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

Petra M. Klinge, Heike Beck, Thomas Brinker, Gerhard F. Walter, and Madjid Samii

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.

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Far-field responses to stimulation of the cochlear nucleus by microsurgically placed penetrating and surface electrodes in the cat

Steffen K. Rosahl, Gerhard Mark, Martin Herzog, Christos Pantazis, Farnaz Gharabaghi, Cordula Matthies, Thomas Brinker, and Madjid Samii

Object. A new generation of penetrating electrodes for auditory brainstem implants is on the verge of being introduced into clinical practice. This study was designed to compare electrically evoked auditory brainstem responses (EABRs) to stimulation of the cochlear nucleus (CN) by microsurgically implanted surface electrodes and insertion electrodes (INSELs) with stimulation areas of identical size.

Methods. Via a lateral suboccipital approach, arrays of surface and penetrating microelectrodes with geometric stimulation areas measuring 4417 µm2 (diameter 75 µm) were placed over and inserted into the CN in 10 adult cats. After recording the auditory brainstem response (ABR) at the mastoid process, the CN, and the level of the inferior colliculus, EABRs to stimulation of the CN were recorded using biphasic, charge-balanced stimuli with phase durations of 80 µsec, 160 µsec, and 240 µsec at a repetition rate of 22.3 Hz. Waveform, threshold, maximum amplitude, and the dynamic range of the responses were compared for surface and penetrating electrodes.

The EABR waveforms that appeared for both types of stimulation resembled each other closely. The mean impedance was slightly lower (30 ± 3.4 kΩ compared with 31.7 ± 4.5 kΩ, at 10 kHz), but the mean EABR threshold was significantly higher (51.8 µA compared with 40.5 µA, t = 3.5, p = 0.002) for surface electrode arrays as opposed to penetrating electrode arrays. Due to lower saturation levels of the INSEL array, dynamic ranges were almost identical between the two types of stimulation. Sectioning of the eighth cranial nerve did not abolish EABRs.

Conclusions. Microsurgical insertion of electrodes into the CN complex may be guided and monitored using techniques similar to those applied for implantation of surface electrodes. Lower thresholds and almost equivalent dynamic ranges indicate that a more direct access to secondary auditory neurons is achieved using penetrating electrodes.

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Cavernous angiomas within the internal auditory canal

Madjid Samii, Makoto Nakamura, Shahram Mirzai, Peter Vorkapic, and Andres Cervio

Object

The aim of this study was to describe the symptomatology, radiological features, and surgical treatment of patients with cavernous angiomas within the internal auditory canal (IAC).

Methods

The authors reviewed the cases of seven patients with cavernous angiomas in the IAC that had been surgically treated in the 22-year period between 1983 and 2005. All the patients had presented with sensorineural hearing loss, and four suffered from tinnitus. Four patients also reported facial symptoms such as hemispasm or progressive palsy; one of these patients had presented with sudden facial paresis due to intrameatal tumor hemorrhage. According to computed tomography (CT) results, the lesions caused enlargement of the IAC. Interestingly, these same angiomas showed variable features on magnetic resonance (MR) imaging, making their differentiation from intrameatal vestibular schwannomas (VSs) sometimes impossible. In all patients the lesions were totally removed via the suboccipital retrosigmoid approach. They could be dissected away from the facial nerve in five cases, whereas in two cases, because of the location of the lesion, the seventh cranial nerve had to be sectioned and repaired with a sural nerve graft. Transient worsening of seventh cranial nerve symptoms occurred in two patients, with postoperative improvement in each of them. The cochlear nerve could not be functionally preserved because of its extreme adherence to the tumor, although its continuity was preserved in four patients. Complete deafness was the only postoperative complication.

Conclusions

Cavernous angiomas of the IAC are very uncommon lesions that can imitate the symptoms of VSs. Although it is the most sensitive study available, MR imaging does not show sufficiently specific findings to differentiate the two lesion types. Thus, the preoperative diagnosis must be based on patient symptoms plus the CT and MR imaging features.

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Evolution of vestibular schwannoma surgery: the long journey to current success

Andrei Koerbel, Alireza Gharabaghi, Sam Safavi-Abbasi, Marcos Tatagiba, and Madjid Samii

The extraordinary improvement of patient outcome after surgical treatment for vestibular schwannomas is relatively recent and has occurred mainly over the last 30 years. The introduction of microsurgical techniques has resulted in increasing degrees of precise anatomical and functional preservation of the facial and cochlear nerves. An expanded microsurgical technique accompanied by continuous electrophysiological monitoring has resulted in marked changes in the primary goals for this surgery. Whereas in the past the primary goal of vestibular schwannoma management was to preserve the patient's life, the objective in vestibular schwannoma treatment today is to preserve neurological function.

Long-term follow-up examinations show negligible recurrence rates, indicating that the aim of preservation of nerve function does not limit the completeness of tumor removal with modern neurosurgical techniques. Despite these advances in preserving the anatomical integrity of, for example, the cochlear nerve, losses of function and even deafness may occur postoperatively in some cases. Current biological and technical research in experimental and clinical settings addresses these problems. In this article, the authors report in detail the developments achieved in vestibular schwannoma surgery and the great clinicians to whom these results can be credited.

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Microvascular Decompression

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Letters to the Editor: Vestibular schwannoma

Bo Wu, Weidong Liu, and Longyi Chen

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Evaluation of a new concept for the management of skull base chordomas and chondrosarcomas

Guenther Christian Feigl, Otto Bundschuh, Alireza Gharabaghi, Sam Safavi-Abassi, Amr El Shawarby, Madjid Samii, and Gerhard A. Horstmann

Object. Chordomas and chondrosarcomas of the skull base are rare locally invasive tumors associated with high recurrence rates. The aim of this study was to evaluate the concept of microsurgical tumor volume reduction followed by early gamma knife surgery (GKS).

Methods. Thirteen patients with 15 tumors were treated between October 2000 and June 2003. There were three patients (23.1%) with chordomas and 10 (76.9%) with chondrosarcomas. There were nine men and four women who ranged in age between 19 and 69 years. All patients first underwent maximal tumor resection. Within 2 to 10 months after surgery they were treated with GKS. The mean postoperative tumor volume treated with GKS was 9.7 cm3 (range 1.4–20.3 cm3). Follow-up computerized tomography and magnetic resonance imaging examinations with volumetric tumor analysis were performed every 6 months after GKS.

The mean treatment dose was 17 Gy and the mean isodose was 52%. The mean follow-up duration was 17 months during which there was only one tumor recurrence at the margin of the radiation field. The mean volume reduction was 35.4%.

Conclusions. Results of this treatment strategy are encouraging but the efficacy of this multimodal treatment combining surgery and early GKS requires a longer follow up.

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Meningiomas of the cerebellopontine angle with extension into the internal auditory canal

Florian Roser, Makoto Nakamura, Mehdi Dormiani, Cordula Matthies, Peter Vorkapic, and Madjid Samii

Object. Only some meningiomas of the cerebellopontine angle (CPA) extend into the internal auditory canal (IAC) or arise from its dural lining. The authors investigated cases of CPA tumors in which the meningioma was inserted in the dura mater in or at the ICA or infiltrated a cranial nerve.

Methods. The authors reviewed patient charts including surgical and clinical records, intraoperative recordings of auditory evoked potentials, records of postoperative auditory examinations, and imaging studies.

In a series of 421 patients harboring CPA meningiomas, 72 patients in whom there was dural involvement of the IAC were investigated. Total tumor resection was achieved in 86.1%. In 34 patients, opening of the IAC was required for total tumor removal; this procedure did not influence the patient functional outcome. Among patients with secondary involvement of the IAC, anatomical preservation of the facial and cochlear nerves was obtained in 94%, whereas among patients in whom the lesion arose from the dura in or at the IAC these values were 80 and 75%, respectively. Functional preservation of the seventh and eighth cranial nerves in cases of tumor extension within the IAC was 86 and 77%, respectively, whereas in cases in which the IAC was involved it was only 60%. In four of five patients in whom the tumor had its origin in the dura mater within the IAC, the seventh or eighth cranial nerve had to be sacrificed to achieve tumor removal because of the lesion's infiltrative behavior. Facial nerve reconstruction by sural grafting was performed in the same operative procedure.

Conclusions. Meningiomas of the CPA involving the IAC require special surgical management. Dural involvement of the IAC requires opening by using a diamond drill, a procedure that does not influence cranial nerve outcome. The increased rate of cranial nerve morbidity is attributed to the infiltrative behavior of these meningiomas. If affected nerve segments have to be sacrificed, immediate reconstruction enables satisfactory long-term results.

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Identification of venous variants in the pineal region with 3D preoperative computed tomography and magnetic resonance imaging navigation

A statistical study of venous anatomy in living patients

Mario Giordano, Karsten H. Wrede, Lennart H. Stieglitz, Madjid Samii, and Wolf O. Lüdemann

Object

The purpose of this study was to determine the ability of software-assisted 3D reconstruction performed using a neuronavigation system to delineate the anatomy and variation patterns of the pineal region venous complex, and then to compare these data with previous anatomical findings.

Methods

The authors retrospectively reviewed the neuroimages obtained in 100 patients with intracranial lesions (50 computed tomography [CT] scans obtained with contrast agents and 50 magnetic resonance [MR] images obtained with gadolinium) by using a neuronavigation workstation for 3D reconstruction. Particular attention was given to the internal cerebral vein, basal vein (BV), and the vein of Galen. The various connection patterns between the major vessels were classified and statistically analyzed.

Conclusions

The venous system of the pineal region shows a wide range of sex-related variations. In the female patient the absence of a BV (Type 0) is significantly more frequent than in the male. In this study the authors illustrate the ability to depict the venous drainage patterns in the pineal region for all cases studied by using 3D neuronavigation software without the need for additional examinations. This simple tool provides important information for surgical planning and may be of significant help intraoperatively.

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Neurenteric cyst of the craniocervical junction

Report of three cases

Flavio Leitao Filho, Marcos Tatagiba, Gustavo A. Carvalho, Wiebke Weichhold, Jörg Klekamp, and Madjid Samii

✓ Neurenteric cysts of the craniocervical junction (CCJ) are very rare lesions. Their origin is the subject of long-standing controversy, but a failure during the embryogenic phase may be responsible for their formation. Accurate histopathological diagnosis may be difficult due to the similarity they share with other cystic lesions such as colloidal cysts, Rathke cysts, and cystic teratomas. Surgical removal is the treatment of choice for intracranial neurenteric cysts, but in some cases, infiltration of the surrounding structures may hinder complete resection. Three cases of neurenteric cysts located at the CCJ are reported.