[Experience of surgical management of trigeminal schwannomas that simultaneously spread to the middle and posterior cranial fossae].

INTRODUCTION: trigeminal schwannomas account for 0.07-0.36% of all intracranial tumors and 0.8-8% of all intracranial schwannomas. Different surgical approaches are used depending on the topographic anatomical variant of the tumor. Dumbbell-shaped tumors that spread both to the middle and posterior cranial fossae are the most challenging ones in terms of their resection. MATERIAL AND METHODS: Five patients with dumbbell-shaped trigeminal schwannomas were operated on at the Burdenko Neurosurgical Institute in 2011-2013. In four cases, tumor resection comprised two stages using the retrosigmoid suboccipital approach (RSA) and lateral extended transsphenoidal endoscopic approach (LETEA); in one case, the tumor was resected in a single session through the LETEA. If there were pronounced symptoms affecting the brainstem and/or cerebellum, tumor resection from the posterior cranial fossa through RSA was resected at the first stage (3 cases). If no symptoms were observed, tumor resection from the middle cranial fossa through LETEA was used as the first stage (2 cases). RESULTS: After two surgical stages, total, subtotal, and partial tumor resection was performed (one case each). Total tumor resection from the middle cranial fossa was achieved through LETEA in two cases. Aggravation of ipsilateral paresis of the craniocerebral nerve VI was observed after the surgery in two cases. No cases of nasal liquorrhea were observed after transnasal surgery. In one case, the cavernous segment of the internal carotid artery was damaged during LETEA, thus requiring endovascular occlusion of the damaged vessel to be performed. CONCLUSION: LETEA is an effective approach that allows resection of tumors from the middle cranial fossa and the cavernous sinus. Combined with RSA, this approach can be used for two-stage resection of dumbbell-shaped trigeminal schwannomas.

[Application of shot-latency cortical somato-sensory evoked potentials for evaluation of swallowing disorders in early period after posterior fossa surgery].

UNLABELLED: Main tasks of early postoperative period in patients after posterior fossa surgery are the timely and safe weaning from mechanical ventilation and extubation. For clinical assessment of the hypopharynx function we use an algorithm developed in the intensive care unit (ICU) of the Burdenko Scientific Research Institute of Neurosurgery. Disadvantages of the clinical test for assessment of patient's readiness for extubation are subjectivity and impossibility to use it in conditions of even superficial sedation. Shot-latency somato-sensory evoked potentials (SSEP) can be applied in conditions of sedation and objectify the brain stem deficit. The goal of the study was to define the changes of cortical SSEP in patients with disorders of swallowing after posterior fossa surgery. To assess the swallowing disorders we used a scale of swallowing disorders in intubated patients with brain stem damage. We compared results of cortical SSEP, test of swallowing disorders in intubated patients and clinical results of extubation. 17 patients with tumors of posterior fossa were included in the study. All patients were divided into two groups depending on duration of mechanical ventilation. Patients of the group-1 were successfully extubated in 4.5 hours. Patients of the group-2 were mechanically ventilated more than 15 hours because of impossibility to pass the test of readiness for extubation. RESULTS: Central conduction time symmetry index after the surgery was lower in the group-1 than in group-2. There was inverse correlation between amplitude of cortical response N20 and time from the patient's admission to the ICU until the moment of extubation. CONCLUSIONS: Asymmetry of central conduction time and decreasing of N20 amplitude can be used as additional predictor of swallowing disorder.

[Patient positioning on the operating table in neurosurgery: sitting or lying].

Efficacy and safety of microvascular decompression of trigeminal nerve depending on the position on the operating table were assessed in 200 neurosurgical patients in retrospective observational study It was shown that efficacy doesn't depend on positioning. Lying position eliminates probability of such complications as postural hypotension, hypotension during surgery, tension pneumocephalus and peripheral nerves injury. Sitting position increases risk of air venous embolism by 25 times. Lying position increases risk of postoperative nasal liquorrhea by 4 times, but eliminates risk of postoperative paresis of trigeminal nerve. It is also decreases risk of corneal reflex reduction by 3 times, hyperpathia by 2 times and paresthesias by 5 times, but increases probability of postoperative hyperesthesia by 4 times. Microvascular decompression of trigeminal nerve in lying position is safer than similar operation in sitting position.

[Botulotoxin type A (lantox) for inducing temporal ptosis in neurosurgical patients].

The aim of our study was to assess the effectiveness of the ptosis induced by injection of Lantox (botulotoxin type A) into levator muscle projection in neurosurgical patients with lagophthalmos and trophic keratitis. The study included 66 patients at the age from 11 to 67 years. Lantox dose used was 10-25 U. Ptosis appeared after 1-7 days. Complete induced ptosis developed in 1-17 days and remained within 6-150 days. Full induced eyelid ptosis developed in 44 patients. Incomplete ptosis was observed in 19 patients. Drug resistance was seen in 3 patients. Our study results demonsrated effectiveness of the induced ptosis: complete recourse of trophic keratitis at development was seen in patients with complete drug-induced ptosis and significant decrease of trophic keratitis was observed in patients with semi-ptosis.

[Endoscopic assistance in microvascular decompression of cranial nerves].

Microvascular decompression (MVD) is an effective method for treatment of trigeminal neuralgia (TN), hemifacial spasm (HFS), glossopharyngeal neuralgia (GPN). The aim of this study was to assess the role of endoscopic assistance in MVD for the treatment of cranial neuropathies. Since 2009 till 2011 133 patients with cranial neuropathies were treated by MVD in Burdenko Neurosurgical Institute, Moscow. In 22 patients (11 patients with HFS, 10 patients with TN, 1 with GPN) endoscopic assistance was applied during the MVD. We used minimally invasive retrosigmoid approach in a unilateral position. Cerebellopontine angle was explored by 30-degree or 70-degree telescope to visualize the root entry zone of trigeminal, facial or glossopharyngeal nerves and to locate the neurovascular conflict. In 9 patients with HFS and in 1 patient with TN and in another patient with GPN endoscopy discovered offending vessels that were not visible through the microscope. In all cases endoscope was used to exclude another site of compression and to verify decompression and to identify position of teflon and offending vessel after MVD. Immediately after the surgery excellent outcome was observed in 10 patients with HFS (89%), one patient was reoperated 1.5 years after first operation with positive effect. Relief of pain in early postoperative period was observed in patients with TN and GPN. There were no major complications and postoperative mortality in our series. Endoscopic assistance is very effective and helpful technique in MVD of cranial nerves, especially in cases with HFS. In this study the use of the endoscope allowed to identify the site of compression and to confirm the position of teflon after MVD.

[Monitoring the depth of anesthesia in neurosurgical patients].

The study reports the results of monitoring the depth of anesthesia with BIS technology in 456 neurosurgical patients with different neurosurgical pathology: sub- and supratentorial tumors, aneurisms, arteriovenous malformations, spinal pathology, etc. BIS reflects hypnotic state of the brain during anesthesia in almost all the cases, except for bifon-tal surgical approach when sensor placement is impossible. BIS monitoring of the depth of anesthesia is most advantageous in the following cases: epilepsy surgery, spine surgery with neurophysiological monitoring, awake craniotomy, severe cardiovascular pathology, massive blood loss, neurosurgery in pregnant patients.

[Meningioma with extracranial metastases].

The paper discusses a case of recurrent posterior skull base meningioma with extracranial metastases. Metastases of meningioma may spread through venous system, lymphatic vessels and cerebrospinal fluid, and also via contact route (implantation). Penetration of dura mater of venous sinuses leads to invasion of tumor cells and their spread into pulmonary circulation, system of vena azygos and hemiazygos, vertebral venous plexuses which may facilitate further dissemination of the tumor. Histological examination of recurrent meningiomas requires additional immunohistochemical investigation with estimation of proliferative activity.

[Bilateral bispectral index monitoring during surgery for posterior cranial fossa tumors].

The analysis of the results of bilateral monitoring of the depth of anesthesia in 22 patients with neurosurgical pathology of the posterior cranial fossa using the technique bispectral index (BIS). The results showed that more than half of the observations (at 19 and 22 patients) during the main phase of the operation (removal of the tumor) were observed differences in the BIS index values between the right and left side. In 1/3 of patients, these differences were driven by higher values of BIS on the side of surgery. By the end of removal of the tumor and, particularly, by the end of surgery there was a complete alignment of values of the BIS on the right and left.

[Endoscopically assisted removal of posterior fossa meningioma combined with microvascular decompression of trigeminal nerve root (early experience)].

The article presents an example of endoscopically assisted neurosurgical removal of petrous apex meningioma associated with trigeminal neuralgia. Endoscopy was used during the operation for control of completeness of tumor removal and for identification of offending vessel and control of position of protector. Total resection of the tumor was achieved, complete regression of trigeminal pain was observed in early postoperative period.

[Stereotactic radiotherapy and radiosurgery in treatment of patients with intracranial schwannomas].

Aim of this study is to assess the role of stereotactic radiosurgery (SRS) and radiotherapy (SRT) in management of cranial nerves schwannomas by analysis of tumor control, clinical response and variables affecting treatment outcomes. Between April 2005 and January 2009 patients with schwannomas of VIII (63), V (14) and caudal nerves (2) were treated in Burdenko Moscow Neurosurgical Institute using linear accelerator. Mean age was 49 years (13-82). In 42 cases radiation treatment was preceded by surgical resection. 13 patients had type I or II neurofibromatosis. Mean volume of the tumor was 3.9 cm3 (0.5-14.4 cm3) and 13.4 cm3 (2.8-41.3 cm3) for SRS and SRT, respectively. Mean SRS dose was 12 Gy (10.8-14.4 Gy) for vestibular schwannomas and 15 Gy (13.2-18 Gy) for schwannomas of other nerves. In hypofractionated SRT the dose of 35 Gy was delivered in 7 fractions or 30 Gy in 6 fractions. In cases of classical fractioning total dose of 50-60 Gy was divided into daily fractions of 1.8-2.0 Gy. Radiographic tumor control rate reached 97.5% at the last follow-up. 5 patients experienced trigeminal dysfunction, it was transient in 3 cases and persistent in 2. Permanent decline in House-Brackmann facial nerve scale developed in 2 of 79 patients. After treatment effective hearing (class I-II) was preserved in 7 of 9 patients (67%) who had same level of hearing before SRS. Linear accelerator-based stereotactic radiation treatment provides long-term tumor control associated with high rates of preservation of neurological functions. No further tumor surgery was necessary in 100% of cases with solitary tumors with a minimal follow-up of 5 years.

[Positional damage of the sciatic nerve during neurosurgical intervention into the posterior cranial fossa in the sitting position].

The paper describes a rare case of severe, but reversible bilateral damage to the sciatic nerve (compression neuropathy) in a patient with Blumenbach's clivus meningioma developing during 12-hour operation removing the tumor in the patient's sitting position on the operating table. The etiology and prevention of this complication are discussed.

[Surgical treatment of skull base chordomas].

The paper analyses the series of 220 observations of patients with cranial chordomas operated in Burdenko Neusurgical Institute (Moscow, Russia) since 1984 till 2007. Tumors were localized in sellar region (34.1%), clival region (32.3%), craniovertebral junction (27.3%); craniofacial chordomas were observed in 5.9% of cases, ectopias (without any connection with clivus and sphenoocipital junction)--in 0.5%. In most cases transnasal, retrosigmoid and pterional approaches were used for excision of the tumor. The paper emphasizes the problem of selection of surgical tactics, early and delayed postoperative results. 5-year survival rate was 62%, 10-year survival--47%.

[Identification of the cochlear nerve in surgical removal of vestibular schwannomas].

Review of methods which allow intraoperative identifying and monitoring of cochlear and facial nerves in resection of vestibular schwannomas is presented. We describe a case of successful identification and functional preservation of facial and cochlear nerves in a patient with acoustic neuroma. Detailed description of neurophysiological and neurosurgical aspects of surgical technique intended to preserve auditory functions is given. According to some authors, application of intraoperative neurophysiological techniques in surgery of vestibular schwannomas allows to preserve not only anatomical but also functional integrity of neural structures as well.

[Topographic variants of cranial chordomas].

The objective of this study was to investigate variants of localization of cranial chordomas. We examined 220 patients treated in Burdenko Neurosurgical Institute (Moscow, Russia) since 1985 till 2007. In the vast majority of cases (93%) tumors were localized in sellar region (34%), clivus (32%) and craniovertebral junction (27%). As addition to previously suggested classifications we distinguish special group of craniofacial chordomas (5%). Although chordomas are theoretically midline tumors, according to our data in many cases (40%) they may be lateralized.

[Rare observation of giant pituitary adenoma spreading into posterior cranial fossa].

A case observation of unusual course of pituitary adenoma is presented. In 47-year old male patient with endo-supra-laterosellar pituitary adenoma and active acromegaly 2 different tumors were discovered intraoperatively during surgery for recurrence of the primary tumor. The first tumor was pituitary adenoma with nuclear polymorphism and the second was meningotheliomatous meningioma with solitary mitoses. After surgery the patient received radiation therapy. After 5 years the patient developed visual deterioration and clinical signs of tumor of left cerebellopontine angle. After removal of posterior fossa lesion, pituitary adenoma was verified.

[Histobiological features of posterior cranial fossa meningiomas and their impact on follow-up].

Total removal of posterior cranial fossa meningiomas often leads to complications due to localization, direction and nature of tumor growth. Radical excision as well as histological grade are the principal factors determining recurrence of disease in follow-up period. The paper evaluates the role of ki67 in progression of posterior cranial fossa meningiomas. We performed 189 immunohistochemical studies and katamnestic analysis of patients operated in Burdenko Neurosurgical Institute (Moscow). We showed that level of expression of ki67 correlates with histological grade of posterior fossa meningiomas. We established that recurrence-free survival depends on ki67. This allows prediction of prognosis. Low expression of ki67 corresponds longer recurrence-free survival. If ki67 expression is over 4% recurrence within 2 years after surgery is observed significantly more frequently. Multifactor statistical analysis confirmed prognostic value of ki67 especially in females and patients below 50 because terms of recurrences in these populations are significantly smaller. Obtained data prove versatility of ki67 in neurooncology which should enable its wider application in neurosurgical clinics.

[Vascular decompression in the treatment of trigeminal neuralgia].

Trigeminal neuralgia is characterized by unilateral paroxysmal facial pain. Patients often describe this pain as "the most sever pain one can suffer". Vascular compression of trigeminal nerve root directly near brainstem by artery or vein is considered the main etiology of trigeminal neuralgia. Consequently, basic pathogenetic treatment is vascular decompression of trigeminal nerve root that allows to eliminate the cause of pain. 140 patients with trigeminal neuralgia were operated in Burdenko Neurosurgical Institute since 1998 to 2007. Pain relief after surgery was observed in 96% of cases. There was no mortality in our series, overall delayed complication rate was less than 1,5%. The article deals with clinical presentation of classic trigeminal neuralgia, evaluation of the role of MRI in diagnosis of this disease and description of surgical types of arterial and venous root compression. Authors demonstrated that high effectiveness of vascular decompression depends on correct clinical diagnosis.

[Malignant tumors involving the skull base: methods of treatment and results].

The paper presents experience with surgical and combined treatment of 197 patients with malignant tumors involving the skull base and extracranially originating. The authors have defined indications for and contraindications to different types of surgical treatment, developed methods for radical and palliative tumor removal, which are based on a comprehensive approach considering the basic principles of oncology and neurosurgery. Assessing the immediate and long-term results of surgical treatment by mathematical statistical methods could reveal the major factors influencing survival rates in patients after surgery and the duration of a relapse-free period.

[Multiple cerebral abscess caused by Nocardia brasilientis].

Streptococcus aureus, streptococci, and enterobacteria were major causative agents of abscesses of the brain. At present, associated infection is responsible for 60% of cerebral abscesses. When systemic and specific immunities are diminished, a risk for cerebral abscesses caused by fungi increases. Among them, there are the most common fungi Candida species or Aspergillus species. The paper gives an example of successful complex treatment of multiple cerebral abscesses caused by an association of Nocardia brasiliensis and Staphylococcus epidermidis. The specific feature of the observation was the correct diagnosis before intraoperative verification of cerebral abscesses. The disease developed in the presence of diminished systemic immunity and in the absence of specific immunity to Nocardia. Immunodeficiency could be caused by prior herpetic infection, Epstein-Barr disease, a wasp bite. The pathogen that was able to cause microstrokes played an indubitable role in the pathogenesis of the disease, which predisposed to the development of cerebral abscesses in patients with immunodeficiency. Impaired blood circulation in the occipital region could be also induced by wasp venom.