[Cochlear nerve continuity preservation during retrosigmoid ablative osteotomy of the internal auditory canal for advanced vestibular schwannomas]. / Kontinuitätserhalt des Nervus cochlearis bei der retrosigmoidalen ablativen Osteotomie des inneren Gehörgangs bei fortgeschrittenen Vestibularisschwannomen.

The data of 86 patients with retrosigmoid microsurgical resection of vestibular schwannoma in tumor stage Koos II-IV were evaluated. In more than two thirds of the cases it was shown that the cochlear nerve followed the facial nerve, which is easily identified by electroneurography, in recurrent similar patterns in the region of the internal auditory canal. Starting from the fundus, this facilitated early identification and thus preservation of continuity of the cochlear nerve in the course of the internal auditory canal. This was of particular importance when safe functional preservation could not be guaranteed due to tumor size or formation despite intraoperative derivation of somatosenoric potentials, but when the possibility of subsequent hearing rehabilitation with a cochlear implant should be granted. Preoperative MRI sequences gave an indication of the possible nerve courses in some cases, but intraoperative imaging in the internal auditory canal was superior to MRI.

MTT Heterogeneity in Perfusion CT Imaging as a Predictor of Outcome after Aneurysmal SAH.

BACKGROUND AND PURPOSE: Impairment of tissue oxygenation caused by inhomogeneous microscopic blood flow distribution, the so-called capillary transit time heterogeneity, is thought to contribute to delayed cerebral ischemia after aneurysmal SAH but has so far not been systematically evaluated in patients. We hypothesized that heterogeneity of the MTT, derived from CTP parameters, would give insight into the clinical course of patients with aneurysmal SAH and may identify patients at risk of poor outcome. MATERIALS AND METHODS: We retrospectively analyzed the heterogeneity of the MTT using the coefficient of variation in CTP scans from 132 patients. A multivariable logistic regression model was used to model the dichotomized mRS outcome. Linear regression was used to eliminate variables with high linear dependence. T tests were used to compare the means of 2 groups. Furthermore, the time of the maximum coefficient of variation for MTT after bleeding was evaluated for correlation with the mRS after 6 months. RESULTS: On average, each patient underwent 5.3 CTP scans during his or her stay. Patients with high coefficient of variation for MTT presented more often with higher modified Fisher (P = .011) and World Federation of Neurosurgical Societies grades (P = .014). A high coefficient of variation for MTT at days 3-21 after aneurysmal SAH correlated significantly with a worse mRS score after 6 months (P = .016). We found no correlation between the time of the maximum coefficient of variation for MTT after bleeding and the patients' outcomes after 6 months (P = .203). CONCLUSIONS: Heterogeneity of MTT in CTP after aneurysmal SAH correlates with the patients' outcomes. Because the findings are in line with the pathophysiologic concept of the capillary transit time heterogeneity, future studies should seek to verify the coefficient of variation for MTT as a potential imaging biomarker for outcome.

Timing of Mean Transit Time Maximization is Associated with Neurological Outcome After Subarachnoid Hemorrhage.

PURPOSE: Computed tomography perfusion (CTP) has gained significant relevance for the radiological screening of patients at risk of developing delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). Particularly, the impact of MTTPEAK, i.e., the maximal mean transit time value in a series of CTP measurements, for the prediction of long-term outcome has recently been demonstrated by our group. Complementing this recent work, the present study investigated how the timing of MTTPEAK affected the long-term outcome after aneurysmal subarachnoid hemorrhage. METHODS: CTP examinations from 103 patients with clinical deterioration attributed to DCI after aSAH were retrospectively analyzed for time interval between SAH ictus and onset of MTTPEAK in association with modified Rankin Scale (mRS) 23.1 months after SAH. RESULTS: Patients with unfavorable outcome (mRS > = 2) suffered significant earlier MTTPEAK onsets than patients with favorable outcome (mRS = 0 and 1). MTTPEAK within the first week was associated with significantly higher mRS scores compared to later MTTPEAK. Timing of MTTPEAK together with the value of MTTPEAK and initial World Federation of Neurosurgical Societies (WFNS) grade was a significant predictor for an unfavorable outcome (mRS > = 2). CONCLUSIONS: The current findings suggest a presumably higher vulnerability of the brain to early microcirculatory impairments after aSAH and highlight that timing of MTT elevations could be considered for the identification of patients at increased risk for poor neurological outcome due to DCI.

An Appeal to Standardize CT- and MR-Perfusion.

Multiple treatment options and risk assessment in cerebrovascular diseases are the actual challenges in diagnostic as well as in interventional neuroradiology.Acute ischemic stroke essentially requires rapid detection of the location and extent of infarction and tissue at risk for making treatment decisions. In the acute setting, modern multiparametric perfusion imaging protocols help to determine infarct core and adjacent penumbral tissue, and they enable the estimation of collateral flow of intra- and extracranial arteries. In subacute delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) or chronic occlusive neurovascular diseases estimation of residual and collateral flow may be even more difficult.Prediction of sufficient or insufficient supply of brain tissue may be essential to balance conservative against interventional therapies. However, so far no established reliable thresholds are available for determining tissue at acute, subacute, chronic progressive, or chronic risk.Reliable and reproducible thresholds require quantitative perfusion measurements with a calibrated instrument. But the measurement instrument is not at all defined-a variety of parameter settings, different algorithms based on multiple assumptions and a wide variety of published normal and pathologic values for perfusion parameters indicate the problem. In the following text, we explain how deep the problem may be enrooted within techniques and algorithms impeding broad use of perfusion for many clinical issues.

[Subtle focal diffusion abnormality in the hippocampus]. / Subtile fokale Diffusionsstörung im Hippokampus.

A 53-year-old female patient presented with sudden onset confusion and disorientation. Further neurological examination was unremarkable and the patient showed a complete recovery after several hours. A magnetic resonance imaging (MRI) examination performed 2 days later revealed a tiny focal lesion in the lateral hippocampus in the diffusion weighted images consistent with transient global amnesia.

A comparative study of perfusion CT and 99m Tc-HMPAO SPECT measurement to assess cerebrovascular reserve capacity in patients with internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Patients with internal carotid artery (ICA) occlusion can demonstrate impaired cerebral vascular reserve (CVR). The detection of CVR using single photon emission CT (SPECT) is nowadays widely accepted as a predictor in the diagnostic pathway in patients considered for cerebral revascularization. Recently perfusion CT (PCT) gained widely acceptance in stroke imaging. The present study was aimed at comparing the results of perfusion CT (PCT) and 99m Tc-HMPAO SPECT with acetazolamide challenge in patients with ICA occlusion. METHODS: 13 patients were included in the prospective evaluation. Both PCT and 99m Tc-HMPAO SPECT were performed before and after the administration of acetazolamide. In detail, regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), adapted time to peak (Tmax) and mean transit times (MTT) were compared with SPECT data. - RESULTS: 99m Tc-HMPAO SPECT demonstrated an impairment of CVR in six patients. A preserved CVR was present in seven patients. All patients with impaired CVR proven by SPECT had a delayed MTT (mean +2.98 s) and a delayed Tmax (mean + 5.9 s), (both p <0.005 compared with the non occluded side). 66% of patients with impaired CVR in SPECT showed a complete correlation of Tmax measurements in PCT with a high positive predictive value (PPV: 88.8%). - CONCLUSION: The prospective study demonstrated a highly significant correlation of perfusion parameters as detected by 99m Tc-HMPAO SPECT and the Tmax as detected by PCT in patients with ICA occlusion. Therefore this easy-to-perform technique seems to be an adequate method for the evaluation of cerebral perfusion in patients with ICA occlusion.

[Neuroradiologic diagnostic and interventional procedures for diseases of the skull base]. / Neuroradiologische Diagnostik und Interventionen bei Prozessen an der Schädelbasis.

Besides image-guided biopsy techniques, the emphasis in the interdisciplinary cooperation between head and neck surgery and neuroradiology is on vessel-occluding and preserving measures. Knowledge of dangerous anastomoses between extracranial and intracranial vessels is crucial. The principles of vessel-occluding procedures including materials are presented and illustrated with case examples. Embolization of glomus tumors or epistaxis and preoperative permanent vessel occlusion techniques are demonstrated as well as vessel-preserving therapies, such as placement of covered stents for improving tumor resectability or after iatrogenic laceration of the internal carotid artery.

Intra-aneurysmal thrombosis as a possible cause of delayed aneurysm rupture after flow-diversion treatment.

BACKGROUND AND PURPOSE: FD technology enables reconstructive repair of otherwise difficult-to-treat intracranial aneurysms. These stentlike devices may induce progressive aneurysm thrombosis without additional implants and may initiate complete reverse vessel remodeling. The associated vascular biologic processes are as yet only partially understood. MATERIALS AND METHODS: From 12 different centers, 13 cases of delayed postprocedural aneurysm rupture were recorded and analyzed. Symptom, aneurysm location and morphology, and the time elapsed from treatment until rupture were analyzed. RESULTS: There were 10 internal carotid and 3 basilar artery aneurysms. Mean aneurysm diameter was 22 ± 6 mm. Eleven patients were symptomatic before treatment. A single FD was used for all saccular aneurysms, while fusiform lesions were treated by using multiple devices. A supplementary loose coiling of the aneurysm was performed in 1 patient only. Ten patients developed early aneurysm rupture after FD treatment (mean, 16 days; range, 2-48 days); in 3 patients, rupture occurred 3-5 months after treatment. In all cases, most of the aneurysm cavity was thrombosed before rupture. The biologic mechanisms predisposing to rupture under these conditions are reviewed and discussed CONCLUSIONS: FDs alone may modify hemodynamics in ways that induce extensive aneurysm thrombosis. Under specific conditions, however, instead of reverse remodeling and cicatrization, aggressive thrombus-associated autolysis of the aneurysm wall may result in delayed rupture.

[Evaluation of ADC mapping as an early predictor for tumor response to chemotherapy in recurrent glioma treated with bevacizumab/irinotecan: proof of principle]. / Evaluation des ADC-Mappings als Prädiktor für ein Ansprechen von Glioblastomrezidiven auf eine Therapie mit Avastin.

PURPOSE: The assessment of the radiological response of recurrent glioma is based on the Macdonald or RECIST criteria 8 to 10 weeks from the start of treatment. Magnetic resonance imaging using an apparent diffusion coefficient map may provide an earlier measure for predicting the response to therapy of recurrent glioma. MATERIALS AND METHODS: Twelve patients with recurrent high-grade glioma were enrolled in a feasibility study of pretreatment MRI on day 1, intra-treatment MRI in week 3, and post-treatment MRI in week 12. Prognostically relevant ADC values (ADCprog) of each recurrent glioma at 3 weeks were calculated as a function of their pre- and intra-therapy ADC values (ADCpre - ADCintra = ADCprog). Because we hypothesized that smaller ADC values correlate with less Brownian motion of water molecules in the extracellular space and that a higher cell density may restrain this water diffusion, we set smaller ADC values at a second time point as "progressive disease" (PD) and higher ADC values as "partial response" (PR). A change in ADCprog of less than 10 × 10⁻6mm² /sec was set as "stable disease" (SD). The ADCprog values were always calculated before the final scan after 3 months was performed. The readers were blinded to the future development of the tumor. RESULTS: In 10 of the 12 patients we could correctly predict the tumor response to chemotherapy. One patient died before the three-month control, and one recurrent glioma did not develop as predicted. ADC mapping is found to predict patient response at 3 weeks from the start of treatment, revealing that early changes in tumor diffusion values could be used as a prognostic indicator also for chemotherapeutically treated recurrences of high-grade glioma.

[Diagnostic work-up and therapy of spinal vascular malformations: an update]. / Diagnostik und Therapie der spinalen vaskulären Malformationen: Ein Update.

INTRODUCTION: Spinal vascular malformations are rare disease patterns with a clinical incidence of about 5-10/year/1 million comprising spinal arteriovenous malformations (sAVM), spinal arteriovenous fistulas (sAVF) and spinal cavernomas. Long courses of disease before diagnosis deteriorate the prognosis despite successful treatment. METHODS: Selective review of the literature in consideration of present guidelines. RESULTS: Spinal vascular pathological conditions can be classified into different subtypes especially by use of magnetic resonance imaging (MRI) and selective digital subtraction angiography (DSA). Diagnosis and treatment of spinal dural arteriovenous fistula (type I) as well as spinal arteriovenous malformations (type II-V) ideally require a close co-operation between neurosurgeons and neuroradiologists. Surgery can in general be considered as curative. Endovascular therapy of arteriovenous malformations results in reduction of size and concomitant haemodynamic effects. A curative approach is generally not possible. Particularly in cases of lumbosacral and craniosacral arteriovenous fistulas the interventional procedure provides advantages. Treatment of spinal cavernomas nowadays consists of neurosurgical approaches exclusively. The significance of radiosurgical therapy, especially with the CyberKnife, remains indistinct. Today, interdisciplinary neurosurgical and neuroradiological co-operation in specialized centres allows most spinal vascular malformations to be diagnosed at an early stage and to be treated with satisfying results.

[Modification of the retrolabyrinthine approach with hearing preservation in CPA tumors]. / Modifizierter retrolabyrinthärer Zugangsweg bei Kleinhirnbrückenwinkeltumoren zum Hörerhalt.

BACKGROUND: In an anatomical study including a CT scan of the cadaver sections by means of a virtual model analysis the option of a modified retrolabyrinthine passage to the cerebellopontine angle (CPA) preserving the Saccus endolymphaticus and the upper petrosus sinus was analysed. METHODS: Due to the individual anatomical variations of the petrosus bone the results showed several limitations with regard to the retrolabyrintine passage to the CPA. The smallest distance between the dura of the posterior fossa and the posterior semicircular canal measured in a high resolution CT was of particular importance as to how much room was available for the surgical manipulation in the retrolabyrinthine space. As the back side angle to the petrosus bone is much flatter in a translabyrinthine approach than in a retrosigmoidal approach the internal auditory canal needed to be controlled by using a 30 degree endoscope. RESULTS: In five patients the translabyrinthine approach was modified by temporarily preserving the labyrinth in an effort to remove the CPA tumors. Based on our clinical experience and on the findings of the anatomical and radiological studies we eventually removed the CPA tumors type B2 or C3 in three patients preserving hearing by using a modified retrolabyrinthine approach.

A multimodal concept in patients after severe aneurysmal subarachnoid hemorrhage: results of a controlled single centre prospective randomized multimodal phase I/II trial on cerebral vasospasm.

OBJECTIVE: Recent publications suggest that a combination of head-shaking and cisternal irrigation might reduce symptomatic cerebral vasospasm after subarachnoid hemorrhage (SAH). The present clinical prospective randomized phase I/II study was initiated in order to analyze the prophylactic effect of intracisternal lysis in combination with kinetic treatment followed by intrathecal nimodipine lavage. METHODS: Twenty patients with aneurysmal SAH, WFNS grade 2 to 5 (GCS 13-3) and Fisher grade 3 or 4 were included in this prospective randomized study which had been approved by the local Ethics Research Committee. Following insertion of a ventricular drain, securing of the aneurysm by a microsurgical or endovascular route and the insertion of two lumbar catheters, intracisternal lysis with urokinase 120 000 IU/d was performed for 48 h in the patients of the study group. Intrathecal pressure was monitored by the second lumbar catheter. After intracisternal lysis, intrathecal nimodipine lavage was applied for 7 d. For comatose patients kinetic head-rotation was also performed. Vasospasm was clinically identified with a focus on delayed neurological deficits (DINDs) by daily transcranial Doppler (TCD), computerized tomography (CT), perfusion CT (pCT) and cerebral angiography (DSA). RESULTS: There was no DIND in the study group among the patients who were awake, while two DINDs occurred in the control group. The pooled TCD flow velocities over an average period of 14 d revealed no statistically significant difference between the groups. Vasospasm-related infarction on CT was seen in two patients of the control group. Evident vasospasm on DSA appeared in three patients of the study group compared with 7 patients in the control group. Moreover there was a neurological improvement in the study population as measured by mRS at 3-month follow-up (P=0.266). In two consecutive patients randomized to the study group a paresis of the lower extremities of unknown origin occurred. As a result of these complications the study was stopped in accordance with the local Ethics Research Committee guidelines. CONCLUSION: A multimodal approach with translumbar lysis in combination with kinetic therapy followed by intrathecal nimodipine lavage proved to be effective against cerebral vasospasm and for clinical outcome. However, due to the observed complications with the occurrence of paraparesis in two patients of the study group the trial was stopped. Nevertheless, the promising preliminary results suggest a further development of the clinical protocol using a modified multimodal concept to prevent and treat cerebral vasospasm after severe SAH.

[Significance of emissary veins in surgical treatment of temporal paragangliomas]. / Stellenwert emissarischer Venen bei der operativen Therapie temporaler Paragangliome.

With the surgical removal of temporal paraganglioma, possible changes of the cerebral blood pathways of the Circle of Willis should be considered. If the cerebral blood drains dominates unilaterally and the pathway of drainage over the Bulbus venae jugularis is inadequate due to vessel malformation or variations or by intraluminal tumor growth, as for instance of temporal paragangliomas, collateral emissary vessels can take over this function by an extraordinary large lumen extension. Ignorance of such a characteristic venous drainage can lead to hemorrhagic apoplexia when such originally redundant veins are sacrificed. A presurgical angiography is, therefore, indicated. In case of vessel malformations or variations the use of computer-assisted surgery could be helpful to preserve such native emissary veins at the bony skull base, such as the condylar emissary vein in the case of a transcondylar infralabyrinthine approach.

Clinical impact of MRI perfusion disturbances and normal diffusion in acute stroke patients.

PURPOSE: In acute ischemic stroke MR-imaging typically shows diffusion abnormalities surrounded by reduced perfusion signifying the so-called ischemic penumbra. Mismatch between diffusion and perfusion abnormalities gives indication for thrombolysis. But is there an indication for thrombolytic treatment, if there is no diffusion abnormality but pathologic perfusion combined with acute stroke symptoms?. MATERIAL AND METHODS: MR-imaging of 1465 patients treated on our Stroke Unit between June 2004 and May 2007 retrospectively are analyzed. 6 patients met the inclusion criteria of severe neurological symptoms, large territorial perfusion disturbances, lack of diffusion abnormalities and complete neurological recovery after treatment. RESULTS: In all six patients MTT measurements showed a significantly depressed perfusion in the symptomatic hemisphere (p<0.02). Time-to-peak delay correlated with the mean transit time delay (0.949, p<0.01). Indication for thrombolysis was based on perfusion abnormalities and clinical symptoms. Stroke symptoms could be reversed in all patients without any complication. CONCLUSION: Whereas diffusion imaging could not reveal any abnormality, perfusion analysis legitimated therapy with systemic thrombolysis in heavily affected patients. This work underlines the importance of multimodal MR imaging for guiding treatment decisions in acute stroke patients.

Fetal MRI of the central nervous system: clinical relevance.

OBJECTIVE: Specific conditions of the mother sometimes reduce the quality of ultrasound. In these cases, fetal magnetic resonance imaging (MRI) can be performed after gestational week (GW) 18. Interpretation of subtle disorders or malformations becomes safe not before GW 23. Clinical development of children with central nervous system (CNS) disorders is not predictable with imaging alone. Statistical evidence and personal experience of the medical team are essential in counseling, but optimized imaging is helpful in being more precise. The value of fetal MRI (fMRI) is evaluated. MATERIALS AND METHODS: Twenty-five pregnant women (30.5 +/- 4.5 years) were investigated by additional fMRI. TECHNIQUE: Breath-hold technique with T2 half-Fourier acquisition single-shot turbo spin-echo and T1 FLASH-2D images in three dimensions with field of view of 350 x 400 mm. All cases have been correlated with postnatal MRI, ultrasound, and clinical follow-up. RESULTS: In all fetuses, diagnostic MRI was performed 3-10 days after ultrasound between GW 22 and 34 (GW 26.1 +/- 3.6). Sedation was not necessary. In eight cases of suspicious ultrasound, fMRI confirmed ultrasound findings. In 13 cases, additional diagnoses or exclusions of suspected findings could be established. Complete revision of diagnosis was realized in four cases. Findings could be confirmed by postnatal MRI in 11 patients. The clinical course was not predictable in cases with ambivalent prognosis. CONCLUSIONS: Prenatal diagnosis of CNS pathologies should result in parental counseling. Sufficient diagnostic information, statistical data, and experience of the involved professionals are essential. These results show that in detecting congenital CNS abnormalities fMRI is superior to ultrasound and should be considered in difficult cases.