Probabilistic Fiber-Tracking Reveals Degeneration of the Contralateral Auditory Pathway in Patients with Vestibular Schwannoma.

BACKGROUND AND PURPOSE: Vestibular schwannomas cause progressive hearing loss by direct damage to the vestibulocochlear nerve. The cerebral mechanisms of degeneration or plasticity are not well-understood. Therefore, the goal of our study was to show the feasibility of probabilistic fiber-tracking of the auditory pathway in patients with vestibular schwannomas and to compare the ipsi- and contralateral volume and integrity, to test differences between the hemispheres. MATERIALS AND METHODS: Fifteen patients with vestibular schwannomas were investigated before surgery. Diffusion-weighted imaging (25 directions) was performed on a 3T MR imaging system. Probabilistic tractography was performed for 3 partial sections of the auditory pathway. Volume and fractional anisotropy were determined and compared ipsilaterally and contralaterally. The laterality ratio was correlated with the level of hearing loss. RESULTS: Anatomically reasonable tracts were depicted in all patients for the acoustic radiation. Volume was significantly decreased on the hemisphere contralateral to the tumor side for the acoustic radiation and diencephalic section, while fractional anisotropy did not differ significantly. Tracking did not yield meaningful tracts in 3 patients for the thalamocortical section and in 5 patients for the diencephalic section. No statistically significant correlations between the laterality quotient and classification of hearing loss were found. CONCLUSIONS: For the first time, this study showed that different sections of the auditory pathway between the inferior colliculus and the auditory cortex can be visualized by using probabilistic tractography. A significant volume decrease of the auditory pathway on the contralateral hemisphere was observed and may be explained by transsynaptic degeneration of the crossing auditory pathway.

Contralateral biopsies in patients with testicular germ cell tumours: patterns of care in Germany and recent data regarding prevalence and treatment of testicular intra-epithelial neoplasia.

The precursor of testicular germ cell tumours (GCTs), called testicular intra-epithelial neoplasia (TIN/CIS), is safely diagnosed immunohistologically. Testicular biopsy provides a valuable tool for early detection of GCTs in risk groups. Although this knowledge is undisputed, testicular biopsies are utilized poorly. The patterns of care regarding the use of biopsies remain unknown. Uncertainty exists about the prevalence and specific treatment of TIN/CIS. We asked clinical urologists in Germany whether or not they employed contralateral biopsies in GCT patients. We evaluated the prevalence of contralateral TIN/CIS in a retrospective analysis of 780 consecutive GCT patients. All had contralateral double biopsies. Discordance of TIN/CIS findings among biopsy pairs as well as age, histology of the primary tumour and clinical stage was noted. Evaluation of data comprised descriptive statistical methods. To evaluate treatment options for TIN/CIS, we performed a literature search. 52.1% of German urologists always perform the biopsy, 17% do it mostly, 27.3% in select cases, 3.5% never. Curiously, there was a geographic north-south gradient regarding biopsy use. Contralateral TIN/CIS was found in 5%. The median ages of patients with TIN/CIS and those without were 31.8 and 34.9 years respectively (p = 0.02). The discordance rate among biopsy pairs was of 33%. Two-site biopsies provide a 17% gain in diagnostic sensitivity. Local radiotherapy with 20 Gy is the safest treatment of TIN/CIS failing in 2%. Chemotherapy has significantly lower efficacy. Contralateral testicular biopsies in GCT patients are well accepted among German urologists. The prevalence of contralateral TIN/CIS found in this series is in accordance with previous reports. Double biopsies should be the diagnostic standard because of their diagnostic superiority. Local radiotherapy with 20 Gy is the safest way of eradicating TIN/CIS. Failures occur in only 2%, usually many years after irradiation. Cisplatin-based chemotherapy is dose dependent and less effective.

Discriminating metastasised from non-metastasised seminoma based on transcriptional changes in primary tumours using NGS.

BACKGROUND: We aimed to better discriminate (occult) metastasised from non-metastasised seminoma based on transcriptional changes of small RNAs in the primary tumour. METHODS: Total RNAs including small RNAs were isolated from five testicular tumours of each, lymphogenic, occult and non-metastasised patients. Next-generation sequencing (SOLID, Life Technologies) was used to examine transcriptional changes. Small RNAs showing ⩾50 reads and a significant ⩾2-fold difference using non-metastasised tumours as the reference group were examined in univariate logistic regression analysis and combinations of two small RNAs were further examined using support vector machines. RESULTS: On average, 1.3 × 10(7), 1.4 × 10(7) and 1.7 × 10(7) small RNA reads were detectable in non-metastasised, occult and lymphogenic metastasised seminoma, respectively, of which 30-32% remained after trimming. Between 59 and 68% represented annotated reads and between 8.6 and 11% were annotated small RNA tags. Of them, 137 small RNAs showed>50 reads and a two-fold difference to the reference. In univariate analysis, 32-38 small RNAs significantly discriminated lymphogenic/occult from non-metastasised seminoma, and among these different comparisons, it were the same small RNAs in 51-88%. Many combinations of two of these small RNAs allowed a complete discrimination of metastasised from non-metastasised seminoma irrespective of the metastasis subtype. CONCLUSIONS: Metastasised and non-metastasised seminoma can be completely discriminated with a combination of two small RNAs.

Prediction of metastatic status in non-seminomatous testicular cancer.

PURPOSE: To examine the significance of 90 biomarkers for predicting metastatic status in non-seminomatous germ cell tumors (NSGCT). By predicting metastatic status, it may be possible to eliminate unnecessary therapeutic or diagnostic efforts. MATERIALS AND METHODS: We investigated 552 males who were diagnosed with non-metastatic (n = 273) and metastatic (n = 279) NSGCT between 2000 and 2011. The sample included cancers of different histologies: embryonal cell carcinoma (n = 131), teratoma (n = 55), and mixed histology (n = 366). We collected and analyzed more than 90 parameters via logistic regression: demographic characteristics, medical history, histopathological parameters, and levels of tumor markers and hormones. RESULTS: Testis histology (p = 0.004), clinical symptoms (p = 0.0005), tumor length (p = 0.005), infiltration of the rete testis (p = 0.008), invasion of lymphatic (pL1) and blood vessels (pV1) (p < 0.0001), and levels of enzymes such as LDH, ßHCG, AFP, and FSH (p values as small as <0.0001) were associated with metastatic status. With one model, we identified 14 out of 76 (18.4 %) metastatic NSGCT cases with 93-100 % certainty (positive predictive value) at 99 % specificity by the peripheral blood levels of LDH (day of operation) in combination with FSH measurements (1 day after operation). A second model included pV, tumor length, and FSH (1 day after operation). It identified 25 out of 90 (27.8 %) non-metastatic NSGCT with approximately 90 % certainty (negative predictive value) at 94-98 % sensitivity. CONCLUSIONS: No single parameter was able to discriminate metastatic from non-metastatic NSGCT, but combinations of parameters in two predictive models accurately identified the metastatic status in 23 % of the cases in our sample.

The search for biomarkers of metastatic seminoma.

PURPOSE: We screened 90 potential parameters as biomarkers of metastatic seminoma to facilitate detection and eliminate unnecessary therapeutic or diagnostic efforts. MATERIALS AND METHODS: A total of 527 men with pure seminoma (diagnosed 2000 to 2011) were followed during therapy. More than 90 demographic/anamnestic (eg age, height, weight) histopathological parameters (testicular/tumor size, testicular intraepithelial neoplasia) and levels of tumor markers (eg α-fetoprotein, ß-human chorionic gonadotropin, lactate dehydrogenase) in peripheral blood and testicular vein were collected for analysis via logistic regression. Previously described risk factors (tumors larger than 4 cm, infiltration of rete testis) were assessed separately. RESULTS: Established parameters such as tumor length (p = 0.0003), involvement of lymphatic (p <0.0001) or vascular channels (p = 0.0009), extent of primary tumor (p <0.0001) and infiltration of the tunica albuginea (p = 0.02) as well as new biomarkers such as absence of testicular intraepithelial neoplasia in tumor bearing testis (p = 0.03), testicular volume (p = 0.04) and tumor volume (p = 0.02) showed a significant association with metastatic disease. This association was also true of lactate dehydrogenase, human chorionic gonadotropin and α-fetoprotein (p <0.0001 at maximum). However, the discriminatory capacity of these biomarkers (concordance or ROC area) did not exceed 65% when examined alone or in combination, and higher values (up to 80%) were detected for enzyme levels. A subset of metastatic seminoma (2% to 27%) was detectable with high accuracy (positive predictive value 92% to 100%) based on enzyme measurements (p <0.0006). CONCLUSIONS: New biomarkers of metastatic seminoma were identified and previously described risk factors were validated. Further prospective studies of these novel parameters are warranted to verify our findings and to explore a potential use for detecting occult metastases.

Treatment of testicular intraepithelial neoplasia (intratubular germ cell neoplasia unspecified) with local radiotherapy or with platinum-based chemotherapy: a survey of the German Testicular Cancer Study Group.

BACKGROUND: The treatment of testicular intraepithelial neoplasia (TIN), the progenitor of testicular germ cell tumours (GCTs), is based on little data. PATIENTS AND METHODS: Two hundred and twenty-eight GCT patients with contralateral TIN were retrospectively enrolled. Ten had surveillance, 122 radiotherapy to testis with 18-20 Gy, 30 cisplatin-based chemotherapy (two cycles), 51 chemotherapy (three cycles), and 15 carboplatin. The study end point was a malignant event (ME), defined as detection of TIN upon control biopsy or occurrence of a second GCT. The Secondary end point was hypogonadism during follow-up. RESULTS: Numbers, proportions of ME, and median event-free survival (EFS) times were: radiotherapy N = 3, 2.5%, 11.08 years; chemotherapy (two cycles) N = 15, 50%, 3.0 years; chemotherapy (three cycles) N = 12, 23.5%, 9.83 years; carboplatin N = 10, 66%, 0.9 years; surveillance N = 5, 50%, 7.08 years. EFS is significantly different among the groups. Hypogonadism rates were in radiotherapy patients 30.8%, chemotherapy (two cycles) 13%, chemotherapy (three cycles) 17.8%, carboplatin 40%, surveillance 40%. CONCLUSIONS: Local radiotherapy is highly efficacious in curing TIN. Chemotherapy is significantly less effective and the cure rates are dose-dependent. Though hypogonadism occurs in one-third of patients, radiotherapy with 20 Gy remains the standard management of TIN.

[Coincidence of adenocarcinoma and MALT lymphoma of the prostate--first report]. / Koinzidenz Adenokarzinom und MALT-Lymphom der Prostata--Eine Erstbeschreibung.

INTRODUCTION: First description of a prostate adenocarcinoma coinciding with the rare MALT lymphoma of the prostate. CASE REPORT: 68-year-old patient with a pT2c, pN0, M0, Gleason 3 + 3 prostate carcinoma (retropubic radical prostatectomy with pelvic lymphadenectomy) and systemic indolent MALT lymphoma of the prostate (bone marrow biopsy). Therapy and course are described and further explained by referring to case reports found in the literature. In this context, possible pathogenetic mechanisms, the prognosis for this special disease and possible therapeutic approaches are discussed. CONCLUSION: MALT lymphomas of the prostate are rare, and so far a coincidence with a prostate carcinoma is unprecedented. The prostate carcinoma is treated according to stage, while the MALT lymphoma is managed according to individual treatment strategies. The histopathological classification is more important for the prognosis. Treatment with antibiotics to eradicate possible copathogenic Helicobacter pylori is discussed as an innovative therapeutic approach. The pathogenesis of the MALT lymphoma of the prostate cannot yet be clarified definitively according to a literature review.

Vestibular schwannomas and auditory function: options in large T3 and T4 tumors?

OBJECTIVE: While hearing preservation has become an accepted treatment goal, there are still major doubts whether and to what extent this aim is feasible in large tumors that cover the auditory nerve and involve the brainstem. METHODS: One thousand eight hundred (1,800) vestibular schwannomas (VS) were operated on at Nordstadt Neurosurgical Department from 1978 to 1999 by the senior surgeon (MS). There were 1,800 tumors in 1,750 patients, 1,605 patients had unilateral tumors, 145 patients had neurofibromatosis type 2 with bilateral tumors, 195 of which were treated surgically in our unit. Preservation of the cochlear nerve was attempted when ever possible. The audiometric data are analyzed by Hannover Classification System graded in steps of 20 dB by audiometry and in steps of 10% to 30% by speech discrimination. Those data were set into relation with the Hannover tumor extension grading T1 to T4. RESULTS: Overall preservation rate was 40% with considerable differences, though, depending on the preoperative hearing quality and the tumor extension. Best results were obtained for intrameatal tumors (T1) with 56% and small intra-extrameatal tumors (T2) with 57% preservation rate. While preservation rate was at 44% in medium-sized tumors (T3), it was at 20% for T4 tumors with brainstem compression or even dislocation. However, satisfactory chances were encountered in cases with normal or good preoperative hearing, on average 54%, specifically 71% in T1, 69% in T2, 58% in T3 and 29% in T4. Regarding the quality of the preserved hearing, up to one third of cases in T1 and T2 may retain their preoperative hearing level, while this ranges around 20% for T3 and 10% to 14% in T4 tumors. DISCUSSION: For long, hearing preservation in medium sized or large tumors has not received any attention because of the presumed lack of realistic chances and the expected bad quality. Obviously, hearing preservation may be achieved in relevant numbers and at satisfactory quality levels. This aspects appears important to be addressed further in view of the fact that over 70% of tumors are presented for surgery at T3 or T4 extensions. CONCLUSION: The summit of hearing preservation has not been reached as improvements are still achieved even in most difficult conditions.

Resting regional cerebral glucose metabolism in advanced Parkinson's disease studied in the off and on conditions with [(18)F]FDG-PET.

Studies of resting regional cerebral glucose consumption (rCMRGlc) in nondemented patients with Parkinson's disease (PD) have produced conflicting results, reporting both reduced and normal metabolism in advanced disease and reduced or normal metabolism after dopaminergic therapy. To investigate these issues, [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) was performed in 11 nondemented PD patients with advanced disease and 10 age-matched controls. PD patients were studied after withdrawal of all dopaminergic medication to produce a practically defined off condition, and a second time 1 hour after levodopa, resulting in a clinical on state. Dynamic PET scans and simultaneous arterialised venous blood samples of [(18)F] activity were obtained. A graphical approach was used to generate parametric images of rCMRGlc and statistical parametric mapping to localise significant metabolic changes in PD. Compared with controls, global rCMRGlc was reduced in the on but not in the off condition in PD. In both states, significant regional reductions of glucose uptake were found in the parietal, frontal, temporal cortex, and caudate nucleus. Reductions correlated with the severity of disability in frontal and temporal cortex. Direct comparison between on and off conditions revealed relatively greater reductions of uptake in the ventral/orbital frontal cortex and the thalamus during on. Results suggest that cortical and caudate hypometabolism are common in advanced PD and that caution is mandatory if [(18)F]FDG PET is being used to differentiate advanced PD from dementia and progressive supranuclear palsy where similar reductions are seen. Furthermore, in PD, administration of levodopa is associated with further hypometabolism in orbitofrontal cortex; an area known to be relevant for reversal learning where performance is typically impaired after dopaminergic treatment.

Surgical management of brainstem cavernomas.

OBJECT: A careful retrospective analysis of 36 cases was performed to evaluate the pre- and postoperative rates of morbidity that occur in patients with brainstem cavernous angiomas. METHODS: The authors evaluated immediate postoperative and follow-up outcomes with regard to clinical findings, the incidence of preoperative hemorrhage(s), location and size of the lesions, and the timing of the surgical procedure after the last hemorrhagic event. Specifically. the following parameters were analyzed: 1) number of hemorrhages; 2) the precise brainstem location (pontomesencephalic, pons, and medulla oblongata); 3) pre- and postoperative cranial nerve status; 4) pre- and postoperative motor and sensory deficits; 5) size (volume) of the lesions; and 6) pre- and postoperative Karnofsky Performance Scale (KPS) scores. Multiple hemorrhages were observed in 16 patients, particularly in those with pontomesencephalic cavernous angiomas (75%). The mean preoperative KPS score was 70.3 +/- 16.3 (+/- standard deviation). Twenty-six patients (72.2%) presented with cranial nerve impairment, 13 (36.1%) with motor deficits, and 17 (47.2%) with sensory disturbance. Volume of the lesions ranged from 0.18 to 18.18 cm3 (mean 4.75 cm3). Postoperative complications included new cranial nerve deficits in 17 patients, motor deficits in three, and new sensory disturbances in 12 patients. In a mean follow-up period of 21.5 months, KPS scores were 80 to 100 in 22 patients. Timing of surgery (posthemorrhage) and multiple hemorrhages did not influence the long-term results. Higher preoperative KPS scores and smaller-volume lesions, however, were factors associated with a better final outcome (p < 0.05). Major morbidity was related mainly to preoperative status and less to surgical treatment. The incidence of new postoperative cranial nerve deficits was clearly lower than that demonstrated preoperatively because of the brainstem hemorrhages. CONCLUSIONS: Based on these findings, resection of brainstem cavernomas is the treatment of choice in the majority of these cases because of the high incidence of morbidity related to one or often several brainstem hemorrhages.

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

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 4,417 microm2 (diameter 75 microm) 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 microsec, 160 microsec, and 240 microsec 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 kohm compared with 31.7 +/- 4.5 kohm, at 10 kHz), but the mean EABR threshold was significantly higher (51.8 microA compared with 40.5 microA, 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.

Auditory brainstem implant: part I. Auditory performance and its evolution over time.

OBJECTIVE: Evaluation of auditory performance and its evolution over time in patients with the auditory brainstem implant. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS AND METHODS: Between May 1996 and April 2000, 14 patients with neurofibromatosis type 2 underwent implantation with a multichannel auditory brainstem implant. Auditory performance data were obtained in 13 patients who had used their device on a regular daily basis for 1 to 41 months (average 19 months). Hearing evaluation was based on the results of four tests (vowel confusion, consonant confusion, Freiburger numbers, and speech-tracking test), which were performed with and without lip-reading at regular intervals after device activation. RESULTS: 12 patients received auditory sensation through the auditory brainstem implant immediately after device activation. In one patient, because of postoperative electrode migration, device activation was not successful. In this case, after the electrode array was repositioned, activation was successful. The results of the audiovisual mode 2 weeks after device activation revealed a lip-reading enhancement above the chance level in about 50% of the patients in the vowel confusion and speech-tracking tests and in 70% of the patients in the consonant confusion test. Lip-reading enhancement improved within the first 6 months and then entered a plateau phase, which was more prominent in the monosyllabic vowel and consonant tests. In the auditory alone mode, more than half of the patients showed their first positive result in the vowel test 3 months after device activation, but it took about 6 months until half of the patients revealed a result above the chance level in the consonant and Freiburger numbers tests. Open set speech recognition in the auditory alone mode (in the speech-tracking test) was not common and happened relatively late (within 1 year or later). DISCUSSION AND CONCLUSION: Although auditory sensation appeared immediately after device activation, a period of 6 months was necessary for relearning and adaptation of the central auditory system to the altered form of auditory information presented by the auditory brainstem implant.

Trigeminal root recording in normal trigeminal function.

Despite many investigations on the detection of trigeminal evoked potentials (TEP), there is still no consensus on a technique or interpretation of its components. In order to obtain clear TEP waveforms and analyze the origin of early components, we recorded TEP by the conventional far-field technique at the ipsilateral auricula as well as by near-field technique with a bipolar electrode at the trigeminal root just distal to the entry zone of its root. Trigeminal recordings were performed in nine patients with intrameatal vestibular schwannomas and in three with trigeminal neuralgia without trigeminal nerve deficits. In near-field recording at the trigeminal root, a triphasic response was recorded, with the first component occurring at 3.16 ms, 2.98 ms, and 4.16 ms following supraorbital, infraorbital, and mandibular nerve stimulation, respectively. Using conventional farfield TEP, the first component recorded at the trigeminal root occurred later than the first component in all other recordings. This suggests that the N2.0 component of far-field TEP is of extra-axial origin and the N5 component is of brainstem origin. The N13.0 component may be of cortical origin. We conclude that the N5.0 component and N5.0-N13.0 interpeak latency may be used as electrophysiological parameters of brainstem function during posterior fossa surgery.

Clostridium uliginosum sp. nov., a novel acid-tolerant, anaerobic bacterium with connecting filaments.

An anaerobic, acid-tolerant bacterium, CK55T, was isolated from an acidic forest bog. Cells of CK55T stained Gram-negative but did not have an outer membrane. Cells were spore-forming, motile rods with peritrichous flagella, formed chains or aggregates and were linked by connecting filaments that were composed of a core and outer sheath. Cellobiose, glucose, xylose, mannose, mannitol, sucrose and peptone supported growth. Arabinose, lactose, raffinose, H2/CO2, CO/CO2, vanillate, Casamino acids and various purines and pyrimidines did not support growth. Growth on carbohydrates yielded acetate, butyrate, lactate, formate and H2 as end-products. Growth was observed at pH 4.0-9.0, with an optimum at pH 6.5, and at 10-30 degrees C, with an optimum at 20-25 degrees C. At 20 degrees C, doubling times were 4 and 6 h at pH 6.5 and 4.0, respectively. Hydrogenase activity in cell-free extracts was 12 U (mg protein)-1. CK55T did not: (i) contain detectable levels of CO, formate, lactate dehydrogenases or cytochromes; (ii) carry out dissimilatory reduction of nitrate or sulfate; or (iii) produce methane. Thus, CK55T was characterized as a non-acetogenic, fermentative chemo-organotroph. The G+C content of CK55T was 28.0 mol%. CK55T was phylogenetically most closely related to Clostridium botulinum (types B, E and F), Clostridium acetobutylicum and other saccharolytic clostridia; the 16S rRNA gene sequence similarity values to the nearest relatives of CK55T were approximately 97%. Based on morphological, physiological and phylogenetic properties of CK55T, it is proposed that CK55T be termed Clostridium uliginosum sp. nov. (= DSM 12992T = ATCC BAA-53T).

Impact of computed tomographic and magnetic resonance imaging findings on surgical outcome in petroclival meningiomas.

OBJECTIVE: The preoperative radiological findings of computed tomographic and magnetic resonance imaging scans of 70 patients with petroclival meningioma were evaluated and statistically compared with the degree of surgical resection and patients' outcomes to depict the most important radiological findings that may influence surgical radicality and outcome. METHODS: The following parameters were evaluated: 1) tumor diameters; 2) tumor extension toward the middle fossa, the internal auditory canal, the brainstem, and the foramen magnum; 3) bone changes; 4) peritumoral edema; 5) signs of tumor infiltrative pattern; and 6) surgical radicality. Postoperative results were analyzed immediately after the surgery and in a long-term follow-up study. RESULTS: Larger tumors affected a younger population and presented a significantly shorter time until symptom onset. In the majority of cases (67%), the tumor extended to the parasellar region. Tumor extension toward the jugular foramen was found in 24% of the patients and reached the level of the foramen magnum in 18%. Irregular tumor margins were found in 67% of the tumors, and 50% of them presented peritumoral edema in addition. Interestingly, edema also was found in 20% of tumors with well-delineated margins. CONCLUSION: Tumor size, brainstem compression, and tumor extension laterally to the internal auditory canal did not influence either the degree of surgical resection or the long-term outcome (P > 0.05). Supratentorial tumor extension to the middle fossa and downward involving the caudal cranial nerves displayed a significant importance in regard to the surgical radicality and the patient's outcome, respectively (P < 0.05). Radiological evidence of infiltrative tumor pattern and peritumoral edema at the brainstem surface were important parameters regarding surgical radicality (P < 0.05). However, only peritumoral edema influenced the long-term results significantly.

Acoustic evoked response following transection of the eighth nerve in the rat.

OBJECT: The auditory brainstem response (ABR) is the most widely used means of intra-operative monitoring of the integrity of the auditory nerve and brainstem pathways during surgery in the cerebellopontine angle (CPA). Reliability of this and other electrophysiological techniques has been questioned because of persisting potentials in direct nerve recordings despite complete eighth nerve section. The study was designed to assess the extent to which an acoustic evoked response persists after the cochlear nerve is lesioned in the CPA of the adult rat. METHODS: The eighth nerve was exposed microsurgically via a lateral suboccipital approach without damage to surrounding structures. The auditory brainstem response to monaurally presented click stimuli was recorded using needle electrodes and a bandpass of 10 to 5000 Hz. FINDINGS: Complete sharp sectioning of the nerve in the CPA resulted in immediate disappearance of brainstem-generated potentials but persistence of a large primary, vertex-positive wave in all but one case. This response was also abolished in recordings three days later and after emptying the inner ear canal. Provided that the cochlea remained intact, two weeks later a single, vertex-positive potential in the latency range of wave Ia of the ABR reappeared, reaching its peak amplitude six weeks after sectioning of the nerve. CONCLUSIONS: The short-latency electrical potential recorded following damage of the eighth nerve in the cerebellopontine angle can be mistaken for an indication that nerve function is still preserved. The evoked injury potential is probably the major contributor to this potential that resembles wave I of the ABR. Monitoring of functional auditory integrity must neither be limited to early components of the ABR, nor to the electrocochleogram (EcoG) and the peripheral compound nerve action potential (CNAP), respectively.

Subarachnoid fat dissemination after resection of a cerebellopontine angle dysontogenic cyst: case report and review of the literature.

OBJECTIVE AND IMPORTANCE: This case report illustrates the clinical and radiological relevance of extensive intracranial subarachnoid and ventricular dissemination in dysontogenic (dermoid) tumors. CLINICAL PRESENTATION: We describe a patient with a cerebellopontine angle dysontogenic tumor. Postoperatively, the cyst disseminated fat particles extensively into the subarachnoid space. Magnetic resonance imaging (MRI) studies revealed continuous dispersion of the fat particles into the cerebral cisterns, subarachnoid space, and ventricles. INTERVENTION: Eight years of clinical and MRI follow-up demonstrated neither neurological deterioration in the patient nor growth of the multiple lesions. CONCLUSION: Intracranial subarachnoid dissemination of fat material may occur during the preoperative or postoperative course of dermoid and epidermoid cysts. Aseptic meningitis or other complications such as hydrocephalus, seizures, or cranial nerve deficits also may occur owing to spillage of intracranial cyst contents into the subarachnoid space. MRI can detect the presence of fat drops that may adhere to the surrounding structures or migrate with the cerebrospinal fluid flow. Intracranial disseminated fat particles can remain silent without radiological or neurological change, justifying a wait-and-see approach. During long-term postoperative follow-up, however, regular MRI studies and clinical examinations are necessary to avoid potential complications.