Multimodale Computertomographie beim akuten Hirninfarkt

Computed tomography (CT) is the standard method of brain imaging in acute stroke. To an experienced examiner, nonenhanced CT will exclude hemorrhage and may indicate early ischemic signs. Reliable description of an ischemic area and the underlying vascular disease is not possible in the acute phase but is possible, particularly within the first hours, when therapeutic decisions on matters such as systemic thrombolysis are to be made. For such rapid decision-making, imaging must provide more information. Novel, contrast-enhanced CT techniques can provide this information. Perfusion CT (CTP) can show brain perfusion, allowing one to distinguish between reversible and irreversible damage in an ischemic area. Also, CT angiography (CTA) can detect occlusion or stenosis in the relevant vasculature. Using a modern, multislice CT scanner, it is now possible to combine these modalities of imaging. In a fast protocol for emergency evaluation, all three methods can be performed and evaluated to provide the crucial information within 15 min. In the first 102 patients examined within 6 h of symptom onset using this protocol, multimodal CT contributed substantially to therapeutic decisions, even though there are some limitations in these methods.

Thrombus am Sideris-Okkludersystem nach 6 Jahren

HISTORY AND CLINICAL FINDINGS

A 61-year-old man was admitted to hospital because of right-sided hypaesthesia. Additionally he reported a brief speech disturbance some weeks before. Neurological examination indicated right-sided sensomotoric hemiparesis and left-sided upper quadrant anopia. 6 years ago recurrent transient ischaemic attacks (TIA) was diagnosed caused by paradoxical embolism through a persistent foramen ovale (PFO). The PFO was closed with a 45 mm Sideris button occluder device. After this, he reported no symptoms of cerebral ischaemia and he did not take any antiplatelet therapy.

INVESTIGATIONS

Transesophageal echocardiography (TEE) showed a left atrial thrombus attached to the occluder. Cerebral computed tomography revealed infarction in regions supplied by the right posterior cerebral artery and left media cerebral artery. As additional risk factor for thrombosis a heterozygous factor V Leiden mutation was diagnosed.

DIAGNOSIS

Multiple cerebral infarctions caused by a thrombus attached to an occluder system 6 years after interventional closure of persistent foramen ovale in a patient with heterozygous factor V Leiden mutation.

TREATMENT AND COURSE

The patient was anticoagulated (phenprocoumon) and the thrombus gradually dissolved.

CONCLUSION

A thrombosis on a Sideris occluder device may cause cerebral infarctions even years after transcatheter closure of a PFO.

Somatosensory evoked magnetic fields following passive movement compared with tactile stimulation of the index finger

Cortical processing of passive finger movement was assessed magnetoencephalographically in 12 healthy volunteers and compared with somatosensory evoked magnetic fields (SEF) following tactile stimulation. A new device comprising a clamp-like digit holder facilitated bilateral guidance of the briskly elevated index finger. Both passive movement and tactile stimulation induced activation of the contralateral primary somatosensory (SI) cortex, indicated by six SEF deflections with inter-individually rather consistent peak latencies of 20-230 ms following proprioceptive and 20-300 ms following tactile stimulation. SEF responses to the two stimulus modalities clearly differed with regard to peak latencies, amplitudes and orientations of equivalent current dipoles (ECDs). The strength and orientation of proprioception-related ECDs suggested sequential activation of SI generators, with possible involvement of areas 3a and/or 2 at around 20 ms, area 4 at approximate peak latencies of 65 and 100 ms and area 3b between 150 to 230 ms. Passive movement elicited additional activation of cortical regions outside SI, including the bilateral perisylvian regions and the contralateral cingulate gyrus at latencies of 40-470 and 150-500 ms respectively. The study provides new results with respect to the spatiotemporal analysis of proprioception-related cortical processing and may contribute to a better understanding of the modality-specific organization of the human somatosensory cortex.

Severe neurological complications of ulcerative colitis

A 37 year old man presented with a 15 year history of ulcerative colitis. On examination he had weakness of the right arm, slurred speech and progressive confusion, followed by a rapid deterioration of consciousness and motor functions resulting in coma, tetraparesis and bilateral Babinski responses. Magnetic resonance imaging of the brain and spinal cord revealed multiple hyper- and hypointense white matter lesions. Clinical symptoms, history and neuroradiological findings led to the diagnosis of an ulcerative colitis-associated CNS disorder. An autoimmune vasculitic process may have played an important pathophysiological role, considering the vasculitic changes observed by skin biopsy as well as the rapid clinical improvement following immunosuppressive therapy with corticosteroids and azathioprine. During a follow up period of more than one year we observed continuous and complete recovery of neurologic symptoms.

Local and remote visualization techniques for interactive direct volume rendering in neuroradiology

The increasing capabilities of magnetic resonance (MR) imaging and multisection spiral computed tomography (CT) to acquire volumetric data with near-isotropic voxels make three-dimensional (3D) postprocessing a necessity, especially in studies of complex structures like intracranial vessels. Since most modern CT and MR imagers provide limited postprocessing capabilities, 3D visualization with interactive direct volume rendering requires expensive graphics workstations that are not available at many institutions. An approach has been developed that combines fast visualization on a low-cost PC system with high-quality visualization on a high-end graphics workstation that is directly accessed and remotely controlled from the PC environment via the Internet by using a Java client. For comparison of quality, both techniques were applied to several neuroradiologic studies: visualization of structures related to the inner ear, intracranial aneurysms, and the brainstem and surrounding neurovascular structures. The results of pure PC-based visualization were comparable with those of many commercially available volume-rendering systems. In addition, the high-end graphics workstation with 3D texture-mapping capabilities provides visualization results of the highest quality. Combining local and remote 3D visualization allows even small radiologic institutions to achieve low-cost but high-quality 3D visualization of volumetric data.

[Rapid interactive 3-D imaging of the temporal bone with "direct volume rendering"]

INTRODUCTION

For the first time, the relatively new method of interactive direct volume rendering (dVR) allows for a fast and direct three-dimensional visualization of spiral CT data without any manual, explicit segmentation. This study was performed to prove whether dVR is capable of providing a meaningful three-dimensional visualization of the structures within the temporal bone.

PATIENTS AND METHODS

In ten patients a three-dimensional visualization of the structures of the inner and middle ear was performed from spiral CT data on a commercially available graphics workstation.

RESULTS

The cochlea and semicircular canals were visualized in good quality in all patients. The ossicles and bony facial canal were visualized in good or fair quality in most cases. The time needed for the visualization of the data and all target structures was less than 15 min in all cases.

CONCLUSIONS

Three-dimensional visualization of the structures within the temporal bone from high-resolution spiral CT data using dVR is easily performed in a very short time on standard graphics workstations. This allows integrating three-dimensional visualizations into routine clinical work.

[Diagnostic imaging in refractory temporal lobe epilepsy. A comparison of MR volumetry and multivoxel-MR-spectroscopy for assessment of postoperative prognosis]

While the importance of magnetic resonance (MR) spectroscopy, volumetry, and T2-relaxometry for preoperative localization has already been verified, the question arises as to what extent the individual techniques are useful for assessing postoperative prognosis with respect to seizures and neuropsychological outcome. In a prospective comparative study, 26 patients were examined preoperatively with a 1.5 T whole-body scanner. The MR spectroscopy was taken by high resolution 1 H proton spectroscopy, the volumetry with MP rage technique. The postoperative outcome was laid down using Engel's classification. Our results show that the metabolic changes can be divided into three groups using MR spectroscopy: unilateral, slightly bilateral, and severely bilateral to contralateral. In case of bilateral changes, the severity of metabolic changes in the nonoperated, contralateral side was decisive for postoperative outcome. The results from volumetry did not correlate with postoperative outcome.

Alteration of the somatosensory cortical map in peripheral mononeuropathy due to carpal tunnel syndrome

Substantial plasticity of the mature mammalian somatosensory cortex was demonstrated after deprivation of sensory input produced by amputation or somatosensory deafferentation. Following transection of the median nerve, adult owl and squirrel monkeys exhibit extensive reorganization in the cortical representation of the hand in areas 3b and 1. In the present study we investigated the possible effect of incomplete median nerve damage on sensory cortex somatotopy in a patient with unilateral carpal tunnel syndrome. We assessed interhemispheric differences of the hand representation in SI by means of magnetic source imaging. Additional intersubject data comparison was performed for specific results on the basis of available normal data from the literature and from own investigations in five healthy volunteers. Our results demonstrated a decreased extension of the cortical zone representing the injured median nerve and suggested invasion of the deprived area by cortical sectors receiving inputs from the little finger (supplied by the ulnar nerve) and from the dorsum of the thumb (innervated by the radial nerve). The study indicates topographic rearrangement of the hand representational zone in the human primary somatosensory cortex in a case of chronic median nerve injury.

Contralateral hearing loss as an effect of venous congestion at the ipsilateral inferior colliculus after microvascular decompression: report of a case

Contralateral hearing loss after surgical procedures within the cerebellopontine angle is rarely seen and its pathophysiological background is not yet understood. A patient with contralateral hearing loss after microvascular decompression for trigeminal neuralgia is described. Ipsilateral brainstem auditory potential (BAEP) monitoring and facial nerve EMG did not show major abnormalities. During otherwise uneventful and successful surgery a branch of the petrosal vein was sacrificed to widen the access to the trigeminal root exit zone. On the third postoperative day the patient complained about contralateral hearing loss, which was verified by audiometry. Contralateral BAEPs showed low amplitudes and delayed interpeak latencies. Brain CT was normal. Brain MRI on the 8th postoperative day disclosed abnormal signals within the ipsilateral inferior colliculus. Intravenous heparinisation was performed and hearing slowly recovered over a 3 month period. Results from this patient offer a pathophysiological mechanism for contralateral hearing loss after cerebellopontine angle surgery, illustrate the importance of venous drainage preservation, gives evidence about the generation of BAEP components within the contralateral brainstem, and stresses the importance of intraoperative BAEP monitoring.

Supratentorial low-grade glioma: results and prognostic factors following postoperative radiotherapy

BACKGROUND AND PURPOSE

To assess treatment outcome and prognostic factors following postoperative external radiotherapy in 77 patients with low-grade glioma.

PATIENTS AND METHODS

Between 1977 and 1996, 45 patients with astrocytoma, 14 with oligodendroglioma and 18 with mixed glioma received postoperative radiotherapy with a median total dose of 52 Gy (range, 45 to 61 Gy). Sixty-seven patients were treated immediately following surgery, 10 patients with tumor progression. The influence of various factors including histology, gender, age, seizures, duration of symptoms (< or = 6 weeks vs > 6 weeks), CT pattern (enhancement vs no enhancement), type of surgery, total radiotherapy dose and timing of radiotherapy on relapse-free survival and overall survival was investigated.

RESULTS

The median overall survival time was 81 months, the 5- and 10-year survival rates were 54% and 31%, respectively. The median time to progression was 56 months, while the 5- and 10-year progression-free survival rates were 45% and 24%. Univariate analyses identified the total radiotherapy dose (p = 0.01), duration of symptoms (p = 0.05), the presence of seizures (p = 0.04), and the CT pattern following intravenous contrast (p = 0.005) as significant prognostic factors for overall survival. Progression-free survival rates were influenced by the total dose (p = 0.04), the duration of symptoms (p = 0.01) and CT pattern (p = 0.006). On multivariate analysis, only the CT pattern (enhancement vs no enhancement) remained as independent prognostic factors for both progression-free survival and overall survival.

CONCLUSIONS

A minimum total dose of 52 Gy is recommended for the postoperative radiotherapy in low-grade glioma. Tumors with CT enhancement seem to need further intensification of treatment.

[MRI spectroscopy, T2 relaxometry, and postoperative prognosis in cryptogenic temporal lobe epilepsy]

The preoperative localization of pharmaco-resistant focal epilepsies before surgery and the prognosis concerning seizure outcome are both of importance. In addition to conventional MRI diagnostics for the detection of small epileptogenic lesions, proton magnetic resonance spectroscopic imaging (HMR spectroscopy) can be useful for assessing the bilaterality of pathological changes in cryptogenic temporal lobe epilepsies. The technique and findings of HMR spectroscopy are reported in patients with cryptogenic temporal lobe epilepsies. The findings indicate that chemical shift imaging (CSI) investigations of the ipsilateral and contralateral hemispheres provide important information for the prediction of seizure outcome after epilepsy surgery.

Virtual labyrinthoscopy: visualization of the inner ear with interactive direct volume rendering

Computed tomography (CT) is the modality of choice for detailed imaging of the bony labyrinth. Usually, information about the complex three-dimensional anatomic structures of the inner ear is presented as two-dimensional section images. Interactive direct volume rendering is a powerful method for visualization of the labyrinth. Unlike other visualization methods, direct volume rendering enables direct visualization of the bony labyrinth without explicit segmentation prior to the visualization process. Direct volume rendering was applied to visualization of the structures of the temporal bone in five patients without pathologic conditions and four patients with pathologic conditions. In all cases, clear representations of the bony labyrinth and the facial canal were provided. Because standard CT examinations combined with interactive visualization based on direct volume rendering are used, the method is fast and flexible. Therefore, this approach is applicable in routine clinical work. Problems occur in patients with effusion in the temporal bone because adjustment of imaging parameters for proper delineation of the target structures is difficult in this situation. However, direct volume rendering can produce meaningful images of high quality even in these problematic cases. The term virtual labyrinthoscopy is suggested for visualization of the labyrinth by using direct volume rendering.

Radiation therapy of optico-hypothalamic gliomas (OHG)--radiographic response, vision and late toxicity

BACKGROUND

Management strategies for optic pathway gliomas include observation, surgery, irradiation, chemotherapy and a combination of these modalities. It has been the policy of our University Hospital to consider radiation as the standard treatment for progressive optic pathway gliomas. This report describes the clinical presentation, treatment patterns and outcome with special emphasis on the long term functional status of patients with optico-hypothalamic gliomas (OHG).

PATIENTS AND METHODS

Between 1975 and 1997, 25 patients with OHG were treated by radiation therapy (RT) following surgery or biopsy. All patients received a local RT with a 0.5-1 cm margin around the lesions as depicted on CT or MRI scans. Age adjusted radiation doses ranged from 45 to 60 Gy with a single fraction size of 1.6-2 Gy. Endpoints of the study were: radiographic response, survival, progression-free survival and time to endocrinologic toxicity as well as the visual function during follow-up. The median follow-up time was 9 years (range, 1.5-23 years).

RESULTS

A partial response was noted in six (24%) of the patients, 13 (52%) patients had a stable tumour throughout the observation period and six (24%) patients had a tumour progression. Overall survival and progression-free survival rates were 94 and 69% at 10 years, respectively. A significant influence on progression-free survival was noted for age at diagnosis (P=0.04) and total dose (P=0.05). Nine out of 13 (69%) patients aged below 10 years compared with 3/12 (25%) patients aged above 10 years experienced hypothalamic-pituitary deficiency (P=0.008) during follow-up. As for visual acuity, nine patients had an improvement, another 13 patients a stable situation and three patients a measurable deterioration. Visual field deficits improved in three, remained unchanged in 16 patients and worsened in only one patient.

CONCLUSION

Postoperative RT with a total dose above 45 Gy should be considered as standard treatment in OHG with documented progression. Close radiographic monitoring and lifelong yearly evaluation for the need of possible hormone replacement are strongly recommended.

Chemical shift imaging spectroscopy and memory function in temporal lobe epilepsy

PURPOSE

Hippocampal neuron loss and associated memory deficits are characteristic of intractable temporal lobe epilepsy (TLE). Proton chemical shift imaging (CSI) spectroscopy is a sensitive tool for detecting neuronal loss. The aim of this study was to investigate the correlation between memory functions and results provided by CSI spectroscopy of the hippocampal structures.

METHODS

Ten patients with cryptogenic TLE participated. The study protocol involved both the acquisition of high-spatial-resolution CSI spectroscopy and neuropsychological evaluation, including memory testing and intracarotid sodium amytal test (IAT). The analysis of the CSI data was based on normative data obtained in 30 healthy volunteers. Memory functions were represented by verbal, visual, and general memory indices.

RESULTS

A significant correlation was found between CSI spectroscopy of the hippocampal formation and the verbal memory indices for the dominant hemisphere. In addition, there was a significant correspondence of the qualitative judgment "hippocampal pathology indicated by CSI spectroscopy" and both "material specific memory deficit" and "memory deficit in the IAT."

CONCLUSIONS

Our results demonstrate that CSI spectroscopy of the hippocampal structures is strongly related to lateralized memory deficits in patients with TLE. This suggests that CSI spectroscopy may be useful in the prediction of postoperative outcome in respect of seizure control and memory.

Middle ear adenocarcinoma with intracranial extension. Case report

Middle ear adenocarcinoma is a very rare, locally invasive neoplasm assumed to arise from the middle ear mucosa. Although endolymphatic sac tumor (aggressive papillary middle ear tumor) and jugulotympanic paraganglioma may show brain invasion, intracranial extension of histologically confirmed middle ear adenocarcinoma has not been previously reported. The authors describe a 53-year-old man who suffered from otalgia and tinnitus for more than 10 years and from neurological deficits for 1 year due to a large temporal bone tumor that invaded the temporal lobe. A combined neurosurgical and otolaryngological resection was performed. Pathological analysis revealed a low-grade adenocarcinoma of a mixed epithelial-neuroendocrine phenotype, which showed a close histological similarity to, and topographical relationship with, middle ear epithelium. The authors conclude that middle ear adenocarcinoma belongs to the spectrum of extracranial tumors that have possible local extension to the brain.

MR cisternography: a new method for the diagnosis of CSF fistulae

The aim of this study was to compare a new MRI method for detecting the existence of cerebrospinal fluid (CSF) fistulae, i. e. MR cisternography, with CT cisternography. In a prospective study, 30 patients with post-traumatic CSF fistulae were examined. The MR examinations were performed with a 1.0-T whole-body MR system, using two T2(*)-weighted sequences, a 3D PSIF (time-inversed fast imaging with steady-state precession, FISP) and a 3D constructive interference steady-state (CISS) sequence. The results of MRI and CT cisternography were compared with the surgical findings. The sensitivity in detecting CSF fistulae with MR cisternography (PSIF: 89.9 %; CISS: 93.6 %) was higher than with CT cisternography (72.3 %). The sensitivity of CT cisternography at detecting CSF fistulae in patients with a size of dural lesion less than 2 mm or in patients with multiple dural lesions is significantly lower compared with the MR method. Although the localization of CSF fistulae always proved possible with MR cisternography, this could only be accomplished wih CT in 70 % of cases. The MR cisternography technique is a new examination method with a higher sensitivity for the detection of CSF fistulae than CT cisternography. The CISS technique is superior compared with PSIF and should be used in patients with high-flow CSF fistulas.

[MR diagnosis of cerebrospinal fluid fistulas using a 3D-CISS sequence]

PURPOSE

We compared a new MR method for diagnosis of CSF fistulas with CT cisternography.

MATERIAL AND METHODS

In a prospective case study we examined 35 patients with posttraumatic CSF fistulas and compared the results with the intraoperative findings. The MR investigation was performed using a 1.0T whole body MR-system. We used a strongly T2*-weighted 3D-CISS sequence. The examinations were performed in prone position, in patients with severe CSF rhinorrhoea additionally in supine position.

RESULTS

The sensitivity and specificity of the MR method (88.9% and 95.1%) is higher compared with CT cisternography (77.8% and 87.8%). The reason for the lower sensitivity of CT compared with MRI are complex fracture systems, involving several paranasal cavities in patients with false positive results in CT cisternography. Reasons for the lower specificity of CT cisternography are false negative results in patients with small dural lesions below 2 mm2.

CONCLUSION

Using a new method MRI can detect CSF-fistulas. The MR method is superior to CT cisternography, is noninvasive, the administration of contrast and agent is no longer necessary.

[Value of CT-angiography in the diagnosis of cerebral artery aneurysms]

PURPOSE

In a clinical study 35 patients with intracranial aneurysms were examined using CT-angiography, MR-angiography (MRA) and digital subtraction angiography (DSA). The aim of the study was to establish the ability of noninvasive techniques to detect intracranial aneurysms.

MATERIAL AND METHODS

The CT examinations were performed using a spiral CT scanner and the MR investigations with a 1.5 T whole body MR-system. We used for MR-angiography Time of Flight (TOF) and Phase Contrast (PC) techniques. For postprocessing reconstructions modalities Maximum Intensity Projection (MIP), Surface and Volume Rendering Technique (VRT) techniques were used. The results were evaluated by the intraoperative findings.

RESULTS

Aneurysms up to 5 mm could be detected best using CTA and DSA. Giant aneurysms could be evaluated best using CTA. Volume rendering technique was the most useful postprocessing procedure. MRA using Time of Flight was superior compared with MRA using PC technique.

CONCLUSION

CTA is the best method to detect and to evaluate giant intracranial aneurysms. Nevertheless the reconstruction mode has a decisive influence on the results.

Neurophysiological findings in long-term survivors of acute lymphoblastic leukaemia in childhood treated with the BFM protocol 81 SR-A/B

Monitoring of therapy-related late effects after acute lymphoblastic leukaemia (ALL) therapy in childhood has become an increasingly important field in posttherapeutic patient surveillance. The usefulness of neurophysiological investigations (e.g. EEG, evoked potentials (EP)) as part of these attempts is controversial. The present report focuses on this problem and the question whether and to what extent routinely performed EEG recordings and visual evoked potentials (VEP) were correlated with further measures of CNS integrity. EEGs and VEPs were recorded in 163 asymptomatic long-term survivors of ALL in childhood during a large retrospective multicentre study evaluating CNS late sequelae following antileukaemic therapy. Fifty-two ALL long-term survivors (4.5-10.6 years after end of therapy, median: 8.8 years), who had been treated according to BFM-81 SR-A (n = 30) or SR-B (n = 22) were selected for this analysis focusing on therapy-related CNS late effects. Therapy protocols differed with regard to the mode for CNS prophylaxis: SR-A, cranial irradiation with intrathecal methotrexate; SR-B, intrathecal and iv methotrexate. Neurophysiological findings were correlated with illness- and treatment-related parameters, as well as with data on the morphological, neurological and psychological status of the CNS. At the time of follow-up neurophysiological measures were abnormal in 28/52 cases (53.8%). Neither illness- nor therapy-specific differences in CNS prophylaxis showed any relationship to EEG/VEP outcome any relationship to EEG/VEP outcome in this reduced group of the whole study population. Children with EEG/VEP abnormalities showed a significantly higher incidence of structural CNS disturbances compared to those with inconspicuous neurophysiological recordings (60.9% vs 31.8%). However, in this special subject group there was no specific neurophysiological finding for a specific morphological substrate, neurological or psychological deficiency and vice versa.

CONCLUSION

Routinely performed EEG/VEP investigations are not very helpful measures to predict the presence or degree of behavioural deficiencies, neurological disturbances, or morphological CNS abnormalities. Patients who received cranial irradiation or systemic methotrexate applications showed the same incidence of neurophysiological disturbances without evidence for specific neurotoxic correlates.

CNS late effects after ALL therapy in childhood. Part II: Conventional EEG recordings in asymptomatic long-term survivors of childhood ALL--an evaluation of the interferences between neurophysiology, neurology, psychology, and CNS morphology. German Late Effects Working Group

Monitoring of therapy-related late effects after acute lymphoblastic leukemia (ALL) therapy in childhood has become an increasingly important area in posttherapeutic patient surveillance. The usefulness of conventional electro-encephalographic (EEG) investigations as part of these attempts is controversially discussed. However, EEG recordings have become a popular approach for judgement on the functional integrity of the central nervous system in this subject group. The present report focuses on this problem and discusses the question whether and to what extent conventional EEG recordings were correlated with further measures of central nervous system (CNS) integrity and therapeutic differences. EEGs were recorded in 110 subjects, asymptomatic long-term survivors of ALL in childhood, during a large retrospective multicenter study evaluating CNS late sequelae following antileukemic therapy in Germany and Austria. EEG findings were correlated with demographic data, illness- and treatment-related parameters, as well as with data on the morphological, neurological and psychological status of the participating subjects. At the time of follow-up the EEG was abnormal in 47 cases (42.7%). The most frequent EEG abnormalities observed were disturbances of the background activity (n = 45, 95.8%), followed by hypersynchrone activities (n = 1.0, 21.3%) and interhemispheric differences/focal slowing (n = 6, 12.8%). With exception of age at diagnosis, none of the observed EEG abnormalities showed a correlation with any of the aforementioned illness- or treatment-related parameters. Eighty percent of the observed EEG abnormalities were found in children younger than 5 years at diagnosis. Children less than 2 years of age as well as those above 5 years at onset of disease showed a significantly reduced prevalence of EEG disturbances compared to subjects between 2 and 5 years at diagnosis. Neither the degree of illness nor therapy-specific differences showed any relationship to EEG outcome. There was no specific EEG finding for a specific morphological substrate, neurological or psychological deficiency and vice versa. Overall, there was no beneficial effect of routine EEG testing in children following therapy for ALL. According to our data, the evaluation of conventional EEG recordings of otherwise asymptomatic ALL long-term survivors is not a very helpful measure for predicting the degree of behavioral deficiencies, neurological disturbances, or morphological CNS abnormalities, which may be present or will develop in this special subject group.

CNS late effects after ALL therapy in childhood. Part I: Neuroradiological findings in long-term survivors of childhood ALL--an evaluation of the interferences between morphology and neuropsychological performance. The German Late Effects Working Group

The effect of cranial irradiation on possible therapy-induced morphological central nervous system (CNS) side effects of children cured from acute lymphoblastic leukemia (ALL) is controversially discussed. In a retrospective multicenter study, 118 former ALL patients in first continuous remission were investigated using cranial computerised tomography (CCT) or magnetic resonance imaging (MRI) scans to evaluate CNS related impairments. Corresponding to the different kinds of CNS prophylaxis, the patient sample was divided: group A (n = 39) receiving intrathecal methotrexate (ITMTX) and systemical medium-high-dose methotrexate (SMHDMTX), group B (n = 41) cranial irradiated (in mean 16.8 Gy) and administering ITMTX and SMHDMTX, group C (n = 38) irradiated (in mean 17.1 Gy) and getting ITMTX. Pathologic scans showed atrophy, leukoencephalopathy, calcifications or grey matter changes. These findings were compared with the neuropsychological test results. Abnormal MRI or CCI scans were found in 61/118 patients (51.7%). Fifteen belonged to group A (38.5%), 23 to B (56.1%) and 23 to C (60.5%). Patients with definite CNS changes show reduced neuropsychological test results. The prevalence of brain alterations seems to appear twice increased after lengthening the posttherapeutic interval in irradiated patients as in nonirradiated patients. Irradiated patients as an age younger than 2 years at diagnosis may show a lower prevalence for developing CNS alterations. CNS alterations are not sex-related. Children treated with cranial irradiation in combination with SMHDMTX and/or ITMTX were at greater risk of developing morphological brain alterations than patients with chemotherapy alone. These alterations are partly correlated with reduced neuropsychological performances and seem to stay with a longer posttherapeutic interval.

Three-dimensional MR myelography of the lumbar spine: comparative case study to X-ray myelography

Conventional myelography was compared with a new type of MR technique using a fat-suppressing 3D fast imaging with steady precession (FISP) sequence for diagnosis of the lumbar root compression syndrome. 80 patients with discogenic disease in the lumbar spine were examined with a 1.0-T whole-body MR system (Siemens Magnetom Impact, Erlangen, Germany). A strongly T2(*)-weighted 3D FISP sequence was applied in the sagittal orientation. To obtain fat suppression, a frequency-selective 1-3-3-1 prepulse was applied prior to the imaging sequence. The acquired 3D data set was evaluated using a maximum intensity projection (MIP) program. The measurement time was 7 min, 47 s. Magnetic resonance myelography has significant advantages over conventional myelography, particularly in cases of extreme spinal canal stenosis. Compared with the conventional method, this new MR technique shows comparable sensitivity in the visualization of the spinal nerve roots in the lumbar spine.

Quantitative EEG in long-term survivors of acute lymphoblastic leukemia

Conventional and quantitative aspects of electroencephalographic recordings obtained during a follow-up surveillance study in long-term survivors of acute lymphoblastic leukemia in childhood were investigated with respect to differences in central nervous system prophylaxis given during antileukemic therapy and compared with data derived from healthy controls. Central nervous system prophylaxis consisted either of cranial irradiation (18 Gray, group A, n = 8) or intermediate high-dose methotrexate (2000 mg/m2; group B, n = 5), each combined with intrathecal methotrexate. Conventional electroencephalographic analysis revealed comparable results in all three study groups. However, quantitative electroencephalography showed significantly increased absolute power scores for all frequency bands in both long-term survivor groups. Relative power estimates revealed a significant increase in delta/tau activities in both prophylaxis groups compared to healthy controls, which were countered by decreased percentage power scores in the alpha-range. Quantitative electroencephalographic comparisons between both central nervous system prophylaxis groups revealed only small differences in quantity, not quality, of the observed power disturbances with slightly higher deviations in irradiated long-term survivors than in nonirradiated ones. Topographical distributions of spectral band power were comparable between all three study groups without evidence for therapy-related topographical differences.

[Dissection of the carotid artery and vertebral artery--diagnosis and therapy]

Carotid and vertebral artery dissections typically occur in young adults after major trauma, although they can arise spontaneously or after trivial injury. Many patients with carotid dissections have minor symptoms such as a subject bruit or Horner's syndrome. Cephalic pain is also frequent and often inaugural in carotid dissection. However, extracranial dissection is a well recognised cause of ischaemic stroke. The diagnosis of dissection was based on angiographic findings. Noninvasive imaging also allows prompt and reliable diagnosis. Our goal was to demonstrate the spectrum of neuroradiologic (CT, MR and angiographic) findings in craniocervical arterial dissection and compare the diagnostic utility of CT, MR, MR angiography. Clinical data imaging studies, and outcome were reviewed and compared with the results in four patients with carotid artery dissection.

[Quality assurance in neuroradiology]

Due to growing economic pressure, quality management in medicine has to be performed under the aspect of rationing and rationalization simultaneously. High quality and cost effectiveness in medicine, however, can only be achieved by institutions with an adequate quality of structure, procedure and outcome. While the technical criteria of the quality of structure can easily be measured, the assessment of the quality of the performance and the outcome are much more difficult so establish. Therefore standards of quality for the various diagnostic and interventional subspecialties of Neuroradiology have to be designed. The same is true for the evaluation of the quality assurance. The quality of neuroradiology has reached a comparatively high level simply because of the specialization compared to general radiology. This advantage should be utilized more often when major diagnostic departments are to be installed, particularly under the aspect of cost effectiveness plus high quality medicine.

High-resolution magnetic resonance imaging of the endolymphatic duct and sac

An anatomical study was carried out to determine the extent to which magnetic resonance imaging (MRI) could delineate inner ear structures. Anatomical preparations of human petrous temporal bone were examined and compared with the results of MRI in 20 healthy subjects to see whether the structures of the inner ear could be visualized. Imaging of the subjects was carried out in a 1.0-T MRI scanner (Siemens Magnetom Impact). Two strongly T2*-weighted sequences were used: a 3D-PSIF sequence and a 3D-CISS sequence. The 3D data sets were postprocessed using a Maximum Intensity Projection (MIP) program. Our investigations show that it is possible to obtain accurate visualization of structures with a diameter of under 1 mm. In all 20 subjects it was possible to identify both the endolymphatic duct and the endolymphatic sac.

Ultra-rapid gradient echo imaging

A novel ultra-rapid gradient echo (URGE) NMR imaging technique is introduced, which is capable of continuous high resolution 3D scanning while neither subject to fast gradient switching nor excessive RF power deposition. Sampling free induction decays instead of creating spin echoes enables maintaining a workable steady state magnetization. Due to segmented k-space acquisition, chemical shift, diffusion, and field inhomogeneity effects do not present major problems. We report on implementations acquiring from 32 x 64 x 64 partial-Fourier image sets in 0.72 s, allowing for single-shot magnetization-prepared 3D imaging, to 128 x 128 x 128 image sets in 13.3 s and 21.5 s on a standard MRI scanner.

[3D-MR myelography in diagnosis of lumbar spinal nerve root compression syndromes. Comparative study with conventional myelography]

65 patients with nerve root compression syndrome were examined using a new type of MR-technique, which is comparable to the conventional X-ray myelography. The results of the prospective case study were compared with previous clinical experiences (1). For the examinations a 1.0T whole body MR-system (Siemens Magnetom Impact) was used. A strong T2*-weighted 3D-FISP sequence (TR = 73 ms, TE = 21 ms, alpha = 7 degrees) was applied in sagittal orientation using a circularly polarized oval spine coil. To obtain fat suppression a frequency selective 1-3-3-1 prepulse was applied prior to the imaging sequence. The acquired 3D-data set was evaluated using a Maximum Intensity Projection (MIP) program. Our results confirmed earlier experiences which showed that the diagnostic sensitivity of 3D-MR myelography (3D-MRM) is comparable to that of conventional X-ray myelography. In cases of severe spinal canal stenosis and spondylolisthesises, and in cases of postoperative scar tissue with nerve root compressions, the sensitivity of the 3D-MRM is higher as compared to that of conventional X-ray myelography.

Magnetic source localization and morphological changes in temporal lobe epilepsy: comparison of MEG/EEG, ECoG and volumetric MRI in presurgical evaluation of operated patients

Is MEG source analysis able to precisely locate the primary focal epileptic activity? 22 patients with pharmacoresistant temporal lobe epilepsy were recorded during presurgical evaluation simultaneously with multichannel MEG/EEG and invasive (subdural) electrodes to evaluate the increase of information gained by MEG concerning the localization of focal epileptic activity and lesions. With this systematic study it should become clearer how often MEG can establish a diagnostic bridge between function and morphology. In addition, MEG localization accuracy of focal epileptic activity was to be validated empirically by invasive EEG recordings and postsurgical outcome. Spikes in the MEG were used for magnetic source localization, and the result was combined with magnetic resonance imaging (MRI). All patients definitely suffered from temporal lobe epilepsy and revealed a structural abnormality in MRI. 17 patients with lesions in the temporal lobe were operated meanwhile and became markedly improved or seizure free. In 7 of 8 patients with a tumor and validated operation outcome, a very close correlation of the 3D-magnetic source localization and the border of the tumor in the brain was found (distance less than 10 mm). In 8 of 9 patients with a temporal/hippocampal atrophy and validated operation outcome, dipoles of epileptiform activity were located within the atrophic lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Raymond's syndrome following petrosal sinus sampling

Inferior petrosal sinus sampling (IPSS) is used to evaluate the pituitary-dependency of Cushing's disease, and to predict the laterality of a microadenoma prior to transsphenoidal operation. A serious complication occurred in a 14-year-old boy: he suffered brain stem ischaemia with abducens nerve palsy and hemiparesis (Raymond's syndrome). The case prompted us to reconsider the indication for this investigation.

[Functional imaging of the brain. Magnetoencephalography (MEG)]

Magnetencephalography (MEG) is a new diagnostic tool for the exact localization of the biomagnetic sources of the electrical activity of the brain. The extremely weak magnetic fields are generated by the postsynaptic activity of the neurons, acting like current dipoles. They are measured with a SQUID (superconducting quantum interference device). Only the tangential components of the dipoles contribute to the measurable field outside the head. For MEG localization of sources, the brain is modelled as a sphere of homogeneous electrical conductivity, the center of which is fitted to MR images of the head. As a model of the current sources a one- or two-dipole model is used. For the analysis of more complex sources, however, a principle component analysis (PCA) should be performed before the dipole analysis, or the current-density distribution should be used. The effect of background activity can be eliminated by alpha wave filtering and the dipole-density plot (DDP), which also increases the signal/noise ratio. MEG seems to be useful in purely functional lesions of the brain. A final decision on the value of MEG for routine diagnosis is not yet possible, however.

Multichannel magneto-electroencephalography recordings of interictal and ictal activity

A lobar or even a intralobar congruence was found when comparing the findings of magnetic source localization with presurgical evaluation (EEG, MRI and intraoperative ECoG) in temporal lobe epilepsy. The first dipolar activity that can be recognized during a spike-wave event (primary focal epileptic activity (PFA)) was localized in temporal neocortical or mesial regions. Further centres of epileptic activity could be localized by the method of spike averaging by correlation. This was interpreted as propagation of the electric activity. The comparison of interictal and ictal MEG localization results showed congruency in a patient with temporal lobe epilepsy. The combination of MEG and MRI helps to build a bridge between morphological and functional localization. MEG can serve as a pointer to discrete lesions in MRI.

The accuracy of CT and MR evaluation of the sella turcica for detection of adrenocorticotropic hormone-secreting adenomas in Cushing disease

PURPOSE

To document the accuracy of CT and MR of the sella turcica for detecting adrenocorticotropic hormone-secreting adenomas in Cushing disease.

METHODS

The radiologic findings of the sella turcica prior to transsphenoidal surgery are reviewed in 141 patients who had biochemical evidence of pituitary-dependent Cushing disease. Axial thin-collimation CT scans with sagittal and coronal reformations before and after contrast enhancement were obtained in 125 patients. Seventy-eight patients had MR examinations with a 1.5-T superconducting magnet. In 11 of the patients gadolinium-enhanced MR scans were also obtained. The preoperative interpretation of the imaging studies was correlated with the surgical findings and patients follow-up.

RESULTS

The sella turcica was enlarged in 43 cases (30%). In 125 patients reformatted or direct coronal thin-collimation CT scans were available. Seventy-eight of the patients had MR. In the 12 patients with pituitary macroadenomas, the accuracy of CT (n = 10) and MR (n = 10) in respect to detection of the lesion was 100%. Of the 98 microadenomas assessed by CT, 47 (48%) were directly depicted as distinct hypodense lesions. In only 31 of 73 cases (42%), however, could CT predict the precise anatomic location and extent of the lesions. Only patients in whom the hypercortisolism was corrected by later surgery were considered for the correlation analysis. Of the 52 microadenomas assessed by MR, 28 (53%) were directly depicted as distinct lesions of reduced signal intensity on T1-weighted images, and in only 21 of 41 cases (52%) did MR show good correlation to the surgical findings. Some degree of partially empty sella was found in 22% of the patients.

CONCLUSIONS

Although both the sensitivity and the diagnostic accuracy of imaging methods of the sella turcica have been considerably improved in comparison with previous reports, they still provide only a minor contribution to the diagnosis and differential diagnosis of Cushing syndrome.

The role of transsphenoidal microsurgery in the management of sellar and parasellar meningioma

We report on eight meningiomas that have been operated on via the transsphenoidal route since May 1988. Six patients harbored cavernous sinus meningiomas with intrasellar extension. The intrasellar tumor extension and the parasellar tumor portion medial to the carotid artery were removed. Decompression of the pituitary gland with normalization of prolactin levels was achieved in all patients. It is a well-tolerated approach to confirm the diagnosis and still allows the option of major transcranial surgery in the event of tumor progression. Additionally, we report complete tumor removal in two rare cases with intrasellar and suprasellar merely subdiaphragmatic meningiomas.

Ictal and interictal activity in partial epilepsy recorded with multichannel magnetoelectroencephalography: correlation of electroencephalography/electrocorticography, magnetic resonance imaging, single photon emission computed tomography, and positron emission tomography findings

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity. Main zones of ictal activity were shown to evolve from the tissue at the centers of interictal activity. Pre- and intra-operative electrocorticography (ECoG) as well as postoperative outcome confirmed localization in the temporal and frontal lobe. Results also correlated with findings from scalp EEG, interictal and ictal single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Combined multichannel MEG/EEG recording permitted dipole localization of interictal and ictal activity.

Echo-planar imaging of the central nervous system at 1.0 T

Echo-planar imaging (EPI) on the authors' 1-T prototype imager provides high-quality 100-msec images of the central nervous system. Contrast parameters can be chosen freely. Three-dimensional EPI sequences provide isotropically resolved data sets with 1-mm resolution. Brain perfusion and blood-brain barrier disruption can be assessed in time-course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.

Magnetic resonance angiography of intracranial aneurysms: comparison with intra-arterial digital subtraction angiography

Magnetic resonance angiography (MRA) with flow rephased gradient-echo sequences is a new non-invasive method for vascular imaging. We compared MRA and intra-arterial digital subtraction angiography in 18 patients with intracranial aneurysms to test whether MRA presently provides an alternative to cerebral angiography for the diagnosis of these anomalies. MRA showed 19 of the 22 aneurysms detected (86.4%). However, problems, especially with turbulent or slow flow, resulted in 6 studies (27.3%) with limited and 2 with questionable demonstration of an aneurysm, and 1 false negative study. At present, MRA is definitely inferior to angiography for the demonstration of intracranial aneurysms, due to its lower resolution and other limitations.

Sodium-23 imaging of supratentorial lesions at 4.0 T

In 27 patients with low and high grade gliomas (n = 17), meningiomas (n = 4), and other supratentorial tumors and lesions (n = 6), the results of sodium-23 MR imaging with high spatial resolution were compared to CT and proton MRI. The Na MR studies were performed with a 4.0-T whole-body MR system and an isotropic 3D-Flash sequence (TR 70 ms, TE 11 ms), which depicts the long T2 component of sodium. All patients tolerated the sodium study at 4.0 T well. The sodium images revealed almost all lesions, but the resolution was inferior to that of the reference methods. Two small meningiomas did not show up at all in the sodium study. Furthermore in one case small hemorrhages and calcifications within one of the tumors could not be found. Sodium imaging of the long T2 component did not provide any additional information regarding the histology, grading, size, and differentiation of the tumor from the surrounding edema which had not already been provided by CT or H MRI.

The neocortico to mesio-basal limbic propagation of focal epileptic activity during the spike-wave complex

In order to localize epileptogenic electrophysiological sources, a multichannel MEG system was used in 3 patients with partial epilepsy during presurgical evaluation. MEG and EEG (including scalp, sphenoidal and intracranial foramen ovale electrodes) were recorded simultaneously during a period of intensive video-EEG monitoring in order to observe single spontaneous spikes. In addition to MRI, SPECT and PET investigations were performed. Electrical activity subsequent to the activity of the epileptic focus could be localized by the MEG after noise reduction using a temporal correlation technique. Simultaneous registration of the magnetic field and the electrical field showed that the source of the primary focal epileptic activity (first period during the total spike wave complex where a dipolar magnetic field pattern is found) is localized in neocortical lateral regions, whereas another focal epileptic activity in a later phase of propagation occurs in temporal mesial regions. In 1 patient (case 1) the primary focal epileptic activity was localized in the surrounding neocortical tissue of an angioma and the middle and inferior temporal gyrus. The second phase of propagation is localized in temporo-basal-mesial regions, including para- and hippocampal structures. The latest center of activity occurred in posterior parts of the gyrus cinguli. In 2 other patients, the primary focal epileptogenic activity was localized at the insula and also spread into temporal basal mesial regions. A multi-modal approach to research of focal epilepsy, combining metabolic, electrical potential, magnetoencephalographic and morphological data, recorded by non-invasive techniques, offers new perspectives for the detection of involved brain regions. The 3-D and time-resolved localization of focal epileptic activity, correlated with the individual anatomy of the human brain, may improve the determination of neuronal populations involved in the individual epileptogenic process, especially in the interaction between temporal or extratemporal neocortex and limbic system.

[In-vitro-study and patient examinations with MRT: the significance of metal implants]

This study presents the results of in-vitro and clinical experiences with metallic implants during MRT investigations. In-vitro temperature measurements of various implants showed little temperature rise depending on the shape and the orientation in the static magnetic field (max. 0.3 degrees C). Ferromagnetic forces could not be detected with these implants. In contrast, severe temperature increase (9.4 degrees C) was observed with an intratracheal spiral tube. Tubes of this type should not be used in MR imaging to avoid the risk of burning. 105 MR examinations were performed in patients with metallic implants (CNS shunts, aortocoronary bypass grafts, aortic-, mitral-prosthesis, orthopedic implants, skin staples, shrapnels). Patients with vascular clips were accepted for MR imaging when the clips were non-ferromagnetic only. No adverse effects were observed in these patients.

Diagnostic significance of flow separation within the carotid bifurcation demonstrated by digital subtraction angiography

The presence of an area of reversed blood flow due to flow separation in the interval carotid artery is a normal finding in Doppler ultrasound studies in vivo as well as in model carotid bifurcations. This flow separation phenomenon is caused by the geometry of the carotid bifurcation and the fluid dynamics of blood. We demonstrated the flow separation phenomenon on lateral-projection intra-arterial digital subtraction angiograms in 99 of 100 carotid bifurcations. The mean duration of flow separation was 5.8 seconds, with values up to 14 seconds in normal carotid bifurcations. The presence of this flow separation phenomenon is almost independent of atherosclerotic lesions and is not correlated with cerebral ischemia. Therefore, the angiographic finding of a flow separation has no diagnostic value. However, our results refer to a factor that may be important in the genesis of atherosclerosis at the carotid bifurcation, namely the duration of the stay of blood and its components within the area of flow separation.