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Biomedical subjects

M Samii

Publications and source records attributed to M Samii.

At least 109 records · Page 6Linked to original sources
PubMed1999

A positron emission tomography study of cerebrovascular reserve before and after shunt surgery in patients with idiopathic chronic hydrocephalus.

OBJECT: In this study the authors use positron emission tomography (PET) to investigate cerebral blood flow (CBF) and cerebrovascular reserve (CVR) in chronic hydrocephalus. METHODS: Ten patients whose mean age was 67 +/- 10 years (mean +/- standard deviation [SD]) were compared with 10 healthy volunteers who were 25 +/- 3 years of age. Global CBF and CVR were determined using (15)O-H2O and PET prior to shunt placement and 7 days and 7 months thereafter. The CVR was measured using 1 g acetazolamide. Neurological status was assessed based on a score assigned according to the methods of Stein and Langfitt. Seven months after shunt placement, five patients showed clinical improvement (Group A) and five did not (Group B). The average global CBF before shunt deployment was significantly reduced in comparison with the control group (40 +/- 8 compared with 61 +/- 7 ml/100 ml/minute; mean +/- SD, p < 0.01). In Group A the CBF values were significantly lower than in Group B (36 +/- 7 compared with 44 +/- 8 ml/100 ml/minute; p < 0.05). The CVR before surgery, however, was not significantly different between groups (Group A = 43 +/- 21%, Group B = 37 +/- 29%). After shunt placement, there was an increase in the CVR in Group A to 52 +/- 37% after 7 days and to 68 +/- 47% after 7 months (p < 0.05), whereas in Group B the CVR decreased to 14 +/- 18% (p < 0.05) after 7 days and returned to the preoperative level (39 +/- 6%) 7 months after shunt placement. CONCLUSIONS: The preliminary results indicate that a reduced baseline CBF before surgery does not indicate a poor prognosis. Baseline CBF before shunt placement and preoperative CVR are not predictive of clinical outcome. A decrease in the CVR early after shunt placement, however, is related to poor late clinical outcome, whereas early improvement in the CVR after shunt placement indicates a good prognosis.

Aged↗
PubMed1999

Induction of heat shock protein 70 in the rat brain following intracisternal infusion of autologous blood: evaluation of acute neuronal damage.

OBJECT: Investigation into a potential treatment for the acute period following onset of spontaneous subarachnoid hemorrhage (SAH) is hampered by the lack of a standardized experimental model. For that purpose the authors elaborated on a small-animal model in which computer-controlled intracisternal blood infusion is used and investigated whether this model can reliably reproduce acute neuronal injury after SAH. METHODS: Whole autologous blood (blood-infused group) or isotonic saline (control group) was infused into the cisterna magna or olfactory cistern of rats. The infusions decreased exponentially during a 5-minute period. Throughout the infusion period, intracranial pressure (ICP) was monitored. Neuronal injury was quantified by observing tissue immunoreactivity to a 70-kD heat shock protein (HSP70) and comparing this with the tissue's reaction to hematoxylin and eosin staining. On Days 1, 3, and 5, the CA1, CA3, and dentate gyrus regions of the hippocampus were analyzed, respectively. During saline infusion ICP increased within seconds beyond 80 mm Hg and afterward decreased in accordance with the infusion rate. During the infusion of blood, the same initial pressure peak was found, but the ICP remained increased beyond this pressure level throughout the 5-minute infusion period. The HSP70 immunoreactivity in the saline-infused group was found only on Day 1 in the CA1 region and the dentate gyrus, but not in the CA3. After injection of whole blood, there was HSP70-positive staining in the CA1, CA3, and dentate gyrus regions throughout the observation period. CONCLUSIONS: The controlled cisternal infusion of blood caused neuronal injury that resembled that of previous experimental models that produce SAH by rupture of intracranial vessels with endovascular techniques. Unlike those experiments, the intracisternal infusion technique presented by the authors provides more standardized bleeding with regard to ICP, the volume of subarachnoid blood, and the extent of acute cellular injury.

Animals↗
PubMed1998

Three-dimensional computed tomographic reconstruction: planning tool for surgery of skull base pathologies.

Three-dimensional (3-D) computed tomographic (CT) reconstruction of the skull base region has added a different perspective to the data set usually presented in axial or coronal slices. It simultaneously demonstrates the spatial relationship of bones, tumors, vessels, and ventricles in a single illustration. Forty-nine patients with skull base lesions (44 with neoplastic and 5 with vascular pathologies) were examined with a spiral CT and 3-D reconstruction prior to surgery. A scanner and a maximum of 95 mL of iodized contrast media were used to enhance either tumor or vessels according to the specific pathology. Preoperative 3-D reconstruction was performed. It rendered a spatial representation of the pathology using data similar to that usually acquired in routine preoperative diagnostics. Complex anatomy can be visualized with only a handful of pictures. It was possible to easily compare various surgical approaches to the lesion on the basis of the 3-D computer model and to simulate the surgeon's view. The short time span (1 h average) necessary for reconstruction and editing allows the application of this method as a routine preoperative procedure for selected skull base pathologies.

Adult↗
PubMed1998

Brain-stem auditory evoked potential monitoring in experimental diffuse brain injury.

The time course of brain-stem auditory evoked potential (BAEP) changes was investigated using an impact-acceleration trauma model in 23 spontaneously breathing rats. Intracranial pressure (ICP), arterial blood pressure and respiratory rate were monitored. The experiments were terminated at four hours after trauma. No significant changes in intracranial pressure (ICP) occurred following the impact. After a short increase, blood pressure returned to baseline values within 5 min. Transient apnea was not followed by prolonged respiratory depression. Diffuse closed head injury (CHI) did not result in general, unidirectional changes of peak latencies or amplitudes of auditory evoked responses. Most BAEP changes developed slowly reaching a maximum at 1 to 4 hours after the injury. In the absence of ICP changes, this pattern reflects secondary ischemia in sensitive brain-stem areas rather than direct traumatic lesions or hypoxia due to respiratory depression.

Animals↗
PubMed1998

Traumatic brain injury in the developing rat pup: studies of ICP, PVI and neurological response.

Diffuse brain swelling is a common complication in young victims of a seven head injury but, there is a lack of data on relevant models of injury. We produced diffuse brain injury in 21 day old Lewis rat pups (N = 33) by modifying a recently established weight-drop-model. The trauma threshold, neurological response, histological changes, intracranial pressure (ICP), and arterial blood pressure (ABP) were determined. In addition, the pressure-volume-index (PVI) was measured 15 min before, 2 min, and 1 h after brain injury. In the 1 m/100 g group 4 of 5 rats died, whereas in the 0.5 m/100 g only 4 of 28 died. The PVI increased at 2 min after traumatic brain injury (TBI) but ICP was unchanged, except for a minor increase immediately after injury. Histological studies revealed diffuse neuronal death, predominantly involving the cortex and hippocampus. The results of the present study indicate that determination of ICP in the developing rat pup during and after diffuse brain injury is possible. A 0.5 m/100 g weight-drop-trauma results in a morphologically severe injury but with low mortality. The increase in PVI can be attributed to a decrease of cerebral perfusion pressure (CPP) after injury. However, the absence of a further increase of ICP after injury in the developing rat indicates that this may not be a primary consequence of injury in paediatric patients.

Age Factors↗
PubMed1998

CSF dynamics in a rodent model of closed head injury.

Using ICP measurements and the bolus injection technique dynamic parameters of the cerebrospinal fluid system as there are pressure-volume-index (PVI) and resistance to CSF outflow (Rout) were investigated in a new model of diffuse closed head injury (CHI) in the rat. It was found that in the absence of brain oedema and ICP alterations an increase in PVI and Rout was present in the early (4h) period following head injury. This may be indicative for a reduction in cerebral blood flow and cerebral blood volume, both shown previously to occur after CHI. Furthermore an early impairment of CSF absorption mechanisms is evident. To answer the question, whether bolus injection techniques are advisable for clinical routine and whether results might have a predictive value, further investigations covering longer observation intervals and in the presence of secondary insults to the brain are necessary.

Animals↗
PubMed1998

Treatment of elevated intracranial pressure by infusions of 10% saline in severely head injured patients.

The management of intracranial pressure (ICP) is a factor in outcome of patients with head trauma. However, recent studies have revealed that the current strategies, which have been applied to control ICP for adequate cerebral perfusion, are unsatisfactory. Against this background, the efficacy of short-term infusions of hypertonic saline on ICP was investigated. In severely head injured (SHI) patients, hypertonic saline (100 ml 10% NaCl) was administered when standard agents (mannitol, sorbitol, THAM) failed in reducing ICP. To evaluate the pressure reduction after saline infusions the resulting ICP relaxations were analysed statistically in respect to the parameters amplitude, duration and dynamic behaviour of the ICP responses. In 42 randomized relaxations, the relative ICP decrease was 43% [28%-58%] (median [interquartile range]). The corresponding pressure drop was 18 mmHg [15-27 mm Hg]. Relaxations lasted for 93 min [64-126 min] and a relative ICP minimum was reached 26 min [12-33 min] after infusion. In the individual cases the temporal course of the parameters amplitude and decline interval depict a tendency toward lower and higher values, respectively, under conditions of a generally increasing ICP. As expected, the infusion of hypertonic saline reduces ICP in patients suffering from SHI. The pressure drop, duration and dynamic behaviour are suspected to depend both on the pressure level to reduce and concomitant medications.

Adolescent↗
PubMed1998

Time-dependent expression of donor- and host-specific major histocompatibility complex class I and II antigens in allogeneic dopamine-rich macro- and micrografts: comparison of two different grafting protocols.

Neural transplantation, as a therapeutic approach to Parkinson's disease, still requires allogeneic graft material and raises questions of immunosuppression and graft rejection. The present study investigated the time course of major histocompatibility complex (MHC) expression and astrocytic response in allogeneic dopaminergic grafts, comparing two different grafting protocols. Adult 6-hydroxydopamine-lesioned Lewis 1.W rats received intrastriatal cell suspension grafts from the ventral mesencephalon of DA rat fetuses, either as single 1-microliter macrograft via metal cannula or as four micrografts of 250 nl/deposit via a glass capillary. No immunosuppression was administered. Immunohistochemistry was performed at 1, 3, 6, and 12 weeks after grafting, using antibodies against donor- and host-specific MHC class I and II antigen, glial fibrillary acidic protein (GFAP) and tyrosine hydroxylase (TH). Most animals showed good allograft survival up to 12 weeks after transplantation with no signs of rejection. Reinnervation of the lesioned striatum by TH-positive neurites was observed from 3-6 weeks on. Expression of donor-specific MHC class I was comparably low in both allogeneic grafting groups, while host MHC class I and II reaction as well as astrocytic response tended to be higher in the macrografted animals. Donor MHC class II was not observed at any time point. It is concluded that intraparenchymal allografts of fetal mesencephalic cell suspensions can survive well in the rat Parkinson model without immunosuppression for at least 12 weeks, and that the expression of moderate amounts of donor-specific MHC class I antigen does not suffice to initiate a rejection process. In addition, the microtransplantation approach may reduce the level of trauma and subsequent MHC and GFAP expression and may, thereby, minimize the risk of graft rejection.

Animals↗
PubMed1998

An experimental approach to image guided skull base surgery employing a microscope-based neuronavigation system.

INTRODUCTION: A cadaveric study was undertaken to investigate the usefulness and reliability of a microscope based navigation system (NS) for skull base surgery. MATERIAL AND METHODS: CT-scans (1 mm slices) were performed in 10 fixed cadaver heads after implantation of fiducials. There upon, various skull base dissections were undertaken: transethmoidal-transsphenoidal approach to sella and clivus, retrosigmoidal approach to the internal auditory canal (IAC) and to the posterior semicircular canal (PSCC). The navigated dissections were performed with the MKM, a microscope based navigation system of Carl Zeiss (Oberkochen, Germany). RESULTS: The registration assessment by the NS yielded a mean deviation of 0.23 mm +/- 0.03 mm (mean +/- SD, n = 7, range 0.19 to 0.27 mm). The real anatomical deviation during dissection was 0.67 mm +/- 0.2 mm for navigation to the IAC and 0.71 mm +/- 0.37 mm to the PSCC. This accuracy was achieved with three fiducials (4 x 1 mm titanium screws) arranged as a triangle (side length 4-6 cm) nearby the surgical field. Navigation data on current position, direction and distance to a target structure were helpful in the transethmoidal-transsphenoidal approach to the clivus, as well as for accessing deep seated structures (C1-C2 junction, petrous bone tip). The contouring feature was beneficial for identifying structures embedded in the bone. However, due to inaccurate 3-D modelling this feature has a restricted reliability. DISCUSSION: Our cadaveric skull base study has shown that the MKM is a reliable tool with high anatomical accuracy and usefulness of most navigation features. However, in order to effectively and reliably use any NS the surgeon must be familiar with its potential features and limitations as is demonstrated in this study.

Equipment Design↗
PubMed1998

Sinusoidal intrathecal infusion for assessment of CSF dynamics in kaolin-induced hydrocephalus.

OBJECTIVE: To evaluate whether changes of CSF outflow resistance and compliance in hydrocephalus can be assessed by an intrathecal infusion which is performed at a sinusoidal varying rate. METHODS: Hydrocephalus was produced in 10 Sprague Dawley rats by instillation of 0.0375 g of kaolin in 0.9% saline into the cisterna magna. Measurements were performed 4 weeks later: With each animal both, three successive constant rate infusions (0-0.02 ml/min) and a sinusoidal infusion (0-0.02 ml/min, frequency 0.006 Hz) were performed. 6 normal animals served as control. The pressure recordings of both infusion techniques were used for the assessment of the CSF outflow resistance. The time constant and the pressure volume index were calculated only from the sinusoidal input testing. RESULTS: The sinusoidal test as well as the constant rate infusion both demonstrated a severe impairment of CSF absorption. By the sinusoidal input, a decreased compliance was confirmed additionally. Thus, the sinusoidal infusion test demonstrated a high resistance and low compliance hydrocephalus in the kaolin-treated group. A simple graphical procedure is presented which allows an easy assessment of CSF dynamics by the sinusoidal infusion test.

Animals↗
PubMed1998

Differences in acquisition and full performance in skilled forelimb use as measured by the 'staircase test' in five rat strains.

Skilled forelimb use was examined in five different rat strains (DA/Ztm, LEW/Ztm-ci, LEW.1W/Ztm, SD/Ztm, SPRD/Ztm-Cu3) by means of the 'staircase test', as originally described by Montoya et al. [20] (C.P. Montoya, H.L. Campbell, K.D. Pemberton, S.B. Dunnett, The 'staircase test': A measure of independent forelimb reaching and grasping abilities in rats, J. Neurosci. Methods 36 (1991) 219-228). Strain-dependent differences were observed most prominently during the acquisition phase, and less pronounced, at the full performance level. SD/Ztm and DA/Ztm rat strains seemed to be particularly skilled in their forelimb use, although with varying levels of activity. Interestingly, significant differences in skilled forelimb movements were found between the related Sprague-Dawley derived and Lewis congenic rat strains. No clear-cut correlation was found between skilled forelimb use and basic nutrition-dependent measures, such as pretest body weight or weightloss during the test period. Based on previous observations on strain-dependent behavioral variations it seems likely that the differences in skilled forelimb use, as observed in the present study, might be caused by morphological and/or functional strain-dependent alterations in the involved neuronal circuitries, such as motor cortex, caudate-putamen unit and mesotelencephalic dopamine system. However, they should also be considered as potentially influencing parameters in studies related to the behavioral effects of lesions and restorative therapies in the central nervous system.

Animals↗
PubMed1998

Ossified and de novo cavernous malformations in the same patient.

We report the case of a 44-year-old patient with a MRI scan showing a newly developed cavernoma after two highly calcified lesions had been excised surgically. Six other cavernous malformations had been followed by MR imaging over a 2-year period. The coexistence of the two extremes of cavernous malformations in terms of lesions development--de novo and ossified lesions has not been reported previously and has implications for both the follow-up and the natural history of these malformations. The potential for developing new cavernous malformations persists and does not seem to be related to the evolutional stage of pre-existing lesions. It is suggested that these patients need to be followed up by MRI on a regular basis.

Adult↗
PubMed1998

Direct magnification technique for cerebral angiography in the rat.

RATIONALE AND OBJECTIVES: The authors evaluated the performance of direct magnification radiography (DIMA) with digital image processing for cerebral angiography in the rat. METHODS: A microfocal x-ray unit with a focal spot of 5 microns was used for cerebral angiography in 10 rats. The animals were examined form x 4 up to x 20 magnification after injection of 0.2 mL x-ray contrast medium into the common carotid artery. RESULTS: Direct magnification radiography technology provides high resolution images and enables the visualization of very small vessels with high quality. It allows the peripheral branches of the middle cerebral artery or the ophthalmic artery to be visualized. Superimposition and noise effects can be excluded with digital subtraction and image processing. CONCLUSIONS: The experiments show that DIMA radiography is a suitable technique for cerebral angiography in the rat.

Animals↗
PubMed1998

Surgery of spinal nerve sheath tumors with special reference to neurofibromatosis.

OBJECTIVE: We conducted a retrospective study of 87 patients with spinal nerve sheath tumors to determine the overall clinical outcome and specific features in 20 patients affected with neurofibromatosis Types 1 and 2 (NF-1 and NF-2, respectively). METHODS: Case records, operation notes, outpatient files, and radiological examinations were analyzed for all patients treated between September 1977 and August 1994. Additional follow-up data were obtained using outpatient examinations, questionnaires, and telephone calls. RESULTS: During the study period, 128 spinal neuromas (i.e., schwannomas) and 6 neurofibromas in 87 patients were treated. Fifty-seven neuromas were associated with NF-2 in 17 patients and six neurofibromas with NF-1 in 3 patients. Patients with NF-2 and symptomatic neuromas presented with more severe neurological deficits compared to patients without NF-2. Eighty-six percent of the neuromas were removed completely. On average, most preoperative deficits or symptoms improved in patients without NF-2, whereas neurological symptoms remained unchanged in patients with NF-2. Multiple regression analysis revealed that partial removal, surgery of a recurrent tumor, NF-2, and old age predisposed for tumor recurrence. No increased risk of recurrence was observed for patients with NF-1. For patients without NF-2, we observed overall recurrence rates of 10.7% after 5 years and 28.2% after 10 and 15 years, respectively, as determined by Kaplan-Meier analysis. For NF-2, the recurrence rate at 5 years was 39.2%, and all tumors had recurred by 9 years. CONCLUSION: Spinal nerve sheath tumors carry an excellent prognosis in patients with NF-1 and in patients without neurofibromatosis. Symptomatic neuromas occurring in association with NF-2 present with more severe neurological deficits, demonstrate little postoperative improvement, and have a very high recurrence rate.

Adolescent↗
PubMed1998

PET and CBF studies of chronic hydrocephalus: a contribution to surgical indication and prognosis.

The authors investigate whether measurement of cerebral blood flow (CBF) in chronic hydrocephalus is a reliable indicator in selecting patients to undergo ventriculoperitoneal shunting. Global and regional CBF is quantified (Kety-Schmidt one-compartment model) by positron emission tomography in 21 patients. CBF is determined following injection of 15O-H2O at three time points: 1 week before, 7 days after, and 7 months after shunting. The neurological status of these patients is classified, and cerebrospinal fluid (CSF) dynamics continuous intracranial pressure [ICP] monitoring and CSF infusion tests) were assessed prior to surgery. Preoperative global CBF values correlate well with clinical outcome. Patients with a significantly lower global CBF value show clinical improvement after 7 months, whereas patients with higher CBF values do not (mean, 33 vs. 45 ml/100 ml per minute; p < 0.05). In contrast to conventional methods, including long-term ICP measurement and CSF infusion tests, preoperative global CBF values are discriminating in terms of clinical outcome. Thus, measurement of CBF may be helpful in evaluating the ultimate utility of shunt therapy in chronic hydrocephalus.

Aged↗
PubMed1998

Microvascular decompression for superior oblique myokymia: first experience. Case report.

Superior oblique myokymia (SOM) is a rare eye movement disorder presenting as uniocular rotatory microtremor due to intermittent contractions of the superior oblique muscle. Medical treatment usually fails to provide long-term benefit for the patient and has considerable side effects. Surgical alternatives including tenotomy or partial tenectomy of the superior oblique tendon often result in incomplete resolution of the visual symptoms. The authors report a patient who experienced immediate cessation of disabling SOM following microvascular decompression of the fourth nerve at the root exit zone. Temporary double vision at downgaze resolved 5 months after surgery. There was no recurrence of oscillopsia during a follow-up of 22 months to date. From this single observation it appears likely that vascular compression of the trochlear nerve could be a significant pathophysiological factor contributing to SOM. In the hands of an experienced surgeon, microvascular decompression at the brainstem exit zone of this nerve may evolve as the method of choice for selected cases of disabling SOM.

Decompression↗
PubMed1998

Dopaminergic graft-induced long-term recovery of complex sensorimotor behaviors in a rat model of Parkinson's disease.

Transplantation of embryonic dopamine neurons has evolved as an alternative neurosurgical treatment strategy for patients with Parkinson's disease and it is therefore of great interest to further optimise this procedure in experimental studies. We have applied a modified microtransplantation approach in unilaterally 6-hydroxydopamine lesioned rats and observed a substantial and long-lasting functional recovery in complex spontaneous behaviors, such as skilled forelimb use and stepping behavior. The results demonstrate that the rat model of Parkinson's disease is a highly useful tool to study mechanisms of neural plasticity and regeneration. The ability of dopaminergic grafts to restore complex sensorimotor behaviors in animals also indicate their great potential for the development of a successful clinical application.

Animals↗