Christoph Ozdoba

Bilateral stimulation of globus pallidus internus for treatment of cervical dystonia

In three selected patients with severe complex cervical dystonia, continuous bilateral stimulation of the globus pallidus internus was associated with improvement of cervical dystonia, dystonia-associated pain, and functional disability.

Accuracy of computer-assisted pedicle screw placement : an in-vivo computed tomography analysis

Study Design. A computer‐assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. Objectives. To evaluate the systems applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. Summary of Background Data. Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. Methods. The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. Results. The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. Conclusions. The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.

Local Intra-Arterial Thrombolysis in Acute Ischemic Stroke

BACKGROUND AND PURPOSE We performed a retrospective analysis of the prognostic factors in patients treated with local intra-arterial thrombolysis (LIT). The purpose of this study was to evaluate the safety and efficacy of LIT using urokinase in patients with acute ischemic stroke of the anterior or posterior circulation and to determine the influence of clinical and radiological parameters on outcome. METHODS Forty-three patients were treated with LIT using urokinase (median dose, 0.75x10(6) IU). The median National Institutes of Health Stroke Scale (NIHSS) score at hospital admission was 18 (range, 9 to 36). Nine patients had occlusions of the internal carotid artery (ICA), 23 of the middle cerebral artery (MCA), 1 of the anterior cerebral artery, and 10 of the basilar artery (BA). Outcome was assessed after 3 months and classified as good for Rankin Scale (RS) scores of 0 to 3 and poor for RS scores of 4 or 5 and death. RESULTS Nine patients (21%) recovered to RS scores 0 or 1, 17 (40%) to scores of 2 or 3, and 7 (16%) to scores of 4 or 5. Ten patients (23%) died. Outcome was good in 17 patients (80%) with MCA occlusions, in 3 patients (33%) with ICA, and in 5 patients (50%) with BA occlusions. Good outcome was associated with an initial NIHSS score of <20 (P<0.001), improvement by 4 or more points on NIHSS score within 24 hours (P=0.001), and vessel recanalization (P=0.02). Recanalization was more likely if LIT was started within 4 hours (P=0.01). Symptomatic cerebral hemorrhage occurred in 2 patients (4.7%). CONCLUSIONS LIT was most efficacious in patients with MCA and BA occlusions when the initial NIHSS score was less than 20 and when treated within 4 hours. It is of limited value in patients with distal ICA occlusions.

Different Ipsilateral Representations for Distal and Proximal Movements in the Sensorimotor Cortex: Activation and Deactivation Patterns

Each hemisphere is known to be also involved in controlling the ipsilateral arm, but with an asymmetry favoring the dominant hemisphere. However, the relative role of primary and secondary motor areas in ipsilateral control is not well defined. We used whole brain functional magnetic resonance imaging in healthy human subjects to differentiate between contributions from primary and secondary areas during discrete unilateral distal finger and proximal shoulder movements. It was found that ipsilateral distal movements activated secondary areas only, while sparing or even significantly deactivating the primary sensorimotor cortex. Ipsilateral proximal movements substantially activated both SM1 and secondary areas. A newly defined small territory within the precentral gyrus, extending from the premotor cortex and intruding toward SM1, showed an activation pattern corresponding to secondary motor areas. Finally, the effects of hemispheric dominance were confirmed, but attributed exclusively to secondary areas. These new imaging findings agree well with functional requirements as well as established anatomical and neurophysiological data.

National Institutes of Health Stroke Scale Score and Vessel Occlusion in 2152 Patients With Acute Ischemic Stroke

Background and Purpose— There is some controversy on the association of the National Institutes of Health Stroke Scale (NIHSS) score to predict arterial occlusion on MR arteriography and CT arteriography in acute stroke. Methods— We analyzed NIHSS scores and arteriographic findings in 2152 patients (35.4% women, mean age 66±14 years) with acute anterior or posterior circulation strokes. Results— The study included 1603 patients examined with MR arteriography and 549 with CT arteriography. Of those, 1043 patients (48.5%; median NIHSS score 5, median time to clinical assessment 179 minutes) showed an occlusion, 887 in the anterior (median NIHSS score 7/0–31), and 156 in the posterior circulation (median NIHSS score 3/0–32). Eight hundred sixty visualized occlusions (82.5%) were located centrally (ie, in the basilar, intracranial vertebral, internal carotid artery, or M1/M2 segment of the middle cerebral artery). NIHSS scores turned out to be predictive for any vessel occlusions in the anterior circulation. Best cut-off values within 3 hours after symptom onset were NIHSS scores ≥9 (positive predictive value 86.4%) and NIHSS scores ≥7 within >3 to 6 hours (positive predictive value 84.4%). Patients with central occlusions presenting within 3 hours had NIHSS scores <4 in only 5%. In the posterior circulation and in patients presenting after 6 hours, the predictive value of the NIHSS score for vessel occlusion was poor. Conclusions— There is a significant association of NIHSS scores and vessel occlusions in patients with anterior circulation strokes. This association is best within the first hours after symptom onset. Thereafter and in the posterior circulation the association is poor.

Radiation dose for pedicle screw insertion. Fluoroscopic method versus computer-assisted surgery.

STUDY DESIGN Comparison of the radiation dose between the traditional fluoroscopic approach and computed tomography (CT)-based computer-assisted surgery for pedicle screw placement was determined. OBJECTIVES To evaluate the radiation dose delivered by fluoroscopy-controlled pedicle screw placement versus insertion guided by computer. To define the CT computer-assisted protocol, involving lower radiation exposure for the patient, that still provides acceptable image quality. SUMMARY OF BACKGROUND DATA There are no published data describing the dose delivered in CT-based image-guided surgery, and there are few studies in which the organ dose and the effective dose delivered during pedicle screw insertion that is performed traditionally with fluoroscopic control are described. METHODS Dose measurements were performed on two types (REMAB and RANDO) of anthropomorphic phantoms. Thermoluminescent dosimeters were used to measure the organ dose. Both phantoms were exposed to the fluoroscopic x-ray beam. The representative intraoperative scenario was determined by observation of 20 consecutive surgical interventions featuring pedicle screw implantation. For the CT dose measurement only, the REMAB phantom was used with two types of CT scanners. Three scanning protocols were evaluated: sequential, spiral optimized, and sequential optimized. Optimization of the scanning protocol included changes of anode current. The CT images were subsequently processed to achieve three-dimensional reconstruction of the lumbar spine for the computer-assisted intervention. RESULTS Organ and effective doses were higher in any of the CT examinations than in the fluoroscopic procedure. There was a slight difference between doses registered during optimized spiral scanning and doses in the calculated optimized sequential CT protocol. Optimized sequential scanning was associated with an effective dose 40% lower than that in nonoptimized sequential scanning. The small anatomic structures of the spine could be easily recognized on each of the three-dimensional reconstructions, and all of them were suitable for use in computer-assisted surgery. CONCLUSIONS Percutaneous pedicle screw insertion in the lumbar region of the spine, performed using fluoroscopic control, requires a lower radiation dose than do CT scans necessary for computer-assisted surgery. The CT radiation dose can be significantly decreased by optimization of the scanner settings for computer-assisted surgery. The advantages of computer-assisted surgery justify CT scans, when based on correctly chosen indications.

Retardation of myelination due to dietary vitamin B12 deficiency: cranial MRI findings.

Vitamin B12 deficiency is known to be associated with signs of demyelination, usually in the spinal cord. Lack of vitamin B12 in the maternal diet during pregnancy has been shown to cause severe retardation of myelination in the nervous system. We report the case of a 14 1/2-month-old child of strictly vegetarian parents who presented with severe psychomotor retardation. This severely hypotonic child had anemia due to insufficient maternal intake of vitamin B12 with associated megaloblastic anemia. MRI of the brain revealed severe brain atrophy with signs of retarded myelination, the frontal and temporal lobes being most severely affected. It was concluded that this myelination retardation was due to insufficient intake of vitamin B12 and vitamin B12 therapy was instituted. The patient responded well with improvement of clinical and imaging abnormalities. We stress the importance of MRI in the diagnosis and follow-up of patients with suspected diseases of myelination.

On how high performers keep cool brains in situations of cognitive overload.

What happens in the brain when we reach or exceed our capacity limits? Are there individual differences for performance at capacity limits? We used functional magnetic resonance imaging (fMRI) to investigate the impact of increases in processing demand on selected cortical areas when participants performed a parametrically varied and challenging dual task. Low-performing participants respond with large and load-dependent activation increases in many cortical areas when exposed to excessive task requirements, accompanied by decreasing performance. It seems that these participants recruit additional attentional and strategy-related resources with increasing difficulty, which are either not relevant or even detrimental to performance. In contrast, the brains of the high-performing participants “keep cool” in terms of activation changes, despite continuous correct performance, reflecting different and more efficient processing. These findings shed light on the differential implications of performance on activation patterns and underline the importance of the interindividual-differences approach in neuroimaging research.

New horizons in forensic radiology: the 60-second digital autopsy-full-body examination of a gunshot victim by multislice computed tomography.

The goal of this study was the full-body documentation of a gunshot wound victim with multislice helical computed tomography for subsequent comparison with the findings of the standard forensic autopsy. Complete volume data of the head, neck, and trunk were acquired by use of two acquisitions of less than 1 minute of total scanning time. Subsequent two-dimensional multiplanar reformations and three-dimensional shaded surface display reconstructions helped document the gunshot-created skull fractures and brain injuries, including the wound track, and the intracerebral bone fragments. Computed tomography also demonstrated intracardiac air embolism and pulmonary aspiration of blood resulting from bullet wound–related trauma. The “digital autopsy,” even when postprocessing time was added, was more rapid than the classic forensic autopsy and, based on the nondestructive approach, offered certain advantages in comparison with the forensic autopsy.

Functional organisation of saccades and antisaccades in the frontal lobe in humans: a study with echo planar functional magnetic resonance imaging

The cortical activation pattern of saccades and antisaccades (versus rest) in the frontal lobe was analysed using an echo planar imaging (EPI) technique in 10 healthy subjects. Statistical analysis of activity in the dorsolateral prefrontal cortex disclosed a significantly greater activation during antisaccades in this region than during saccades. On the other hand, activity in the frontal eye fields was not statistically different in both tasks. These results confirm the important role of the dorsolateral prefrontal cortex for the correct performance of antisaccades obtained by studies in humans with isolated lesions of the dorsolateral prefrontal cortex.