Role of enhanced MRI in the follow-up of patients with medically refractory trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife: initial experience.

PURPOSE: The purpose of this work was to evaluate the early posttreatment MR findings, and their clinical utility, in patients with trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife. METHOD: Twenty-six patients with medically refractory trigeminal neuralgia underwent stereotactic radiosurgery. A single dose of 70-90 Gy was administered to the proximal root entry zone (n = 21) or the retrogasserian portion (n = 5) of the trigeminal nerve. Posttreatment enhanced MRI and clinical assessment were performed at 3-6 months. RESULTS: Five patients did not have radiologic follow-up. There were no changes identified in the treated trigeminal nerve or adjacent brainstem in 19 of 21 patients. Two patients with multiple sclerosis developed abnormal signal and enhancement in the brainstem and/or trigeminal nerve; neither had clinical complications. Onset of therapeutic effect ranged from 3 weeks to 3 months; 19 patients had a beneficial response. CONCLUSION: Results of enhanced MRI 3-6 months after stereotactic radiosurgical treatment of trigeminal neuralgia do not correlate with the clinical response. Because beneficial clinical responses or treatment failures are apparent by 3 months, routine posttreatment MRI in these patients is not warranted.

Stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of acoustic schwannomas: comparative observations of 125 patients treated at one institution.

BACKGROUND: Stereotactic radiosurgery (SRS) and, more recently, fractionated stereotactic radiotherapy (SRT) have been recognized as noninvasive alternatives to surgery for the treatment of acoustic schwannomas. We review our experience of acoustic tumor treatments at one institution using a gamma knife for SRS and the first commercial world installation of a dedicated linac for SRT. METHODS: Patients were treated with SRS on the gamma knife or SRT on the linac from October 1994 through August 2000. Gamma knife technique involved a fixed-frame multiple shot/high conformality single treatment, whereas linac technique involved daily conventional fraction treatments involving a relocatable frame, fewer isocenters, and high conformality established by noncoplanar arc beam shaping and differential beam weighting. RESULTS: Sixty-nine patients were treated on the gamma knife, and 56 patients were treated on the linac, with 1 NF-2 patient common to both units. Three patients were lost to follow-up, and in the remaining 122 patients, mean follow-up was 119 +/- 67 weeks for SRS patients and 115 +/- 96 weeks for SRT patients. Tumor control rates were high (> or =97%) for sporadic tumors in both groups but lower for NF-2 tumors in the SRT group. Cranial nerve morbidities were comparably low in both groups, with the exception of functional hearing preservation, which was 2.5-fold higher in patients who received conventional fraction SRT. CONCLUSION: SRS and SRT represent comparable noninvasive treatments for acoustic schwannomas in both sporadic and NF-2 patient groups. At 1-year follow-up, a significantly higher rate of serviceable hearing preservation was achieved in SRT sporadic tumor patients and may therefore be preferable to alternatives including surgery, SRS, or possibly observation in patients with serviceable hearing.

Image-guided transorbital roof craniotomy via a suprabrow approach: a surgical series of 72 patients.

OBJECTIVE: Many subfrontal and orbitofrontal craniotomy techniques have been developed. We present our results with the transorbital roof craniotomy, a frontal craniotomy that incorporates the orbital roof and is performed via a suprabrow incision. This technique was used in 72 patients, primarily for tumor resection. METHODS: Charts were retrospectively reviewed for all patients undergoing transorbital procedures. A total of 72 patients underwent 82 transorbital craniotomies from September 1995 to July 1999. The primary indication for the transorbital approach was mass lesion of the orbit, anterior fossa, or parasellar region. RESULTS: A total of 47 women and 25 men with a mean age of 53 years underwent 82 procedures. The primary pathological finding was meningioma, which occurred in 40 patients (55.6%), followed by craniopharyngioma (6.9%), pituitary macroadenoma (6.9%), schwannoma (5.5%), and hemangioma (5.5%). Simpson Grade I or II resection was achieved in 54% of patients, with Simpson Grade III to V resection achieved in the remaining 46%. Forty-one patients presented with visual loss in 43 cases, with 44.2% experiencing postoperative visual improvement, 46.5% remaining unchanged, and 9.3% worsening. Overall morbidity was 18.4%, with cerebrospinal fluid leak being the most common complication (6.6%). No patients died. CONCLUSION: The transorbital roof craniotomy is an evolutionary approach that provides excellent exposure to the orbit, anterior fossa, and parasellar region with little significant morbidity and, in our series, no mortality. Although we have used this approach primarily for resection of mass lesions, future directions for this procedure will likely lie in treating vascular lesions and lesions of the interpeduncular fossa.

Automated Gamma Knife dose planning using polygon clipping and adaptive simulated annealing.

The Gamma Knife (Elekta Instruments, Inc., Norcross, GA), a neurosurgical, highly focused radiation delivery device, is used to eradicate deep-seated anomalous tissue within the human brain by delivering a lethal dose of radiation to target tissue. This dose is the accumulated result of delivering sequential "shots" of radiation to the target, where each shot is approximately three-dimensional (3-D) Gaussian in shape. The size and intensity of each shot can be adjusted by varying the time of radiation exposure and by using one of four collimator sizes ranging from 4-18 mm. Current dose planning requires that the dose plan be developed manually to cover the target, and only the target, with a desired minimum radiation intensity using a minimum number of shots. This is a laborious and subjective process that typically leads to suboptimal conformal target coverage by the dose. We have previously presented a forward-direct-method, which, using adaptive simulated annealing and Nelder-Mead simplex optimizers, automates the selection and placement of generic Gaussian-based kernels or "shots" to form a simulated dose plan. In order to make the computation of the problem tractable, the algorithm exploits 2-D contouring and polygon clipping and takes a 2 1/2-D approach to defining the problem. In the current paper we present the results of four experiments on two historical clinical datasets, where the generic kernels have been replaced by patient specific kernels calculated by Elekta's Leksell Gamma Plan software. For these experiments the user only selects the maximum number of shots to use and the optimizers are then given the freedom to vary the number of shots as well as the weight, collimator size, and 3-D location of each shot. Highly conformal and competitive dose plans were generated for these two difficult cases.

Evaluation of the spatial accuracy of magnetic resonance imaging-based stereotactic target localization for gamma knife radiosurgery of functional disorders.

PURPOSE: This study was undertaken to determine the impact of geometric distortions on the spatial accuracy of magnetic resonance imaging (MRI)-guided stereotactic localization for gamma knife functional radiosurgery. METHOD: The spatial accuracy of MRI was evaluated by comparing stereotactic coordinates of intracranial targets, external fiducials, and anatomic structures defined by computed tomographic and MRI studies of the Radionics skull phantom (Radionics, Inc., Burlington, MA), the Rando head phantom, and 11 patients who underwent gamma knife functional radiosurgery. The distortion in MRI was assessed from computed tomographic and MRI fusion studies for these patients, as well as from MRI studies acquired by swapping the direction of the magnetic field gradients for five patients who underwent gamma knife radiosurgery and three patients who underwent MRI-guided frameless surgery. A follow-up program to compare the location of the created lesion with the intended target complemented the analysis. RESULTS: The average difference between computed tomographic and MRI stereotactic coordinates of external fiducials, intracranial targets, and anatomic landmarks was of the order of 1 pixel size (0.9 x 0.9 x 1 mm3) along the x, y, and z axes. The average linear scaling along these axes as determined by fusion studies was approximately 0.8% and consistent with a single pixel. The follow-up studies, available for seven patients, revealed good agreement between the location of the created lesion and the intended target. CONCLUSION: The spatial accuracy of an MRI-based localization system can be comparable to computed tomography-based localization with the added benefit of MRI resolution. Both machine- and object-related MRI distortions can be reduced to an acceptable level with contemporary scanners, optimized scanning sequences, and distortion-resistant stereotactic instruments.

Stereotactic radiosurgical pallidotomy and thalamotomy with the gamma knife: MR imaging findings with clinical correlation--preliminary experience.

PURPOSE: To evaluate the temporal evolution and appearance of a radiosurgical lesion at magnetic resonance (MR) imaging and the clinical response in patients undergoing stereotactic radiosurgical pallidotomy or thalamotomy with the gamma knife. MATERIALS AND METHODS: Seventeen patients with medically refractory movement disorders underwent stereotactic radiosurgical pallidotomy (n = 2) or thalamotomy (n = 15). A single dose of 120-140 Gy was administered to a target in the globus pallidus interna or ventralis intermedius thalamic nucleus. Postprocedure gadolinium-enhanced MR imaging and clinical assessment were performed at 1 month and 3 months. RESULTS: At 3 months, the radiosurgical lesion most commonly (n = 11) appeared as a ring-enhancing focus 5 mm or less in diameter surrounded by vasogenic edema that extended less than 7 mm in radius beyond the target. Five patients had ring-enhancing lesions 7 mm or more in diameter; four of these developed symptomatic perilesional edema at 3 (n = 2) or 8 (n = 2) months after the procedure. Onset of therapeutic effect began approximately 4 weeks after treatment. In the 15 patients with tremor, there was a mean decline of 2.1 on the Tremor Rating Scale. CONCLUSION: Findings in this pilot study suggest that radiosurgical thalamotomy is a promising treatment for medically refractory tremor. Three-month follow-up MR studies show a ring-enhancing lesion surrounded by a variable amount of vasogenic edema. Visualization of the radiosurgical lesion and the clinical response are delayed compared to that with radio-frequency procedures.

Removal of orbital apex hemangioma using new transorbital craniotomy through suprabrow approach.

PURPOSE: To describe a technique combining the expertise of the oculoplastic orbital surgeon and the neurosurgeon which allows access to the posterior orbit, anterior fossa, cavernous sinus and suprasellar region with minimal brain manipulation. METHODS: A transorbital craniotomy through a suprabrow incision is performed removing part of the frontal bone and orbital roof as a single piece. This allows wide access with only minimal, if any, brain retraction. The superior, lateral and medial orbit is clearly visualized, as well as the apex of the orbit. The bone flap is replaced at the end of the case with Tantalum plates. RESULTS: A cavernous hemangioma at the orbital apex was removed without complications. The exposure was superb and allowed identification and preservation of orbital structures. CONCLUSIONS: Transorbital craniotomy allows for wide access to the posterior orbit and parasellar region and anterior fossa of the brain with minimal brain manipulation. The use of a suprabrow incision results in an excellent cosmetic result. There is minimal postoperative morbidity, which decreases hospitalization time.

Endoscopic treatment of a symptomatic pineal cyst: technical case report.

Symptomatic pineal cysts are rare and typically managed with an open surgical approach. We report the successful treatment of a symptomatic pineal cyst using a stereotactic endoscopic technique.

Nonvisualization of a large cerebral aneurysm despite high-resolution magnetic resonance angiography. Case report.

The use of magnetic resonance (MR) angiography as a safe, accurate, and reliable substitute for invasive cerebral arteriography has been anticipated as refinements in this technique are introduced. We present the case of an unruptured, 11-mm pericallosal arterial aneurysm not visualized on high-resolution MR angiography. Although this case may be atypical, we caution against complete reliance on this test for exclusion of the presence of cerebral aneurysms.

Atypical monoclonal plasma cell hyperplasia of the central nervous system: precursor of plasmacytoma with evolutionary considerations.

Hematopoietic proliferations rich in plasma cells rarely occur within the central nervous system without the involvement of other organ systems. Depending on their histological pattern and cellular composition, several different terms, including plasmacytoma, plasma cell granuloma, hyalinizing plasmacytic granulomatosis, and inflammatory meningioma, are used for these lesions. We report a left temporal dural lesion composed of plasma cells, lymphocytes, histiocytes, and rare eosinophils with hyaline changes and a suggestion of follicle formation, which stained predominantly for IgG and kappa light chains. This lesion arose in an otherwise healthy 52-year-old woman. Free kappa light chains without a monoclonal peak were found in the urine. We are aware of only two other heterogeneous, predominantly plasmacytic, solitary dural lesions that were found to be monoclonal on immunohistochemical examination. The label atypical monoclonal plasma cell hyperplasia appears to suit the morphological characteristics of our lesion. We suggest that a spectrum of solitary plasmacytic lesions may occur within the central nervous system and that atypical plasma cell hyperplasias have the potential to evolve into plasmacytoma. The preneoplastic nature of this lesion and its potential for evolution to malignant myeloma should be considered when planning treatment and lifelong follow-up for patients.

Embolization from a fusiform middle cerebral artery aneurysm.

A 34-year-old man had a transient ischemic attack and subsequently a completed stroke. Arteriography revealed a large fusiform aneurysm of the left middle cerebral artery with intraluminal thrombus. At surgery, the thrombus was seen within the lumen of the aneurysm. Absolute evidence for embolization is lacking as no examination for this could be done. Embolization from intracranial aneurysms seems to occur exclusively in large or giant aneurysms. Turbulent flow and a "stagnant zone" probably promotes thrombus formation. The reasons for the relative rarity of subsequent embolization are discussed. Because embolization from intracranial aneurysm is so uncommon and because aneurysms usually produce focal deficit by other mechanisms, 4 criteria are presented to determine whether embolization is likely.

The importance of angiotensin II formation in the CNS in angiostensin I - elicited thirst.

The drinking response produced by direct injection of angiotensin I and II into the brain of the rat, was studied, using the angiotensin blocking agents SQ-20,881 (SQ) and P-113 (Saralasin). SQ inhibits angiotensin converting enzyme, preventing formation of angiotensin II, while P-113 is an analogue and competitive inhibitor of angiotensin II. SQ blocked central angiotensin I drinking, but only when the enzyme inhibitor was injected into the ventricle. Angiotensin II induced thirst was not blocked by SQ. P-113 inhibited angiotensin I and II drinking responses in both the preoptic area of the hypothalamus and the lateral ventricle. These data indicate that conversion of angiotensin I to angiotensin II is important in angiotensin-induced drinking, although an independent action of angiotensin I on drinking can not be ruled out at this time.

Renin-angiotensin role in thirst: paradoxical enhancement of drinking by angiotensin converting enzyme inhibitor.

A competitive angiotensin converting enzyme antagonist SQ 20, 881 (SQ), was used to examine the role of the renin-angiotensin system in putative renin-dependent thirst in the albino rat. Significant enhancement of "renin-dependent" as well as renin-independent drinking was observed in the presence of peripheral SQ. Intraventricular SQ obviated this enhancement of drinking but did not affect the water intake caused by the original stimulus itself, whereas it sharply reduced drinking evoked by peripheral renin in nephrectomized rats. Prior renin depletion likewise had no influence on so-called renin-dependent thirst.