Biomedical subjects

Gebhard Schmid

Publications and source records attributed to Gebhard Schmid.

13 recordsLinked to original sources

PubMed2006

Dissociation of grey and white matter reduction in spinocerebellar ataxia type 3 and 6: a voxel-based morphometry study.

The aim of this study was to examine the different patterns of cerebellar and/or brainstem atrophy in spinocerebellar ataxia (SCA) type 3 and 6. Eighteen patients (SCA3 n=9, SCA6 n=9) and 15 healthy volunteers were studied. Voxel-based morphometry (VBM) was applied to segmented grey matter (GM) and white matter (WM) of high-resolution T1-weighted brain volumes of each group. We found reduction of grey matter in the pons as well as in the vermis in SCA3 as compared to control subjects. In SCA6 significant grey matter loss was found in hemispheric lobules bilaterally as well as in the vermis. White matter analysis revealed significant changes in SCA3, especially in the pons, in the white matter surrounding the dentate nucleus (DN) and in the cerebellar peduncles, whereas no significant white matter reduction was found in SCA6 patients. Our results demonstrate different patterns of grey and white matter affection detected by magnetic resonance imaging (MRI) in SCA3 and SCA6 patients, confirming the pathological concept of cortical cerebellar atrophy in SCA6. In contrast, SCA3 represents a form of ponto-cerebellar atrophy with predominant affection of pontine nuclei and fibre tracts.

Aged↗

PubMed2005

Cross-modal processing in auditory and visual working memory.

This study aimed to further explore processing of auditory and visual stimuli in working memory. Smith and Jonides (1997) [Smith, E.E., Jonides, J., 1997. Working memory: A view from neuroimaging. Cogn. Psychol. 33, 5-42] described a modified working memory model in which visual input is automatically transformed into a phonological code. To study this process, auditory and the corresponding visual stimuli were presented in a variant of the 2-back task which involved changes from the auditory to the visual modality and vice versa. Brain activation patterns underlying visual and auditory processing as well as transformation mechanisms were analyzed. Results yielded a significant activation in the left primary auditory cortex associated with transformation of visual into auditory information which reflects the matching and recoding of a stored item and its modality. This finding yields empirical evidence for a transformation of visual input into a phonological code, with the auditory cortex as the neural correlate of the recoding process in working memory.

Adult↗

PubMed2004

Supracubital perineurioma misdiagnosed as carpal tunnel syndrome: case report.

BACKGROUND: Perineuriomas have been defined as tumorous lesions of the peripheral nerves which derive from perineurial cell proliferation and may be associated with abnormalities on chromosome 22. CASE PRESENTATION: Three years after a painful cubital vein procaine injection, a 33 year-old man developed a median nerve lesion, initially diagnosed as carpal tunnel syndrome. Symptoms progressed despite appropriate surgery. Clinical and electrophysiological re-evaluation revealed a fusiform mass at the distal upper arm, confirmed by MRI. Immunohistochemical studies classified the tumor as a mixed perineurioma and neuroma. CONCLUSIONS: Perineurioma mixed with neuroma may potentially caused by the previous trauma or cytotoxic effects of procaine.

Adult↗

PubMed2004

Sensitivity and reproducibility of a new fast 3D segmentation technique for clinical MR-based brain volumetry in multiple sclerosis.

Fast, reliable and easy-to-use methods to quantify brain atrophy are of increasing importance in clinical studies on neuro-degenerative diseases. Here, ILAB 4, a new volumetry software that uses a fast semi-automated 3D segmentation of thin-slice T1-weighted 3D MR images based on a modified watershed transform and an automatic histogram analysis was evaluated. It provides the cerebral volumes: whole brain, white matter, gray matter and intracranial cavity. Inter- and intra-rater reliability and scan-rescan reproducibility were excellent in measuring whole brain volumes (coefficients of variation below 0.5%) of volunteers and patients. However, gray and white matter volumes were more susceptible to image quality. High accuracy of the absolute volume results (+/-5 ml) were shown by phantom and preparation measurements. Analysis times were 6 min for processing of 128 slices. The proposed technique is reliable and highly suitable for quantitative studies of brain atrophy, e.g., in multiple sclerosis.

Adult↗

PubMed2004

Clinical symptoms in lumbar disc herniations and their correlation to the histological composition of the extruded disc material.

STUDY DESIGN: Fifty-five consecutive patients undergoing microdiskectomy due to lumbar disc herniation were included in this clinical study over 12 months. OBJECTIVES: To investigate possible correlations between the histologic composition of the herniated disc fragments and pain, disability, clinical signs, and operative findings. SUMMARY OF BACKGROUND DATA: Previous studies have investigated the histologic composition of herniated lumbar disc fragments. Few publications, however, examined correlations with clinical data. METHODS: Before treatment, patients were examined using a standardized clinical protocol; subjective disability and pain were assessed by the Oswestry Disability Questionnaire and the McGill Pain Questionnaire. The herniated disc fragments were examined semiquantitatively for the relative percentages of nucleus pulposus, anulus fibrosus, and cartilaginous endplate. RESULTS: In patients less than 30 years of age, significantly higher percentages of nucleus pulposus were found than in the older group, whereas anulus fibrosus was found in significantly higher percentages in patients > or =30 years. Both higher percentages of cartilage and nucleus pulposus correlated with increased pain intensity values from the McGill Pain Questionnaire. Impaired reflexes before treatment occurred significantly more often in patients with > or =20% of cartilage in the herniated fragments. If nucleus pulposus was <30%, sensory impairment tended to be more severe before treatment. CONCLUSION: The histologic composition of the herniated disc fragments seems to affect pain and clinical symptoms.

Adolescent↗

PubMed2004

Lumbar disk herniation: correlation of histologic findings with marrow signal intensity changes in vertebral endplates at MR imaging.

PURPOSE: To compare findings at preoperative magnetic resonance (MR) imaging with data for tissue composition of herniated disks in patients after microsurgical removal of herniated material. MATERIALS AND METHODS: Fifty-one patients underwent MR imaging before microsurgical removal of extruded lumbar disk herniation material. Marrow signal intensity changes along the cartilaginous endplates were classified according to Modic types 1-3. Severity of changes was evaluated with respect to extension along the endplate in the anteroposterior diameter (0%, <33%, 33%-66%, >66%). The existence of a dorsal vertebral corner defect was evaluated in relation to the existence of hyaline cartilage in the disk extrusion material. RESULTS: Mean tissue composition of herniated material in all patients was 63% anulus fibrosus, 30% nucleus pulposus, and 8% cartilaginous endplate. Twenty-five of the 51 patients had hyaline cartilaginous material in the extrusion (range, 5%-50%). Patients without marrow signal intensity changes along the cartilaginous endplate showed significantly less cartilaginous material in the extruded disk (P =.023, Fisher exact test). Mean percentage hyaline cartilage in patients without changes was 2% +/- 4 (SD) (Modic type 1, 16% +/- 15; type 2, 10% +/- 12). When the changes extended 33% of the vertebral endplate, there was cartilaginous endplate material in the extruded disk (P =.006). Cartilage from the endplate was present in the extruded disk material in 40% (16 of 40) of patients without a vertebral corner defect and in 82% (nine of 11) of patients with a vertebral corner defect (P =.019). CONCLUSION: Avulsion-type disk herniation seems to be common, and vertebral endplate marrow signal intensity changes on MR images are indicative of cartilaginous material in the extruded disk herniation material.

Adolescent↗

PubMed2004

Imaging of infected total arthroplasty with Tc-99m-labeled antigranulocyte antibody Fab'fragments.

OBJECTIVE: The objective of this study was to evaluate the diagnostic accuracy of Tc-99m-labeled antigranulocyte antibody Fab' fragments in infected total arthroplasty. MATERIALS AND METHODS: A total of 38 immunoscintigrams were evaluated retrospectively with 15 to 25 mCi Tc-99m-labeled antigranulocyte antibody-Fab' fragments. The final diagnosis was assessed by articular puncture or intraoperative sampling. RESULTS: In the total hip replacement group the authors found 10 true positives, 7 true negatives, 8 false positives, and 1 false negative; and in the total knee replacement group they found 4 true positives, 8 true negatives, and no false positives or false negatives. They also found a sensitivity of 93%, a specificity of 65%, and a positive predictive accuracy of 63%. There was a negative predictive accuracy of 94%. CONCLUSION: The high negative predictive accuracy in the whole group suggests that the scan can be used to exclude infection in most cases. Negative results with a high clinical suspicion merits further investigation. A positive result will require further correlative imaging, especially for total knee replacement.

Aged↗

PubMed2003

Apomorphine reduces BOLD signal in fMRI during voluntary movement in Parkinsonian patients.

Our group investigated modulatory effects of apomorphine on cerebral activation patterns during finger tapping movements in seven Parkinson's disease (PD) patients off medication. Cerebral activation was measured according to an established fMRI protocol. Apomorphine application disclosed a reduction of cerebral activation patterns to the contralateral precentral gyrus affecting both clinically affected and unaffected sides; tapping with the unaffected hand additionally revealed activation in the contralateral postcentral gyrus. These findings contradict those of similar functional imaging studies performed in PD to date, which variously found augmentation of cerebral activation patterns in Parkinsonian patients after dopaminergic stimulation. One conceivable explanation for our singular results would be preferred binding of apomorphine to presynaptic dopaminergic receptors, leading to inhibition of endogenous dopamine release and resultant diminished dopaminergic stimulation, reflected in diminished cerebral activation patterns. These findings warrant future consideration and further investigation of possible central inhibitory effects of dopaminergic therapy in functional imaging studies in PD.

Antiparkinson Agents↗

PubMed2003

Imaging osteomyelitis with Tc-99m-labeled antigranulocyte antibody Fab' fragments.

PURPOSE The purpose of this study was to evaluate the diagnostic value of Tc-99m-labeled antigranulocyte antibody fragments in the diagnosis of osteomyelitis. MATERIALS AND METHODS Thirty immunoscintigrams were evaluated retrospectively with 740 MBq (20 mCi) Tc-99m-labeled antigranulocyte antibodies. The final diagnoses were confirmed by histology, magnetic resonance imaging, computed tomography, and clinical follow-up. RESULTS In the retrospective analysis, 20 of 30 patients (67%) demonstrated a true-positive result. Three of 30 patients (10%) had a false-positive result. A false-negative result was found in a diabetic patient with a perforating ulcer of the foot. Six of 30 patients had a true-negative result. A high sensitivity of 95%, a relatively high specificity of 67%, and a high diagnostic accuracy of 86% were present in this study. CONCLUSION Tc-99m labeled monoclonal antibody-Fab' fragments are suitable for the detection of osteomyelitis. Its clinical application is simple. Its use guarantees a reliable and accurate diagnostic result just 1 to 2 hours after injection, making a late scan unnecessary. Coxarthrosis or hyperostosis can lead to false-positive results. A perforating ulcer of the foot may result in a false-negative conclusion.

Adult↗

PubMed2003

Contrast burst depletion imaging (CODIM): a new imaging procedure and analysis method for semiquantitative ultrasonic perfusion imaging.

BACKGROUND AND PURPOSE: Established methods of ultrasonic perfusion imaging using a bolus application of echo contrast agent provide only qualitative data because of various physical phenomena. This study was intended to investigate whether a new ultrasound perfusion imaging method termed contrast burst depletion imaging (CODIM) may provide semiquantitative measures of parenchymal perfusion independent of examination depth and acoustic energy distribution. METHODS: In a system with a constant concentration of contrast agent, analyzing the decrease in image intensity that occurs with microbubble-destructive imaging modes yields parameters that are considered to correlate with tissue perfusion. This method was first evaluated with a perfusion model that showed that the main resulting parameter "perfusion coefficient" (PC) is a monotonic nonlinear function of flow velocity. Seventeen human volunteers were then scanned according to this method with the use of 2 different contrast agents. Results were correlated with those from perfusion-weighted MRI examinations. RESULTS: The PC did not show significant differences in gray matter areas (ranging from 1.466x10(-2) x s(-1) to 1.641x10(-2) x s(-1)) of the brain despite different insonation depths (eg, ipsilateral and contralateral thalamus). In contrast, white matter exhibited significantly lower perfusion values in both imaging modes (PC: 0.604x10(-2) x s(-1) to 0.745x10(-2) x s(-1); P<0.05). CONCLUSIONS: CODIM is a promising new tool of imaging parenchymal (brain) perfusion in healthy persons. The method provides semiquantitative and depth-independent perfusion parameters and in this way overcomes the limitations of the perfusion methods using a bolus kinetic. Further investigations must be done to evaluate the potential of the method in patients with perfusion deficits.

Adult↗

PubMed2002

Comparison between echo contrast agent-specific imaging modes and perfusion-weighted magnetic resonance imaging for the assessment of brain perfusion.

BACKGROUND AND PURPOSE: Contrast burst imaging (CBI) and time variance imaging (TVI) are new ultrasonic imaging modes enabling the visualization of intravenously injected echo contrast agents in brain parenchyma. The aim of this study was to compare the quantitative ultrasonic data with corresponding perfusion-weighted MRI data (p-MRI) with respect to the assessment of brain perfusion. METHODS: Twelve individuals with no vascular abnormalities were examined by CBI and TVI after an intravenous bolus injection of 4 g galactose-based microbubble suspension (Levovist) in a concentration of 400 mg/mL. Complementary, a dynamic susceptibility contrast MRI, ie, p-MRI, of each individual was obtained. In both ultrasound (US) methods and p-MRI, time-intensity curves were calculated offline, and absolute time to peak intensities (TPI), peak intensities (PI), and peak width (PW) of US investigations and TPI, relative cerebral blood flow (CBF) and relative cerebral blood volume (CBV) of p-MRI examinations were determined in the following regions of interest (ROIs): lentiform nucleus (LN), white matter (WM), posterior (PT), and anterior thalamus (AT). In addition, the M(2) segment of the middle cerebral artery (MCA) was evaluated in the US, and the precentral gyrus (PG) was examined in the p-MRI examinations. In relation to a reference parenchymal ROI (AT), relative TPIs were compared between the US and p-MRI methods and relative PI of US investigations with the ratio of CBF (rCBF) of p-MRI examinations in identical ROIs. RESULTS: Mean TPIs varied from 18.3+/-5.0 (AT) to 20.1+/- 5.8 (WM) to 17.2+/-4.9 (MCA) seconds in CBI examinations and from 19.4+/-5.3 (AT) to 20.4+/-4.3 (WM) to 17.3+/-4.0 (MCA) seconds in TVI examinations. Mean PIs were found to vary from 581.9+/-342.4 (WM) to 1522.9+/-574.2 (LN) to 3400.9+/- 621.7 arbitrary units (MCA) in CBI mode and from 7.5+/-4.6 (WM) to 17.5+/-4.9 (LN) to 46.3+/-7.1 (MCA) arbitrary units in TVI mode. PW ranged from 7.3+/-4.5 (AT) to 9.1+/-4.0 (LN) to 24.3+/-12.8 (MCA) seconds in CBI examinations and from 7.1+/-3.9 (AT) to 8.7+/-3.5 (LN) to 26.7+/-18.2 (MCA) seconds in TVI examinations. Mean TPI was significantly shorter and mean PI and mean PW were significantly higher in the MCA compared with all other ROIs (P<0.05). Mean TPI of the p-MRI examinations ranged from 22.0+/-6.9 (LN) to 23.0+/-6.8 (WM) seconds; mean CBF ranged from 0.0093+/- 0.0041 (LN) to 0.0043+/-0.0021 (WM). There was no significant difference in rTPI in any ROI between US and p-MRI measurements (P>0.2), whereas relative PIs were significantly higher in areas with lower insonation depth such as the LN compared with rCBF. CONCLUSIONS: In contrast to PI, TPI and rTPI in US techniques are robust parameters for the evaluation of cerebral perfusion and may help to differentiate physiological and pathological perfusion in different parenchymal regions of the brain.

Adult↗

PubMedDate not supplied

Effective dose of CT- and fluoroscopy-guided perineural/epidural injections of the lumbar spine: a comparative study.

The objective of this study was to compare the effective radiation dose of perineural and epidural injections of the lumbar spine under computed tomography (CT) or fluoroscopic guidance with respect to dose-reduced protocols. We assessed the radiation dose with an Alderson Rando phantom at the lumbar segment L4/5 using 29 thermoluminescence dosimeters. Based on our clinical experience, 4-10 CT scans and 1-min fluoroscopy are appropriate. Effective doses were calculated for CT for a routine lumbar spine protocol and for maximum dose reduction; as well as for fluoroscopy in a continuous and a pulsed mode (3-15 pulses/s). Effective doses under CT guidance were 1.51 mSv for 4 scans and 3.53 mSv for 10 scans using a standard protocol and 0.22 mSv and 0.43 mSv for the low-dose protocol. In continuous mode, the effective doses ranged from 0.43 to 1.25 mSv for 1-3 min of fluoroscopy. Using 1 min of pulsed fluoroscopy, the effective dose was less than 0.1 mSv for 3 pulses/s. A consequent low-dose CT protocol reduces the effective dose compared to a standard lumbar spine protocol by more than 85%. The latter dose might be expected when applying about 1 min of continuous fluoroscopy for guidance. A pulsed mode further reduces the effective dose of fluoroscopy by 80-90%.

Female↗

PubMedDate not supplied

Magnetic resonance imaging of the lumbar spine after epidural and nerve root injection therapy: evaluation of soft tissue changes.

OBJECTIVE: Magnetic resonance imaging (MRI) was performed to evaluate soft tissue changes after nerve root and epidural injections in lumbar spine in patients with radiculopathy. MATERIALS/METHODS: Patients underwent a multiple-shot injection protocol to nerve root/epidural space. The MRI protocol included T1-weighted, T2-weighted, STIR, and contrast-enhanced, fat-saturated T1-weighted sequences before and after treatment. RESULTS: In all treated patients, a diffuse wedge-shaped edema in paravertebral tissues with a slight contrast enhancement was seen. Two small hematomas in the paravertebral muscle were noted. No changes in the epidural space, the abscess, or a lipodystrophy in epidural/nerve root space occurred. CONCLUSION: Normal tissue changes after injection therapy of lumbar radiculopathy include wedge-shaped tissue edema at the injection level. In a minority of patients, small hematomas may occur.

Adult↗