Vascular lesions of the internal auditory canal

We report here two cases of vascular tumors arising within the internal auditory canal, both of which presented with cerebellopontine angle symptoms and simulated acoustic neurinomas. The first case was an arteriovenous malformation that caused moderate sensorineural hearing loss, tinnitus, vertigo with lateropulsion, facial weakness, and trigeminal hypoesthesia on the same side. The second case was a venous angioma, to our knowledge the first ever reported in this location, which presented with sudden complete deafness and progressive hemifacial spasm. The latter subsided completely after successful total extirpation of this unique tumor. The literature on these extremely rare lesions is also reviewed.

Presigmoid sinus approach to petroclival meningiomas

Between August 1987 and May 1989 five patients with petroclival meningiomas were operated on at the Neurosurgical Clinic of the Krankenhaus Nordstadt. Hannover, Germany, using an original combined supra- and infratentorial presigmoid sinus approach. There were two men and three women, ranging in age from 34 to 61 years (mean, 48 years; median, 46 years). Follow-up ranged between 1 and 22 months. There was no death. Postoperatively, two patients had no useful hearing, one had a permanent facial palsy (the facial nerve had to be sacrificed intraoperatively due to its involvement with tumor), one had a permanent abducens palsy (the VI nerve was involved with tumor and had to be cut). Temporary lower (IX to XII) cranial nerve palsy was observed in all the patients; temporary VI, in two patients; temporary VII, in two patients, temporary hemiparesis, in one patient, temporary gait ataxia, in three patients; and persistent gait ataxia, in one patient. All patients had total tumor removal as assessed at surgery and with postoperative enhanced computed tomography. Four patients were independent and able to carry on normal activity, and one patient was independent at home but not outside due to severe ataxia 4 months after the operation. The presigmoid sinus avenue to the petroclival region shortens the distance to the clivus, permits a multiangled exposure of this difficult surgical area, minimizes the amount of temporal lobe retraction, preserves the integrity of the transverse sinus, and allows for better preservation of the neurovascular structures. These factors translate into a high percentage of total tumor removal and a low incidence of permanent morbidity.

Cerebellopontine angle lipoma: a rare differential diagnosis

Intracranial lipomas in an infratentorial and extra-axial location are extremely rare. The presented case of an extensive lipoma of the cerebellopontine angle (CPA) represents 0.05% of all CPA tumors operated on in our department from 1978 to 1996. The lipoma constitutes an important differential diagnosis because the clinical management differs significantly from other CPA lesions. The clinical presentation and management of the presented case are analyzed in comparison to all previously described cases of CPA lipomas. The etiology and the radiological features of CPA lipomas are reviewed and discussed. CPA lipomas are maldevelopmental lesions that may cause slowly progressive symptoms. Neuroradiology enables a reliable preoperative diagnosis. Attempts of complete lipoma resection usually result in severe neurological deficits. Therefore, we recommend a conservative approach in managing these patients. Limited surgery is indicated if the patient has an associated vascular compression syndrome or suffers from disabling vertigo.

Histopathological features of the brain, liver, kidney and spleen following an innovative polytrauma model of the mouse

OBJECT

Among the various introduced experimental traumatic brain injury models, there is a clear paucity of proper experimental polytrauma models. To overcome this experimental gap we introduced such a polytrauma model in the mouse including traumatic brain injury. Here, we report on the histopathological features of the brain, lung, kidney, spleen and liver.

MATERIALS AND METHODS

20 male C57BL mice with a mean weight of 23 g were anesthetized with ketamine and xylazine. The anaesthetized animals were subjected to a controlled cortical impact (CCI) over the left parieto-temporal cortex using rounded-tip impounder for application of a standardized brain injury. Following fracture of the right femur using a guillotine, a volume-controlled hemorrhagic shock was induced. The control groups included animals with CCI only (n=20) and animals with femur fracture plus hemorrhagic shock without CCI (n=20). Subjects were sacrified at 96 h following trauma. Brain, lung, kidney, spleen and liver of the animals underwent histopathological examinations.

RESULTS

The mortality rate at 96 h was 25% in the polytrauma group versus 10% in the control groups. Within the histopathological investigations, polytraumatized animals differ from those with a single trauma (traumatic brain injury or femur fracture with hemorrhagic shock) with various severity.

CONCLUSION

The findings of this study show that such a polytrauma model can be standardized resulting in a reproducible damage. This model fulfills the requirements of a standardized animal model. It allows adequate analogies and inferences to the clinical situation of a polytrauma in humans.

An electrophysiological study on the safety of the endoscope-assisted microsurgical removal of vestibular schwannomas

BACKGROUND

Endoscopy is being increasingly used in skull base surgery. The issue of its safety, however, has not been definitely solved.

METHODS

We evaluated the risk of thermal or mechanical iatrogenic nerve injury related to endoscope application during microsurgical removal of vestibular schwannomas (VS) in a prospective group of 30 patients (Group A). Main analysed parameters were electrophysiological monitoring data (auditory evoked potentials and EMG) during and after endoscopic observation. The structural and functional preservation of facial and cochlear nerves, radicality of tumour removal, and CSF leak rate were evaluated and compared to historical group of 50 patients (Group B), operated consecutively with classical microsurgical technique.

RESULTS

No electrophysiological changes directly related to endoscope were registered. The rate of loss of waves I, II, and V did not depend on application of endoscope and was similar in both groups. The functional and general outcome was also similar. Endoscopic inspection provided early and detailed view of anatomical relations within cerebellopontine angle and internal auditory canal and confirmed completeness of tumour removal. Total tumour removal was achieved in all patients from Group A and in 49/50 from Group B. Useful hearing after the surgery had 17/30 patients in Group A and 26/50 in Group B.

CONCLUSIONS

The application of endoscope during microsurgical removal of VS is a safe procedure that does not lead to heat-related or mechanical neural or vascular injuries. The actual significance of this additional endoscopic information, however, is related to the particular operative technique and experience of the surgeon.

Late outcome of surgical treatment of the non-specific neurogenic thoracic outlet syndrome

OBJECTIVE

Despite the relatively high incidence of the thoracic outlet syndrome, diagnostic criteria, role of surgery and optimal operative approach remain controversial. The main goal of the current study is to determine the long-term outcome of operative treatment of a series of patients with non-specific neurogenic thoracic outlet syndrome.

METHODS

A retrospective study of a consecutive group of patients with thoracic outlet syndrome was carried out. The indications for surgery relied on clinical examination. Patients with diffuse pain were excluded. In all cases, the supraclavicular approach was used. Main outcome measures were neurological status and subjective complains.

RESULTS

Nineteen patients have been operated over a period of 5 years. Total number of surgeries was 23. Pain and paresthesia on exertion were the leading symptoms in all cases. The causes of thoracic outlet syndrome were fibromuscular compression in 43.5%, cervical rib alone or in combination with a fibromuscular component in 30.4% and the first rib in 26.1%. The average follow-up was 36.3 months. In 91.7%, improvement of at least 50% was observed; 20.8% of the patients were completely symptom-free, and in 25%, the improvement was 90%. Recovery of the pre-operative motor weakness was recorded in 66.6%. The mortality and the permanent morbidity rates of the procedure were 0%.

DISCUSSION

Operative decompression of the brachial plexus via the supraclavicular approach in patients with non-specific neurogenic thoracic outlet syndrome is a safe procedure that leads to a significant neurological improvement and amelioration of complains. The indication for surgery should be based chiefly on the neurological and clinical findings.

Real-time 3T fMRI data of brain tumour patients for intra-operative localization of primary motor areas

INTRODUCTION

In patients with tumours in or near the motor cortex reliable intra-operative identification of the precentral gyrus can be difficult due to anatomical dislocation. Maps of functional magnetic resonance imaging (fMRI) based on the blood oxygen level dependent (BOLD) effect are used to localize eloquent functional areas of the brain but require postprocessing for reduction of false positive activations. We set the focus of this study on the evaluation of feasibility and clinical usefulness of using real-time fMRI t-maps without postprocessing for pre-operative planning and intra-operative localization of functional motor areas.

METHODS

Real-time fMRI t-maps from a 3-T MRI scanner were co-registered with MRI data. Ten patients were operated under general anaesthesia using 3D neuronavigation with integrated real-time fMRI t-maps. Surgical and functional outcome was compared to results of 12 patients who previously underwent wake surgeries.

RESULTS

Good neurological outcome was achieved in all treated patients. Main activation clusters on fMRI real-time maps were easily identified. Co-registered real-time fMRI data without additional postprocessing were useful in planning the surgical approach. However, due to brain shift and large voxel size of BOLD contrast signals on t-maps exact localization of borders between tumours and functional areas was not possible intra-operatively.

CONCLUSION

Our method is very simple to use and effective in guiding the neurosurgeon safely through minimally invasive craniotomies to tumours in eloquent areas without setting lesions to functional areas. Furthermore, the neurosurgeon is more independent when tumour location requires acquisition of fMRI data for pre-operative planning and intra-operative navigation.

Venous complications following petrosal vein sectioning in surgery of petrous apex meningiomas

OBJECTIVE

Meningiomas involving the petrous apex regularly show a close relationship with the superior petrosal vein which is sometimes obliterated during surgery due to its proximity to the tumour. However, there is no study available so far focusing on the frequency of postoperative venous congestion related complications following petrosal vein obliteration as well as on pre- and intraoperative findings related to them.

METHODS

Fifty-nine patients with meningiomas involving the petrous apex were analyzed concerning the intraoperative preservation or sacrifice of the petrosal vein and postoperative complications related to venous occlusion.

RESULTS

When a petrosal vein was occluded, in 9 of 30 cases venous-related complications occurred with a minor venous-congestion phenomenon in seven cases and major complications in two cases. When the petrosal vein complex was preserved, there were no similar complications.

CONCLUSION

Preservation of the petrosal venous complex, especially of large caliber veins, should be attempted whenever possible to increase the safety of surgery. In cases of petrosal vein obliteration, effective brainstem decompression following tumour removal is essential to minimizing the risk of cerebellar congestion.

Surgical planning for retrosigmoid craniotomies improved by 3D computed tomography venography

OBJECTIVE

It is impossible to precisely anticipate the crooked course of the transverse and sigmoid sinuses and their individual relationship to superficial landmarks such as the asterion during retrosigmoid approaches. This study was designed to evaluate this anatomical relationship with the help of a surgical planning system and to analyze the impact of these in vivo findings on trepanation placement in retrosigmoid craniotomies.

METHODS

In a consecutive series of 123 patients with pathologies located in the cerebellopontine angle, 72 patients underwent surgical planning for retrosigmoid craniotomies based on 3D volumetric renderings of computed tomography venography. By opacity modulation of surfaces in 3D images the position of the asterion was assessed in relationship to the transverse-sigmoid sinus transition (TST) and compared to its intraoperative localization. We evaluated the impact of this additional information on trepanation placement.

RESULTS

The spatial relationship of the asterion and the underlying TST complex could be identified and recorded in 66 out of 72 cases. In the remaining 6 cases the sutures were ossified and not visible in the 3D CT reconstructions. The asterion was located on top of the TST in 51 cases, above the TST in 4 cases, and below the TST in 11 cases. The location of the trepanation was modified in 27 cases due to the preoperative imaging findings with major and minor modifications in 10 and 17 cases, respectively.

CONCLUSION

Volume-rendered images provide reliable 3D visualization of complex and hidden anatomical structures in the posterior fossa and thereby increase the precision in retrosigmoid approaches.