摘要:

Meningiomas are the second most common cerebellopontine angle (CPA) tumor. The reported rates of hearing preservation following surgical removal vary between 32% and 100%. There is only one recent report discussing vestibular function after CPA meningioma removal. In this series of 31 patients with CPA meningiomas, 16 patients had their tumors removed via the retrosigmoid approach. All 16 had audiovestibular assessment pre- and postsurgery and were the subjects of this study. Class A hearing is socially useful hearing and is defined as a pure tone average (PTA; average of 500 Hz and 1, 2 and 4 kHz) of <30 dB and speech descrimination scores (SDS) of >70%. Class B hearing is serviceable hearing, defined as PTA of <50 dB and SDS of >50%. Nine patients had class A hearing, and two had class B hearing presurgery. Socially useful hearing was preserved in six of nine (67%) patients in whom it was present before surgery, and serviceable or better hearing was preserved in eight of 11 (73%). Vestibular symptomatology and examination findings improved despite a decrease in the number of patients with intact caloric function postsurgery. Patients who retained vestibular function on caloric testing were symptomatically better than those who lost caloric function. These results confirm that excellent audiovestibular function is possible after CPA meningioma surgery.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:An interesting case is reported of an 11-year-old girl who experienced a sudden, profound right-sided hearing loss at the age of 5 years after hearing a “pop” and the sound of rushing water in her right ear. At that time the patient was thought to have Mondini's deformity, and a perilymphatic fistula of the oval window in the right ear. Six years later she was diagnosed with a juvenile pilocytic astrocytoma of the pons with an exophytic component extending into the cerebellopontine angle. Of particular interest in this case is the presence of evoked otoacoustic emissions in the right ear with a profound neural hearing loss. The presence of transient evoked and distortion product otoacoustic emissions confirmed normal sensory outer hair cell function and an intact peripheral auditory system in a clinically deaf ear, thus indicating hearing loss due to a neural component instead of a sensory component, which was previously assumed.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:The successful removal of vestibular schwannomas requires a team approach by skillful and appropriately trained surgeons. It is generally perceived that the results of surgery, especially facial nerve outcome, will improve as the surgical team acquires more experience. This study of 300 patients undergoing surgical removal of vestibular schwannomas confirms that there was a significant learning curve for facial nerve outcome. In the first 50 cases, 52% had satisfactory outcomes (House grades I—III), whereas in the last 50 cases 92% had satisfactory outcomes. The major improvement came between the first 50 cases and the second 50 cases (House grades I—III results at 12 months improved from 52% to 78%). After the second 50 patients there was a gradual, but continued improvement, which is also attributable to increased surgical experience. Most of this learning curve was related to the translabyrinthine approach. House grades I—III results were attained for 45% of the first 40 and 70% of the second 40 translabyrinthine tumor removals.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:Enhancement in the region of the jugular foramen on magnetic resonance imaging (MRI) is highly sensitive to the presence of a skull base neoplasm. Unfortunately, this imaging method lacks the specificity to be the sole criterion in the diagnosis of a lesion of the jugular foramen. Although well described in the radiological literature, the phenomenon of gadolinium enhancement of the relatively static blood in the jugular system continues to be erroneously diagnosed as glomus jugulare tumor. Instances of this phenomenon present in patients referred to our practice for surgical opinions before radiation therapy and/or definitive resection will be presented. The purpose of this communication is to bring this potential treatment pitfall to the attention of the neurotology community. Treatment planning for lesions of the lateral skull base cannot singularly be based on MRI findings but requires a healthy skepticism satisfied only by more complete evaluation.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:A new application of auditory evoked potentials using direct cochlear nerve action potentials (CNAPs) for monitoring middle fossa acoustic neuroma resection with attempted hearing preservation is described. Twenty patients have been studied to date. With this technique, a monitoring electrode is secured between the floor of the internal auditory canal and the dura adjacent to the cochlear nerve in an extradural location. Standard auditory evoked potential techniques with click stimuli and microelectrical recording allow observation of nearfield waveforms in seconds versus several minutes required for farfield potentials recorded from the scalp. Advantages of this technique over auditory brainstem response monitoring may include nearly real time measurement of potentials, improved surgeon learning curve and possibly higher rates of hearing preservation, and applicability to all patients undergoing hearing-preservation surgery independent of presence or absence of ABR tracing. Immediate changes in amplitude and latency of waveforms appear to compare with reversible and irreversible intraoperative auditory system damage, thereby guiding surgical maneuvers.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:Tumors involving the jugular foramen (JF) have a variable relationship to the neurovascular structures (jugular vein, cranial nerves IX-XI) that traverse this conduit through the skull base. The surgeon familiar with the site of origin, growth pattern, and geometry of each of the common lesions affecting this region with respect to surrounding nerves and vessels is at a considerable advantage when undertaking a function-sparing procedure. Anatomically, the JF has two vascular compartments that may be affected by tumor: the jugular bulb laterally and a passage for the inferior petrosal sinus medially. Tumors may also penetrate the JF along the fibro-osseous diaphragm, which divides these two vascular channels. The lower cranial nerves lie on either side of this partition, which is connected to the posterior cranial fossa via a curved, funnel-shaped cone of dura. Tumors that arise within or penetrate the JF lateral to this neural plane displace the nerves medially, a positionfavorablefor their preservation during tumor extirpation. By contrast, medially positioned tumors displace the cranial nerves onto the lateral tumor surface, where they interpose between surgeon and tumor—anunfavorablelocation. Glomus tumors consistently arise in the lateral aspect of the JF, displacing the lower cranial nerves medially. This positioning accounts for the high rate of neural preservation in small and medium-size glomus tumors that have not invaded the foramen's central partition. Meningiomas that arise lateral to the JF (e.g., the posterior petrous surface, sigmoid sinus) favorably displace the lower cranial nerves medially. By contrast, tumors that originate medial to the JF (e.g., clivus, foramen magnum) are unfavorable, laterally displacing the multiple small rootlets that coalesce into cranial nerves IX-XI into a vulnerable location. Schwannomas arise within the neural plane and have a variable geometry that depends, in part, upon the nerve of origin. Theoretically, tumors that arise from the ninth nerve, which is located on the lateral surface of the neural plane, should be more favorable than those originating from the tenth or eleventh nerves, which lie on its deep surface. The propensity of these three tumor types toward thrombosis of the jugulosigmoid complex also carries important surgical implications. Because glomus tumors arise from the jugular bulb, the jugulosigmoid complex is nearly always occluded. In both meningiomas and schwannomas, however, the jugular system may occasionally remain patent. This is important to recognize through angiography and/or magnetic resonance venography, since sacrifice of a patent, dominant system risks intracerebral venous infarction.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Summary:The middle cranial fossa (MCF) approach for acoustic neuromas has been criticized for limited exposure, anatomic surgical difficulty, and increased risk to facial nerve and temporal lobe. From 1986 to the present, 49 patients' acoustic neuromas were removed via the MCF approach. Hearing was preserved or improved in 69% of patients regardless of preoperative hearing levels, and facial nerve function was Grade II or better in 94%. Both results demonstrate improvement improvement from our report 8 years ago. In addition, all patients are without recurrence. Our results continue to demonstrate the surgical advantages of the MCF approach and that, in experienced hands, it is as efficacious as other hearing preservation approaches.

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0192-9763    

出版商:OVID    

年代:1996

数据来源: OVID