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Biomedical subjects

M U Schuhmann

Publications and source records attributed to M U Schuhmann.

At least 19 recordsLinked to original sources
PubMed2005

Brain tissue biomechanics in cortical contusion injury: a finite element analysis.

The controlled cortical impact model has been used extensively to study focal traumatic brain injury. Although the impact variables can be well defined, little is known about the biomechanical trauma as delivered to different brain regions. This knowledge however could be valuable for interpretation of experiment (immunohistochemistry etc.), especially regarding the comparison of the regional biomechanical severity level to the regional magnitude of the trauma sequel under investigation. We used finite element (FE) analysis, based on high resolution T2-weighted MRI images of rat brain, to simulate displacement, mean stress, and shear stress of brain during impact. Young's Modulus E, to describe tissue elasticity, was assigned to each FE in three scenarios: in a constant fashion (E = 50 kPa), or according to the MRI intensity in a linear (E = [10, 100] kPa) and inverse-linear fashion (E = [100, 10] kPa). Simulated tissue displacement did not vary between the 3 scenarios, however mean stress and shear stress were largely different. The linear scenario showed the most likely distribution of stresses. In summary, FE analysis seems to be a suitable tool for biomechanical simulation, however, to be closest to reality tissue elasticity needs to be determined with a more specific approach, e.g. by means of MRI elastography.

Animals↗
PubMed2005

Brain injury and proteomics/peptidomics: is it relevant? an overview.

Proteomics and peptidomics are different and supplemental to genomics, since in contrast to the basically constant genome - the proteome and peptidome are dynamic, constantly changing, and complex networks. Proteomics is traditionally linked to 2D-gel electrophoresis techniques. Concerning peptidomics, three different approaches are currently available, all using mass spectrometry as a key element. The use of proteomics or peptidomics in traumatic brain injury (TBI) research is demanding. From the technical point of view there are high-level requirements concerning the preanalytical phase, specific machinery, sophisticated software and skilled manpower/intellectual input. There are currently no bedside techniques and most methods are suitable for experimental TBI research in specialized laboratories. In screening experiments of CSF following controlled cortical impact in rats we identified several peptides, which, although previously known, were so far not reported in the TBI context or in CSF. Peptidomics and proteomics, as highly complex screening technologies, thus seem to carry a large potential to lead TBI science. Newly "discovered" peptide targets have to be validated with different methodology to establish a real diagnostic or therapeutic value.

Animals↗
PubMed2005

Correlation of continuously monitored regional cerebral blood flow and brain tissue oxygen.

BACKGROUND: The purpose of this study was to investigate the relationship between continuously monitored regional cerebral blood flow (CBF) and brain tissue oxygen (PtiO2). METHODS: Continuous advanced multimodal neuromonitoring including monitoring of PtiO2 (Licox, GMS) and CBF (QFlow, Hemedex) was performed in eight patients after severe subarachnoid haemorrhage (n=5) and traumatic brain injury (n=3) for an average of 9.6 days. Parameters were measured using a flexible polarographic PtiO2-probe and a thermal diffusion CBF-microprobe. FINDINGS: Regarding the whole monitoring period in all patients, the data indicated a significant correlation between CBF and PtiO2 (r=0.36). In 72% of 400 analysed intervals of 30 minutes duration with PtiO2 changes larger than 5 mmHg, a strong correlation between CBF and PtiO2 existed (r>0.6). In 19% of intervals a still statistically significant correlation was observed (0.3<r<0.6). During the remaining 9% no correlation was found (r<0.3). Regarding the clinical stability of the monitoring devices, the CBF monitoring system allowed monitoring of CBF in 64% of the time when PtiO2 monitoring was possible only. Phases of non-monitoring were mostly due to fever of the patient, when the system does not allow monitoring to avoid overheating of the cerebral tissue. CONCLUSIONS: This study suggests a correlation between CBF and PtiO2. The level of PtiO2 seems to be predominately determined by regional CBF, since changes in PtiO2 were correlated in 90% of episodes to simultaneous changes of CBF.

Brain↗
PubMed2004

The neurosurgeon on duty -- quality and quantity of acute care.

OBJECTIVE: An important part of the daily routine in neurosurgery is the treatment of emergency room admissions, acute cases from other departments or from outside hospitals. This acute care is not normally included in performance figures or budget management nor analysed scientifically with respect to quantity and quality of care provided by neurosurgeons. METHOD: Over a one-year period, all acute care cases managed by two neurosurgical on-call teams in Hannover (Northern Germany, 522 000 inhabitants) were recorded prospectively on a day-by-day basis. A large database of 1 819 entries was created and analysed using descriptive statistics. RESULTS: The minimum incidence of neurosurgical acute care cases was estimated to be 75-115/100 000 inhabitants/year. This corresponds to a mean of approximately 6 per day. The majority of patients was admitted after 5 p. m. and on weekends. Only 30 % of cases came directly via the emergency room. The fate of 70 % of patients depended initially on the "neurosurgical qualification" of primary care doctors and here deficits existed. Over one year the additional workload from acute care amounted to 1 000 unplanned admissions, 900 acute imaging procedures and almost 600 emergency operations. CONCLUSION: The current policy in public health which includes cuts in resources, transport facilities and manpower is not compatible with the demonstrated extent of acute neurosurgical care. In addition to routine elective work, a high number of extra admissions, evening or night-time surgery, and imaging procedures has to be carried out. These conclusions hold a special importance if health authorities wish to not just maintain present standards but to improve existing deficits.

Adolescent↗
PubMed2002

Dynamic shunt testing applying short lasting pressure waves--inertia of shunt systems.

Laboratory shunt testing often comprises only static pressure flow and flow pressure tests. We applied shorter acting pressure waves using a computerised shunt testing rig to investigate shunt behaviour under conditions that might occur in the clinical situation, e.g. during nocturnal vasogenic pressure waves or shorter rises in ICP at movements or exercise. Additionally the influence of a human-like compliance situation compared to a fixed pressure/volume relationship was investigated. Shunts behaved very differently than seen in static tests and demonstrated a marked inertia the shorter pressure waves acted. Although some valves opened at higher pressure, all valves showed marked hysteresis and none did close--if at all--at the specified pressure level. This behaviour might be a cause of shunt overdrainage not related to siphoning. The simulation of a human-like variable pressure-volume relationship with higher compliance at lower pressures had a positive effect on shunt function by decreasing the amount of drained volume. We therefore suggest to include dynamic pressure wave testing if hydrodynamic properties of shunts are to be evaluated.

Cerebrospinal Fluid↗
PubMed2002

Long-time in-vivo metabolic monitoring following experimental brain contusion using proton magnetic resonance spectroscopy.

In a Sham-controlled study we applied proton magnetic resonance spectroscopy (1H-MRS) at 4.7 T to a model of experimental traumatic brain contusion. The time course of cerebral metabolite changes was monitored in serial investigation in 14 Sprague Dawley rats up to 4 weeks after trauma. 6 animals served as controls. 1H-MRS spectra were acquired from a voxel covering the hippocampus/basal ganglia ipsi and contralateral to the lesion. Metabolites ratios of the injured hemisphere were compared to those ipsilateral in Sham animals and to those of the contralateral side in the trauma animals. NAA/Cr ratio and Glu/Cr ratio, possible markers of neuronal loss, persistently decreased after trauma to a minimum of -40% and -20% versus controls, respectively. One week after trauma Cho/Cr ratio was strongly increased by 73%. This might indicate a high inflammatory activity at that time. Lac/Cr ratio showed long-lasting and continuing increases up to 2000% versus controls as a sign of permanently shifted posttraumatic energy metabolism. 1H-MRS proved to be a useful non-invasive method for in-vivo monitoring of posttraumatic metabolism also in models of brain contusion. In single cases however, accompanying haemorrhage can potentially prevent useful data acquisition.

Animals↗
PubMed2002

Determination of contusion and oedema volume by MRI corresponds to changes of brain water content following controlled cortical impact injury.

The time-course of brain contusion/oedema development as visualised by high-resolution MRI was compared to brain water content following experimental brain contusion. 36 Sprague-Dawley rats underwent Controlled Cortical Impact Injury (CCII), 24 served as controls. In 16 animals serial T2 weighted MRI investigations at 1 h, 4 h, 24 h and 7 d after CCII were performed, in 44 rats hemispheric brain water content was determined at the same time points by wet dry weight method. MRI lesion volume (mm3) and brain water content of injured hemisphere (%) showed for absolute and relative values a strictly parallel course. Significant posttraumatic increases had a maximum at 24 hours. Values on day 7 were below those of 1st h in both methods. The simple non-invasive MRI method quantifies contusion and surrounding penumbra according to elevated tissue water signal. The invasive wet dry weight method quantifies changes of hemispheric brain water content that are likely to take place in contusion core and surrounding penumbra. Therefore, from a theoretical aspect both methods seem comparable. Following experimental brain contusion, the simple MRI method might be an equally sufficient way to describe post-traumatic or post-therapeutic changes of lesion size and brain oedema.

Animals↗
PubMed2002

Traumatic subarachnoidal hemorrhage in the developing rat.

The aim of the present study was to utilize an experimental traumatic subarachnoidal hemorrhage model in the developing rat. Diffuse brain injury was produced in intubated and ventilated 21 to 25 days old Sprague-Dawley rats (N = 10) using a modification (1 m/100 g) of the Marmarou-model. Before induction of the injury heparin was administered i.v. and antagonised after injury by protamine. Mean arterial blood pressure and intracranial pressure was measured continuously. Histopathological investigations were performed. The results were compared to readings in adult animals (N = 12) subjected to a 1.5 m/500 g injury. In the developing rat ICP increased immediately following injury from 11.4 +/- 2.1 mm Hg to 55.9 +/- 20.3 mm Hg. It remained elevated till the end of the experiment 1 h after injury. MABP increased from 79.8 +/- 8.7 mm Hg to 100.2 +/- 21.7 mm Hg immediately following injury, returning to 61.3 +/- 28.7 mm Hg at the end of the experiment resulting in a marked decrease of CPP. The mortality rate was 60%. All brains showed a severe subarachnoidal hemorrhage in the basal cisterns. The increase of ICP following injury is attributable to the bleeding similar as in adult animals. The high mortality is due to the marked decrease of CPP. Rat pups are more vulnerable to t-SAH compared to adult rats.

Aging↗
PubMed2001

Acute care in neurosurgery: quantity, quality, and challenges.

OBJECTIVE: Part of the daily routine in neurosurgery is the treatment of emergency room admissions, and acute cases from other departments or from outside hospitals. This acute care is not normally included in performance figures or budget management, nor analysed scientifically in respect of quantity and quality of care provided by neurosurgeons. METHOD: Over a 1 year period, all acute care cases managed by two neurosurgical on call teams in a large northern German city, were recorded prospectively on a day by day basis. A large database of 1819 entries was created and analysed using descriptive statistics. RESULTS: The minimum incidence of patients requiring neurosurgical acute care was estimated to be 75-115/100 000 inhabitants/year. This corresponds to a mean of about 6/day. Only 30% of patients came directly via the emergency room. The fate of 70% of patients depended initially on the "neurosurgical qualification" of primary care doctors and here deficits existed. Although most intracerebral and subarachnoid haemorrhages were managed with the participation of neurosurgeons, they were not involved in the management of most mild and moderate traumatic brain injuries. Within 1 year the additional workload from acute care amounted to 1000 unplanned admissions, 900 acute imaging procedures, and almost 400 emergency operations. CONCLUSION: The current policy in public health, which includes cuts in resources, transport facilities, and manpower, is not compatible with the demonstrated extent of acute neurosurgical care. In addition to routine elective work, many extra admissions, evening or night time surgery, and imaging procedures have to be accomplished. An education programme for generalists is required to improve overall patient outcome. These conclusions hold special importance if health authorities wish to not only maintain present standards but aim to improve existing deficits.

Adolescent↗
PubMed2000

1H-MR spectroscopic monitoring of posttraumatic metabolism following controlled cortical impact injury: pilot study.

Proton magnetic resonance spectroscopy (1H-MRS) has been increasingly utilised in experimental traumatic brain injury for characterisation of posttraumatic metabolic dysfunction. Following human brain injury pathological findings correlated with outcome measures. Combined with conventional T2-weighted MR imaging MRS is a sensitive tool to evaluate metabolic changes in brain tissue following trauma. Studies have been restricted so far to diffuse axonal injury models and fluid percussion injury. Using a high resolution scanner at 4.7 T, MRI combined with 1H-MRS was applied in a pilot study to the controlled cortical impact injury model of experimental brain contusion (CCII). Eight Sprague-Dawley rats were investigated, of which two served as controls. Four animals were injured 24 h after craniotomy, two investigated at 72 h post craniotomy. MRS/MRI indicated a transient brain oedema development and metabolic changes induced by the craniotomy itself. Following CCII MRI demonstrated that the area of contusion as well as the surrounding brain oedema increased twofold in size within 24 h (p < 0.05). MRS showed an immediate increase of N-acetylaspartate (NAA) and glutamate ipsilateral to the contusion and a drop of NAA on the contralateral side. MRS/MRI investigations in the CCII model demonstrated a potential to further elucidate the pathophysiology following traumatic brain contusion.

Animals↗
PubMed2000

ICP and MABP following traumatic subarachnoid hemorrhage in the rat.

Traumatic subarachnoidal hemorrhage (t-SAH) is a common finding in head-injured patients occurring with a frequency of 39% according to data of the Traumatic Coma Data Bank. The present study is the first description of a t-SAH-model with particular emphasis on patterns of intracranial pressure (ICP) changes and mean arterial blood pressure (MABP) response. Diffuse brain injury was produced in intubated and ventilated adult Sprague-Dawley rats (N = 24) using a brass weight (500 gm) free falling from a predetermined height (1.5 m) on a steel disc glued to the skull of the rat. Before induction of the injury, heparin was administered intra-arterially (i.a.) and antagonised after injury by protamine. MABP-recordings and ICP-recordings were performed continuously. Histopathology was undertaken. Following injury MABP decreased from 138 +/- 14 mmHg to 89 +/- 22 mmHg. During 5 to 15 min ICP increased up to 89.4 +/- 50.4 mmHg, decreasing slowly within 60 min in surviving animals. The mortality rate was 41.6%. All brains showed a severe subarachnoid hemorrhage in the basal cisterns and cell-loss within the brainstem. Experimental t-SAH is possible. Following t-SAH there is a subacute increase of ICP due to the actual bleeding. The model may provide deeper understanding in the basic physiological patterns of t-SAH.

Animals↗
PubMed2000

Influences of secondary injury following traumatic brain injury in developing versus adult rats.

Hypoxia and hypotension are both common findings following traumatic brain injury occurring with a frequency of up to 46% according to data of the Traumatic Coma Data Bank. In the present study the influence of secondary injury on intracranial pressure and the cardiovascular response is investigated in developing rats. Differences from adult rats are determined. Diffuse brain injury was produced in intubated and ventilated 17-20 days old Sprague-Dawley rats (N = 16) using a modification of the Marmarou-model. Hypoxia was induced by reducing O2-concentration to 8% lasting for 15/30 min. Mean arterial blood pressure recordings and intracranial pressure recordings were performed continuously. Animals were divided into two groups, sustaining hypoxia alone (N = 9) and trauma/hypoxia (N = 7). The results were compared to readings in adult animals subjected to hypoxia (N = 5) and trauma/hypoxia (N = 5) (450 gm/150 cm). Immediately following the onset of hypoxia in the developing rat, MABP decreased from 76.5 +/- 13 mm Hg to 35.8 +/- 7 mm Hg. In the adult rat the decrease was more marked (from 93.3 +/- 8 mm Hg to 33.5 +/- 5.7 mm Hg) (p < 0.05). Mortality rate in developing rats with trauma/hypoxia was 43% with no significant change of ICP (from 13 +/- 5.2 to 22.3 +/- 11). All adult animals recovered following trauma/hypoxia with no relevant ICP-increase within one hour post-trauma. Hypoxia induces hypotension in adult and developing rats. However, developing rats appear to be more vulnerable to hypoxia associated with trauma.

Age Factors↗
PubMed2000

Application of clinically recorded ICP patterns--an extension of conventional shunt testing.

Various methods of laboratory testing are currently being used to explore the hydrodynamic properties of shunts. We constructed a novel shunt-testing rig with a human-like compliance to be able to subject shunts to in-vivo recorded ICP patterns. The human-like situation was realized with a pear-shaped glass container with a non-linear, third-order pressure/volume characteristic similar to the CSF system. The new device also allows conventional shunt testing. Shunt performance in conventional pressure/flow tests (linear compliance) was compared to tests with human-like compliance. No clinically relevant differences were seen. Clinically recorded ICP waves (Lundberg type A and B) were reproduced before and after shunt implementation. Shunt insertion reduced pressure in the A-wave pattern to slightly negative values. Reproducing B-waves, the shunt dampened wave amplitude and pressure decreased below the opening pressure of the valve. In conclusion, the presented device allows a standardized reproduction of ICP patterns. The effects of shunt implantation can be studied.

Cerebrospinal Fluid↗
PubMed2000

[Accuracy of intraoperative urinary bladder temperature monitoring during intra-abdominal operations].

OBJECTIVE: This study investigates whether the site of abdominal surgery or the urine flow rate affects the accuracy of urinary bladder temperature monitoring. METHODS: After approval by the local ethics committee we studied 7 patients during upper abdominal and 10 patients during lower abdominal surgery. Temperatures were recorded with a Hi-Lo Temp Esophageal-Stethoscope (Mallinckrodt Medical) and a Foley Catheter Temperature Sensor FC400-18 (Respiratory Support Products, Mallinckrodt Medical). Each probe and its recording unit were calibrated over a range of 30-40 degrees C against a reference quartz thermometer (Hewlett Packard Model 2801 A) in a water bath before the investigation. Urine flow rate was measured using a urometer. Temperatures and urine flow rate were recorded every 30 min. Agreement between the methods of measurement was assessed as described by Bland and Altman. RESULTS: 124 measuring points could be analyzed. Bladder temperature had a bias (B) of -0.06 degree C compared to oesophageal temperature. Limits of agreement (LOA; +/- 2 s) were +/- 0.68 degree C. In upper abdominal surgery (B: 0.02 degree C; LOA: +/- 0.42 degree C) a higher precision of oesophageal temperature estimation could be demonstrated compared to lower abdominal surgery (B: -0.14 degree C; LOA: +/- 0.82 degree C). Lower urine flow rates generally increased the limits of agreement. Regarding lower abdominal surgery the bias additionally increased to -0.22 degree C. CONCLUSION: Urinary bladder temperature recording is a clinically acceptable method to measure core temperature during abdominal surgery. The accuracy during lower abdominal surgery is decreased compared to upper abdominal surgery, especially in case of a urine flow rate below 250 ml/h.

Abdomen↗
PubMed2000

Ectopic choroid plexus within a juvenile arachnoid cyst of the cerebellopontine angle: cause of cyst formation or reason of cyst growth.

The unusual and rare case of a 6-year-old boy is reported who presented with an arachnoid cyst located in the cerebellopontine angle incorporating an ectopic piece of choroid plexus tissue. A microneurosurgical cyst wall resection was performed and the plexus tissue identified and removed. The rare occurrence of ectopic choroid plexus tissue within cysts of the CNS is discussed.

Arachnoid Cysts↗
PubMed1999

Arachnoid cysts of the posterior fossa.

BACKGROUND: The surgical indications and management of posterior fossa arachnoid cysts (AC) are still controversial. Different surgical techniques and management have already been suggested for arachnoid cysts of the posterior fossa. AC involving the posterior fossa and especially the cerebellopontine angle may carry a high surgical morbidity because of the involvement of important neurovascular structures (e.g., brain stem and cranial nerves). Only long-term follow-up will determine the best surgical technique for such lesions. METHODS: Between 1990 and 1996 a total of 12 patients underwent surgery for arachnoid cysts involving the posterior fossa. In seven cases AC were located within the cerebellopontine angle (CPA), in three cases in the CPA with major extension dorsal to the brainstem, and in two cases at the CPA extending into the internal auditory canal. RESULTS: A suboccipital retrosigmoid approach was performed in all patients. Radical resection of the cyst could be accomplished in all but one case. There was no mortality. Major postoperative morbidity was present in one case because of an intraoperative air embolism in the semisitting position and strong adherence of the cyst wall to the surrounding neurovascular structures. Long-term follow-up (mean, 3.3 years) revealed improvement of most preoperative symptoms. CONCLUSION: Open surgery and radical removal of the AC located at the posterior fossa, based on our retrospective analysis, provide very good long-term postoperative results. The suboccipital approach provides a good and safe exposure of vascular structures and cranial nerves in the CPA and allows radical resection of the cyst, reducing the chance of recurrence.

Adolescent↗
PubMed1999

Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery.

Mild hypothermia is assumed to protect against secondary brain injury. However, the accuracy of brain temperature estimation remains debatable if direct measurement in the target area is to be avoided or is impossible. Furthermore, intracerebral temperature gradients exist, especially under intraoperative conditions. We aimed to establish how brain surface temperatures (TBrain) relate to temperatures taken at standard sites in posterior fossa surgery. Ten patients undergoing cerebellopontine angle tumor removal were monitored for TBrain, esophageal temperature (TEso), bladder temperature (TBlad), ipsi- and contralateral tympanic membrane (TTymp-I, TTymp-C), and scalp temperatures (TScalp). During monitoring, TEso increased from 35.3+/-0.2 degrees C to 36.0+/-0.3 degrees C. After dura opening, TBrain was -0.14+/-0.1 degrees C below TEso. At the end of tumor removal, this difference increased to -0.43+/-0.31 degrees C (P < 0.05). TTymp-C was -0.29+/-0.18 degrees C below TBrain at dura opening. TTymp-C reflected the behavior of TEso adequately (r = 0.938), however, with a mean difference of -0.39+/-0.04 degrees C. In contrast, TTymp-I readings closely followed temperature changes in the area of surgery. TBlad reflected TEso except in periods of rapid temperature changes. In posterior fossa (PF) surgery, local TBrain is most accurately reflected by TEso. For clinical use TBlad and TTymp-C are also sufficient to assess brain surface temperature in the PF. Intraoperative surface cooling of the brainstem is less than the previously described cooling rate of exposed cerebral cortex.

Adult↗