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Biomedical subjects

N Egemen

Publications and source records attributed to N Egemen.

At least 19 recordsLinked to original sources
PubMed2006

The neurotoxic effects of intrathecal midazolam and neostigmine in rabbits.

In parallel with improvements in understanding pain neurophysiology, many chemicals have recently been investigated for spinal anaesthesia and analgesia. However, studies discussing the effects of these drugs on neural tissue indicate that knowledge about some aspects of neurotoxicity is limited. Forty-nine New Zealand albino rabbits, weighing 2.2 +/- 0.2 kg, were randomly assigned to seven groups of seven animals each. Single dose groups received intrathecally through the atlantooccipital membrane 0.9% saline 1.5 ml; midazolam 100 microg/kg (low dose midazolam group) or 500 microg/kg (high dose midazolam group); neostigmine 10 microg/kg (low dose neostigmine group) or 50 microg/kg (high dose neostigmine group). Two groups had seven days of repeated dosing with either midazolam 100 microg/kg/day (repeat midazolam group) or 10 microg/kg/day neostigmine (repeat neostigmine group). The animals were sacrificed on day 8, and two spinal cord sections from the fourth cervical level and fourth lumbar level were removed and prepared for histopathological study. Transmission electron microscopic evaluations were performed on transverse spinal cord sections by a neuropathologist blinded to the group allocation. Twenty myelinated axons and neurones in the cervical and lumbar sections were investigated for the histopathological study. This study indicates that midazolam and neostigmine have different neurotoxic effects that depend on the dose and the repetition of dosing when these drugs are administered intrathecally.

Analysis of Variance↗
PubMed2003

Stereotactically-guided fourth ventriculo-peritoneal shunting for the isolated fourth ventricle.

The isolated fourth ventricle (IFV) develops in which obstruction to the out flow of cerebrospinal fluid from the choroid plexus of the fourth ventricle occurs rostrally and caudally. IFV has been a rare occurrence and is difficult to treat. We had an occasion to admit a 28-year-old female to our hospital due to hydrocephalus: she also had a history of meningitis a year ago. The patient was initially managed by a lateral ventriculo-peritoneal shunting procedure. Six months after the procedure the patient began to suffer from vomiting, nausea, and diplopia. CT and MRI scans demonstrated an isolated fourth ventricle enlargement; and thus, a fourth ventriculo-peritoneal shunting procedure was performed under stereotactic conditions. The authors present a case of an isolated fourth ventricle after lateral ventriculo-peritoneal shunting for hydrocephalus, which was treated with a stereotactically guided fourth ventriculo-peritoneal shunting procedure. The technique of this procedure is described below.

Adult↗
PubMed2002

Subarachnoid heamorrhage-induced chronic cerebral vasospasm in the rabbit: IV-DSA versus IA-DSA.

BACKGROUND: Chronic cerebral vasospasm is delayed-onset cerebral arterial narrowing in response to blood clots left in the subarachnoid space after aneurysmal subarachnoid haemorrhage (SAH). Rabbit models of vasospasm have been developed as in vivo experimental pathogenesis and the treatments of cerebral vasospasm using human vessels are not possible. The present study assessed the diagnostic accuracy of the intravenous digital subtraction angiography (IV-DSA) in chronic cerebral arterial spasm following induced SAH in the rabbit. METHOD: Ten rabbits' left leg veins catheterised by intravascular access needle and 3F catheters introduced to the right leg arteries probing the proximal of the vertebral arteries. Initially IV-DSA and intra-arterial digital subtraction angiography (IA-DSA) was performed. Three millilitres of fresh autologous arterial blood was injected into the cisterna magna of the ten rabbits' in order to produce in vivo model of chronic SAH. Angiograms were obtained 15 minutes and 72 hours after the SAH. FINDINGS: Diameters of the basilar arteries were similar to each other in both methods and reduced after the SAH. INTERPRETATION: The present study shows that IV-DSA is a relatively simple and effective method for demonstrating cerebral vessels, especially the basilar artery.

Animals↗
PubMed2001

Lumbar pedicle: surgical anatomic evaluation and relationships.

Although several clinical applications of transpedicular screw fixation in the lumbar spine have been documented for many years, few anatomic studies concerning the lumbar pedicle and adjacent neural structures have been published. The lumbar pedicle and its relationships to adjacent neural structures were investigated through an anatomic study. Our objective is to highlight important considerations in performing transpedicular screw fixation in the lumbar spine. Twenty cadavers were used for observation of the lumbar pedicle and its relations. After removal of whole posterior bony elements including spinous processes, laminae, lateral masses, and inferior and superior facets, the isthmus of the pedicle was exposed. Pedicle width and height (PW and PH), interpedicular distance (IPD), pedicle-inferior nerve root distance (PIRD), pedicle-superior nerve root distance (PSRD), pedicle-dural sac distance (PDSD), root exit angle (REA), and nerve root diameter (NRD) were measured. The results indicated that the average distance from the lumbar pedicle to the adjacent nerve roots superiorly, inferiorly and to the dural sac medially at all levels ranged from 2.9 to 6.2 mm, 0.8 to 2.8 mm, and 0.9 to 2.1 mm, respectively. The mean PH and PW at L1-L5 ranged from 10.4 to 18.2 mm and 5.9 to 23.8 mm, respectively. The IPD gradually increased from L1 to L5. The mean REA increased consistently from 35 degrees to 39 degrees. The NRD was between 3.3 and 3.9 mm. Levels of significance were shown for the P < 0.05 and P < 0.01 levels. On the basis of this study, we can say that improper placement of the pedicle screw medially and inferiorly should be avoided.

Adult↗
PubMed2001

Perforating branches of the anomalous anterior communicating complex.

The anterior communicating complex was studied in 25 cadaver specimens obtained at routine autopsy. In 15 specimens (60%), an anomalous anterior communicating artery was found. The most common anomaly identified was a multi-channeled anterior communicating artery. The first channel was always the smallest channel, and all of the perforators arose from this smallest channel 45% of the time. All other anomalous anterior communicating arteries presented with concomitant anomalous perforator anatomy.

Anterior Cerebral Artery↗
PubMed2001

Surgical treatment of intracranial cavernous angiomas.

We present a surgical series of 35 patients (25 males and 10 females) with histopathologically verified intracranial cavernous angiomas. The 35 malformations were located as follows: 21 were in the cerebral hemispheres; 4 in the lateral ventricles, 4 in the brain stem; and 6 in the cerebellum. Seizures and focal neurological deficits were the main clinical features observed in patients with intracranial cavernous angiomas. A number of these vascular malformations were misdiagnosed by computerized tomography. In the last 10 years, magnetic resonance imaging has been the most sensitive method for detecting these lesions. Thirty-five cavernous angiomas were treated surgically; in 33 patients a complete excision, and in 2 patients subtotal excision were obtained. One of the patients died one year after the operation. The overall outcome was good in all of the 34 remaining patients, resulting in improved seizure control or neurological deficit. The rationale for neurologic differential diagnosis and surgical treatment and follow up results are discussed.

Adolescent↗
PubMed2001

Thoracic pedicle: surgical anatomic evaluation and relations.

This anatomic study investigated the thoracic pedicle and its relations. The objective was to emphasize the importance of the thoracic pedicle for transpedicular screw fixation to avoid complications during surgery. Twenty cadavers were used to observe the cervical pedicle and its relations. The isthmus of the pedicle was exposed after removal of whole-posterior bony elements, including spinous processes, laminas, lateral masses, and the inferior and superior facets. The pedicle width and height, interpedicular distance, pedicle-inferior nerve root distance, pedicle-superior nerve root distance, pedicle-dural sac distance, root exit angle, and nerve root diameter were measured. There was no distance between the pedicle and dural sac in eight specimens. There was, however, a short distance in 12 remaining specimens in the upper and lower thoracic regions. The distances between the thoracic pedicle and the adjacent nerve roots ranged from 1.5 to 6.7 mm and 0.8 to 6.0 mm superiorly and inferiorly at all levels. The mean pedicle height and width at T1-T12 ranged from 2.9 to 11.4 mm and 6.2 to 21.3 mm, respectively. The interpedicular distance decreased gradually from T1 to T5 and then increased gradually to T12. The mean root exit angle decreased consistently from 104 degrees to 60 degrees. The nerve root diameter was between 2.3 and 2.5 mm at the T1-T5 level and then increased consistently from 2.5 to 3.7 mm. All significant differences were noted at p < 0.05 and p < 0.01. The following suggestions are made based on these results. 1) More care should be taken when a transpedicular screw is placed in the horizontal plane. 2) Improper medial placement of the pedicle screw, especially in the middle thoracic spine, should be avoided, and the anatomic variations between individuals should be considered. 3) Because of substantial variations in the size of thoracic pedicles, utmost attention should be given to the findings of a computed tomographic evaluation before thoracic transpedicular fixation is begun.

Adult↗
PubMed2001

Effects of iloprost on vasospasm after experimental spinal cord injury: an electron and light microscopic study.

It has been increasingly reported that traumatic and ischemic insults to the spinal cord may produce tissue damage through both direct and indirect mechanisms. In spite of many theories about post-traumatic spinal cord injury, there is still no satisfactory account of the exact mechanism. Vasospasm may be related to the trauma and release of vasoconstrictor or vasoactive amines. This study aims at studying the possible protective mechanisms of iloprost, a stable analogue of prostacyclin, after spinal cord injury on the rabbit. Forty-two adult male rabbits (New Zealand albino) were inflicted injuries by epidural application of an aneurysm clip to the spinal cord. Twenty-one rabbits received an i.v. infusion of 25 microg kg(-1) x h(-1) iloprost. The remaining twenty-one rabbits received an i.v. infusion of saline as the control group. Intravenous treatment started immediately after the infliction of the spinal cord injury and lasted for 1 h. Iloprost treatment had no side effects on the general physiological parameters in the rabbits. Control and iloprost treatment groups were divided into three sub-groups. The first group of animals was deeply anesthetized and spinal cords were removed 15 min after treatment. Second and third group animals were sacrificed in the 3rd and 24th hours respectively. All spinal cords were removed for light and electron microscopic examination. The width of anteriolar smooth muscle cells and the ultrastructural analysis of sulcal arterioles and venules in the ventral median fissure of spinal cords treated by iloprost revealed less thickening in all groups especially on the 24th hour group (p < 0.01), but less thickening was observed on the 3rd hour group. Iloprost-treated groups had limited edema and moderate protection of myelin and axons. These results suggest that iloprost treatment after spinal cord injury has a highly protective effect, and the possible protective effect of iloprost is resolution of vasospasm due to spinal cord injury.

Animals↗
PubMed2000

Early protective effects of iloprost after experimental spinal cord ischemia in rabbits.

The potential role of Iloprost, a stable analogue of prostocyclin, in treating spinal cord ischemia was investigated in rabbits subjected to aortic occlusion for 15 minutes. Ten adult rabbits weighing 2-2.5 kg received an intravenous infusion of saline (SF) as a control group and 14 rabbits received an intravenous infusion of Iloprost, 25 microg/kg/h. Iloprost infusion was started immediately after clamping of the aorta and continued 60 minutes thereafter. Cortical somatosensorial evoked potentials (CSEP) were recorded during the pre-ischemic period as a baseline and post-ischemic readings were taken at 15, 30 and 60 minutes. There was no statistically significant difference between CSEP of the saline and Iloprost treated groups (p < 0.05). All animals were examined neurologically by using a modification of Tarlov scale and all subjects were then deeply anesthetized and their spinal cords were removed for light and electron microscopic examinations at 24 h after spinal cord ischemia. In order to obtain an accurate comparison of ultrastructural changes between saline treated and Iloprost treated groups, a grading scale was performed. The light microscopic and ultrastructural analysis of the Iloprost treated group revealed that there was moderate protection of the myelin and axons and edema was attenuated. Findings of this study suggest that Iloprost exerts a protective effect on spinal cord ischemia. However, further studies are needed to reveal possible mechanisms of protection provided by Iloprost.

Animals↗
PubMed2000

Effects of different doses of epidural midazolam on spinal somatosensory evoked potentials.

The aim of this study is to find out the effects of different doses of midazolam, when used epidurally, on somatosensory evoked potentials (SEP) by delaying neuronal conduction. Thirty two New Zeland albino male rabbits were divided into four groups. All rabbits were anesthetised with ketamine and xylasine combination and atracurium was used as muscle relaxant. 10 mg/kg/hr ketamine infusion was used for maintenance of anesthesia. After insertion of the epidural catheter surgically; Group 1 received 1.5 ml isotonic saline (Control), Group 2 received 150 microg/kg, Group 3 received 250 microg/kg, and Group 4 received 500 microg/kg midazolam epidurally. With the stimulation of sciatic nerve. SEP records were recorded from the epidural space. Records were received before the injection of the drug, and 20, 40, 60 minutes after injection of the drug. "Latency" results were increased according to control in all groups (including isotonic saline-control-group). Increase in latency in the control group was interpreted as due to the effect of temperature mismatch of the saline and the rabbits. While in the first and second group amplitudes showed no differences, group 3 and 4 showed decreases of up to 50%. Epidurally administered midazolam up to 150 microg/kg caused no change in SEP records, but 250 and 500 microg/kg doses caused decreases in SEP records which can lead to misinterpretation as neurological damage.

Adjuvants, Anesthesia↗
PubMed2000

The early protective effects of L-arginine and Ng-nitro-L-arginine methyl ester after experimental acute spinal cord injury. A light and electron microscopic study.

The purpose of this study was to investigate the early protective effects of L-arginine and Ng-nitro-L-arginine methyl ester (L-NAME) after acute spinal cord injury. Acute spinal cord injury was performed by epidural application of an aneurysm clip at thoracic (T) 7 - 11 level. L-arginine at a dose of 750 microg/kg/min was administered 10 min before acute spinal cord injury and continued for 30 min to 10 animals (Group II). L-NAME at a dose of 250 microg/kg/min was administered 10 min before acute spinal cord injury and continued for 30 min to 10 animals (Group III). No drug was administered to 10 animals after acute spinal cord injury (Group I). Light and electron microscopic analysis were performed in all of the groups. Oedema of perineural, axoplasm or white matter in the L-arginine-treated group was less than in Group I and Group III. Thickening in the walls of the arterioles and venules in the L-arginine-treated group was much milder than in Group I and Group III. Degeneration of myelinated axons in the L-arginine-treated group was milder than in the control group. But there was no different between Group II and Group III.

Acute Disease↗
PubMed2000

The vasorelaxant effect of dipyrone on an experimental cerebral vasospasm model in rabbits.

Cerebral vasospasm is an important clinical phenomenon associated with a high mortality rate and therefore any promising findings in the laboratory deserve assessment in clinical practice. Dipyrone (Metamizol) has been in clinical use for its non-narcotic analgesic effect since 1922. In addition to its analgesic effect, dipyrone has been shown to possess spasmolitic activity in various smooth muscle organs. In our recent study, it was shown that dipyrone also has a relaxing effect in vascular smooth muscle preparations and that the smooth muscle relaxing effect on the rabbit thoracic aorta was produced by one of dipyrone's spontaneous degradation products. The present study was designed to examine the possible effects of dipyrone on the rabbit basilar artery in a model of cerebral vasospasm. Dipyrone was shown to have a clear spasmolitic effect in the rabbit basilar artery vasospasm produced by an intracisternal injection of autologous blood. This effect was apparent with either local or intravenous administration of dipyrone. These data suggest that dipyrone is potentially useful in the treatment of patients suffering from cerebral vasospasm in combination with other agents or alone.

Animals↗
PubMed2000

Surgical anatomic evaluation of the cervical pedicle and adjacent neural structures.

OBJECTIVE: Although several clinical applications of transpedicular screw fixation in the cervical spine have been documented recently, few anatomic studies concerning the cervical pedicle are available. This study was designed to evaluate the anatomy and adjacent neural relationships of the middle and lower cervical pedicle (C3-C7). The main objective is to provide accurate information for transpedicular screw fixation in the cervical region and to minimize complications by providing a three-dimensional orientation. METHODS: Twenty cadavers were used to observe the cervical pedicle and its relationships. After removal of the posterior bony elements, including spinous processes, laminae, lateral masses, and inferior and superior facets, the isthmus of the pedicle was exposed. Pedicle width, pedicle height, interpedicular distance, pedicle-inferior nerve root distance, pedicle-superior nerve root distance, pedicle-dural sac distance, medial pedicle-dural sac distance, mean angle of the pedicle, root exit angle, and nerve root diameter were measured. RESULTS: The results indicate that there was no distance between the pedicle and the superior nerve root and between the pedicle and the dural sac in 16 specimens, whereas there was a slight distance in the lower cervical region in the 4 other specimens. The mean distance between the pedicle and the inferior nerve root for all specimens ranged from 1.0 to 2.5 mm. The mean distance between the medial pedicle and the dural sac increased consistently from 2.4 to 3.1 mm. At C3-C7, the mean pedicle height ranged from 5.2 to 8.5 mm, and the mean pedicle width ranged from 3.7 to 6.5 mm. Interpedicular distance ranged from 21.2 to 23.2 mm. The mean root exit angle ranged from 69 to 104 degrees, with the largest angle at C3 and the smallest at C6. The mean angle of the pedicle ranged from 38 to 48 degrees. The nerve root diameter increased consistently from 2.7 mm at C3 to 3.8 mm at C6 and then decreased to 3.7 mm at the C7 level. Differences in measurements were considered statistically significant at levels ranging from P < 0.05 to P < 0.01. CONCLUSION: This study indicates that improper placement of the pedicle screw medially and superiorly in the middle and lower cervical spine should be avoided and that the anatomic variations between individuals should be established by measurement.

Adult↗
PubMed2000

Anatomical projection of the cervical uncinate process in ventral, ventrolateral, and posterior decompressive surgery.

OBJECT: The cervical uncinate processes (UPs), their variations, and the relationships between the neurovascular structures and surrounding bone were investigated in this anatomical study. The object of this study was to highlight the important surgery-related considerations associated with ventral, ventrolateral, and posterior decompressive surgery. METHODS: Forty-nine adult C3-7 dry bone samples were used, and 10 measurements were obtained for each vertebra. The anterior measurements involved the cervical uncinate process (UP): height, width, length, distance between its tip and vertebral foramina, interuncinate process distance, sagittal angle with the superior margin of the vertebral body (VB), VB anteroposterior diameter, and VB width. Posterior measurements involved the vertical distance between the superior border of the lamina at the lamina-facet joint and the tip of the UP, as well as the horizontal distance between the medial-most border of the superior facet and the tip of the UP. All symmetrical structures were measured bilaterally. There were no statistically significant differences between right- and left-sided measurements in this series. The height of the UP increased gradually at each segmental level between C-3 and C-7. The width of the UP did not change with segmental level (5.0 mm at C-3 compared with 5.3 mm at C-7). On average, the length of the UP was relatively constant. The distance from the tip of the UP to vertebral foramina averaged 1 mm at the C2-3 level and 1.5 mm at the C5-6 level. Interuncinate distance and VB width gradually increased and were highly variable, which appeared to be related with osteophyte formation. There was a slight gradual increase from C-3 to lower segments, and it paralleled with the midline anteroposterior diameter of the same VB. The angle between the UP and the superior margin of the VB exhibited great variety. The posterior measurements decreased gradually from C-3 to C-7. CONCLUSIONS: Based on the data obtained in this study, a surgeon is provided with a three-dimensional orientation as well as anatomical knowledge. This knowledge also allows for a more effective neurovascular decompression by minimizing the surgery-related complications.

Adult↗
PubMed2000

The neurosurgical management of prolactinomas.

BACKGROUND: The objective was to discuss the neurosurgical management of the prolactinomas. METHODS: Five-hundred-fifty patients suffering from prolactinoma were treated with trans-sphenoidal and transcranial approach. The diagnosis of prolactinoma was based on various degree of high level prolactinemia, galactorrhea, gonodal disturbance, neurological examination and radiological findings. In all cases the adenoma was histologically verified. The patients were investigated according to the anatomo-radiological classification of Hardy and Vesina, and the range of preoperative PRL basal levels. RESULTS: Follow-up was ascertained in 81% of patients who were followed for a mean of 7.2 year (1-10 year). While the total removal percentage was 98% in the group with microprolactinoma, this ratio dropped to 63.9% for macroadenomas and 23.5% for giant adenomas. Early improvement of prolactin level ratio was 81.6% in microprolactinomas, 28.3 in macroadenomas and 11.7% in giant adenomas. Hormonal cure was 64.3% in microadenomas, 6.7% in macroadenomas and 0% in giant adenomas. The ratio of hormonal cure was decreasing in patients with high prolactin levels. In the follow-up recurrence of prolactinomas occurred in 39% of the patients. CONCLUSIONS: Medical treatment is the first step in prolactin secreting adenomas. Trans-sphenoidal microsurgery became popular in treatment of prolactinomas because of low operative morbidity and mortality. Patients with recurrence should be evaluated for second step treatment (surgery, bromocriptine, or radiotherapy).

Adolescent↗
PubMed1998

Tumours of the lateral ventricle. A retrospective review of 112 cases operated upon 1970-1997.

Between the years 1970 and 1997, 112 patients with tumors of the lateral ventricle were operated on at the University of Ankara, School of Medicine, Department of Neurosurgery. Seventy-one patients (63.4%) were male and 41 patients (36.6%) female. Headache (35.7%), nausea and vomiting (22.3%) were the most common presenting complaints. Papilloedema (42.9%), motor and sensory loss (25%) were the most common findings at neurological examination. Complete tumor removal was accomplished in 38.4% of the patients. Histopathologically, the most commonly seen types of the tumor were ependymoma (25%) and astrocytoma (21.4%). Among the various approach, the anterior transcortical (53.6%) and the posterior transcortical (16%) were the most commonly used. Eleven patients were reoperated for tumor recurrence. After surgery, radiation therapy was also performed on fourty-two patients. The morbidity and mortality rates were considerably higher before 1976 when the use of microneurosurgical techniques was introduced. After this, our morbidity and mortality rates decreased dramatically. The overall surgical mortality rate was 7.1% before 1976; during the last 10 years (n:46), it was 6.5%. In this report, our choice of operative approaches and the results will be discussed.

Adolescent↗
PubMed1998

Early protective effects of Iloprost after experimental spinal cord injury.

This investigation was undertaken to study the early protective effects of Iloprost, a stable analogue of prostacyclin, after spinal cord injury in rabbit. Sixteen adult male rabbits (New Zealand Albino) were injured by application of epidural aneurysm clip. Eight rabbits received an intravenous (i.v.) infusion of 30 micrograms kg-1 Iloprost, and eight rabbits received an infusion of saline (SF). Treatment with Iloprost started immediately after spinal cord injury and continued for one hour. Evoked potentials were recorded for each rabbit at one, 15, and 60 minutes after the spinal cord injury. Twenty-four hours later, all the rabbits were deeply anesthetized and spinal cords were removed for histopathological examinations. There was no meaningful statistical difference between cortical somatosensorial evoked potentials (CSEP) of the saline and Iloprost group. However, light and electron microscopic studies showed that the Iloprost treated group had moderate protection of myelin and axons; and limited edema. These results suggest that intravenous Iloprost treatment after spinal cord injury has a highly protective effect without any side effects.

Animals↗