Noninvasive linear accelerator radiosurgery as the primary treatment for trigeminal neuralgia

The application of a dedicated linear accelerator (DLINAC) as a noninvasive surgical treatment for trigeminal neuralgia has not yet been demonstrated. This work evaluates the outcome and indications of 22 patients submitted to DLINAC radiosurgery as a primary treatment for essential trigeminal neuralgia. At last follow-up evaluation, 21 patients (95.5%) had sustained significant pain relief. DLINAC radiosurgery is safe and effective as a primary noninvasive surgical treatment for selected patients with essential trigeminal neuralgia.

Radiosurgery and stereotactic radiation therapy of skull base meningiomas: proposal of a grading system

OBJECTIVE

The development of a grading system to guide treatment selection, and predict treatment difficulty and outcome of skull base meningiomas infiltrating the cavernous sinus which are managed by stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT), based on an 8-year experience with stereotactic radiation of skull base meningiomas.

METHODS

T1 gadoliniun-enhanced magnetic resonance imaging (MRI) of 40 patients with skull base meningiomas, with or without prior surgery, who underwent radiosurgery or stereotactic radiation therapy from 1991 to 1998 at the UCLA Medical Center were reviewed, and the result of treatment was related to the tumor grade. Grade was based on tumor infiltration of the cavernous sinus and extension into adjacent structures. Treatment was performed with a linac-based system. The dose prescribed to the periphery of the tumor for SRS patients (n = 34) ranged from 12 to 22 Gy, and the maximum dose delivered to the tumor ranged from 24 to 46 Gy. SRT (n = 6). Treatment was planned using a single isocenter, usually prescribed to the 90% isodose volume, bringing the fractionation scheme to the maximal tolerance of the optic apparatus. The periphery dose ranged from 24 to 46 Gy with a maximum dose of 45 to 51 Gy. Clinical and MRI follow-up was performed every six months for the first 3 years and every year thereafter.

RESULTS

Grade I meningiomas were restricted to the cavernous sinus (n = 12). Grade II cavernous sinus meningiomas extended to the clivus and/or the petrous bone, without compression of the brainstem (n = 9). Grade III meningiomas had superior and/or anterior extension with compression of the optic nerve or tract (n = 9). Grade IV tumors compressed the brain stem (n = 8), and Grade V were bilateral lesions (n = 2). Tumor control rates were 90% for Grade I, 86% for Grade II, 86% for Grade III, 42% for Grade IV and no control for tumors Grade V. Complications were not related to tumor grade.

CONCLUSION

This grading system correlated with outcome and difficulty in planning radiosurgery. Failure of treatment was more likely to occur in patients with higher Grade tumors.

Radiosurgery performed with the aid of a 3-mm collimator in the subthalamic nucleus and substantia nigra of the vervet monkey

OBJECT

Radiosurgery for functional neurosurgery performed using a linear accelerator (LINAC) has not been extensively characterized in preclinical studies. In the present study, the properties of a newly designed 3-mm-diameter collimator were evaluated in a dedicated LINAC, which produced lesions in the basal ganglia of vervet monkeys. Lesion formation was determined in vivo in three animals by examining magnetic resonance (MR) images to show the dose-delivery precision of targeting and the geometry and extent of the lesions. Postmortem immunohistochemical studies were conducted to determine the extent of lesion-induced radiobiological effects.

METHODS

In three male vervet monkeys, the subthalamic nucleus (STN; one animal) and the pars compacta of the lateral substantia nigra (SN; two animals) were targeted by a Novalis Shaped Beam Surgery System that included a 3-mm collimator and delivered a maximum dose of 150 Gy. Magnetic resonance images obtained 4, 5, and 9 months posttreatment were reviewed, and the animals were killed so that immunohistological characterizations could be made.

CONCLUSIONS

The generation of precise radiosurgical lesions by a 3-mm collimator was validated in studies that targeted the basal ganglia of the vervet monkey. The extent of the lesions created in all animals remained restricted in diameter (< 3 mm) throughout the duration of the studies, as assessed by reviewing MR images. Histological studies showed that the lesions were contained within the STN and SN target areas and that there were persistent increases in glial fibrillary acidic protein immunoreactivity. Increases in immunoreactivity for tyrosine hydroxylase, the serotonin transporter, and the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate glutamate receptor in penumbral regions of the lesion were suggestive of compensatory neuronal adaptations. This radiosurgical approach may be of particular interest for the induction of lesions of the STN and SN in studies of experimental parkinsonism, as well as for the development of potential radiosurgical treatments for Parkinson disease.

Experimental radiosurgery simulations using a theoretical model of cerebral arteriovenous malformations

BACKGROUND AND PURPOSE

A novel biomathematical arteriovenous malformation (AVM) model based on electric network analysis was used to investigate theoretically the potential role of intranidal hemodynamic perturbations in elevating the risk of rupture after simulated brain AVM radiosurgery.

METHODS

The effects of radiation on 28 interconnected plexiform and fistulous AVM nidus vessels were simulated by predefined random or stepwise occlusion. Electric circuit analysis revealed the changes in intranidal flow, pressure, and risk of rupture at intervals of 3 months during a 3-year latency period after simulated partial/complete irradiation of the nidus using doses <25 and >/=25 Gy. An expression for risk of rupture was derived on the basis of the functional distribution of the critical radii of component vessels. The theoretical effects of radiation were also tested on AVM nidus vessels with progressively increasing elastic modulus (E:) and wall thickness during the latency period, simulating their eventual fibrosis.

RESULTS

In an AVM with E=5. 0x10(4) dyne/cm(2), 4 (14.3%) of a total 28 sets of AVM radiosurgery simulations revealed theoretical nidus rupture (risk of rupture >/=100%). Three of these were associated with partial nidus coverage and 1 with complete treatment. All ruptures occurred after random occlusion of nidus vessels in AVMs receiving low-dose radiosurgery. Intranidal hemodynamic perturbations were observed in all cases of AVM rupture; the occlusion of a fistulous component resulted in intranidal rerouting of flow and escalation of the intravascular pressure in adjacent plexiform components. Risk of rupture was found to correlate with nidus vessel wall strength: a low E: of 1.9x10(4) dyne/cm(2) resulted in a 92.8% incidence of AVM rupture, whereas a higher E: of 7.0x10(4) dyne/cm(2) resulted in only a 3.6% incidence of AVM rupture. A dramatic reduction in rupture incidence was observed when increasing fibrosis of the nidus was modeled during the latency period.

CONCLUSIONS

It was found that the theoretical occurrence of AVM hemorrhage after radiosurgery was low, particularly when radiation-induced fibrosis of nidus vessels was considered. When rupture does occur, it would appear from a theoretical standpoint that the occlusion of intranidal fistulas or larger-caliber plexiform vessels could be a significant culprit in the generation of critical intranidal hemodynamic surges resulting in nidus rupture. The described AVM model should serve as a useful research tool for further theoretical investigations of cerebral AVM radiosurgery and its hemodynamic sequelae.

Stereotactic radiosurgery of cerebral arteriovenous malformations: appearance of perinidal T(2) hyperintensity signal as a predictor of favorable treatment response

The purpose of this study was to analyze the significance of perinidal T(2) hyperintensity appearance after radiosurgery of arteriovenous malformations (AVMs), as a predictor of treatment response. Our initial experience with linear accelerator (LINAC) radiosurgery at University of California, Los Angeles, between 1990 and 1997 involved treatment of 129 patients affected by cerebral AVMs. Based upon availability of neuroimaging follow-up, 48 patients with 50 AVMs were selected for review. Forty (80%) of the AVMs underwent complete obliteration or significant reduction on follow-up MRI, on average 20 months after radiosurgery. Thirteen (72%) of 18 obliterated AVMs were associated with perinidal T(2) hyperintensity signal, on average 18 months (6-49) after radiosurgery. Ten (20%) of 50 AVMs (average volume 23.1 cm(3), ranging 7.5-46.5) were unchanged. Furthermore, only 3 AVMs in this group showed reversible T(2) signal changes. In patients with complete nidal obliteration, appearance of T(2) hyperintensity signal achieves 72% sensitivity in predicting successful treatment response.

Correlation between MRI-based stereotactic thalamic deep brain stimulation electrode placement, macroelectrode stimulation and clinical response to tremor control

In this study we compared the position of the electronically active contact of the thalamic (Vim) deep brain stimulation (DBS) electrode to the stereotactic location of its tip. Fifteen patients with either Parkinson's disease (PD) or essential tremor (ET) underwent stereotactic, MRI-based placement of the Medtronic quadripolar DBS electrode. An overall improvement of 69% was achieved in the tremor scores during a period of 1-13 months after implantation of the DBS electrode. Eleven patients with ET showed 70% clinical improvement of tremor, compared to a 58% response observed in the 4 patients with PD. The electrode tip center was 11.2 +/- 1.54 mm lateral to the third ventricular wall, 5.38 +/- 1.02 mm anterior to the posterior commissure and 2.9 +/- 3.57 mm inferior to the level of AC-PC line. The most significant deviation from the planned stereotactic target was observed in the Z-coordinate. In our group of patients, stimulation settings favored the contacts closer to the AC-PC line, correcting the electrode tip position to 0.80 +/- 2.84 mm (p < 0.001) inferior to the level of the AC-PC line. In our experience, thalamic DBS offers a reversible and adjustable 'lesion' to compensate for the anatomic variabilities encountered in the positioning of the DBS electrode tip.

MRI of thermally denatured blood: methemoglobin formation and relaxation effects

Focal regions of T1-shortening have been observed in magnetic resonance imaging (MRI)-monitored thermal ablations of perfused tissues. The aims of this study were two-fold: to find evidence for heat-induced conversion of hemoglobin (Hb) to methemoglobin (mHb), and to investigate the effects of heat treatment of in-vitro blood components upon their MR relaxation times. Spectrophotometric studies were performed to confirm the heat-induced formation of methemoglobin. Preparations of whole and fractionated blood, previously submitted to elevated temperatures of 40 degrees C to 80 degrees C, were imaged and the relaxation times were calculated. Optical absorption spectra of samples containing free Hb, heated to 60 degrees C, showed increased light absorption at 630 nm, evident of mHb presence. Short T1 values in whole blood (1.13 s) and packed red blood cell (0.65 s) compartments, heated at 60 degrees C, compared to their baseline values (1.62 s and 0.83 s, respectively), were attributed to mHb formation. In relation to MRI-guided thermal interventions, these results suggest a possible explanation for observation of hyperintense regions on T1-weighted images.

Sequential postoperative appearance of radiofrequency pallidotomy lesions on MRI

We analyzed 10 radiofrequency (RF) lesions over time in 9 patients who had follow-up MRI 1 h to 43 weeks following stereotactic pallidotomies performed for medically intractable idiopathic Parkinson's disease. Pallidotomies were performed under MRI guidance, microelectrode recording, and electrical stimulation with neurological monitoring. We compared the MRI taken within 1 h after surgery for each patient to their respective follow-up MRI to determine the changes in size and signal characteristics of RF lesions over time. The postoperative follow-up MRI of RF lesions roughly fell into 4 time periods: 1 h (n = 10), 2 months (n = 3), 6 months (n = 3), and 10 months (n = 4). The average volume (+/- SD, mm3) of these lesions at each phase were as follows: 1 h = 124.35 +/- 58.48; 2 months = 50.5 +/- 30.71; 6 months = 32.36 +/- 21.07; 10 months = 53.19 +/- 28.91. The steep decline in the size of the lesion stabilizes by the 2-month period. Thereafter, the lesion size at 6 and 10 months remains stable. Eventually, the center of coagulative necrosis completely disappears, and the lesions persists as a cystic cavity. The contrast uptake of these RF lesions appears to resolve by the 6-month period. Immediate postoperative images show strong enhancement with gadolinium. There is a lesser degree of enhancement at 2 months, and no appreciable enhancement by 6 months. Interestingly, the patients with better outcome tended to have larger RF lesions. However, this difference was not statistically significant.

Delayed internal capsule infarctions following radiofrequency pallidotomy. Report of three cases

The authors report on a series of patients with idiopathic Parkinson's disease (IPD) who underwent stereotactic radiofrequency (RF) pallidotomies, three of whom suffered delayed postoperative strokes. These three belonged to a group consisting of 42 patients with medically intractable IPD in whom 50 pallidotomies were performed. All three patients had significant previous vascular disease and were in a high-risk group for cerebral infarction. A postoperative magnetic resonance (MR) image was obtained immediately after the pallidotomy was performed to document the placement of the RF lesion and to rule out any hematoma. The delayed strokes occurred on postoperative Days 10, 51, and 117 in patients with previous vascular disease (Group 1, 11 patients). No strokes occurred in the group with the vascular disease risk factor (Group 2, 11 patients) or in the group with no risk factors for vascular disease (Group 3, 20 patients). This observation is statistically significant (p < 0.05). The T2-weighted MR images showed the lesions as high-intensity signals extending to the posterior limb of the internal capsule ipsilateral to the pallidotomy site. The poststroke T1-weighted images obtained in two patients showed persistent contrast enhancement of the RF lesion and no enhancement around the stroke lesion. Clinically and radiographically, these discrete new lesions represent delayed infarctions, suggesting that RF lesioning can induce delayed injury in adjacent tissue. Patients with previously identified vasculopathy may be at risk for delayed capsular infarction following RF pallidotomy.

Presence of herpes simplex DNA in surgical tissue from human epileptic seizure foci detected by polymerase chain reaction: preliminary study

OBJECTIVES

To determine whether herpes simplex virus causes monofocal epilepsy and to assess the presence of herpes simplex virus 1 (HSV-1) and HSV-2 in surgical specimens from patients with epilepsy by using polymerase chain reaction and Southern blot analysis.

BACKGROUND

Herpes simplex virus is a common neurotropic virus capable of latency within the central nervous system; it has a predilection for the temporal lobe. Central nervous system infection with HSV has been associated with seizure activity.

DESIGN AND METHODS

Surgical specimens were removed from 50 patients as part of a treatment protocol for monofocal epilepsy. Neuropathological classification was done, and adjacent sections were screened for HSV by using polymerase chain reaction. Tissues obtained post mortem from the temporal lobe cortex of persons with Alzheimer disease (n=17), Parkinson disease (n=14), or nonneurological disease (n=17) served as controls.

RESULTS

Twenty (40%) of the 50 epilepsy cases and 2 (4%) of the 48 control cases had at least one sample that tested positive for HSV (P<.001). Sixty-seven percent (8/12) of the epilepsy cases with heterotopia were positive for HSV.

CONCLUSIONS

There was a statistically significant difference in the frequency of HSV-positive surgical specimens from monofocal seizure epicenters compared with nonepilepsy control specimens. These data suggest an association of the virus with seizure activity. All specimens positive for HSV (surgical specimens and control specimens) should be examined to determine the activity or latency state of the virus and cellular localization.

Endoscopic-assisted clipping of cerebral aneurysms

Our experience suggests that, with current technology, it is possible to visualize, dissect, and clip cerebral aneurysm using only the endoscope for visualization. Each of the endoscopes requires little or no brain retraction and could be introduced through a bur hole. The penscope would need the largest opening (1.0 x 1.5 cm), because work is done alongside the scope. However, it overcomes the inherent problem of bur hole surgery for aneurysms: what to do in case of a rupture. Working through a slightly larger opening allows the introduction of other instruments outside of and parallel to the penscope, such as suction and aneurysm clips. The penscope is, therefore, most currently suited for aneurysm surgery.

The side-effects and complications of posteroventral pallidotomy

The side-effects and complications of posteroventral pallidotomy are analysed in 138 consecutive patients who underwent 152 pallidotomies. Transient side-effects, lasting less than three months, appeared in 18% of the patients, that is, 16.5% of the surgical procedures. Long term complications, lasting more than 6 months, were noted in 10% of the patients, that is, 9.2% of the surgical procedures. Sixteen complications occurred alone or in various combinations in 14 patients and included fatigue and sleepiness (2), worsening of memory (4), depression (1), aphonia (1), dysarthria (3), scotoma (1), slight facial and leg paresis (2) and delayed stroke (2). Complications such as dysarthria and paresis could be attributed to MR- or CT-verified pallidal lesions lying too medially and encroaching on the internal capsule. Two of the patients with deterioration in memory had some memory impairment before surgery, and the aphonic patient had dysphonia preoperatively. The study suggests that stereotactic MRI and careful impedance monitoring and macro-stimulation of the posteroventral pallidum area should be sufficient for minimizing the risk of complications; the stereotactic lesion should be centered within the posterior ventral pallidum without involvement of internal capsule. It is concluded that pallidotomy is a safe procedure if performed on cognitively alert patients, and it seems that both the incidence and especially the severity of complications are lower for posteroventral pallidotomy than for thalamotomy.

Role of stereotaxis in the treatment of cerebral palsy

There is a renewed interest in basal ganglia surgery for improvement of motor symptoms in cerebral palsy. Rigidity, choreoathetosis, and tremor can be improved or abolished by a well-placed radiofrequency lesion, either in the ventrolateral nucleus of the thalamus or ventroposterior pallidum. The target is chosen based on the predominance of the symptoms in a given patient. A review of the main reports on surgery of the basal ganglia for cerebral palsy, as well as the author's data, shows that the surgery can have a remarkable impact on patients' quality of life when motor dysfunction is improved. An update of the physiopathology of cerebral palsy motor symptoms related to anatomic findings on experimental work, magnetic resonance imaging, and autopsy is used to rationalize surgery of the basal ganglia. Modern stereotactic technique based on exquisite demonstration of the basal ganglia anatomy by magnetic resonance imaging is described and supported by intraoperative electricophysiologic studies. The author stresses the importance of a multidisciplinary approach to provide the cerebral palsy patient with a comprehensive treatment plan before stereotactic surgery.

Arteriovenous malformation animal model for radiosurgery: the rete mirabile

PURPOSE

To study the effects of single-dose radiation on the porcine rete mirabile, a tangle of microvessels that mimics human arteriovenous malformations of the brain.

METHODS

Eight retia mirabilia received a single dose of radiation under stereotactic location with digital angiography and CT. The following doses were applied: 20, 30, 40, 50, 60, 70, 80, and 90 Gy. The animals were followed up for a period of 7 months. Findings at neurologic examination, serial angiography, and histopathologic examination were analyzed.

RESULTS

Progressive occlusion as observed by angiography corresponded to the histopathologic finding of intimal hyperplasia; that is, marked thickening of the vessel wall, progressing to occlusion of the vascular lumen, and associated thrombosis. A direct dose response was noted for these changes. Neurologic findings were related to the dose distribution and to histologic findings in structures adjacent to the rete mirabile.

CONCLUSION

The rete mirabile is an excellent model by which to study the radiologic and histologic effects of single-dose radiation to the microvasculature of the central nervous system.

Hyperacute thermal lesions: MR imaging evaluation of development in the brain

PURPOSE

To determine the natural time course of development of hyperacute thermal lesions in the brain.

MATERIALS AND METHODS

Ten interstitial lesions were created in five rabbit brains with a radio-frequency probe; an electrode-tip temperature of 80 degrees C was maintained for 60 seconds. Continuous fast spin-echo magnetic resonance (MR) imaging was used to follow lesion development for a minimum of 30 minutes. Temporal variations in lesion size and signal intensity were examined. Findings in final images were correlated with histologic findings.

RESULTS

Images demonstrated a focal hyperintense zone, which developed into an expanding ring of edema surrounding a necrotic center in about 10 minutes. Quantitative analysis revealed a 23% +/- 6 (standard deviation) increase in average signal intensity of the edema layer and a 152% +/- 41 increase in overall lesion size.

CONCLUSION

Full development of a thermal lesion is delayed for a period of minutes. Clinical implications of this effect should be considered when MR imaging-guided thermal ablation is performed.

Early postoperative appearance of radiofrequency lesions on magnetic resonance imaging

Eleven patients who underwent stereotactic radiofrequency lesions in the central nervous system had magnetic resonance imaging follow-up within 72 hours of surgery to determine the early appearance of their lesions. Eight patients with severe tremor, one with chronic pain, and two with dystonia were analyzed. There were six female patients and five male patients, age 7 to 75 years (mean +/- standard deviation = 42 +/- 21). Magnetic resonance imaging was performed postoperatively at 32 +/- 25 hours (range, 3-72). Postoperative T1-weighted spin echo images demonstrated foci of iso- to hyperintensity surrounded by an edge of hypointensity, and corresponding T2-weighted images showed a lesion with three concentric zones consisting of inner hypointense, middle hyperintense, and outer hypointense zones. Gadolinium increased T1-weighted image lesion visibility, and a ring of enhancement around the zone of hypointensity was observed. Lesions could be seen as early as 3 hours after surgery. The lesions were best shown on gadolinium-enhanced T1-weighted images and on T2-weighted images. The edema surrounding the lesion increased over time, up to the 72 hours studied. These data provide important information on the development of lesion appearance, which may be applied in the development of real-time magnetic resonance imaging monitoring of radiofrequency lesion formation. This technique associated with electrophysiological response and the real-time visualization of the anatomic correlation of the probe may allow for a very precise and selected lesion in the central nervous system for the treatment of functional disorders and brain tumors.

Implications of tissue heterogeneity for radiosurgery in head and neck tumors

PURPOSE

This study was undertaken to investigate the perturbation of small radiation beams by low density heterogeneities and to evaluate the ability of a Monte Carlo code to account for such perturbation. Performance of an inexpensive film scanning system was also evaluated.

METHODS AND MATERIALS

Film and diode measurements were made in an acrylic phantom in which the size and position of an air gap were varied. Monte Carlo analysis was used to obtain additional verification of the measurements, to provide insight into photon and electron transport phenomena not directly measurable, and as a benchmark for the code.

RESULTS

With 10 MV photons and a 1 cm circular field, a small 3-mm air cavity placed 2.6 cm deep in acrylic (full buildup) results in a reduction in central axis dose of 21% immediately following the cavity. Equilibrium is then reestablished over the next centimeter, after which the dose exceeds that of the homogeneous case by 3-4%. The loss in central axis equilibrium is highly field-size dependent, with some loss occurring even for the largest (32 mm) collimator. In addition, the presence of the air cavity produces a significant increase in dose up to 2 cm lateral and outside the primary field.

CONCLUSIONS

Tissue heterogeneities are not presently accounted for in radiosurgery calculations, yet have the ability to perturb dose significantly. Targets may potentially be underdosed, and adjacent critical structures overdosed. Inability to account for tissue heterogeneities may limit the use of the radiosurgery approach in some areas. A Monte Carlo approach may be the method of choice for small field dose calculation when tissue heterogeneities are encountered.

CO2 reactivity in arteriovenous malformations of the brain: a transcranial Doppler ultrasound study

Arteriovenous malformations (AVM's) are congenital tangles of vessels that have a high blood flow through a low-resistance nidus. The vessels in the nidus may lack normal vasoreactivity in response to changes in PaCO2 or perfusion pressure (autoregulation). Arteriovenous malformation hemodynamics have been assessed based on the response of AVM feeding arteries to hypocapnia. Twenty-five AVM patients, aged 34 +/- 11 years (mean +/- standard deviation), were admitted to the Massachusetts General Hospital for proton-beam radiation therapy. Fourteen healthy volunteers aged 30 +/- 7 years served as control subjects. Angiograms with calibrated markers permitting magnification correction were available for all patients. The limits of the middle cerebral artery, as determined by transcranial Doppler ultrasonography, were compared to measurements made on the angiograms. Hyperventilation was induced at a rate set by a metronome. Fixed bilateral Doppler probes allowed almost simultaneous sampling of two vessels. Volunteer control subjects were hyperventilated in two steps. The two PaCO2 step decreases were significant (mean resting PaCO2 40.6 +/- 3.5 mm Hg, Step 1 level 29.4 +/- 3.5 mm Hg and Step 2 level 23.8 +/- 3.5 mm Hg; p < 0.01). These decreases induced a significant decrease in mean flow velocity (Vm) and an increase in the pulsatility index (p < 0.001). Mean carbon dioxide reactivity (% delta Vm/delta PaCO2) was 2.74 +/- 1.0 for Step 1 and 1.44 +/- 1.8 for Step 2 (p < 0.003). The mean PaCO2 decrease in patients was from 39.5 +/- 4.0 mm Hg to 27.0 +/- 3.5 mm Hg. Carbon dioxide reactivity was 0.92 +/- 1.12 for feeding vessels and 2.59 +/- 1.78 for nonfeeding vessels (p < 0.001). Transcranial Doppler ultrasound and angiographic depth measurements correlated well. Hyperventilation induced significantly more hemodynamic changes in control and nonfeeding middle cerebral arteries than in feeding vessels. Impaired CO2 reactivity may help to identify AVM feeding vessels as well as the relative magnitude of the flow provided to the malformation.

Thalamic pain syndrome: anatomic and metabolic correlation

We report a patient with thalamic pain induced by stereotactic biopsy; therefore, the location of the anatomical lesion causing the syndrome is precisely known. The location of the lesion was confirmed by postoperative magnetic resonance imaging and computed tomography. The metabolic consequences of the anatomic lesion were documented by positron emission tomography using as marker 18F-fluoro-2desoxy-glucose. The anatomic, metabolic, and clinical findings are discussed, as well as the neurophysiologic theories of the mechanisms of the thalamic pain syndrome.

Subdural recording and electrical stimulation for cortical mapping and induction of usual seizures

Chronic subdural strip electrodes were used for recording of seizure origin, cortical mapping and confirmation of seizure foci by electrical stimulation. Seventeen patients were comprehensively evaluated for epilepsy surgery. All patients had failed medical treatment. Intracranial recording was necessary in 12 patients. Speech area was determined in 50% of the patients stimulated. Seizure origin was confirmed by stimulation-induced usual seizures or aura in 75% of the patients stimulated. Intracranial chronic recordings were safe and added important prognostic information, as well as helped decide the extent of resection.

A universal, multi-modality localization system for animal radiosurgery

We have developed a stereotactic localization system allowing a radiosurgical approach in a number of animal models. The system utilizes fixation adapters specially designed for a particular animal, which in turn are attached to a common Brown-Roberts-Wells (BRW) compatible Delrin head ring. Each fixation adapter is constructed using materials compatible with CT, MRI, PET, and angiographic imaging studies. With such a system, radiographic localization, computerized treatment planning, and stereotactic radiation delivery can subsequently be performed in a manner identical to the procedures used for humans.

Arteriovenous malformation hemodynamics: a transcranial Doppler study

Congenital arteriovenous malformation (AVM) of the brain represents a defect in capillary development resulting in a high flow fistula between arterial and venous systems. In this study, AVM hemodynamics were related with clinical findings. Volume flow was calculated based on transcranial Doppler (TCD) and angiographic data. Forty patients admitted to the Massachusetts General Hospital for proton beam therapy (33 +/- 10 yr old; mean +/- SD) were studied. Four symptoms were considered: intracranial bleeding, progressive neurological deficit, seizures, and headache. Fourteen control subjects aged 30 +/- 7 years (mean +/- SD) were normal volunteers. Angiography with calibrated markers permitting magnification correction was available for all patients. Lateral and medial depth limits of the intracranial basal arteries in relation to the TCD temporal window were determined by TCD and angiogram with excellent correlation. Selected depth for data acquisition was determined independently in the angiogram and by TCD. The difference between the two techniques was less than 4 mm. Mean flow velocity, pulsatility index, and vessel diameter were studied. Flow volume was calculated from these data. Mean flow velocity, pulsatility index, vessel diameter, and flow volume were significantly different among AVM feeders, non-feeders, and control arteries. The non-feeding middle cerebral artery, anterior cerebral artery, and posterior cerebral artery flows were 254 +/- 13, 136 +/- 14, and 79 +/- 8 ml/min, respectively. Accordingly, the estimated cerebral flow volume was 938 ml/min. The feeding middle cerebral artery, anterior cerebral artery, and posterior cerebral artery flows were 552 +/- 47, 369 +/- 70, and 484 +/- 67 ml/min, respectively (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Radiosurgery of cavernous sinus tumors

Stereotactic radiosurgery was applied to concentrate high dose of photon irradiation to tumors enclosed in the cavernous sinus. We have treated 10 meningiomas, five pituitary tumors, and three metastatic lesions in the past two years. Follow-up time ranges from 3 to 18 months with an average of 10 months. Tumor volume ranged from 0.92 to 53.31 cc with an average 10.79 cc. CT scans and MRIs were used to demonstrate the tumor relationship to cranial nerves and structures of the brain. One to 6 isocenters were used. Collimator size varied from 7 to 28 mm, and the dose to the margin of the tumor ranged from 1400 to 2500 cGy with an average of 1650 cGy. Maximal dose range of 1575 to 5000 cGy. The margin of the tumor was encompassed within the 50 to 95% isodose volume with an average treatment prescribed to the 57% isodose volume. Symptomatic response was seen in 12 patients, and stabilization of symptoms in three patients with progression of symptoms observed in three patients. Radiographic imaging revealed response in eight patients, unchanged in three patients and progression in three patients. This report shows the feasibility of applying linear accelerator radiosurgery to the treatment of cavernous sinus tumors. This form of therapy promises to play an important role in complementing tumor resection.

Comparison between radiosurgery and stereotactic fractionated radiation for the treatment of brain metastases

This study evaluates the treatment of intracerebral brain metastases with single dose stereotactic radiosurgery in comparison to stereotactic fractionated radiotherapy (SFR). Twenty six patients with 41 lesions were evaluated. Thirty four lesions in 19 patients were treated with radiosurgery, and 7 lesions in 7 patients were treated with SFR. The radiosurgery group was treated with an average number of isocenters of 1.4, and an average of 9 arcs. The average dose was 2140 cGy delivered to the 70% isodose line. The average volume of the lesions was 5.22 cc. The SFR group lesions received a mean dose to the indicated area delivered by 4 to 6 coplanar fields. The dose was 600 cGy per fraction, 2 to 3 fractions were given. The average volume of the treated lesions was 21.2 cc. Follow-up extended from 2-18 months. Twenty five lesions of the radiosurgery group had image follow-up. The overall local control was seen in 92% of the patients. Six lesions of the SFR group had image follow-up, the local control was 83%. The small number in each group, the non-randomized nature of the study, and the relatively short follow-up preclude a definitive conclusion. SFR may be the method of choice for large lesions surrounded by significant edema. The delivery of the dose in large fractions may obviate the transient acute reactions seen when radiosurgical dose is delivered to large lesions surrounded by edema. However, both forms of therapy have proven to be effective in the control of brain metastases.

Cerebral vasospasm

Cerebral vasospasm is an important component of pathological entities such as migraine, subarachnoid hemorrhage (SAH), head trauma, post cerebral ischemia and/or hypoxia. The mechanisms underlying cerebral vasospasm in these diseases are not completely understood. Neurochemical and morphological factors involved in the cerebral circulation control are reviewed in this article. The circulatory changes observed after subarachnoid hemorrhage are taken as a model. It is concluded that multiple biochemical, physiological and morphological factors are involved in the cerebral vascular responses after SAH. Possible treatment alternatives for cerebral vasospasm based on its etiology are discussed.

Hyperglycemia, cerebrospinal fluid lactic acidosis, and cerebral blood flow in severely head-injured patients

Cerebrospinal fluid (CSF) lactate concentration is known to increase during the acute phase after severe head injury. To determine the influence of glycemia or cerebral ischemia on this lactate increase, we studied 69 head-injured patients aged 28.7 +/- 15.4 (SD) years with a mean Glasgow coma score of 5.7 +/- 1.7 (SD). They were intubated, paralyzed, and artificially respired. We measured lactate and glucose concentrations in ventricular CSF (VCSF), arterial blood, and jugular bulb blood for 5 days. Samples were obtained within 12 hours after injury and at regular 12-hour intervals. These patients were not treated for hypo- or hyperglycemia. Cerebral blood flow (CBF) was also measured within 12 hours and at 12- to 48-hour intervals. Hyperglycemia was found consistently within 12 hours after injury (224 +/- 98 mg/dl, P less than 0.001), and mild hyperglycemia persisted during the entire period of study. The VCSF glucose course was parallel to that in blood (the initial VCSF glucose value was 128 +/- 37 mg/dl, P less than 0.001). The blood lactate value was also elevated during the first 12 hours (4.2 +/- 2.0 mmol/litre, P less than 0.001), normalizing within 24 to 36 hours. The VCSF lactate course was independent from that of the blood lactate value. It was significantly elevated within 12 hours after injury (5.3 +/- 2.6 mmol/litre, P less than 0.001) and remained so during the 5 days of study. A high initial VCSF glucose value was associated with a high initial VCSF lactate value. However, a high VCSF lactate concentration was present even when the glucose value was close to the normal level.(ABSTRACT TRUNCATED AT 250 WORDS)

Transposition of target information from the magnetic resonance and computed tomography scan images to conventional X-ray stereotactic space

A technique to apply reconstructed X-ray computed tomography (CT) and magnetic resonance imaging (MRI) for target determination in stereotactic Bragg peak proton beam therapy of intracranial lesions was developed. Twenty-one benign intracranial tumors and vascular abnormalities were managed using this technique. Clinical features of these lesions, as well as targeting problems associated with the MRI and CT image interpretation, are presented.