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The article discusses issues related to ensuring secure operation of the National Power System. The tasks of transmission system operators in that scope were presented and the power demand of the Polish National Power System on critical days in terms of power generation and demand was characterized. The article also presents the causes and course of events which took place in August 2015 when there was a critical imbalance in the Polish National Power System leading to the introduction of limitations. Then, the possibilities and types of costs connected with the possibilities of balancing the system in the periods of peak loads were characterized. The summary of the article contains the presentation of conclusions related to power balancing in the power system and reduction of related costs.

Background: Assessment of the relationship between preoperative neurological deficits and diffusion tensor imaging (DTI) parameters in patients with brain tumour within/adjacent to pyramidal tract and motor cortex. Evaluation of the difference in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in patients with low and high grade gliomas. Material and Metthods: 20 patients with supratentorial brain tumours were divided into two groups: I with preoperative neurological deficits and II without preoperative neurological deficits. 8/20 tumours were classified as low grade gliomas, 10/20 as high grade gliomas and 2/10 as metastases. All MR examinations were performed on a 3T scanner . FA and ADC values were calculated for a precentral gyrus (PCG), a posterior limb of the internal capsule (PLIC) and a pyramidal tract (PT) ipsilateral and contralateral to the tumour side. These values were compared between patients with and without preoperative neurological deficits, with low and high grade gliomas. Results: A statistical analysis revealed significant differences between patients with and without preoperative neurological deficits in PCGs and PTs ipsilateral to the tumour side. Separate analysis conducted in the group with preoperative neurological deficits showed significant statistical differences only in terms of FA values comparing ipsilateral and contralateral tumour side. No statistically significant difference was observed comparing FA and ADC values ipsilateral and contralateral to the tumour side in the group without preoperative neurological deficits and between patients with low and high grade gliomas. Conclusions: There is a relation between FA and ADC values and preoperative deficits in patients with brain tumour adjacent/within the main white matter tracts. Tumour relation to the white matter tracts is more important than the glioma WHO grade. [ABSTRACT FROM AUTHOR]

Background: Differentiation between tumor recurrence/vital tumor tissue and radionecrosis based on conventional diagnostic imaging is impossible because of the likeness of the images. In such circumstances advanced MRI techniques (PWI, DWI, 1HMRS) seem to be helpful. The aim of our study was to evaluate the diagnostic effectiveness of PWI, DWI and 1HMRS in the differentiation of the tumor recurrence from radiation related injury., Material and Methods: The retrospective analysis comprised 11 contrast-enhancing lesions observed in 8 patients treated for gliomas with radiotherapy or radiochemotherapy. 5 out of 11 contrast-enhancing lesions were tumor recurrences whereas 6 out of 11 radiation-related injuries. The MR examinations comprised of conventional MR imaging (T1-SE, T1-MPRAGE with CE, T2-TSE, T2 FLAIR) and PWI, DWI, 1HMRS. Mean and maximum rCBV values of each contrast-enhancing lesion were calculated. These values were normalized to normal appearing white matter. Mean normalized ADC ratio to normal appearing white matter and mean ADC obtained from contrast-enhancing lesions were analysed. In 1HMRS only those voxels which were placed in solid part of the contrast-enhancing lesion were analysed and Cho/Cr, Cho/NAA ratios presented., Results: Mean normalized rCBVmax (2.44 +/- 0.73 for tumor recurrence vs. 0.78 +/- 0.46 for radiation injury; p < 0.001) and mean normalized rCBVmean (1.46 +/- 0.49 for tumor recurrence vs. 0.49 +/- 0.38 for radiation injury; p < 0.005) were significantly higher in the recurrent gliomas group than in the radiation injury one. It was observed that normalized rCBVmax higher than 1.7 and normalized rCBVmean higher than 1.25 is highly indicative for recurrent glioma whereas normalized rCBVmax lower than 1.0 and normalized rCBVmean lower than 0.5 is highly indicative for radiation injury. Results obtained in DWI and 1HMRS were not statistically significant different between two analysed groups. Mean ADCce: 1.06 +/- 0.18 x 10-3 mm2/s for tumor recurrence vs. 1.13 +/- 0.13 x 10-3 mm2/s for radiation injury; p = 0.51. Mean normalized ADC: 1.55 +/- 0.39 x 10-3 mm2/s for tumor recurrence vs. 1.55 +/- 0.18 x 10-3 mm2/s for radiation injury; p = 0.98. Median Cho/Cr ratio: (2.16min/max [1.67-3.15] for tumor recurrence vs. 1.34min/max [1.13-2.37] for radiation injury; p = 0.15), median Cho/NAA ratio (1.9min/max [0.86-2.36] for tumor recurrence vs. 2.11min/max [0.97 vs. 2.87] for radiation injury; p = 0.51)., Conclusions: Among the analyzed advanced neuroimaging methods PWI seems to be most reliable in differentiation between tumor regrowth/recurrence and radiation necrosis. In these results mean rCBV is a better differing factor than max rCBV. Proton MR spectroscopy (1HMRS) and DWI do not differentiate analyzed groups with statistical significance, despite tendency to lower ADC values in recurrence group than in radiation injury one.

Background and Purpose: To present our results of the surgical treatment of central skull base tumours using the extended subfrontal approach (ESA)., Material and Methods: Twenty-six patients (8 women, 18 men) with central skull base tumours were included in the study. The neurological and performance status of the patients was assessed before and after surgery as well as at the conclusion of treatment. The approximate volume of the operated tumour, its relation to the large blood vessels, cranial nerves and brainstem, as well as consistency and vascularisation were assessed., Results: The symptom duration ranged from 1.5 to 18 months (mean: 8.3 months). Loss of olfaction was the predominant symptom in 38% of patients. Less frequent symptoms were: paresis/paralysis of the 6th cranial nerve, psychoorganic syndrome, impaired visual acuity, nasal obstruction and headache. Approximate volume of the tumours ranged from 10 to 105 ml (mean: 54.3). The most frequent histological diagnosis was chordoma (19%), meningioma (15%), followed by haemangiopericytoma, fibroma and esthesioneuroblastoma (12%). Total or subtotal resection was achieved in 77% of patients. The postoperative performance status was improved in 39%, unchanged in 27% and impaired in 15% of patients. Five patients died after the surgery., Conclusions: Extended subfrontal approach is a useful technique for removal of benign tumours expanding along the midline, superiorly and inferiorly to the skull base. For removal of malignant tumours at the same location, ESA is an alternative to a combination of transcranial approach and one of the craniofacial approaches.

Background and Purpose: The aim of this study was to present results obtained by the authors after surgical treatment of tumours involving the cavernous sinus (CS) and its surroundings., Material and Methods: Thirty-eight patients (23 females and 15 males) with tumours of the CS and its surroundings were included in the study. The neurological condition of patients and their ability to perform activities of daily living were evaluated prior to treatment, postoperatively and after completion of therapy. The following parameters were measured: approximate volume of the operated lesions; their relation to larger vessels, cranial nerves and the brainstem; consistency and vascularization., Results: The medical history of the disease ranged from 1.5 to 48 months, mean 12 months. In 89.5% of cases impaired ocular motility on the side of the lesion was the symptom indicative of the condition. The second most common group of symptoms (29%) included impairments of trigeminal nerve function. The approximate volume of all resected tumours ranged from 0.6 to 60 mL (mean 12.2 mL). In 50% of cases the resected tumours were diagnosed as meningiomas. The remaining entities included: perithelioma, hypophyseal adenoma, adenoid cystic carcinoma, neuroendocrine carcinoma, trigeminal neurinoma, chordoma, cavernous angioma and lymphoma. In 63% resections were complete. Functional capacity of patients improved in 34% of cases, remained unchanged in 53%, deteriorated in 10.5%, and one patient died., Conclusions: Surgical intervention involving the CS and its surroundings enables resection of neoplastic tumours of this anatomical region with satisfactory clinical results and low mortality. Most patients suffer from temporary paresis or paralysis of the oculomotor, trochlear and abducent nerves. Reduction of completeness of resections of CS tumours decreases the number of postoperative neurological deficits without a significant increase in the rate of lesion regrowth.

Background and Purpose: The paper aims to present individual stages of a surgical approach to the cavernous sinus (CS) and its surroundings., Material and Methods: Twelve simulations of a surgical approach to the CS and its surroundings were performed in non-fixed cadavers. The subsequent stages of simulation were recorded in photographs and drawings., Results: The starting point for the approach to the CS is a pterional craniotomy, as well as an osteotomy encompassing the anterior clinoid process and the surroundings of the superior orbital fissure, the optic canal, the foramen rotundum and the foramen ovale. The important phases of the approach include the delamination of the lateral CS wall and the mobilization of the dural rings of the internal carotid artery. Opening of the CS should be preceded with establishing proximal and distal control over the internal carotid artery., Conclusions: The surgical approach to the CS and its surroundings constitutes a repeatable method of penetration in this area of the cranial base, and it allows for limiting brain traction and preserving the anatomical integrity of the related vessel and nerve structures.

Background and Purpose: Pathological lesions of the middle cerebellar peduncle include tumours, arteriovenous malformations, cavernous angiomas and spontaneous haematomas. Because of the very low incidence of these lesions, surgical approaches to the middle cerebellar peduncle are not commonly known. The authors decided to present their own experience based on five cases operated on at the authors' institution., Material and Methods: Five patients were operated on, four with tumours and one with spontaneous haematoma of the middle cerebellar peduncle. In three patients the cerebellomedullary fissure approach was used, in one patient the paramedian supracerebellar approach, and in one patient the retrosigmoid approach., Results: In all cases neoplastic lesions and haematoma were totally removed. In each case, balance disturbances and ataxia of extremities increased or occurred as a new sign. These disturbances diminished within several weeks after the procedure. In the case of location of the lesion also in the lateral part of the pons, the authors observed peripheral paresis of the seventh cranial nerve and paresis of the sixth cranial nerve, which tended to resolve., Conclusions: Pathological lesions of the middle cerebellar peduncle can be effectively treated surgically. The cerebellomedullary fissure approach has been found to be the best because it provides greater access to the dorsal surface of the middle cerebellar peduncle and to the lateral part of the pons. The most frequent complications of the procedure were instability and ataxia as well as paresis of the sixth and seventh cranial nerve when the lesion was found in the lateral part of the pons.

Cerebral aneurysms coexistent with iatrogenic (after surgical ligation or occlusion) or idiopathic (due to atheromatosis) occlusion of an extracranial cerebral artery are very rare. The occlusion of the brachiocephalic vessels leads to the formation of a collateral circulation at two levels: the circle of Willis and the connections between collaterals of the extracranial cerebral arteries. The authors discuss different types of collateral arterial pathways as well as hemodynamic abnormalities in the case of the occlusion of the brachiocephalic vessels, particularly internal carotid artery or the innominate artery occlusion. The paper analyses the etiopathogenesis of cerebral aneurysms in view of the hemodynamic theory of cerebral aneurysms formation. The article is illustrated with own three cases of ruptured cerebral aneurysms coexistent with the occlusion of the innominate artery.

Unlabelled: The aim of the study was to assess the intermediate results of the intramedullary tumors treatment with neuroprotection including the methyvlprednisolone (MP) usage., Material and Method: In the 1995-2003 period 33 patients with intramedullary tumors were operated on in Department of Neurosurgery in Sosnowiec. They were 10 females and 23 males in the age range of 11-61 years. Neuroprotection of the spinal cord in the course of treatment included: determining operational tactics on the basis of magnetic resonance imaging (MRI) performed in three planes, using MP according to NASCIS II and in maintenance dose in the 2-7 day after the operation, SSEP monitoring, myelotomy in the form of anatomical preparation of the posterior longitudinal fissure, sparing big transverse branches of the vasocorona of the posterior column, debulking of the tumor with an ultrasonic aspirator or CO2 laser, closure of the spinal cord after the removal of the tumor with pial sutures and sutures of the arachnoidea., Results: Among the operated tumors 16 had a clear border, the remaining ones were 14 astrocytomas of varying malignancy and infiltration of the white matter of the spinal cord and 3 lipomas. Control MRI revealed a total removal of the lesion in 23 patients (70%), gross total removal in 7 patients (21%) partial removal in three patients (9%). The postoperative condition of the patients 2-3 weeks after the operation showed improvement in 12 cases (37%), no significant changes in 10 cases (30%) and deterioration in 11 cases (33%)., Conclusion: Appropriate operative tactics together with the use of the MP make the acceptable morbidity rate after radical removal of intramedullary tumors .

Background and Purpose: New surgical approaches to the tumors of the skull base necessitate removal of certain bone structures of the base. In the case of the transcondylar far-lateral approach, the whole occipital condyle and lateral mass of C1 are removed resulting in iatrogenic instability. Consequently, an occipitocervical fixation is needed. The aim of the study was to assess the usefulness of the CCD cervical system for the occipitocervical fixation in the surgery of the tumors of the craniovertebral junction., Material and Methods: The authors present the application of the CCD cervical system produced by Medtronic Sofamor-Danek in three patients who underwent surgery of tumors of the foramen magnum, clivus or craniovertebral junction. The system consists of two titanium rods, which adjusted to the curvature of the spine and the occiput, are fixed by laminar cervical and occipital hooks, fixed to the trepanation hole edge or the edge of the foramen magnum. It is also possible to use screws driven to the occipital bone if it is more than 7 mm thick., Results: The system fixation is simple and relatively short. Good stabilization was achieved in all patients. No complications caused by the implants have been observed., Conclusions: The CCD cervical system can be successfully used for the occipitocervical fixation in a lateral transcondylar approach and in the cases of other non-traumatic craniocervical instability. It is especially recommended in cases of unusual thinning of the occipital bone or in osteoporotic states.

Background and Purpose: The results of the treatment of patients with deep, supratentorial arteriovenous malformations (AVMs) located in medial hemisphere or intraventricularly are presented., Material and Methods: The paper presents the results of treatment of 17 patients. AVMs were located in the trigonum of the lateral ventricle in 4 cases (23.5%), in the splenium of the corpus callosum and its neighborhood in 4 cases (23.5%), in the parahippocampal and lingual gyrus in 3 cases (17%), in the head of the caudate nucleus in 2 cases (12%), in the hippocampus and the nucleus amygdalae in 2 cases (12%), in the anterior part of the gyrus cinguli in 1 case (6%) and in the truncus of the corpus callosum in 1 case (6%)., Results: AVMs most often manifested as intracerebral or subarachnoid hemorrhage (82%). The surgical treatment has been applied (total removal--90%), embolization with histoacryl glue (total embolization--20%) and irradiation with LINAC. The surgical treatment was performed in all patients with hemiparesis and intracerebral hematomas., Conclusion: The results of the surgical treatment are good and it fastest prevents recurrent hemorrhage from deep AVM. Incomplete embolization of AVM without the surgical treatment or radiosurgery is life threatening for the patients.

Background and Purpose: After the introduction of MR imaging to the diagnostics of brainstem tumors and after the introduction of microsurgical procedures to their treatment, the successful treatment, particularly of focal and exophytic forms of these tumors has begun all over the world. The objective of this paper is to establish indications for surgical treatment of gliomas and other tumors of brainstem, to determine surgical approaches and to establish the outcome., Material and Methods: Within the last 6 years, 12 patients with focal and exophytic tumors of the brainstem in adults were operated on. 5 tumors were located in the midbrain, 4 in the pons, 2 in the medulla oblongata and 1 was a cervicomedullary one. With one exception, all tumors were approached via the posterior fossa., Results: The total removal was performed in 75% and a subtotal one in 25% of cases. A serious complication in 2 patients was bilateral ptosis after the removal of midbrain tumors. This lesion gradually regressed. A similar dangerous complication is impaired swallowing and coughing reflex loss which, by exposing the patient to the risk of aspiration pneumonia, occurred in 2 patients. One of these patients died after the operation., Conclusions: Patients with focal and exophytic forms of the brainstem tumors in MR imaging are qualified for surgical treatment. Immediate results of the treatment depend on the localization and size of the neoplasm. A precise operative approach, use of the neurophysiological examination and postoperative care at the Intensive Care Unit are essential conditions to obtain good results of the operative treatment.

The article presents an MRI-based classification of brainstem gliomas into focal, cervicomedullary, dorsal exophytic and diffuse ones. This classification provides the basis for specifying indications for surgical treatment and outcome. The article also presents the most frequent approaches to the midbrain, pons and medulla oblongata. These approaches include the pterional, orbito-zygomatic, subtemporal transtentorial and supracerebellar approaches to the midbrain. Suboccipital, trans fourth ventricle, subtonsillar, retrosigmoid and anterior petrosal approaches were used in the case of the pons. Suboccipital, trans fourth ventricle and transcondylar approaches were applied for the removal of tumors of medulla oblongata. This paper elaborates on rare approaches: transcondylar, paramedian-supracerebellar, subtonsillar and anterior petrosal ones effectively applied in our clinic. The resection of brain stem tumors is performed by piecemeal resection and not by removal en bloc. We stress the significance of safe entry zones to the brain stem and places at the fossa rhomboidea whose impairment may cause severe disability. Lesion of trigonum nervi hypoglossi, trigonum nervi vagi, colliculus facialis and fasciculus longitudinalis medialis leads to severe disability or death of the patient.

Background and Purpose: To assess the results of the operative treatment of intramedullary gliomas., Material and Methods: In 1995-2002, 30 patients with intramedullary tumors were treated surgically in the Department of Neurosurgery in Sosnowiec. Among them 23 intramedullary gliomas were recognized. There were 8 females and 15 males aged from 11 to 61. The condition of the patients before the operation was assessed according to a modified McCormick's scale. Only two patients were found to be in a good condition -- I degree, 17 patients (74%) -- II degree or III degree and 4 patients were in a serious condition -- IV degree. Among the operated tumors only 9 had a clear border. There were 5 ependymomas (grade I) and 4 anaplastic ependymomas (grade III). The remaining ones were astrocytomas of varying malignancy and infiltration of the white matter of the spinal cord: 8 cases of fibrillary astrocytoma, 3 cases of gemistocytic astrocytoma, but one anaplastic and one case of pilocytic astrocytoma, oligoastrocytoma mixtum and anaplastic oligoastrocytoma., Results: Control MRI revealed a total removal of the lesion in 16 patients (70%), gross total removal in 5 patients (21%), partial removal in two patients (8%). Four patients died among those operated on: two in the perioperative period, the other two 9 months and 2 years after the surgery, respectively. In four patients there was observed regrowth of the lesion and one patient was re-operated on. In the second case fatal recurrence in region C2-Th6 was observed and the patient died, in the last two cases the patients were stable and thus it was decided to delay the re-operation., Conclusion: Low mortality, morbidity and recurrence rates recommend surgery as an effective treatment for intramedullary gliomas.

Background: Peridural fibrosis developing after lumbar discectomy may be responsible for as much as 20% of all Failed Back Surgery Syndrome. A variety of biological and non-biological materials have been used as a barrier to invasion of fibrous tissue into the vertebral canal., Aim: The purpose of this study was to evaluate the use of expanded polytetrafluoroethylene (ePTFE) surgical membrane (Gore-Tex membrane) to inhibit peridural fibrosis and reduce FBSS symptoms after lumbar discectomy., Material and Methods: In a prospective study we compared postoperative results in 20 patients who had an ePTFE membrane implanted during lumbar discectomy with the results in 20 patients in whom no material was implanted. The outcomes were evaluated using a questionnaire on activities of daily living according to the Low Back Outcome Score, pain grading scale -- Visual Analog Scale, assessment of Lasegue sign and MRI 18-24 months after the operation for all patients., Results: The authors found no evident positive clinical and radiological effects of using ePTFE surgical membrane during lumbar discectomy., Conclusions: 1. It is impossible to prove that ePTFE membrane used during lumbar discectomy essentially prevents postoperative peridural scar formation. 2. The use of ePTFE membrane does not improve the outcome of the surgical treatment of lumbar disc herniation.

Recent reports have shown that spontaneous spinal cord herniation in the thoracic segment of the spine may be one of the causes of the progressive spinal cord lesion. Although it was described for the first time by Wortzman in 1974, it was only in early 1990s that a growing number of publications on single cases of the condition started to be observed. In the relevant literature collected by us we found reports on 53 patients altogether. In a number of cases herniation was diagnosed only intraoperatively in spite of complex radiological diagnostics. The analysis of relevant literature shows that spontaneous or idiopathic spinal cord herniation has a very typical clinical picture and most cases share a number of features, such as the clinical condition, age and sex of the patient as well as the level and location of the entity and its radiological picture. We conclude that spontaneous herniation of the spinal cord may be not as rare as previously thought and that it should be always taken into account in differential diagnostics of progressive myelopathy in the thoracic segment in middle-aged patients, especially females.

In the last 11 years we operated on 20 patients (1.03% of all operated brain tumors) with lateral ventricular masses. Anamnesis lasted from 6 months in the case of epileptic seizures to 6 years when headache was the main symptom of disease only. Tumor was located in the anterior cornu and pars centralis in 15, in the trigonum of lateral ventricle in 2, and in the posterior cornu of the lateral ventricle in 3 cases. 13 tumors were large and in MRI the largest diameter was above 5 cm. Tumors located in the anterior cornu and pars centralis were removed using transcortical (10 cases) or transcallosal approaches (5 times). The tumor of the trigonum of ventricle was removed twice through superior parietal lobulus. Tumors of the posterior cornu were operated on via precuneus in order to save visual fields or through the occipital cortex. In 4 cases after removal of tumor the orifice in the frontal lobe was closed with fibrine glue. We totally removed tumors from lateral ventricles in 85% and subtotally in 15% of all cases. Histopathological examination revealed: astrocytoma anaplasticum in 5 cases, astrocytoma pilocyticum 4, oligodendroglioma 2, oligodendroglioma mixtum 1, papilloma plexus chorioidei 2, cystis epidermalis 2, subependymoma 1, ependymoma 1, pineocytoma 1 and haemangiona arterio-venosum 1. Two patients (10%) with diagnosis of anaplastic astrocytoma died after the operation as a result of ischemia and edema cerebri. During the follow-up examination, where the average time of observation was 3.7 years, 15 patients were found to be in a good condition (GR+MD), 1 patient was severely disabled (SD), 2 patients with anaplastic astrocytoma and pineocytoma died because of enlargement of the remnants of tumors left at first operation in spite of reoperation. Tumors of the lateral ventricle grow slowly and often achieve a large size before their clinical appearance. Most of tumors are accessible for a total or subtotal removal with acceptable morbidity and mortality rate after the operation. Long-term results depend on the size of resection and histopathological investigation.

The present study was carried out in 12 patients (7 males and 5 females) aged 16-56 years (mean age 35.9) with arteriovenous malformation diagnosed in cerebral angiography. The examination was performed by means of ATL ULTRAMARK 9 with low-frequency (2MHz to 3MHz) transducer. Assessment was made of possibilities of imaging arteriovenous malformations by transcranial colour-coded duplex sonography and of blood flow values in the studied intracranial arteries. Statistical analysis was applied of the following blood flow parameters: mean velocity, peak systolic velocity, end diastolic velocity, pulsatility index (PI), resistance index (RI), pulsatility transmission index (PTI) and relative flow velocity (RFV). The malformations were imaged using TCCS in 9 (75%) patients. In two-dimensional B mode image the angiomas displayed echogenicity similar to the surrounding brain parenchyma and could not be precisely delineated. The colour-coded imaging made possible depicting the image of the vessel loops in the AVM nidus. In two other patients the presence of angiomas was confirmed by blood flow disturbances in the feeder vessel: increased blood flow, decreased pulsatility and resistance indices, and collateral circulation. Collateralization by the contralateral internal carotid artery via the anterior communicating artery was disclosed in 9 cases. The TCCS results corresponded closely to angiographic findings. Collateral circulation via the posterior communicating artery ipsilateral to the AVM was found in 3 of 5 patients in whom it was diagnosed in cerebral angiography. Doppler findings in the patients were similar to the conventional TCD examination. In the feeding vessels significant increase in blood flow velocity and decreased pulsatility and resistance indices was observed. RFV value for the end diastolic velocity was higher than RFV for the peak systolic velocity (p < 0.001) and mean velocity. These findings suggest that the increased end diastolic velocity in the feeding vessel is higher than the mean velocity and peak systolic velocity. It is thought that the TCCS can be successfully used in early diagnosis of cerebral arterio-venous malformations and as an instrument in follow-up examination.