Intraoperative clinical testing overestimates the therapeutic window of the permanent DBS electrode in the subthalamic nucleus.

BACKGROUND: Intraoperative test stimulation is established to optimize target localization in STN DBS, but requires a time-consuming awake surgery in off-medication state. The aim of this study was to compare the thresholds of stimulation-induced effects of test stimulation and the permanent electrode. METHODS: Fifty-nine PD patients receiving bilateral STN DBS were clinically examined with stepwise increasing monopolar stimulation during surgery and DBS programming at matched stimulation depths. Thresholds of therapeutic and side effects were obtained from standardized examination protocols. RESULTS: Postoperative stimulation via the permanent electrode caused side effects at a significantly lower threshold than predicted during intraoperative test stimulation (P < 0.001); whereas sufficient therapeutic effects were achieved at significantly higher thresholds (P < 0.001). CONCLUSIONS: Intraoperative testing may lead to an overestimation of the therapeutic window. The two different electrodes lead to distinct spreading of the electric field in the STN and surrounding tissues that causes different volume of tissue activated (VTA). Clinicians involved in DBS surgery and programming should be aware of the differences in both stimulation settings, concerning electrodes geometry, stimulation modes as well as the impact of time. Therapeutic and side effects of permanent stimulation are not predictable by intraoperative test stimulation. Test stimulation may be an orientating test for very low thresholds of side effects instead.

The impact of white matter lesions on the cognitive outcome of subthalamic nucleus deep brain stimulation in Parkinson's disease.

OBJECTIVES: White Matter lesions (WML) are a risk factor for cognitive impairment in Parkinson's disease. There is no clear evidence of reduced general cognitive function after DBS. However, a subgroup of patients develops dementia rapidly after DBS despite careful patient selection processes. The aim of this study was to evaluate the load of WML as a possible risk factor for cognitive decline following STN DBS. PATIENTS AND METHODS: 40 PD-patients receiving bilateral STN-DBS were followed at least three years after surgery to detect dementia. All patients underwent comprehensive neuropsychological assessment and MRI before surgery. The extent of WML was assessed using an automated approach. WML volume was correlated to the onset of dementia and the decline of a cognitive composite score retrospectively. RESULTS: Patients with a rapid onset of dementia within one, respective three following DBS showed significant higher WML volumes compared to cognitive normal and MCI patients (55.8cm3±18.836 vs. 9.3cm3±12.2; p=0.002). The same significant association was found in a multivariable model, including the covariables age, gender and PD disease duration (p=0.01). WML volume was associated to the rate of decline in cognitive composite score within three years after DBS surgery (p=0.006; R2=0.40) after correction for age. CONCLUSIONS: Damaged white matter may lead to a reduced compensation of disconnections in cognitive circuits caused by the implantation of the DBS electrodes or by chronic stimulation. The role of WML as a prognostic factor for the cognitive outcome after DBS may be underestimated. The WML burden should be taken seriously in preoperative risk stratification.

Anesthesiologic regimen and intraoperative delirium in deep brain stimulation surgery for Parkinson's disease.

BACKGROUND: In many centers the standard anesthesiological care for deep brain stimulation (DBS) surgery in Parkinson's disease patients is an asleep-awake-asleep procedure. However, sedative drugs and anesthetics can compromise ventilation and hemodynamic stability during the operation and some patients develop a delirious mental state after the initial asleep phase. Further, these drugs interfere with the patient's alertness and cooperativeness, the quality of microelectrode recordings, and the recognition of undesired stimulation effects. In this study, we correlated the incidence of intraoperative delirium with the amount of anesthetics used intraoperatively. METHODS: The anesthesiologic approach is based on continuous presence and care, avoidance of negative suggestions, use of positive suggestions, and utilization of the patient's own resources. Clinical data from the operations were analyzed retrospectively, the occurrence of intraoperative delirium was extracted from patients' charts. The last 16 patients undergoing the standard conscious sedation procedure (group I) were compared to the first 22 (group II) psychologically-guided patients. RESULTS: The median amount of propofol decreased from 146 mg (group I) to 0mg (group II), remifentanyl from 0.70 mg to 0.00 mg, respectively (P<0.001 for propofol and remifentanyl). Using the new procedure, 12 of 22 patients (55%) in group II required no anesthetics. Intraoperative delirium was significantly less frequent in group II (P=0.03). CONCLUSIONS: The occurrence of intraoperative delirium correlates with the amount of intraoperative sedative and anesthetic drugs. Sedation and powerful analgesia are not prerequisites for patients' comfort during awake-DBS-surgery.

Levetiracetam compared to phenytoin for the prevention of postoperative seizures after craniotomy for intracranial tumours in patients without epilepsy.

Anticonvulsant drugs are frequently given after craniotomy. Phenytoin (PHT) is the most commonly used agent; levetiracetam (LEV) is a new anticonvulsant drug with fewer side effects. To compare the incidence of seizures in patients receiving either prophylactic PHT or LEV perioperatively, 971 patients undergoing a craniotomy were analysed retrospectively during a 2-year period. PHT was used routinely and LEV was administered when PHT was contraindicated. Seizures documented during the first 7 days after craniotomy were considered. A total of 235 patients were treated with an antiepileptic drug: 81 patients received LEV, and 154 patients, PHT. Two patients receiving LEV (2.5%) and seven receiving PHT (4.5%) had a seizure despite this treatment. No patient had a documented side effect or drug interaction. The data show that LEV may be an alternative option in patients with contraindications to PHT.

Analysis of risk factors influencing the development of severe dizziness in patients with vestibular schwannomas in the immediate postoperative phase.

OBJECTIVE: Dizziness, a common postoperative symptom in patients with vestibular schwannomas (VSs) has a negative effect on the course of recovery, particularly in patients with severe symptoms. Reports on incidence and possible risk factors contributing to these symptoms are inconsistent and sometimes even contradictory. In order to establish a profile of patients at risk of severe symptoms in the immediate postoperative phase we retrospectively analyzed data of patients with unilateral VSs focusing on the incidence of severe dizziness and nausea during the immediate postoperative period and up to 1 year after surgery. METHODS: In a retrospective study data of 104 consecutive patients with VSs were analyzed. All patients underwent microsurgical tumor resection via a lateral-suboccipital approach. Factors that were assumed to affect the development of severe dizziness, such as age, gender, tumor size, tumor side, and cranial nerve function, were analyzed by means of univariate and multivariate logistic regression analyses. A three step grading system was used to describe symptoms of patients included in this study: 0=no symptoms of dizziness, 1=slight dizziness including light-headedness or feeling of disequilibrium and 2=severe dizziness with nausea including imbalance or insecurity when walking, requiring antiemetic treatment. RESULTS: Data of 92 patients, 41 men and 51 women, were available for analyses. Mean age of treated patients was 53 years (range 17-81). There was no predilection of side (52.2% right/47.8% left). Before surgery 39 patients (42.4%) were symptom free (grade 0), 13 patients (14.1%) had slight symptoms (grade 1) and 40 patients (43.5%) suffered from severe symptoms (grade 2). Immediately after surgery two patients (2.2%) where symptom free (grade 0), 19 patients (20.7%) had slight symptoms (grade 1) and 71 patients (77.2%) suffered from severe symptoms (grade 2). All patients with grade 2 symptoms required antiemetic treatment ranging between 1 and 10 days (mean 4 days). Logistic regression analyses showed young age, large tumor size (T3/T4), female gender, and severe preoperative symptoms to be main factors increasing the odds for patients to develop severe symptoms postoperatively. CONCLUSION: Patients at risk to develop severe symptoms should receive antiemetic treatment even before surgery. If in doubt about the actual risk for a specific patient with a large tumor (T3 or T4) available data suggests that patients will benefit if antiemetic treatment is started early, even before surgery.

Improving the spatial accuracy in functional magnetic resonance imaging (fMRI) based on the blood oxygenation level dependent (BOLD) effect: benefits from parallel imaging and a 32-channel head array coil at 1.5 Tesla.

Geometric distortions and low spatial resolution are current limitations in functional magnetic resonance imaging (fMRI). The aim of this study was to evaluate if application of parallel imaging or significant reduction of voxel size in combination with a new 32-channel head array coil can reduce those drawbacks at 1.5 T for a simple hand motor task. Therefore, maximum t-values (tmax) in different regions of activation, time-dependent signal-to-noise ratios (SNR(t)) as well as distortions within the precentral gyrus were evaluated. Comparing fMRI with and without parallel imaging in 17 healthy subjects revealed significantly reduced geometric distortions in anterior-posterior direction. Using parallel imaging, tmax only showed a mild reduction (7-11%) although SNR(t) was significantly diminished (25%). In 7 healthy subjects high-resolution (2 x 2 x 2 mm3) fMRI was compared with standard fMRI (3 x 3 x 3 mm3) in a 32-channel coil and with high-resolution fMRI in a 12-channel coil. The new coil yielded a clear improvement for tmax (21-32%) and SNR(t) (51%) in comparison with the 12-channel coil. Geometric distortions were smaller due to the smaller voxel size. Therefore, the reduction in tmax (8-16%) and SNR(t) (52%) in the high-resolution experiment seems to be tolerable with this coil. In conclusion, parallel imaging is an alternative to reduce geometric distortions in fMRI at 1.5 T. Using a 32-channel coil, reduction of the voxel size might be the preferable way to improve spatial accuracy.

Diffusion-weighted imaging with calculated apparent diffusion coefficient of enhancing extra-axial masses.

BACKGROUND AND PURPOSE: Sometimes intracranial contrast-enhancing tumors like meningiomas, metastases, lymphomas, and schwannomas can mimic each other. It was the aim of the present study to investigate if intracranial contrast-enhancing lesions can be reliably differentiated with the help of diffusion-weighted imaging with calculated apparent diffusion coefficients (ADCs). METHODS: 29 patients (ages ranging from 22 to 82 years, mean age of 58.6 years) were included. Nine meningiomas, 7 metastases, 6 lymphomas, and 7 schwannomas were investigated. The ADC value in the lesions and in the perifocal edema was analyzed. RESULTS: For the lymphomas, the authors measured the lowest ADC values in the contrast-enhancing part (0.59 +/- 0.09 . 10(-3) mm2/sec). The meningiomas showed a mean ADC value of 0.98 +/- 0.18 . 10(-3) mm2/sec. The schwannomas and metastases showed higher ADC values of 1.33 +/- 0.28 . 10(-3) mm2/sec and 1.05 +/- 0.20 . 10(-3) mm2/sec. The authors saw a statistically significant difference between lymphomas, meningiomas, and metastases concerning the ADC values in the contrast-enhancing part. CONCLUSIONS: In spite of a small sample size and partly a wide range of values, the authors found statistically significant differences between meningiomas, metastases, and lymphomas concerning ADC values. Nevertheless, a differentiation of these lesions only with the help of ADC values seems questionable.

Reliability of atlas-derived coordinates in deep brain stimulation.

BACKGROUND: In deep brain stimulation the way to define and localize the optimal target for the individual patient is still under debate. The objective of our study was to investigate the reliability of atlas derived data by comparing them with direct targeting on MR images. METHOD: We investigated 28 STN targets in 14 volunteers. The stereotactic coordinates of the dorso-lateral subthalamic nucleus (STN), were determined in 5 different ways for both STNs of each individual volunteer: 1. directly, on axial T2WI spin echo slices, 2. directly, on coronal T2WI spin echo slices and after fusion of data sets: 3. indirectly, on an axial atlas plate, 4. indirectly, on a coronal atlas plate, 5. indirectly, 12 mm lateral, 3 mm posterior and 3 mm inferior to mid-AC-PC. FINDINGS: The differences between MRI derived targets on axial vs. coronal slices were not statistically significant. After detection of the atlas derived targets the resulting x-coordinates were found more lateral than after direct detection on both, axial and coronal T2-weighted images (p < 0.001). On axial images y-coordinates were located more anterior (p = 0.240) on atlas derived targets and more posterior when target localizations were compared on coronal slices (p < 0.001). z-Coordinates were more superior after atlas targeting compared to MRI targeting (p < 0.001). Differences up to 6.21 mm occurred. CONCLUSIONS: Despite the limitations concerning image distortions and slice thickness, direct target planning on MRI, regarding our results, is more reliable than targeting solely based on atlas derived data. Only MRI gives us detailed information about the individual configurations of central structures in every single patient. However, targets, which are not detectable on MRI like the nucleus ventralis intermedius have to be planned using stereotactic atlas information. In these cases intra-operative micro-electrode recording might help to better define the target region.

Diffusion-weighted imaging with calculated apparent diffusion coefficient in intracranial hemorrhagic lesions.

In the literature published so far, measurement of values of the apparent diffusion coefficient (ADC) using an echo-planar imaging (EPI) technique in intracranial hemorrhagic lesions show no uniform results. Furthermore, no data exist for bleedings into intracranial lesions. We investigated the ADCs of 18 intracranial hemorrhagic lesions of different stages using echo-planar diffusion-weighted imaging (DWI). The ADC values measured in the hemorrhagic lesions ranged from 1.42 x 10(-3) to 0.22 x 10(-3) mm(2)/s. There were no significant differences between the ADC values in the hemorrhagic lesions and the contralateral white matter (P=.39). A differentiation between the lesions only with the ADC value was not possible as well. Using EPI DWI in intracranial hemorrhagic lesions of different stages, no reliable ADC values were found and a dependable differentiation between the lesions is not possible.

[Diffusion-weighted imaging in the diagnostic evaluation of the hydrocephalus in patients with acute or chronic increase in cerebral pressure]. / Diffusionsgewichtete Bildgebung in der Diagnostik des Hydrocephalus -- Untersuchungen an Patienten mit akuter und ohne akute Hirndrucksymptomatik.

PURPOSE: To investigate whether diffusion-weighted imaging (DWI) in magnetic resonance imaging (MRI) provides additional information about the periventricular white matter for the assessment of hydrocephalus. MATERIALS AND METHODS: Sixteen MRI examinations (11 with acutely increased cerebral pressure, 5 without symptoms) on 15 patients with hydrocephalus (4 patients with communicating hydrocephalus and 11 patients with obstructive hydrocephalus) were analyzed. One symptomatic patient subsequently became asymptomatic. We investigated the "apparent diffusion coefficient" (ADC) in the subcortical and periventricular white matter. The ADCs of the study patients were compared with those of a healthy control group. RESULTS: Symptomatic patients with hydrocephalus, 6/11 showed periventricular edema and a significantly higher ADC values in the periventricular region than in the subcortical white matter. 5/11 symptomatic patients showed significantly higher ADC values even in the absence of periventricular interstitial edema (both groups contained patients with communicating and obstructive hydrocephalus). All 5 asymptomatic patients with hydrocephalus did not have a significantly higher ADC values in the periventricular region. CONCLUSION: In patients with hydrocephalus and acutely increased cerebral pressure, DWI showed a significantly higher ADC values in the periventricular region even without visible interstitial edema on conventional MRI sequences.

Degenerative diseases of the cervical spine: comparison of a multiecho data image combination sequence with a magnetisation transfer saturation pulse and cervical myelography and CT.

Assessing degenerative disease in the cervical spine remains a challenge. There is much controversy about imaging the cervical spine using MRI. Our aim in this prospective study was to compare a T2*-weighted 2D spoiled gradient-echo multiecho sequence (MEDIC) with a magnetisation transfer saturation pulse with cervical myelography and postmyelographic CT. Using an assessment scale we looked at the vertebral bodies, intervertebral discs, neural foramina, anterior and posterior nerve roots, grey matter, ligamentaflava, oedema in the spinal cord and stenosis of the spinal canal. We also evaluated postmyelography CT and the MEDIC sequence for assessing narrowing of the neural foramina in a cadaver cervical spine. We examined 67 disc levels in 18 patients, showing 18 disc prolapses and 21 osteophytes narrowing the spinal canal or the neural foramina. All MRI studies showed these abnormalities findings equally well. Postmyelography CT was significantly better for showing the bony structures and the anterior and posterior nerve roots. The MEDIC sequence provided excellent demonstration of soft-tissue structures such as the intervertebral disc and ligamentum flavum. No statistical differences between the imaging modalities were found in the assessment of narrowing of the neural foramina or the extent of spinal stenosis. The cadaver measurements showed no overestimation of abnormalities using the MEDIC sequence.

Image fusion of MR images and real-time ultrasonography: evaluation of fusion accuracy combining two commercial instruments, a neuronavigation system and a ultrasound system.

OBJECTIVE: The aim of our study was to evaluate MRI/Ultrasonography fusion accuracy depending on three ultrasonographic parameters. METHOD: An ultrasonography and MRI compatible model was created, consisting of a plastic box, which contained 3 objects. MRI scans were performed with 128 sagittal slices. The objects were segmented and 3D reconstructions were created. A special ultrasound adapter with 3 reflective markers was fixed to the ultrasound probe. Thus, the probe could be tracked by the navigation system (Vector Vision(2), BrainLab, Heimstetten, Germany) and the segmented shape of the 3D-objects obtained from the MR images were overlaid onto the ultrasound display (Elegra, Siemens, Erlangen, Germany). The dependency of fusion accuracy on different depth of ultrasound display, different distances between probe and objects and different angles between the axis of the ultrasound probe and the centre of the spheres was evaluated. 435 single measurements were performed. FINDINGS: Overall fusion accuracy was 1.08 mm+/-0.61 mm (mean +/- standard deviation) for spheres and 1.6 mm+/-1.1 mm for arrow heads. If the ultrasound probe was directed more tangentially to the surface of the spheres the fusion became increasingly inaccurate (P<0.05). Fusion accuracy decreased the more distant the US probe was held to the object (P<0.05). Different depth of ultrasound display had no significant effect on fusion accuracy. CONCLUSIONS: Highly accurate fusion of MR images and real-time ultrasonography could be achieved. However, careful interpretation of the fused data is necessary, when different angles and distances of the US probe to the object are concerned.

Diffusion-weighted echo-planar MRI of the brain with calculated ADCs: a useful tool in the differential diagnosis of tumor necrosis from abscess?

BACKGROUND AND PURPOSE: It was the aim of this study to evaluate whether brain abscesses could be distinguished reliably from necrotic brain tumors using diffusion-weighted imaging (DWI) with calculated apparent diffusion coefficients (ADCs). METHODS: The authors studied 27 lesions in 26 patients (21 tumors and metastases, 5 pyogenic brain abscesses, and 1 cerebral toxoplasmosis). DWI was obtained with a single-shot echo-planar imaging spin-echo sequence. ADCs were calculated for all images. RESULTS: ADCs (x 10(-3) mm2/s) measured in the necrotic parts of the tumors ranged from 2.94 (glioblastoma) to 1.51 (astrocytoma III). In the inflammatory lesions, ADCs ranged between 0.91 and 3.07 (cerebral toxoplasmosis and pyogenic abscess). The contrast-enhanced parts of the lesions showed ADC values from 0.77 (pyogenic abscess) up to 1.68 (glioblastoma). CONCLUSIONS: DWI with calculated ADC values does not allow the reliable differentiation of enhanced central necrotic intracranial lesions.

Registration accuracy and practicability of laser-directed surface matching.

The aim of our study was to evaluate the registration accuracy and practicability of a new laser registration technique in comparison to marker registration. From January to August 2001, 36 patients (23 male, 13 female) with brain lesions were operated with navigational guidance. Thirty-five patients were registered by paired-point registration. In 16 patients, a second registration was carried out using a special laser pointer for surface matching (z-touch trade mark, BrainLab, Heimstetten, Germany). Accuracy was evaluated by touching seven anatomic landmarks and a target fiducial with the nonsterile pointer. The distance from the virtual pointer tip to these points was determined on the monitor display (600% zoom). Laser registration is fully retrospective and allows registrations when no markers are applied. z-touch trade mark registration is more sophisticated and time-consuming than marker-based registration (registration time for z-touch trade mark = 7.4 +/- 3.7 min; for markers = 4.1 +/- 1.7 min; p < 0.005). Marker registration proved to be more accurate than z-touch trade mark registration with regard to localization of anatomical landmarks and target fiducials (precision with z-touch trade mark = 2.77 +/- 1.64 mm; with markers = 1.31 +/- 0.87 mm; p < 0.01). Although the registration error was increased and preparation time prolonged with the z-touch trade mark technique, it proved to be a valuable option, especially in children.

Comparison between magnetic resonance phase contrast imaging and transcranial Doppler ultrasound with regard to blood flow velocity in intracranial arteries: work in progress.

OBJECTIVE: The authors evaluate blood flow velocities in the medial cerebral artery (MCA) and the basilar artery using magnetic resonance (MR) phase contrast technique in comparison with transcranial Doppler ultrasound (TCD). Eleven healthy male volunteers were studied. TCD of the MCA (n = 22) and basilar artery (n = 11) was performed. MR phase velocity mapping was done in each vessel at the same location where the TCD signal had been acquired. A 2-dimensional FLASH sequence with retrospective cardiac gating and an average temporal resolution of 45 ms was used. Resistance indices (RIs) and pulsatility indices (PIs) were calculated for both modalities. The TCD insonation angle was measured retrospectively with MR, and TCD velocities were corrected based on these measurements. The comparison of flow velocities obtained with TCD and MR led to a low correlation coefficient with regard to the basilar artery and the MCA: maximum systolic velocity, r = 0.02 and r = 0.50, respectively; enddiastolic velocity, r = 0.47 and r = 0.65, respectively; mean velocity, r = 0.52 and r = 0.66, respectively. The average PIs in the basilar artery and the MCA were 0.80 and 0.81 with MR and 0.65 and 0.85 with TCD, respectively. The average RIs in the basilar artery and the MCA were 0.52 and 0.54 with MR and 0.52 and 0.55 with TCD, respectively. The TCD insonation angle differed significantly from the ideal value in the basilar artery (mean value = 32.6 degrees) and the MCA (mean value = 26.5 degrees). The authors find a low correlation between velocities measured with MRI and TCD but similar results with regard to the PIs and RIs. Several sources of error, such as a nonideal TCD insonation angle, were identified.

Functional MR imaging of the motor cortex in healthy volunteers and patients with brain tumours: qualitative and quantitative results.

The purpose of this study was to compare functional magnetic resonance (MR) imaging of the motor cortex in healthy volunteers and patients with brain tumours. Functional MR imaging was performed in 14 healthy volunteers and 14 patients with tumours in or near the primary motor cortex with groups being matched for age, sex, and handedness. Functional images were acquired during motion of the right and left hand. Time courses of signal intensity within the contralateral, ipsilateral, and supplementary motor cortex as well as z-maps were calculated, their quality being assessed visually. Mean signal increase between activation and rest were evaluated within the contralateral, ipsilateral, and supplementary motor cortex, the activated area in those regions of interest was measured using z-maps. The quality of functional MR experiments was generally lower in patients than in volunteers. The quantitative results showed a trend towards increased ipsilateral activation in volunteers during left hand compared to right hand motion and in patients during motion of the affected compared to the non-affected hand. Considering quantitative and qualitative results, significantly increased ipsilateral activation was found in patients compared to healthy volunteers. In conclusion, functional MR imaging quality was significantly reduced in patient studies compared to healthy volunteers, even if influences of age, sex, and handedness were excluded. Increased ipsilateral activation was found in patients with brain tumours which can be interpreted by an improved connectivity between both hemispheres.

The quality of functional MR images in patients with brain tumors: influences of neurological disorders and tumor location.

The aim of our study was to investigate the influence of neurological disorders, and the influence of tumor and perifocal edema location on functional magnetic resonance imaging (fMRI) quality. fMRI quality tended to be better the closer the tumor and the perifocal edema were located to the pmc. Hemipareses and seizures had no significant influence on fMRI quality. Therefore, hemiparetic patients do not have to be excluded beforehand. The evaluation of time courses is essential before using z-maps to localize eloquent brain regions preoperatively.

Functional MRI of the motor cortex using a conventional gradient system: comparison of FLASH and EPI techniques.

Gradient echo (GE) and echo planar imaging (EPI) techniques are two different approaches to functional MRI (fMRI). In contrast to GE sequences, the ultra short EPI technique facilitates fMRI experiments with high spatial and temporal resolution or mapping of the whole brain. Although it has become the method of choice for fMRI, EPI is generally restricted to modern scanners with a strong gradient system. The aim of our study was to evaluate the applicability of EPI for fMRI of the motor cortex using a 1.5 T scanner with a conventional gradient system of 10 mT/m (rise time: 1 ms). Therefore, EPI was compared with a well-established high-resolution fast low-angle shot (FLASH) technique (matrix size 1282). The FLASH technique was applied additionally with a 64(2) matrix size to exclude influences caused by different spatial resolution, because the EPI sequence was restricted to a 64(2) matrix size. A total of 35 healthy volunteers were included in this study. The task consisted of clenching and spreading of the right hand. FLASH and EPI techniques were compared regarding geometric distortions as well as qualitative and quantitative fMRI criteria: Mean signal increase between activation and rest and the area of activation were measured within the contralateral, ipsilateral, and supplementary motor cortex. The quality of subtraction images between activation and rest, as well as the quality of z-maps and time course within activated regions of interest, was evaluated visually. EPI revealed significant distortions of the anterior and posterior brain margins; lateral distortions (relevant for the motor cortex) could be neglected in most cases. The mean signal increase was significantly higher using FLASH 1282 compared to FLASH 64(2) and EPI 64(2), whereas the activated areas proved to be smaller in FLASH 1282 functional images. Both results can be explained by well-documented partial volume effects, caused by different voxel size. Similar quality of the subtraction images and of the time courses in different regions of interest were found for all techniques under investigation, but slightly reduced quality of z-map in FLASH 1282. Within the limits of reproducibility and measurement accuracy, the location of contralateral activation was similar using FLASH and EPI sequences. In conclusion, EPI proved to be a reliable technique for fMRI of the motor cortex, even on an MR scanner with a conventional gradient system.

Short-term prognostic factors in lumbar disc surgery: the low back prognostic score is of predictive value.

In order to determine prognostic factors of lumbar disc surgery, we examined 107 patients who were conventionally operated on in a prospective, consecutive study. We analysed general data, the case history, the neurological examination at admission and all data from imaging examinations and therapy. In addition, all patients received a questionnaire based on the Low Back Outcome Score [9, 10]. The patients were re-examined after 2-8 months (103 days mean). According to their ratings on a pain grading scale, the patients were divided into a group with favorable and another with unfavorable results. These groups were analysed in relation to the patients' initial condition. At follow up, 88% of the patients had either completely recovered or their complaints had been relieved. According to the Low Back Outcome Score (LBOS), 64.5% went well. Used to evaluate the initial condition of the patients on admission the LBOS was able to predict favorable outcome in 68% and unfavorable outcome in 50%. To improve the prognostic value, we combined significant questions of the LBOS with the pain grading scale and significant prognostic factors to form a new prognostic score (Low Back Prognostic Score). With this new score we were able to predict a favorable outcome in 84% of our patients, and an unfavorable outcome in 71%. The Low Back Prognostic score seems to provide a sensitive method for predicting a favorable or unfavorable outcome for patients scheduled to undergo lumbar disc surgery.

Are there differences in the symptoms, signs and outcome after lumbar disc surgery in the elderly compared with younger patients?

Age is claimed by several authors to be a predictor of bad outcome after lumbar disc surgery. The aim of this study is to evaluate the influence of the patients age on preoperative symptoms and the outcome. General data, symptoms, signs and neurological findings of 219 patients were recorded preoperatively Ninety-two per cent of the patients received a follow-up examination by an independent investigator after a mean of 298 days. All patients older than 59 years were defined as belonging to the group of elderly patients (n = 30). The other patients were defined as the younger group (n = 189). The outcome was measured by a visual analogue rating scale. Outcome was not statistically different in both groups. In our opinion, the indications for surgery for a lumbar disc herniation should be no different for older patients even though nerve root tension signs appear to be less marked in older patients.