Cerebellopontine Angle Pathology Research Articles

Factors associated with cerebrospinal fluid leak after a retrosigmoid approach for cerebellopontine angle surgery.

Background: The retrosigmoid approach represents a crucial surgical route to address different lesions in the cerebellopontine angle but cerebrospinal fluid (CSF) leak still remains the most frequent complication after this approach. Here, we analyzed the impact of different factors in CSF leak development after a retrosigmoid approach. Identifying risk factors related to a specific approach may help the surgeon to tailor the perioperative management and to appropriately counsel patients regarding their risk profile.Methods: We retrospectively reviewed the clinical, surgical, and outcome data of 103 consecutive patients (M/F, 47/56; mean follow-up 35.6 ± 23.9 months) who underwent a retrosigmoid approach for different cerebellopontine angle pathologies and studied the impact of different factors on the occurrence of a CSF leak to univariate and multivariate analysis.Results: Seventy-nine patients (76.7%) were operated for tumors growing in the cerebellopontine angle. Twenty-four patients (23.2%) underwent microvascular decompression to treat a drug-resistant trigeminal neuralgia. Sixteen patients (15.5%) developed CSF leak in the postoperative course of which six underwent surgical revision. Performing a craniectomy as surgical procedure (P = 0.0450) and performing a reopening procedure (second surgery; P = 0.0079) were significantly associated to a higher risk of developing CSF leak. Moreover, performing a reopening procedure emerged as an independent factor for CSF developing on multivariate analysis (P = 0.0156).Conclusion: Patients submitted to craniectomy and patients who underwent a second surgery showed an higher CSF leak rate. Ongoing improvement of biomaterial technology may help neurosurgeons to prevent this potentially life-threatening complication.

P41 Endoscopy in cerebellopontine angle lesions: feasibility and technical considerations

ObjectivesTo define selection criteria and describe technique nuances for the use of endoscopy in surgery for cerebello-pontine angle (CPA) lesions.DesignProspective observational study.SubjectsPatients undergoing CPA lesion resection were selected for endoscope-assisted and/or endoscope-guided lesion resection.MethodsCPA interventions without mass lesions were excluded. 10 CPA lesions were identified pre-operatively for intra-operative endoscopic use across two neurosurgical centres. We describe equipment and technique selection.Results10 cases were selected over a one year period. Histology revealed 3 vestibular schwannomas (VS) (30%), 1 cyst (10%), 3 epidermoids (30%), 3 meningiomata (30%). Three cases were planned and carried out fully endoscopically (including two VS and the cyst) based on patient factors and favourable anatomy. Four cases were carried out with endoscopic assistance. The endoscope was used in three cases for anatomical orientation ‘around the corner’ only. Techniques and equipment vary depending on surgical aims, surgical anatomy and working area. Tips and pitfalls are identified and described.ConclusionsEndoscopy can be applied safely in CPA pathologies, as an alternative to the operating microscope for highly selected cases, or as an adjunct for specific surgical steps, especially when microscope optics do not allow angled visualisation. It is particularly useful in identifying lesion residuum and ‘working around the corner’. High level training is required before applying endoscopy to the CPA.

Microsurgical Resection of the Epidermoid Tumor in the Cerebellopontine Angle.

In this video, we demonstrate epidermoid tumor microsurgical resection of the cerebellopontine angle (CPA) performed by the senior author (K.I.A.). Epidermoid tumors arise from ectoderm trapped within/displaced into the central nervous system. They show predilection for CPA Angle (up to 40%), 4th ventricle, suprasellar region, and spinal cord. 1 They are the 3rd most common CPA tumor, comprising approximately 7% of CPA pathology. CPA lesions can produce 5th and 7–12th cranial nerve neuropathies. 2 3 4 Recurrent episodes of aseptic meningitis caused by cyst content rupture may occur. Symptoms include fever, meningeal irritation, and hydrocephalus. A 26-year-old female presented with headaches. Head magnetic resonance imaging (MRI) revealed right CPA tumor with brain stem compression ( Fig. 1 , A – C ). There was evidence of restricted diffusion in diffusion-weighted imaging, typical of epidermoid tumor. Surgery was performed in prone position with head turned 25 degrees to the ipsilateral side using retrosigmoid craniotomy. 5 Tumor was ventral to the 7th and 8th cranial nerve complexes, between the 5th nerve as well as toward the brainstem. The surgical plan was gross total resection with tumor capsule resection to prevent recurrence. 6 (Small residuals can be left behind when capsule is adherent to critical structures.) Tumor was adherent to brain stem perforators which were preserved using meticulous dissection. Cranial nerves and vascular structures were also left intact. We irrigated with antibiotic saline and used perioperative treatment to prevent aseptic meningitis. The pathohistological diagnosis revealed epidermoid tumor cyst. Postoperative MRI revealed complete resection ( Fig. 1 , D – F ). The patient recovered fully and was neurologically intact. The link to the video can be found at: https://youtu.be/LyWl-KZUSGY .

Piezosurgery-A Safe Technique to Perform Lateral Suboccipital Craniotomy?

Piezosurgery (PS) is a relatively new technique based on microvibrations generated by the piezoelectric effect. It selectively cuts bone tissue and preserves the surrounding soft tissue. To evaluate the use of PS for performing lateral suboccipital craniotomy. PS was used to perform a lateral suboccipital craniotomy in 22 patients who underwent surgery for different cerebellopontine angle (CPA) pathologies in the neurosurgical department. The applicability of PS for lateral suboccipital craniotomy was evaluated with respect to safety, preciseness of bone cutting, and in particular the preservation of the adjacent dura and sigmoid and transverse sinuses. Lateral suboccipital craniotomy in 22 patients who underwent surgery for different CPA pathologies (13 vestibular schwannoma, 5 petrous bone meningioma, 1 petroclival meningioma, 2 epidermoid cysts, and 1 petrous bone cholesterol granuloma) was performed with PS without any complications. A burr hole was set before piezosurgical craniotomy in 6 patients, with no prior burr hole in 16 patients. Incidental durotomy during piezosurgical craniotomy occurred in 6 patients, and small lacerations of the sigmoid sinus caused by the piezosurgical device were observed in 3 patients. Although PS is a safe and selective bone cutting technique that preserves the surrounding soft tissue, it can still lead to unintended dural tears during lateral suboccipital craniotomy. This must be kept in mind when using PS for craniotomies and relying on the selective bone cutting properties of PS.

Magnetic resonance imaging of cerebellopontine angle lesions

Background: Cerebellopontine angle (CPA) tumors are usually benign, and they are divided into extra-axial, intra-axial, extradural, and petrous axis tumors. CPA pathologies can be asymptomatic or it may present with vertigo, tinnitus, or unilateral hearing loss depending upon the site of tumor origin and displacement of the neurovascular structure. Aim and Objectives: To evaluate the role of magnetic resonance imaging (MRI) aided with contrast-enhanced MRI as an imaging modality for diagnosis of CPA lesions. Materials and Methods: Analysis of 36 patients of CPA lesions over a period of 2 years was done. MRI was performed on Siemens 1.5 Tesla MAGNETOM Avanto Machine. Conclusion: There are spectrums of pathologies, which can present with these symptoms, which includes tumors, vascular malformations, and vascular loop compressing vestibulocochlear nerve or mastoid pathology so it is important to investigate the patient by MRI. Contrast-enhanced MRI is the most sensitive investigation in the evaluation of the CPA lesions, its characteristic, and its extent.

Clinical Anatomy and Diagnostic Visualization of Emissary Veins

Objective: Emissary veins are often neglected in their clinical relevance. However, at the retrosigmoid approach especially during semisitting positions these transosseous venous connections become potentially live threatening. Therefore, knowledge of presence and the configuration of emissary veins is essentially in the preoperative planning. Methods: A total of 200 consecutive patients planned for the retrosigmoid approach, due to cerebellopontine angle pathology, were evaluated by computed tomography in standard technique (5-mm slices) and spiral technique for the posterior fossa (1-mm slices). The presence and size of emissary veins, entry point in the sigmoid sinus, the predilection side, and the visibility in either CT technique were evaluated. Results: Emissary veins were present in 80% of the patients, varying from 0.3 to 4 mm in diameter, whereas 1% (right)and 2% (left) of the patients have more than one emissary vein, respectively. The mean length of the intraosseous course of the vein to the entry point in the sigmoid sinus was 7.6 mm (right side) and 5.1 mm (left side). The study shows that with standard CT technique only emissary veins larger than 1.0mm can be identified and that either entry point in the skull base or sigmoid sinus cannot be securely visualized. On the other hand, spiral technique CT scans visualized emissary veins of 0.3mm with their exact course from the skull to the entry point in the sigmoid sinus. Conclusions: Thin sliced CT scans are inevitable in the preoperative planning of the retrosigmoid approach to identify the presence and the course of emissary veins, reducing unnecessary morbidity during surgery.

An In Situ Repositioning Bone Flap in Retrosigmoid Craniotomy for Cranial Reconstruction

Osteoplastic craniotomy in retrosigmoid approaches to the cerebellopontine angle region has been suggested as an alternative to traditional osteoclastic craniectomy. It is important both for prevention of postoperative complications and for cosmetic purposes. The authors investigated a safe and effective method of cranial reconstruction by repositioning a 1-step formed bone flap without bone window extension in lateral suboccipital craniotomy. Twenty-three cases of various cerebellopontine angle pathologies, managed at the Department of Neurosurgery of the Third Affiliated Hospital of Sun Yat-Sen University from January 2011 to November 2011, had bone-flap repositioning at the original site after craniectomy during the same operative setting. All patients had preoperative three-dimensional computed tomography reconstruction of the skull. Anatomical markers were made in three-dimensional images, and individualized bone windows were designed. During operation, a 1-step formed bone flap was made according to the preoperative simulation scheme. After the intradural procedure was completed, the bone flap was repositioned and fixed in situ. No complication was observed. No delayed postcraniectomy pain occurred to any patient. Postoperative computed tomography scan of the skull showed good healing and shaping of the suboccipital bone at the surgical region. The present report provides acceptable results both clinically and radiologically. More comparative studies are required to evaluate possible advantages of this technique over osteoclastic craniectomy.

Risk Factors for Vagal Palsy following Cerebellopontine Angle Surgery

Describe the incidence, risk factors, and outcomes of postoperative vagal palsy in patients undergoing surgical excision of cerebellopontine angle (CPA) tumors. Case series with chart review. Academic tertiary care center. One hundred eighty-one consecutive patients undergoing surgical excision of CPA pathology from January 1, 2008, to December 31, 2010, at Johns Hopkins Hospital. Postoperative unilateral vagal palsy was identified by laryngoscopy or videofluoroscopy, and clinical variables were collected from medical records. Postoperative unilateral vagal palsy was identified in 19 of 181 (10%) patients. Vocal fold motion impairment (VFMI) in combination with pharyngeal palsy was more common than VFMI or pharyngeal palsy alone. Those with vagal palsy had a larger mean tumor size (30 mm) than those without vagal palsy (20 mm, P = .0002) and a significantly longer mean hospital stay (9 vs 5 days, P < .0001). Vagal palsy was not associated with tumor pathology, prior treatment (stereotactic radiation or prior surgery), or surgical approach (suboccipital craniotomy vs translabyrinthine approach). Significant rates of aspiration were observed in patients with vagal palsy (67%). Voice and swallowing function can be affected by surgical excision of pathology of the CPA. Tumor size is an independent risk factor for postoperative vagal palsy, which in turn has important consequences for prolonged hospital stay, aspiration, and voice and swallowing impairment.

Diagnostic and surgical challenges in resection of cerebellar angle tumors and acoustic neuromas.

Background:Cerebellopontine angle (CPA) lesions can mimic more common tumors through nonspecific symptoms and radiologic findings.Methods:To increase the preoperative diagnostic accuracy for CPA pathologies, the authors review the full spectrum of reported CPA lesions.Results:A wide spectrum of lesions mimics vestibular schwannoma (VS) in the space of the CPA.Conclusion:The presence of any suspicious clinical and radiographic finding uncharacteristic of VS makes it necessary to maintain a broad differential diagnosis list. Differentiation of CPA lesions, although challenging, may be best achieved by incorporating the clinical history, physical exam findings, audiometry results, and multi-modality imaging studies to construct a comprehensive preoperative knowledge of the lesion. This knowledge will allow improved operative execution and outcomes.

Prevalence, Characteristics, and Management of Swallowing Disorders following Cerebellopontine Angle Surgery

To describe swallowing disorders encountered after cerebellopontine angle surgery and to explore variables associated with increased incidence of postoperative dysphagia. Case series with chart review. Single academic medical institution. Chart review of 181 consecutive patients undergoing surgical excision of cerebellopontine angle pathology from January 2008 to December 2010 at the Johns Hopkins Hospital. Presence and characteristics of dysphagia were determined by review of speech pathologist reports. Other clinical variables were extracted from the electronic medical record, and statistical analyses were applied to determine factors associated with postoperative dysphagia. Immediate postoperative dysphagia was identified in 57 of 181 patients (31%). Oral, oropharyngeal, and pharyngeal deficits accounted for 51%, 37%, and 12% of dysphagic symptoms, respectively. Facial nerve weakness in the immediate postoperative period was noted in 91% of dysphagic subjects compared with 43% of those without. Mean House-Brackmann score for dysphagic individuals was 4 compared with 2 in the nondysphagic group. Diet alterations were required for 65% of dysphagic individuals, and an additional 9% required tube feeding. Common findings during videofluoroscopic swallowing studies were pharyngeal residue, reduced pharyngeal constriction, and anterior bolus loss. Abnormal penetration-aspiration scores (≥3) were found in 59% of those undergoing videofluoroscopic swallow studies. Oral and pharyngeal swallowing deficits are commonly encountered after cerebellopontine angle surgery. Consultation with the speech-language pathologist appears most critical for any individuals demonstrating postoperative cranial nerve dysfunction, particularly for those with evidence of facial nerve weakness. Early consultation may help to manage short- and long-term functional difficulties.

Characteristics of Dysphagia after Cerebellopontine Angle Surgery

Objective: Describe swallowing disorders encountered after Cerebellopontine Angle (CPA) surgery as well as to explore variables associated with increased incidence of postoperative dysphagia. Method: Retrospective chart review of 181 consecutive patients undergoing surgical excision of CPA pathology from January 1, 2008, to December 31, 2010, at Johns Hopkins Hospital. Presence and characteristics of dysphagia were determined by speech pathologist reports. Clinical variables were extracted from the electronic medical record. Results: Postoperative dysphagia was identified in 57 out of 181 patients (31%). Oral, oropharyngeal, and pharyngeal deficits accounted for 49%, 37%, and 12% of dysphagic symptoms respectively. Facial nerve weakness in the immediate postoperative period was noted in 91% of dysphagic subjects (mean House-Brackmann score of 4) compared with 43% of those without dysphagia (mean House-Brackman score of 2). Diet alterations were required for 65% of dysphagic individuals, and an additional 9% required tube-feeding. Common findings during Videofluoroscopic Swallowing Studies (VFSS) were pharyngeal residue, reduced pharyngeal constriction, and anterior bolus loss. Abnormal Penetration-Aspiration Scores (≥3) were found in 59% of those undergoing VFSS. Conclusion: Oral and pharyngeal swallowing deficits are commonly encountered after CPA surgery. Consultation with a speech-language pathologist appears most critical for any individuals demonstrating postoperative cranial nerve dysfunction, particularly for those with evidence of facial nerve weakness. Early consultation may help to manage short- and long-term functional difficulties.

Vagal Palsy Following Cerebellopontine Angle Surgery

Objective: 1) Understand that the vagus nerve is at risk during excision of lesions of the cerebellopontine angle (CPA), with a potential impact on voice and swallowing function. 2) Describe the incidence and risk factors for vagal palsy in patients undergoing excision of CPA tumors. Method: Retrospective chart review of 181 consecutive patients undergoing surgical excision of CPA pathology from January 1, 2008, to December 31, 2010, at Johns Hopkins Hospital. Unilateral vagal palsy was identified by laryngoscopy or cine-esophagram, and clinical variables were collected from medical records. Results: Unilateral vagal palsy was identified in 19 out of 181 (10%) patients. Vocal fold motion impairment (VFMI) in combination with pharyngeal palsy was more common than VFMI or pharyngeal palsy alone. Those with vagal palsy had a larger mean tumor size (30 mm) than those without vagal palsy (20 mm, pp with vagal palsy (67%). Conclusion: Voice and swallowing function can be affected by surgical excision of pathology of the CPA. Tumor size is an independent risk factor for postoperative vagal palsy, with consequences for prolonged hospital stay, aspiration, and voice, and swallowing impairment.

Step-by-step education of the retrosigmoid approach leads to low approach-related morbidity through young residents

Neurosurgery requires a profound knowledge of anatomy and surgical skills. The skull base approach is the crucial step for successful intradural performance. Resident training at experienced institutions must consider this background when educating young neurosurgeons. From 2006-2008, 223 retrosigmoid approaches for various cerebellopontine angle pathologies have been performed at the Department of Neurosurgery Eberhard-Karls-University, Tübingen. After a minimum time of 6 months assisting, followed by participation of dissection courses and continuous anatomical training, later performing their first approaches under direct supervision of an experienced surgeon, residents perform their first retrosigmoid approaches autonomously in the operating theatre. With this study, we evaluate the surgical morbidity and the time factor related to the educational level of the surgeon. Comparing surgical-related morbidity between approaches performed by experienced neurosurgeons (>100 procedures) and young residents (<20 procedures), we found no significant differences concerning the incidence of cerebrospinal fluid fistulae, sinus lacerations, wound infections, cranioplasty dislocations, or occipital nerve neuromas. Even the mean time for the procedure (positioning, time-to-dural incision) was not significantly longer in the trainee group. Respecting the stepwise educational levels for skull base surgery, including microanatomical studies, educational courses, and expert guidance at surgery, the retrosigmoid approach can be performed by young residents without increased morbidity at experienced institutions.

Virtual rendering techniques in otologic imaging

Virtual postprocessing techniques combine the advantages of condensing the large amounts of data provided by high-resolution (HR) cross-sectional imaging modalities with those of three-dimensional (3D) imaging. The techniques and indications for virtual representations in imaging of the middle ear (ME), internal ear (IE), and cerebellopontine angle (CPA) are presented together with practical examples. HR data sets acquired by computed tomography (CT) and magnetic resonance imaging (MRI) in patients with ME, IE, and CPA pathologies were transferred to a workstation via an internal network to generate endo- or extraluminal 3D views by means of the volume rendering technique (VRT). The source data were acquired using scanners and imaging protocols with the highest resolution available at present: a multislice spiral CT (MSCT) with a slice thickness of 0.5 mm and a reconstruction increment of 0.2 mm and a 3D CISS sequence with a slice thickness of 0.5 mm for MRI. Virtual endoscopy was superior to cross-sectional images for assessing ME pathologies like dysplasia, postoperative changes, and destructive bone processes with extensive soft-tissue involvement; fibrous obliterations of the internal ear and labyrinthine dysplasia were depicted with a superior image quality on 3D renderings compared to conventional reconstruction techniques. Virtual endoscopy of the CPA and external acoustic meatus (EAM) was helpful in detecting and visualizing neurovascular conflicts and in assigning small intrameatal tumors to components of the acousticofacial bundle. A common feature of all applications was that the large numbers of source images could be reduced to a few 3D reconstructions for documentation and optimized communication of the findings between the radiologist and otologist. Virtual rendering makes an important contribution towards establishing, presenting, and documenting the findings when certain otologic pathologies have to be assessed. It can be used for routine imaging and allows for more efficient handling of the large amounts of imaging data generated by high-resolution cross-sectional imaging modalities.

Vaskuläre Ursachen des „Kleinhirnbrückenwinkel-Syndroms”?

The seventh and eighth cranial nerves course toward the internal auditory canal within the cerebellopontine angle. Lesions in this region are usually related to malfunctions of these cranial nerves. Although an acoustic schwannoma is one of the main etiologies of cerebellopontine angle pathology, various inflammatory processes and vascular anomalies even though rare must be considered. We describe 5 cases with vascular loops of the basilar or vertebral arteries as a possible cause for hearing loss, vertigo and pulsatile tinnitus. In two cases the vascular lesion was confirmed at surgery, in which a decompression procedure was performed. The work-up for each patient included an auditory test battery and electronystagmography. Imaging studies included MRI and angiography in two cases. Our experiences show that while the cerebellopontine angle syndrome is mostly caused by benign tumors an abnormal vascular loop has to be considered in any differential diagnosis.

Gadolinium-DTPA-enhanced magnetic resonance scanning in cerebellopontine angle tumors.

Magnetic resonance (MR) imaging has quickly emerged and already replaced computerized tomography (CT) in the evaluation of cerebellopontine angle (CPA) lesions, although even MR scanning may occasionally yield equivocal results. We recently studied six patients with a new MR image-enhancing contrast, gadolinium-DTPA (Gd-DTPA). All patients were suspected of having CPA pathology, and the standard MR scan was either negative, equivocal, or left unanswered questions regarding confirmed lesions. The Gd-DTPA-enhanced MR scan confirmed tumors or added useful information in five of six patients.

Cerebellopontine pantopaque cisternography and tomography of the internal acoustic meatus in the diagnosis of angle tumors.

The results of 106 consecutive Pantopaque cisternographies performed at the neuro-radiological department, Rigshospitalet, are presented. 41 positive and 65 negative examinations were found. Good accordance between radiological tumor size estimation and size of actual, surgically verified tumor was noted. A comparison between tomography of the internal auditory canal and pantopaque cisternography of the posterior fossa has been made, and we found 6 cases with normal tomography and positive cisternography. Furthermore 17 cases (26%) with pathological tomographic examination of internal auditory canal as well as a negative finding at Pantopaque cisternography, were encountered. Therefore we conclude that asymmetry of the radiological appearance of the internal auditory canal at tomography is not of decisive importance in the indication for cisternography, but the examination should be included in the test battery in search for cerebellopontine angle pathology. We agree with other authors that Pantopaque cisternography is without any doubt the final and most conclusive examination available for the diagnosis of cerebellopontine angle tumors. A system of grading the different objective findings giving indication for Pantopaque cisternography has been made.

Computer tomography in the diagnosis of cerebellopontine angle tumours.

53 patients clinically suspected of having a cerebellopontine angle (CPA) lesion were examined by computer tomography (CT) with 160 X 160 matrix EMI scanner. 17 cases (32%) had tumour positive CT, of which 12 were neurinomas and 1 meningioma. 1 CT suggestive of a CPA lesion was false positive and 1 unoperated case is probably a false negative CT. Three of the eleven verified neurinomas (27%) were of the medial type originating in the angle cistern. One neurinoma protruding 1 cm into the cistern showed no contrast enhancement. 2 CT scans (3.8%) were unsatisfactory due to movements and the large size of the head. CT is valuable for the investigation of CPA pathology and the diagnostic efficiency compares favourably to other neuroradiological procedures.

Intermedius nerve involvement and testing in acoustic neuromas.

The clinical findings in 125 patients with surgically confirmed acoustic neuromas are presented, with special regard to the involvement of the intermedius nerve in the diagnosis. In assessing the function of the intermedius nerve the examination of the nasolacrimal reflex and the sensation of taste on the anterior two-thirds of the tongue are used. The methods of investigation are described in detail. The material consisted of 20 medium-sized and 105 large tumours; no intracanalicular tumor was found. Hearing loss was the initial symptom in 85% of the patients, 10% had tinitus and 4% vertigo as the first symptom. Apart from the VIII cranial nerve symptoms, a defective nasolacrimal reflex was the most significant evidence of cerebellopontine angle pathology. The test was positive in 65% of the medium-sized tumours, in the entire material, 85%. The figures are higher than the incidence of trigeminal nerve symptoms. This in contrast to the reports of most authors. The tests described are simple and quick to perform, and it is emphasized that they should be applied to all patients with unilateral hearing loss of unknown origin.