If the initial operation was performed by an experienced surgeon, however, reoperation is not likely to yield a chemical cure.

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Joseph C. T. Chen, Michael L. Levy, Ziv Corber, and Murwarid Mura Assifi

Applications of endoscopic technique neurosurgery are becoming increasingly popular as greater evidence of the safety and efficacy of these techniques is reported. Nevertheless, significant technical limitations need to be solved before neuroendoscopy can achieve widespread popularity. One limitation is the surgeon's difficulties in becoming anatomically oriented in a two-dimensional (2-D) environment. The lack of appropriate visual cues to orient oneself in three-dimensional (3-D) space makes relatively simple anatomical regions difficult to navigate. The authors describe an endoscopy system that allows for stereoscopic visualization during minimally invasive procedures and that acts as an adjunct to conventional open craniotomies. Four cases are described in which stereoendoscopy was used as either a primary means of visualization or as an adjunct to the operating microscope in conventional open neurosurgical procedures. The authors believe that stereoendoscopic vision is a significant advance in endoscope technology and will play a large role in the popularization of minimally invasive techniques in neurosurgery.

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Michael L. Levy, Joseph C. T. Chen, Arun P. Amar, Shinya Yamada, Koji Togo, Yoshiro Iizuka, and Murwarid Mura Assifi

Modern radiographic techniques have allowed the creation of high-definition planar images that can provide important anatomical as well as physiological data. Planar imaging sets can be reformatted into three-dimensional (3-D) data sets that can then be manipulated to demonstrate important anatomical or gross pathological features. Three-dimensional data sets have been used with success in modern image-guided or frameless stereotactic surgery. Another potential application is so-called "virtual endoscopy" or "scopeless endoscopy," in which a 3-D anatomical data set is reformatted into a volume-rendered image that can then be viewed. By reformatting images in this way, a "surgeon's-eye" view can be obtained, which can aid in presurgical planning and diagnosis. The use of virtual endoscopy has the potential to increase our understanding of the appropriate anatomy and the anatomical relationships most apparent during neurosurgical approaches. In so doing, virtual endoscopy may serve as an important means of planning for therapeutic interventions.

On the other hand, one must always be cognizant of the technical limitations of these studies regardless of the quality of the reconstructed images. Prospective, correlative, clinical studies in which the anatomical advantages of virtual-based endoscopy are evaluated in large cadaver or patient series must be performed. Until then, the only potential ways to compensate for errors that exist in the algorithms and reconstructions of 3-D endoscopic images are based on the surgeon's understanding of the clinical state of the patient and prior experience with the anatomy in the region of question.