Birgit Westermann

Olfactory Impairment Predicts Brain Atrophy in Parkinson's Disease

Olfactory dysfunction is a frequent nonmotor symptom in idiopathic Parkinsons disease (PD) and may be considered as an early clinical feature of the disease preceding motor symptoms by years. According to recent neuropathological staging concepts, impaired olfaction is assumed to indicate an early pathological process and might be associated with structural changes in the brain. A morphometric analysis of magnetic resonance images [voxel-based morphometry (VBM)] was used to investigate gray matter atrophy related to psychophysically measured scores of olfactory function in early PD patients (n = 15, median Hoehn and Yahr stage 1.5), moderately advanced PD patients (n = 12, median Hoehn and Yahr stage 2.5), and age-matched healthy controls (n = 17). In PD patients, but not in controls, cortical atrophy in olfactory-related brain regions correlated specifically with olfactory dysfunction. Positive correlations between olfactory performance and gray matter volume were observed in the right piriform cortex in early PD patients and in the right amygdala in moderately advanced patients. The results provided first evidence that olfactory dysfunction in PD is related to atrophy in olfactory-eloquent regions of the limbic and paralimbic cortex. In addition, olfactory-correlated atrophy in these brain regions is consistent with the assumption that olfactory impairment as an early symptom of PD is likely to be associated with extranigral pathology.

Functional imaging of the cerebral olfactory system in patients with Parkinson’s disease

Background: Olfactory dysfunction is a frequent non-motor symptom in Parkinson’s disease (PD) and is considered to be an early manifestation of the disease. Objective: To establish the cortical basis of olfactory function in patients with PD. Method: Functional magnetic resonance imaging (fMRI) was used to investigate brain activity related to olfactory processing in patients with hyposmic PD at mild to moderate stages of the disease (n = 12, median Hoehn and Yahr stage 2.0) and in healthy, age-matched controls (n = 16) while passively perceiving a positively valenced (rose-like) odorant. Results: In both patients with PD and healthy controls, olfactory stimulation activated brain regions relevant for olfactory processing (ie the amygdaloid complex, lateral orbitofrontal cortex, striatum, thalamus, midbrain and the hippocampal formation). In controls, a bilateral activation of the amygdala and hippocampus was observed, whereas patients with PD involved these structures in the left hemisphere only. Group comparison showed that regions of higher activation in patients with PD were located bilaterally in the inferior frontal gyrus (BA 44/45) and anterior cingulate gyrus (BA 24/32), and the left dorsal and right ventral striatum. Conclusions: In patients with PD, results obtained under the specific conditions used suggest that neuronal activity in the amygdala and hippocampus is reduced. Assuming an impact on olfactory-related regions early in PD, our findings support the idea that selective impairment of these brain regions contributes to olfactory dysfunction. Furthermore, neuronal activity in components of the dopaminergic, cortico-striatal loops appears to be upregulated, indicating that compensatory processes are involved. This mechanism has not yet been demonstrated during olfactory processing in PD.

Noninvasive Tracking of Patient's Head Movements During Computer-Assisted Intranasal Microscopic Surgery

A noninvasive system designed for patient tracking during image‐guided intranasal sinus surgery is described. It is based on optical digitizing with a custom‐made registration and reference system, locatable surgical instruments, and a self‐localizing operating microscope. Experimental and clinical results reveal a high degree of accuracy for the system. A mean spatial error of 0.82 ± 0.31 mm was determined for repositioning of the reference system in a plastic model of the skull. For the positioning of the microscope, a mean error of 2.3 ± 0.83 mm was calculated. Measurements of repositioning accuracy in 24 patients who received surgery for various sinus diseases had a mean spatial error of 1.56 ± 0.76 mm. The 95% error interval for locating intranasal structures using the surgical instrument was 2.05 mm, and it was 4.92 mm using the microscope. These results suggest that the use of our noninvasive registration and reference system may be effective, accurate, and useful for noninvasive tracking of patient movements in computer‐assisted intranasal surgery.

Exploration of the Neural Correlates of Ticklish Laughter by Functional Magnetic Resonance Imaging

The burst of laughter that is evoked by tickling is a primitive form of vocalization. It evolves during an early phase of postnatal life and appears to be independent of higher cortical circuits. Clinicopathological observations have led to suspicions that the hypothalamus is directly involved in the production of laughter. In this functional magnetic resonance imaging investigation, healthy participants were 1) tickled on the sole of the right foot with permission to laugh, 2) tickled but asked to stifle laughter, and 3) requested to laugh voluntarily. Tickling that was accompanied by involuntary laughter activated regions in the lateral hypothalamus, parietal operculum, amygdala, and right cerebellum to a consistently greater degree than did the 2 other conditions. Activation of the periaqueductal gray matter was observed during voluntary and involuntary laughter but not when laughter was inhibited. The present findings indicate that hypothalamic activity plays a crucial role in evoking ticklish laughter in healthy individuals. The hypothalamus promotes innate behavioral reactions to stimuli and sends projections to the periaqueductal gray matter, which is itself an important integrative center for the control of vocalization. A comparison of our findings with published data relating to humorous laughter revealed the involvement of a common set of subcortical centers.

Optical tracking of a microscope for image-guided intranasal sinus surgery

The objective of this study was to examine the effects of optical and tracking properties on the accuracy of an optically locatable operating microscope. The intraoperative arrangement was based on experimental results obtained from a skull model. Measurements were taken from 24 patients undergoing intranasal microscopic sinus surgery for various disorders. Two major groups of influencing factors were determined from measurements on the model: 1) optical properties of the microscope, such as the method of focal point adjustment, focal length, and magnification of the lens; and 2) tracking properties of the microscope, such as the distance of the digitizer to the tracked object, the number of reference infrared light-emitting diodes (IR-LEDs), and the area circumscribed by these IR-LEDs. Patient measurements showed an overall spatial error of 2.39 ± 1.15 mm with a laser-supported adjustment of the focal point of the microscope. Although the associated 95th percentile was at 4.36 mm, such a value is encouraging for further development of microscopically navigable systems. It must be noted that the noninvasive patient-to-image registration was performed on the basis of a computed tomographic image with a slice distance of 2 mm.

Non-invasive 3-D patient registration for image-guided skull base surgery

Abstract Image-guided, computer-assisted surgery systems require a common reference between the preoperative image data and the corresponding patient pathology. Therefore, the problem of an accurate and reliable 3-D patient registration and referencing has to be solved. Considering that during image data acquisition patient misalignment and movement can arise in three dimensions, an automatic image registration method must be based on a three-dimensional approach. The method presented in this paper provides accurate 3-D patient registration for correction of these movement errors during data acquisition and active patient referencing to update the position of the head during surgery. Experimental data concerning the accuracy of repeated positionings of our patient registration and reference system demonstrated a high degree of accuracy with mean spatial errors of 0.82 mm ± 0.31 mm in a plastic skull and 1.56 ± 0.76 mm in patients, respectively. Results suggest that non-invasive 3-D patient registration for image-guided surgery may be a precise and useful method for computer-assisted identification of anatomical structures.

Online Head Motion Tracking Applied to the Patient Registration Problem

Image-guided systems for surgical procedures in the region of the head require a method to correlate the diagnostic image data with the corresponding site of pathology in the patient. Considering that patient movement can occur, detection and correction of such movement errors during the acquisition of images is a basic prerequisite for accurate treatment. For this reason, we developed a new registration method based upon on-line tracking of the patients head to solve the problem of registration in the presence of head motion. The method provides non-invasive active patient registration for correction of movements during imaging and continuous update of the patients head position during surgery. The patient motion correction applies the rigid body model to register the images using feature correspondence. The new registration method is described, and results of experiments that were performed to evaluate its accuracy and reliability in a plastic skull model and in patients are presented. The error analysis resulted in a final target registration error of 0.90 mm +/- 0.16 mm using experimental model data and 1.58 mm +/- 0.26 mm using clinical patient data. In addition, the residual registration error is modeled as a function of the measured and predicted head motion in order to determine the error that is introduced by motion tracking during image data acquisition. Furthermore, the clinical application of the method is demonstrated for oto-, rhino-, and neurosurgical procedures in the region of the head.

Early bilingualism influences early and subsequently later acquired languages in cortical regions representing control functions

Early acquisition of a second language influences the development of language abilities and cognitive functions. In the present study, we used functional Magnetic Resonance Imaging (fMRI) to investigate the impact of early bilingualism on the organization of the cortical language network during sentence production. Two groups of adult multilinguals, proficient in three languages, were tested on a narrative task; early multilinguals acquired the second language before the age of three years, late multilinguals after the age of nine. All participants learned a third language after nine years of age. Comparison of the two groups revealed substantial differences in language-related brain activity for early as well as late acquired languages. Most importantly, early multilinguals preferentially activated a fronto-striatal network in the left hemisphere, whereas the left posterior superior temporal gyrus (pSTG) was activated to a lesser degree than in late multilinguals. The same brain regions were highlighted in previous studies when a non-target language had to be controlled. Hence the engagement of language control in adult early multilinguals appears to be influenced by the specific learning and acquisition conditions during early childhood. Remarkably, our results reveal that the functional control of early and subsequently later acquired languages is similarly affected, suggesting that language experience has a pervasive influence into adulthood. As such, our findings extend the current understanding of control functions in multilinguals.

Insular cortex activity and the evocation of laughter

The insular cortex is fundamentally involved in the processing of interoceptive information. It has been postulated that the integrative monitoring of the bodily responses to environmental stimuli is crucial for the recognition and experience of emotions. Because emotional arousal is known to be closely coupled to functions of the anterior insula, we suspected laughter to be associated primarily with neuronal activity in this region. An anatomically constrained re‐analysis of our imaging data pertaining to ticklish laughter, to inhibited ticklish laughter, and to voluntary laughter revealed regional differences in the levels of neuronal activity in the posterior and mid‐/anterior portions of the insula. Ticklish laughter was associated specifically with right ventral anterior insular activity, which was not detected under the other two conditions. Hence, apparently, only laughter that is evoked as an emotional response bears the signature of autonomic arousal in the insular cortex. J. Comp. Neurol. 524:1608–1615, 2016.

Non-invasive 3D patient registration for image-guided intranasal surgery - experimental and clinical results

Image-guided, computer-assisted surgery systems base on a common reference between the pre-operative image data and the corresponding patient pathology. Therefore, accurate 3D patient registration and referencing is necessary. Considering that during image data acquisition patient misalignment and movement can arise in three dimensions, an automatic image registration method must base on a three-dimensional approach. Our method provides non-invasive 3D patient registration for correction of such movement errors during data acquisition and active referencing to update the position of the patients head during surgery. Experimental data concerning the accuracy of repeated positionings of our patient registration and reference system demonstrated an accuracy with mean spatial errors of 0.82 mm ± 0.31 mm in a plastic skull and 1.39 mm ± 0.61 mm in patients, respectively. Results suggest that non-invasive 3D patient registration for image-guided surgery may be a precise and useful method for computer-assisted identification of anatomical structures. Clinical experiences for different pathologies are presented (30 patients).