Subarachnoid hemorrhage without evident cause on initial angiography studies: diagnostic yield of subsequent angiography and other neuroimaging tests

2003 ◽  
Vol 98 (6) ◽  
pp. 1235-1240 ◽  
Author(s):  
Mehmet A. Topcuoglu ◽  
Christopher S. Ogilvy ◽  
Bob S. Carter ◽  
Ferdinando S. Buonanno ◽  
Walter J. Koroshetz ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Mr Imaging ◽  
Ct Angiography ◽  
Mr Angiography ◽  
Diagnostic Yield ◽  
Catheter Angiography ◽  
Content Type ◽  
Spine Mr ◽  
Susceptibility Contrast ◽  
Fine Print

Object. The aim of this study was to assess the diagnostic yield of imaging tests performed in patients in whom the cause of subarachnoid hemorrhage (SAH) had not been demonstrated on initial angiography. Methods. By reviewing medical records of 806 patients with SAH who had been admitted during a 6.5-year period, the authors identified 86 in whom initial transfemoral catheter angiography failed to reveal the cause of SAH. Clinical and radiological data were analyzed to determine the diagnostic yield of subsequent catheter angiography, computerized tomography (CT) angiography, magnetic resonance (MR) angiography, and MR imaging of the brain and spine for various subtypes of SAH (bleeding not visualized on CT studies [CT-negative SAH], perimesencephalic SAH, and nonperimesencephalic SAH). Of 41 patients with nonperimesencephalic SAH, 36, 32, and 21 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 23 patients (18 with Gd and 15 with susceptibility contrast sequences), and spine MR imaging in 17. Of 36 patients with perimesencephalic SAH, 31, 23, and 17 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 18 patients (17 with Gd and 11 with susceptibility contrast sequences), and spine MR imaging in 14. Of nine patients with SAH not visualized on CT scanning, three, one, and six underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in eight patients (five with Gd and three with susceptibility contrast sequences), and spine MR imaging in seven. The cause of SAH could be determined in only four patients, all with nonperimesencephalic SAH. The only test that yielded a diagnosis was catheter angiography (three aneurysms on the second and one on the third angiography, all surgically secured). Diffusion-weighted MR imaging demonstrated small, deep infarcts in five patients. Conclusions. Repeated catheter angiography remains the most sensitive test to determine the cause of SAH that is not demonstrated on initial angiography, particularly in the subtype of nonperimesencephalic SAH. Newer, noninvasive imaging techniques provide little diagnostic yield.

Neuroradiological findings in adult cranially conjoined twins

1998 ◽  
Vol 89 (4) ◽  
pp. 635-639 ◽  
Author(s):  
Olav Jansen ◽  
V. A. Mehrabi ◽  
Klaus Sartor
Keyword(s):  
Mr Imaging ◽  
Ct Angiography ◽  
Mr Angiography ◽  
Cross Flow ◽  
Conjoined Twins ◽  
Radiological Anatomy ◽  
Content Type ◽  
Temporal Lobes ◽  
Sagittal Sinus ◽  
Fine Print

✓ The authors demonstrate the radiological anatomy and review the accepted embryological theories in a case of total craniopagus. These 24-year-old female cranially conjoined twins were studied with computerized tomography (CT) and CT angiography, magnetic resonance (MR) imaging and MR angiography as well as selective arterial digital subtraction (DS) angiography to clarify whether surgical separation was possible. The neuroradiological findings are discussed, taking into consideration both the embryological and surgical literature. The malformation was classified as a total parietooccipitotemporal craniopagus. Whereas CT angiography and MR imaging including MR angiography demonstrated a common superior sagittal sinus, only selective arterial DS angiography revealed a significant arterial and venous cross-flow between the two adjacent temporal lobes. Selective intraarterial DS angiography is required in the neuroradiological evaluation of complex malformations, even when the anatomy of brain and skull can be well demonstrated with high-quality MR and CT studies.

Use of spiral computerized tomography angiography in patients with subarachnoid hemorrhage in whom subtraction angiography did not reveal cerebral aneurysms

2000 ◽  
Vol 92 (2) ◽  
pp. 278-283 ◽  
Author(s):  
Hiroyuki Hashimoto ◽  
Jun-Ichi Iida ◽  
Yasuo Hironaka ◽  
Masato Okada ◽  
Toshisuke Sakaki
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Ct Angiography ◽  
Cerebral Aneurysms ◽  
Spiral Ct ◽  
The Other ◽  
Anterior Communicating Artery ◽  
Content Type ◽  
Spiral Ct Angiography ◽  
Spiral Computerized Tomography ◽  
Fine Print

Object. Patients with subarachnoid hemorrhage (SAH) in whom angiography does not demonstrate diagnostic findings sometimes suffer recurrent disease and actually harbor undetected cerebral aneurysms. The management strategy for such cases remains controversial, but technological advances in spiral computerized tomography (CT) angiography are changing the picture. The purpose of this prospective study was to examine how spiral CT angiography can contribute to the detection of cerebral aneurysms that cannot be visualized on angiography.Methods. In 134 consecutive patients with SAH, a prospective search for the source of bleeding was performed using digital subtraction (DS) and spiral CT angiography. In 21 patients in whom initial DS angiography yielded no diagnostic findings, spiral CT angiography was performed within 3 days. Patients in whom CT angiography provided no diagnostic results underwent second and third DS angiography sessions after approximately 2 weeks and 6 months, respectively.Six patients with perimesencephalic SAH were included in the 21 cases. Six of the other 15 patients had small cerebral aneurysms detectable by spiral CT angiography, five involving the anterior communicating artery and one the middle cerebral artery. Two patients in whom initial angiograms did not demonstrate diagnostic findings proved to have a ruptured dissecting aneurysm of the vertebral artery; in one case this was revealed at autopsy and in the other during the second DS angiography session. A third DS angiography session revealed no diagnostic results in 13 patients.Conclusions. Spiral CT angiography was useful in the detection of cerebral aneurysms in patients with SAH in whom angiography revealed no diagnostic findings. Anterior communicating artery aneurysms are generally well hidden in these types of SAH cases. A repeated angiography session was warranted in patients with nonperimesencephalic SAH and in whom initial angiography revealed no diagnostic findings, although a third session was thought to be superfluous.

Surgical anatomy of the cerebral arteries in patients with subarachnoid hemorrhage: comparison of computerized tomography angiography and digital subtraction angiography

2001 ◽  
Vol 95 (2) ◽  
pp. 206-212 ◽  
Author(s):  
Birgitta K. Velthuis ◽  
Maarten S. van Leeuwen ◽  
Theodoor D. Witkamp ◽  
Lino M. P. Ramos ◽  
Jan Willem Berkelbach van der Sprenkel ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Ct Angiography ◽  
Computerized Tomography ◽  
Cerebral Arteries ◽  
Digital Subtraction ◽  
Aneurysm Surgery ◽  
Content Type ◽  
Computerized Tomography Angiography ◽  
Vertebrobasilar Artery ◽  
Fine Print

Object. The purpose of this study was to compare computerized tomography (CT) angiography and digital subtraction (DS) angiography studies in patients with subarachnoid hemorrhage (SAH) to assess their vascular anatomy relevant to cerebral aneurysm surgery. Methods. From a prospective series of 100 patients with SAH, the authors selected 73 patients whose CT angiography studies were of adequate quality and in whom DS angiography of both carotid arteries had been performed. Eleven patients with no DS angiographic studies of the vertebrobasilar artery were only evaluated for the anterior half of the circle of Willis. Anterior communicating arteries (ACoAs), both precommunicating anterior cerebral arteries (A1 segments), both posterior communicating arteries (PCoAs), and both precommunicating posterior cerebral arteries (P1 segments) were assessed on CT angiography and DS angiography by two independent observers. Conclusions. Computerized tomography angiography compares well with DS angiography for visualizing normal-sized arteries, and is superior for visualizing ACoAs and hypoplastic A1 and P1 segments. Important preoperative aspects such as dominant A1 segments and PCoAs are equally well seen using either modality. Neither method enabled the authors to visualize more than 50% of PCoAs. Use of CT angiography can provide the required preoperative anatomical information for aneurysm surgery in most patients with SAH.

Combined MRI and PET imaging in brain stem mass lesions: diagnostic yield in a series of 30 stereotactically biopsied patients

2000 ◽  
Vol 93 (6) ◽  
pp. 951-957 ◽  
Author(s):  
Nicolas Massager ◽  
Philippe David ◽  
Serge Goldman ◽  
Benoît Pirotte ◽  
David Wikler ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Stereotactic Biopsy ◽  
Diagnostic Yield ◽  
Emission Tomography ◽  
Histological Findings ◽  
Content Type ◽  
Positron Emission ◽  
Pet Scanning ◽  
Mass Lesions ◽  
Fine Print

Object. In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET) scanning, and histological studies obtained in 30 patients who underwent MR imaging— and PET-guided stereotactic biopsy procedures for a brainstem mass lesion.Methods. Between July 1991 and December 1998, 30 patients harboring brainstem mass lesions underwent a stereotactic procedure in which combined MR imaging and PET scanning guidance were used. Positron emission tomography scanning was performed using [18F]fluorodeoxyglucose in 16 patients, methionine in two patients, and both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only was in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. Treatment based on information derived from MR imaging was concordant with therapy based on histological findings in only 17 patients (57%). Combining MR imaging and PET scanning data, the concordance between the neuroimaging-based treatment and treatments based on histological findings increased to 19 patients (63%). In seven patients who underwent biopsy procedures with one PET-defined and one MR imaging—defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging—guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases.Conclusions. Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combining information provided by MR imaging and PET scanning in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the biopsy sample; an MR imaging— and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.

Detection of hyperacute subarachnoid hemorrhage of the brain by using magnetic resonance imaging

2002 ◽  
Vol 96 (4) ◽  
pp. 684-689 ◽  
Author(s):  
Martin Wiesmann ◽  
Thomas E. Mayer ◽  
Indra Yousry ◽  
Ralph Medele ◽  
Gerhard F. Hamann ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Magnetic Resonance ◽  
Mr Imaging ◽  
High Field ◽  
Ct Scanning ◽  
Proton Density ◽  
Imaging Protocol ◽  
Content Type ◽  
Cerebrospinal Fluid Flow ◽  
Fine Print

Object. The purpose of this study was to determine the diagnostic accuracy of high-field (1.5-tesla) magnetic resonance (MR) imaging in the assessment of hyperacute (< 12 hours after onset of symptoms) subarachnoid hemorrhage (SAH). Methods. This investigation included 13 patients who were examined 2 to 12 hours posthemorrhage by using an MR imaging protocol consisting of T2-weighted and proton-density (PD)-weighted images, T1-weighted images, fast echoplanar—diffusion-weighted (EP-DW) images, and fluid-attenuated inversion-recovery (FLAIR) images. Subarachnoid hemorrhage had been diagnosed using computerized tomography (CT) scanning in all cases. In all 13 cases, SAH was reliably detected on both PD-weighted and FLAIR images. In contrast with FLAIR studies, the PD-weighted images were free of cerebrospinal fluid flow artifacts. The SAH was detected on T1-weighted images in only two cases and could not be detected on any T2-weighted or EP-DW images. Conclusions. Even hyperacute SAH can be diagnosed reliably from high-field MR images obtained using PD-weighted or FLAIR sequences. Use of these sequences in an emergency MR protocol may preclude the need for additional CT studies to rule out SAH.

Role of magnesium in the reduction of ischemic depolarization and lesion volume after experimental subarachnoid hemorrhage

2002 ◽  
Vol 97 (2) ◽  
pp. 416-422 ◽  
Author(s):  
Walter M. van den Bergh ◽  
J. Karel Zuur ◽  
Niels A. Kamerling ◽  
Jan Thies H. van Asseldonk ◽  
Gabriël J. E. Rinkel ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Mr Imaging ◽  
Tissue Injury ◽  
Minor Role ◽  
Lesion Volume ◽  
Parent Vessel ◽  
Vessel Occlusion ◽  
Content Type ◽  
The Mean ◽  
Fine Print

Object. Ischemia-induced tissue depolarizations probably play an important role in the pathophysiology of cerebral ischemia caused by parent vessel occlusion. Their role in ischemia caused by subarachnoid hemorrhage (SAH) remains to be investigated. The authors determined whether ischemic depolarizations (IDs) or cortical spreading depressions (CSDs) occur after SAH, and how these relate to the extent of tissue injury measured on magnetic resonance (MR) images. In addition, they assessed whether administration of MgSO4 reduces depolarization time and lesion volume. Methods. By means of the endovascular suture model, experimental SAH was induced in 52 rats, of which 37 were appropriate for analysis, including four animals that underwent sham operations. Before induction of SAH, serum Mg++ levels were measured and 90 mg/kg intravascular MgSO4 or saline was given. Extracellular direct current potentials were continuously recorded from six Ag/AgCl electrodes, before and up to 90 minutes following SAH, after which serum Mg++ levels were again measured. Next, animals were transferred to the MR imaging magnet for diffusion-weighted (DW) MR imaging. Depolarization times per electrode were averaged to determine a mean depolarization time per animal. No depolarizations occurred in sham-operated animals. Ischemic depolarizations occurred at all electrodes in all animals after SAH. Only two animals displayed a single spreading depression-like depolarization. The mean duration of the ID time was 41 ± 25 minutes in the saline-treated controls and 31 ± 30 minutes in the Mg++-treated animals (difference 10 minutes; p = 0.31). Apparent diffusion coefficient (ADC) maps of tissue H2O, obtained using DW images approximately 2.5 hours after SAH induction, demonstrated hypointensities in both hemispheres, but predominantly in the ipsilateral cortex. No ADC abnormalities were found in sham-operated animals. The mean lesion volume, as defined on the basis of a significant ADC reduction, was 0.32 ± 0.42 ml in saline-treated controls and 0.11 ± 0.06 ml in Mg++-treated animals (difference 0.21 ml; p = 0.045). Serum Mg++ levels were significantly elevated in the Mg++-treated group. Conclusions. On the basis of their data, the authors suggest that CSDs play a minor role, if any, in the acute pathophysiology of SAH. Administration of Mg++ reduces the cerebral lesion volume that is present during the acute period after SAH. The neuroprotective value of Mg++ after SAH may, in part, be explained by a reduction in the duration of the ID of brain cells.

Volume-rendered helical computerized tomography angiography in the detection and characterization of intracranial aneurysms

2000 ◽  
Vol 93 (2) ◽  
pp. 254-264 ◽  
Author(s):  
J. Pablo Villablanca ◽  
Neil Martin ◽  
Reza Jahan ◽  
Y. Pierre Gobin ◽  
John Frazee ◽  
...  
Keyword(s):  
Ct Angiography ◽  
Computerized Tomography ◽  
Intracranial Aneurysms ◽  
Mr Angiography ◽  
Content Type ◽  
Aneurysm Neck ◽  
Computerized Tomography Angiography ◽  
Impact On Treatment ◽  
Fine Print

Object. The goal of this study was to evaluate the utility of volume-rendered helical computerized tomography (CT) angiography in patients with intracranial aneurysms. The authors compared the abilities of CT angiography, digital subtraction (DS) angiography, and three-dimensional time-of-flight magnetic resonance (MR) angiography to characterize aneurysms.Methods. Helical CT angiography was performed in 45 patients with suspected intracranial aneurysms by using volume-rendered multiplanar reformatted (MPR) images. Digital subtraction angiography was performed using biplane angiography. These studies and those performed using MR angiography were interpreted in a blinded manner. Two neurosurgeons and two interventional neuroradiologists independently graded the utility of CT angiography with respect to aneurysm characterization.Fifty-five aneurysms were detected. Of these, 48 were evaluated for treatment. Computerized tomography angiography was judged to be superior to both DS and MR angiography in the evaluation of the arterial branching pattern at the aneurysm neck (compared with DS angiography, p = 0.001, and with MR angiography, p = 0.007), aneurysm neck geometry (compared with DS angiography, p = 0.001, and with MR angiography, p = 0.001), arterial branch incorporation (compared with DS angiography, p = 0.021, and with MR angiography, p = 0.001), mural thrombus (compared with DS angiography, p < 0.001), and mural calcification (compared with DS angiography, p < 0.001, and with MR angiography, p < 0.001). For surgical cases, CT angiography had a significant impact on treatment path (p = 0.001), operative approach (p = 0.001), and preoperative clip selection (p < 0.001). For endovascular cases, CT angiography had an impact on treatment path (p < 0.02), DS angiography study time (p = 0.01), contrast agent usage (p = 0.01), and coil selection (p = 0.02). Computerized tomography angiography provided unique information about 39 (81%) of 48 aneurysms, especially when compared with DS angiography (p = 0.003). The sensitivity and specificity of CT angiography compared with DS angiography was 1. The sensitivity and specificity of CT and DS angiography studies compared with operative findings were 0.98 and 1, respectively.Conclusions. Computerized tomography angiography is equal to DS angiography in the detection and superior to DS angiography and MR angiography in the characterization of brain aneurysms. Information contained in volume-rendered CT angiography images had a significant impact on case management.

Computerized tomography angiography in patients with subarachnoid hemorrhage: from aneurysm detection to treatment without conventional angiography

1999 ◽  
Vol 91 (5) ◽  
pp. 761-767 ◽  
Author(s):  
Birgitta K. Velthuis ◽  
Maarten S. van Leeuwen ◽  
Theodoor D. Witkamp ◽  
Lino M. P. Ramos ◽  
Jan Willem Berkelbach van der Sprenkel ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Ct Angiography ◽  
Computerized Tomography ◽  
Intracranial Aneurysms ◽  
Parent Artery ◽  
Imaging Method ◽  
Content Type ◽  
Computerized Tomography Angiography ◽  
Ruptured Intracranial Aneurysms ◽  
Fine Print

Object. The purpose of this study was to determine prospectively whether and to what extent computerized tomography (CT) angiography can serve as the sole imaging method for a preoperative workup in patients with ruptured intracranial aneurysms.Methods. During a 1-year period, all patients who presented to the authors' hospital with subarachnoid hemorrhage demonstrated by unenhanced CT scanning or lumbar puncture underwent CT angiography. Two radiologists evaluated the CT angiography source images and maximum intensity projection slabs and arrived at a consensus. They categorized the quality of the CT angiography as adequate or inadequate and classified aneurysms that were detected as definitely or possibly present. The parent artery of anterior communicating artery aneurysms was identified by asymmetrical anterior cerebral artery size and asymmetrical aneurysm location. The parent artery was indicated by the larger A1 segment in cases of asymmetrical A1 size. Only CT angiograms of adequate quality that revealed aneurysms classified as definitely present and with an unequivocal parent artery were presented to the neurosurgeons, who decided whether preoperative digital subtraction (DS) angiography should still be performed.Forty-nine of the 100 studied patients did not undergo surgery because of poor clinical condition, nonaneurysmal cause of the hemorrhage, or endovascular treatment of the ruptured aneurysm. Of the 51 patients who underwent surgery, radiologists required DS angiography in 17 patients; the imaging technique provided greater certainty in 13 instances. The neurosurgeons required DS angiography 11 times; this provided additional information in two instances. Twenty-three (45%) of the 51 patients were surgically treated successfully on the basis of CT angiography findings alone.Conclusions. Computerized tomography angiography can replace DS angiography as the preoperative neuroimaging technique in a substantial proportion of patients with ruptured intracranial aneurysms.

Gamma knife radiosurgery in the management of cavernous sinus meningiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 68-73 ◽  
Author(s):  
Pierre-Hugues Roche ◽  
Jean Régis ◽  
Henry Dufour ◽  
Henri-Dominique Fournier ◽  
Christine Delsanti ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Tumor Growth ◽  
Gamma Knife ◽  
Cavernous Sinus ◽  
Gamma Knife Radiosurgery ◽  
Surgical Removal ◽  
Content Type ◽  
Cavernous Sinus Meningioma ◽  
The Mean ◽  
Fine Print

Object. The authors sought to assess the functional tolerance and tumor control rate of cavernous sinus meningiomas treated by gamma knife radiosurgery (GKS). Methods. Between July 1992 and October 1998, 92 patients harboring benign cavernous sinus meningiomas underwent GKS. The present study is concerned with the first 80 consecutive patients (63 women and 17 men). Gamma knife radiosurgery was performed as an alternative to surgical removal in 50 cases and as an adjuvant to microsurgery in 30 cases. The mean patient age was 49 years (range 6–71 years). The mean tumor volume was 5.8 cm3 (range 0.9–18.6 cm3). On magnetic resonance (MR) imaging the tumor was confined in 66 cases and extensive in 14 cases. The mean prescription dose was 28 Gy (range 12–50 Gy), delivered with an average of eight isocenters (range two–18). The median peripheral isodose was 50% (range 30–70%). Patients were evaluated at 6 months, and at 1, 2, 3, 5, and 7 years after GKS. The median follow-up period was 30.5 months (range 12–79 months). Tumor stabilization after GKS was noted in 51 patients, tumor shrinkage in 25 patients, and enlargement in four patients requiring surgical removal in two cases. The 5-year actuarial progression-free survival was 92.8%. No new oculomotor deficit was observed. Among the 54 patients with oculomotor nerve deficits, 15 improved, eight recovered, and one worsened. Among the 13 patients with trigeminal neuralgia, one worsened (contemporary of tumor growing), five remained unchanged, four improved, and three recovered. In a patient with a remnant surrounding the optic nerve and preoperative low vision (3/10) the decision was to treat the lesion and deliberately sacrifice the residual visual acuity. Only one transient unexpected optic neuropathy has been observed. One case of delayed intracavernous carotid artery occlusion occurred 3 months after GKS, without permanent deficit. Another patient presented with partial complex seizures 18 months after GKS. All cases of tumor growth and neurological deficits observed after GKS occurred before the use of GammaPlan. Since the initiation of systematic use of stereotactic MR imaging and computer-assisted modern dose planning, no more side effects or cases of tumor growth have occurred. Conclusions. Gamma knife radiosurgery was found to be an effective low morbidity—related tool for the treatment of cavernous sinus meningioma. In a significant number of patients, oculomotor functional restoration was observed. The treatment appears to be an alternative to surgical removal of confined enclosed cavernous sinus meningioma and should be proposed as an adjuvant to surgery in case of extensive meningiomas.

Thalamic lesions produced by gamma thalamotomy for movement disorders

2002 ◽  
Vol 97 ◽  
pp. 600-606 ◽  
Author(s):  
Chihiro Ohye ◽  
Tohru Shibazaki ◽  
Jie Zhang ◽  
Yoshitaka Andou
Keyword(s):  
Mr Imaging ◽  
Involuntary Movement ◽  
Gamma Knife Radiosurgery ◽  
Target Point ◽  
High Signal ◽  
Thalamic Lesion ◽  
Content Type ◽  
Stereotactic Thalamotomy ◽  
Thalamic Lesions ◽  
Fine Print

Object. The treatment of Parkinson disease and other kinds of involuntary movement by gamma knife radiosurgery (GKS) is presented. This is an extension of previous work. The clinical course and thalamic lesions were the main factors examined. Methods. Seventeen new cases were added to the previously reported 36 cases. The course and results for the whole series of 53 patients were examined. Treatment was undertaken using a single 4-mm collimator shot to deliver 130 Gy to the target. The target was determined in the previously treated patients by using classic methods involved in conventional stereotactic thalamotomy with microrecording. More recently, target localization has been performed by relating the target point to the total length of the thalamus. Points may then be defined as percentages of that length measured from the anterior pole. Targets can then be determined in relationship to the appropriate percentage. Thirty-five patients have been followed for more than 2 years and the longest follow up was 8 years. Two kinds of thalamic lesion were seen after GKS. Volumetric analysis on MR imaging revealed that the larger lesion was 400 to 500 mm3 at the beginning and gradually decreased in size. The smaller lesion occupied approximately 200 mm3 and also shrank over several months. Eighty percent of the treated cases showed good results and no significant complications, with the tremor subsiding at 1 year (Type 1). Several cases deviated from this standard course in four different ways (Types 2–5). If tremor persisted, conventional stereotactic thalamotomy with microrecording was performed. During such operations, normal neuronal activity was recorded from the region adjacent to the GKS thalamotomy target. This was the region showing a high signal on MR imaging. The activity patterns included the rhythmical grouped discharge of tremor rhythm. Conclusions. Gamma thalamotomy for functional disorders is still under development, but because the results with careful target planning are satisfactory, there are grounds for increasing optimism.

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