Urs Schwarz

On the generation of vertical and torsional rapid eye movements in the monkey

SummaryThe role of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) in generating the vertical and torsional components of rapid eye movements was examined. The on-directions of burst neurons in the riMLF of alert Rhesus monkeys were obtained during quick phase nystagmus in three dimensions. The distinguishing feature of these burst neurons was the torsional component of their on-directions; neurons on the right side exhibited a clockwise component, from the point of view of the subject, while those on the left had a counterclockwise component. Vertical components could have up or down directions. This organization was verified by means of unilateral reversible inactivation of the riMLF using Muscimol. An injection in the right riMLF impaired the generation of quick phases with clockwise components while one on the left impaired counterclockwise components.

Cancellation of self-induced retinal image motion during smooth pursuit eye movements

When our eyes are tracking a target that is moving in front of a structured background, global motion of equal speed is induced in the opposite direction. This effect has been termed reafference, which, astonishingly, does not significantly affect the execution of such pursuit eye movements. Employing brief and unexpected injections of full-field motion during ongoing human smooth pursuit, we demonstrate that the sensitivity for full-field motion is reduced strongly in the direction opposite to the eye movement, i.e. the direction of reafferent background motion. Our experiments further characterize this asymmetry in visual motion processing and provide a preliminary explanation for the accuracy of the pursuit system despite self-induced motion.

Serial EEG findings in sporadic and iatrogenic Creutzfeldt-Jakob disease.

OBJECTIVE To study temporal and spatial development of EEG patterns in sporadic and iatrogenic Creutzfeldt-Jakob disease patients. METHODS Temporal and spatial development of EEG patterns in 4 patients with sporadic Creutzfeldt-Jakob disease and 2 patients with iatrogenic Creutzfeldt-Jakob disease due to implantation of contaminated brain depth electrodes were investigated. A total of 56 EEGs were analyzed, over time spans ranging from 1272 to 3 days prior to death. RESULTS Frontal intermittent rhythmical delta activity (FIRDA) was seen at early timepoints in 4/6 patients and might represent an early EEG pattern that is associated, with human prion diseases. EEG patterns associated with CJD are sensitive to midazolam. Initial EEG changes were seen at the site of prion exposure in iatrogenic Creutzfeldt-Jakob disease patients, before they could be observed at distant sites, suggesting that prion disease was initiated at the site of prion exposure. CONCLUSIONS Serial EEG recordings are a valuable tool not only in the early diagnosis of sporadic CJD, but also in the determination of prion exposure in iatrogenic Creutzfeldt-Jakob disease. SIGNIFICANCE FIRDA occur at an early stage of CJD and are progressively replaced by the classical PSWC. The EEG patterns of CJD are sensitive to midazolam. The initial EEG changes in iatrogenic CJD are seen at the site of prion exposure.

Flow Impairment during Protected Carotid Artery Stenting: Impact of Filter Device Design

Purpose: To investigate the impact of filter design on blood flow impairment in the internal carotid artery (ICA) among patients undergoing carotid artery stenting (CAS) using filtertype emboli protection devices (EPD). Methods: Between July 2003 and March 2007, 115 filter-protected CAS procedures were performed at an academic institution in 107 consecutive patients (78 men; mean age 68 years, range 38–87). The Angioguard, FilterWire EZ, and Spider filters were used in 68 (59%), 32 (28%), and 15 (13%) of cases, respectively. Patient characteristics, procedural and angiographic data, and outcomes were prospectively entered into an electronic database and reviewed retrospectively along with all angiograms. Results: Flow impairment while the filter was in place was observed in 25 (22%) cases. The presumptive reason of flow impairment was filter obstruction in 21 (18%) instances and flow-limiting spasm at the level of the filter in 4 (4%). In all cases, flow was restored after retrieval of the filter. Flow obstruction in the ICA occurred more frequently with Angioguard (22/68; 32.3%) than with FilterWire EZ (2/32; 6.2%) or Spider (1/15; 6.7%; p=0.004). No flow occurred in 13 (19%) procedures, all of them protected with Angioguard; no patient treated with other devices experienced this event (p=0.007). Two (8.0%) strokes occurred in procedures associated with flow impairment, while 1 (1.1%) event was observed in the presence of preserved flow throughout the intervention (p=0.11). Conclusion: Flow impairment in the ICA during filter-based CAS is common and related to the type of filter used.

Hierarchical visual processing is dependent on the oculomotor system.

Using functional MRI and eye movement recordings we studied the processing of hierarchical stimuli. In agreement with others, we found a minor left hemispheric dominance during local and right dominance during global processing. When attention was directed locally, well-known oculomotor cortical areas were activated, and saccades were elicited in 41% of the trials. Their latencies were similar to pro-saccades. During global processing virtually no saccades occurred. These results suggest two different operational modes of attention. Attending to local features induces a shift of attention, which simultaneously computes a saccade on any level above the brainstem with a computational burden equal to reflexive saccades. Conversely, attending to global features induces an expansion of the focus of attention, which reinforces fixation.

Asymmetry in visual motion processing.

The smooth pursuit system is traditionally employed using a single small target moving on a homogeneous background. It still is not fully understood, however, how accurate tracking is sustained in the presence of a structured background, which will activate global motion processing in the opposite direction as a consequence of the ongoing eye movement. To further study this interaction, we used brief shifts of a textured background injected at various times during the initiation of smooth pursuit. While shifts opposite to the target direction did not alter smooth pursuit performance, those in the same direction resulted in a marked transient perturbation of the pursuit. These results suggest a simple yet limited mechanism that adjusts the sensitivity of global motion processing.

Complete thromboendarterectomy of the calcified ascending aorta and aortic arch

BACKGROUND Arteriosclerotic plaques of the ascending aorta and transverse arch increase the operative risk of cardiac operations and are strong predictors for late cerebrovascular events. METHODS Twenty-two patients, mean age 68 +/- 6 years (range, 55 to 77 years), with grade IV + V plaques of the ascending aorta and transverse arch underwent coronary artery bypass grafting (n = 21) and aortic valve replacement (n = 8). Cerebrovascular emboli from unknown sources were found preoperatively in 8 patients (36%). All were in sinus rhythm. Complete thromboendarterectomy of the ascending aorta and transverse arch was performed during hypothermic circulatory arrest. After 21 +/- 12 months (range, 4 to 44 months), magnetic resonance imaging and transthoracic echocardiography of endarterectomized vessels was performed. RESULTS There was one perioperative death (4.5%), one early (4.5%), and one late (4.7%) adverse neurologic event. Follow-up examinations revealed normal diameters of the endarterectomized aorta. CONCLUSIONS For patients with grade IV + V plaques, thromboendarterectomy of the ascending aorta and transverse arch can be performed with an acceptable surgical risk and a low recurrence rate for cerebrovascular events. Dilatation of the endarterectomized aorta was not observed.

Topography of foramen ovale electrodes by 3D image reconstruction

To date, the foramen ovale (FO) electrode recording technique has been used in 234 patients at our center to assist in the evaluation of epilepsy surgery. Most of the patients suffered from mesial temporal lobe epilepsy (MTLE) and were candidates for a selective amygdalohippocampectomy. Knowledge of the exact topography of the FO electrodes is mandatory for a more precise anatomo-electro-clinical correlation of seizures and for a better understanding of FO electrode recorded electroencephalogram (EEG) and evoked potentials generated in the hippocampal formation or in nearby thalamic relays or brainstem structures. Here, we describe and illustrate a 3D image reconstruction of FO electrodes in situ as an important step to better define the generators of MTLE seizures as well as of interictal spikes and physiological EEG signals recorded with FO electrodes.

Retinal microangiopathy and rapidly fatal cerebral edema in a patient with adult-onset Still's disease and concurrent macrophage activation syndrome.

Hemophagocytic lymphohistiocytosis (HLH) is a complex inflammatory disease with multiple diagnostic and therapeutic pitfalls. The congenital form, referred to as familial hemophagocytic lymphohistiocytosis (FHL), is often associated with cerebromeningeal involvement, whereas neurological complications are not characteristic of the adult form of secondary HLH (sHLH). Here we report the case of a 20‐year‐old woman with adult‐onset Stills disease (AOSD), retinal microangiopathy and concurrent macrophage activation syndrome (MAS), in the context of sHLH. Following treatment with etanercept, ibuprofen, methylprednisolon, and phenylbutazone for 3 weeks, MAS deteriorated and fatal cerebral edema occurred within only 24 h. The clinical signs and neuropathological findings are discussed with special emphasis on possible relationships between the aggravation of MAS and therapeutic interventions for AOSD. In conclusion, even the slightest sign of mental decline in a patient with AOSD must be considered central nervous system MAS which can be rapidly fatal. Am. J. Hematol., 2008.

Reactivation of herpesvirus under fingolimod: A case of severe herpes simplex encephalitis

Fingolimod (FTY720, Gilenya, Novartis Pharma AG, Basel, Switzerland) is a sphingosin-1-phosphate (S1P) receptor modulator with immunomodulatory properties that traps naive and central memory T cells in lymph nodes, leading to reduced numbers of peripheral blood lymphocytes, and is the first licensed oral drug for multiple sclerosis (MS).1,2 We report a case of a near fatal herpes simplex virus 1 (HSV-1) encephalitis under the licensed dose of fingolimod in a patient with MS.