Rare tumors of the cerebellopontine angle]

Tumours of the cerebellopontine angle are essentially benign in adults, are generally treated surgically and require a preoperative assessment as precise as possible. MRI simplifies the diagnostic assessment; it is indicated as the first-line investigation and is usually sufficient whenever a tumour of the posterior cranial fossa is suspected. Acoustic neuromas represent 75% of all tumours of the cerebellopontine angle. Other tumours are rare and essentially consist of meningioma, detected in 10 to 14% of cases and cholesteatoma in 1 to 5% of cases. Cholesteatoma, with a pathognomonic appearance, must be distinguished from arachnoid cyst. Other tumours are exceptional. The authors define the diagnostic criteria based on their experience and present a recent review of the literature.     

桥小脑角区肿瘤的磁共振成像诊断

目的：探讨桥小脑角区肿瘤的磁共振成像（MRI）的影像学表现及鉴别诊断,以提高其诊断水平。方法总结分析经影像学及手术病理证实的桥小脑角区肿瘤共33例。其中听神经瘤14例,三叉神经瘤8例,脑膜瘤2例,胆脂瘤3例,蛛网膜囊肿4例,恶性肉芽肿1例,颈静脉球瘤1例。所有患者均行MRI平扫及增强扫描,部分病例结合CT扫描。总结分析肿瘤的形态、大小、生长方式、信号特征及强化方式。结果桥小脑角区的肿瘤以听神经瘤占首位,其次为三叉神经瘤、胆脂瘤、蛛网膜囊肿、脑膜瘤。还有一些少见的肿瘤,诸如恶性肉芽肿、颈静脉球瘤等。结论桥小脑角区肿瘤MRI表现各具有不同特性,了解这些特征有助于诊断及鉴别诊断,为临床治疗及手术提供依据。     

The radiology of epidermoid tumors of the cerebellopontine angle

Summary Angiographic, pneumoencephalographic and iophendylate cisternographic features of three recently investigated primary epidermoid tumors of the cerebellopontine angle are presented and the radiology of these lesions is reviewed. Modern neuroradiological techniques, including magnification vertebral angiography with subtraction,and fractional pneumoencephalography with multidirectional laminographic capability, can provide the correct preoperative diagnosis. Combined techniques exclude cerebellopontine angle lesions such as acoustic neuromas, meningiomas, posterior fossa aneurysms and arteriovenous malformations. The appropriate studies fully outline the epidermoid lesions, with their relationship to adjacent neural and vascular structures.

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Die Röntgendiagnostik von Epidermoiden des Kleinhirnbrückenwinkels

Zusammenfassung Beschreibung von angiographischen, pneumoencephalographischen und Pantopaque-Cisternographie-Befunden von 3 primären Epidermoiden im Kleinhirnbrückenwinkel. Durch die modernen neuroradiologischen Untersuchungsmethoden kann eine korrekte präoperative Diagnose möglich werden. Es können damit raumfordernde Prozesse im Kleinhirnbrückenwinkel-Bereich anderer Genese, wie z.B. Akustikus-Neurinome oder Meningeome, ausgeschlossen werden.

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La radiologie des tumeurs épidermoïdes de l'angle pontocérebelleux

Résumé Les auteurs rapportent les caractéristiques angiographiques pneumoencéphalographiques et cisternographiques positives de trois cas de tumeurs épidermoïdes de l'angle pontocérébelleux examinés récemment et font la revue de la radiologie de ces lésions. Les techniques neuro-radiologiques modernes comprenant l'agrandissement de l'angiographie vertébrale avec soustraction et l'encéphalographie gazeuse fractionnée avec tomographie multi-directionnelle, fournit un diagnostic pré-opératoire correct. La combinaison de ces techniques permet d'exclure des lésions de l'angle pontocérébelleux tels que neurinomes de l'acoustique, méningiome, anévrysme de la fosse postérieure et malformations artérioveineuses. Les investigations appropriées délimitent entièrement les lésions épidermoïdes, avec leur relation avec les structures nerveuses et vasculaires adjacentes.

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Supported in part by Grants # 5-T01-NS-05646-02 NSR B & # 1-F11-NS-2591-01 NSR B     

Brain stem auditory evoked potentials in various tumors in the cerebellopontine angle

Abnormalities of brainstem auditory evoked potentials of 63 patients with tumours in the pontocerebellar angle were classified in 7 types and correlated by size and nature of tumours. Types A and B brainstem responses are characteristic for small tumours up 20 mm and are indicated for computed pneumocysternography in spite of the negative CT of the brain. Type C is statistically more frequently found than larger tumours over 22 mm in size. Other types of responses which are more characteristic for tumours which are not neurinomas are described. Auditory evoked potentials are the most reliable neuro-otologic methods in detection of PCU tumours and their careful analysis provides valuable data both about the size and nature of tumours.     

Auditory evoked potentials and tumor of the cerebellopontine angle]

The technique of auditory evoked potentials evaluates the auditory pathways along the vestibulocochlear nerve and in the brainstem. The authors stress the importance of this examination in the diagnosis of tumours of the cerebellopontine angle and they discuss its place in relation to radiological investigations.     

Disorders of the cerebellopontine angle

Disorders of the cerebellopontine angle may present by symptoms like vertigo, hearing problems, affection of the trigeminal or facial nerve. Ipsilateral ataxia and contralateral hemiparesis develop in case of a rather large tumor in this region and display an involvement of the cerebellum and/or brainstem. However, some of these typical symptoms are not recognized by the patient. Thus, in case of a suspicion of a disorder of the cerebellopontine angle the relevant functions have to be tested clinically. In addition, electrophysiology can confirm dysfunction of these cranial nerves. Mainstay of the therapy should be the treatment of the underlying cause. Nevertheless, not seldom it is necessary to treat symptoms like vertigo or facial pain.     

Vascular anomalies of the cerebellopontine angle

Vascular anomalies of the cerebellopontine angle are rare compared to tumors in this area. Irritation of the trigeminal, facial, or vestibulocochlear nerve may cause trigeminal neuralgia, hemifacial spasm and vertigo, or tinnitus accordingly. Vessel loops in the cerebellopontine cisterns may cause compression at the root entry or exit zone of the cranial nerves V, VII, and VIII, a phenomenon which is called "vascular loop syndrome." Megadolichobasilar artery and aneurysms of the vertebrobasilar system can also lead to dislocation and compression of the cranial nerves and brain stem. Three-dimensional CISS MR imaging and MR angiography are useful in the detection of neurovascular compression. Microvascular decompression is an effective surgical procedure in the management of compression syndromes of the cranial nerves V, VII, and VIII.     

Cavernous angioma of the cerebellopontine angle

Although cavernous hemangiomas are commonly found supratentorially, their presence in the internal auditory canal is uncommon. We describe a case that was initially mistaken for a vestibular schwannoma due to its location in the cerebellopontine angle. Although there can be overlap in their presentations, familiarity with the characteristic magnetic resonance imaging findings of both entities will aid in their differentiation and potentially affect preoperative planning.     

Contribution to x-ray diagnostics of tumors of the cerebellopontine angle (author's transl)]

A scrutiny of the palette of possibilities in the radiological examination for the discovery and identification of neurinomas of the auditory nerve, shows that, apart from plain roentgenography, which continues to occupy the first rank after clinical examination, computer tomography represents the most important contribution towards identifying tumors of the cerebellopontine angle. For the identification of neurinomas (of the Brunner type) of the medial type this method of examination is the method of choice. We are not so confident with regard to the small lateral neurinomas which are situated within the auditory meatus. We consider that the discovery of these extremely small lateral neurinomas of the auditory nerve remains extremely difficult and is mainly left to positive cisternography. Probably, the discovery of these neurinomas remains one of the happy chances of early radiological diagnosis. Nevertheless, the knowledge acquired during the past few years must be considered an essential step forward in radiodiagnostics, and hence represents a great aid in the curative treatment of the patient.     

岩尖斜坡区肿瘤手术入路探讨

报告了自１９８３年以来收治的２０例岩尖斜坡区肿瘤，其中脑膜瘤９例，神经鞘瘤６例，胆脂瘤５例。肿瘤位于幕下９例，向幕上生长侵及颅中窝１１例，侵及海绵窦３例。手术入路：枕下开颅９例，颞下经小脑幕手术９例，颞枕枕下联合开颅１例，另有１例颞下入路手术后３周行二期枕下开颅手术。手术结果：全切除９例，次全切除１０例，大部切除１例。并着重就岩尖斜坡区肿瘤的手术入路等问题进行扼要的讨论。     

桥小脑角区病变的MRI表现

目的探讨桥小脑角（cerebellopontineangle,CPA）区占位性病变在磁共振检查中的影像表现。方法分析83例行MRI平扫＋增强检查,且经手术病理证实,具有完整临床资料的CPA占位性病变的MRI表现,重点观察病灶的大小、形态、边缘轮廓、瘤周水肿、周围结构的改变、平扫及增强后的信号强度。结果本组83例CPA病变中,听神经瘤50例,脑膜瘤13例,表皮样囊肿13例,三又神经瘤4例,蛛网膜囊肿1例,星形细胞瘤1例,室管膜瘤1例。肿瘤位于左侧CPA区38例,右侧CPA区45例。术前定位准确率为98．8％,定性准确率为95．2％。结论MRI检查是检查桥小脑角区占位性病变的首选方法,对该区病变的诊断和鉴别诊断有重要价值。     

Optimizing MR imaging for detecting small tumors in the cerebellopontine angle and internal auditory canal

Relative resolving power was used to determine the optimal MR imaging pulse sequence for detecting small tumors of the internal auditory canal and the cerebellopontine angle. Resolving power takes into consideration these important image characteristics: signal-to-noise ratio, contrast, and spatial resolution. The study was performed on a 1.5-T magnet using a 256 X 256 matrix and a 3-mm slice thickness. The TR ranged from 400-2000 msec; the number of excitations was either two or six; and the pixel size was 0.94, 0.78, or 0.63 mm. Theoretical calculations of relative resolving power were compared with the relative resolving power of 45 control patients and 15 patients with small tumors of the cerebellopontine angle or internal auditory canal. A TR of 800 msec was optimal from theoretical calculations and proved optimal in control and tumor patients. Scans obtained with TR = 2000 msec, TE = 80 msec were inferior to short TR scans; such scans could fail to detect intracanalicular tumors. The relative resolving power in patients exceeded theoretical calculations because of greater than expected image contrast caused by low CSF signal intensity secondary to CSF pulsation.     

Dense epidermoid cyst of the cerebellopontine angle

Summary A case of epidermoid cyst in the cerebellopontine angle which appeared as a hyperdense mass on CT is presented with clinical and radiological features. The preoperative tentative diagnosis proved erroneous. The literature is reviewed on this exceptinally rare radiological finding of epidermoid cysts and highlights of preoperative diagnosis are discussed.