1/159. Suboccipital resection of a medial acoustic neuroma with hearing preservation.BACKGROUND: Many reports indicate that acoustic neuromas greater than 2.0 cm should be removed without hearing preservation attempted, even if hearing is present preoperatively. These studies advocate a translabyrinthine approach because the likelihood of hearing preservation is low. Medial acoustic neuromas, unlike the more common lateral tumors that involve the internal auditory canal, originate medial to that portion of the eighth nerve complex where the cochlear and vestibular nerves are fused. This anatomical feature suggests that these tumors may be amenable to resection with hearing preservation. methods: A patient with a 3.5 cm medial acoustic neuroma and useful preoperative hearing is presented. RESULTS: Gross total tumor removal with functional hearing was achieved after a two-stage procedure using a suboccipital approach. CONCLUSION: Based on the anatomico-pathologic features in this case, we believe that, if a patient has reasonable preoperative hearing (speech discrimination score > 70%) and a medial acoustic neuroma, an approach to preserve hearing should be considered regardless of tumor size.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
2/159. Delayed intracranial abscess after acoustic neuroma surgery: a report of two cases.OBJECTIVE: The use of antibiotics before and after surgery has made infectious complications of neurotologic surgery rare. The neurosurgical literature cites a rate of postoperative meningitis between 1% and 2% for "clean" cases and 1.5% to 2.5% for "clean contaminated" cases, such as cerebrospinal fluid contact with the middle ear or mastoid. Reports of infections after neurotologic procedures are rare in the otologic literature. In this report, two patients with brain abscess occurring in a delayed fashion after surgery are described. STUDY DESIGN: The study design was a retrospective chart review and case report. SETTING: The study was conducted at a tertiary referral center. RESULTS: Patient 1 underwent a suboccipital craniotomy for removal of an acoustic neuroma and had an uneventful postoperative recovery. Three months after surgery, he reported mild unsteadiness. Examination revealed mild ataxia, which led to repeat magnetic resonance imaging (MRI) and a diagnosis of cerebellar abscess. Patient 2 underwent translabyrinthine removal of an acoustic neuroma complicated by postoperative pseudomonas aeruginosa meningitis, which responded promptly to intravenous antibiotics. Fifteen months after surgery, he visited a neurologist after having a seizure and was treated with anticonvulsants. After a second episode of seizure, imaging studies showed a temporal lobe abscess. CONCLUSIONS: The signs of intracranial abscess may be subtle and can occur weeks or months after surgery, requiring vigilance and a high index of suspicion for diagnosis. A change in postoperative symptoms after acoustic neuroma surgery should signal further investigation using MRI with gadolinium.- - - - - - - - - - ranking = 0.0053786631179875keywords = spinal (Clic here for more details about this article) |
3/159. Magnetic resonance cisternography using the fast spin echo method for the evaluation of vestibular schwannoma.neuroimaging of vestibular schwannoma was performed with the fat-suppression spoiled gradient recalled acquisition in the steady state (SPGR) method and magnetic resonance (MR) cisternography, which is a fast spin echo method using a long echo train length, for the preoperative evaluation of the lateral extension of the tumor in the internal auditory canal, and the anatomical identification of the posterior semicircular canal and the nerves in the canal distal to the tumor. The SPGR method overestimated the lateral extension in eight cases, probably because of enhancement of the nerves adjacent to the tumor in the canal. The posterior semicircular canal could not be clearly identified, and the cranial nerves in the canal were shown only as a nerve bundle. In contrast, MR cisternography showed clear images of the lateral extension of the tumor and the facial and cochlear nerves adjacent to the tumor in the internal auditory canal. The anatomical location of the posterior semicircular canal was also clearly shown. These preoperative findings are very useful to plan the extent to which the internal auditory canal can be opened, and for intraoperative identification of the nerves in the canal. MR cisternography is less invasive since no contrast material or radiation is required, as with thin-slice high-resolution computed tomography (CT). MR cisternography should replace high-resolution CT for the preoperative neuroradiological evaluation of vestibular schwannoma.- - - - - - - - - - ranking = 10keywords = canal (Clic here for more details about this article) |
4/159. Stereotactic radiosurgery, X: clinical isodosimetry of gamma knife versus linear accelerator X-knife for pituitary and acoustic tumours.Several review articles have compared gamma unit versus linear accelerator (linac)-based radiosurgery systems, concluding that the dose gradient 'fall-off' at the margin of the target (expressed as the distance between isodoses) is very similar for both techniques as far as single isocentre treatment volumes up to 1.5 cm diameter are concerned, and that the two radiosurgical systems are, in general, comparable. 'Fine tuning' of the gamma unit can be carried out by using multiple isocentre plans, the differential use of small collimator sizes (down to 4 mm) and field weightings, and adroit use of the gamma angle, and selective beam blocking. Multiple isocentre plans, beam modification, restriction of gantry angles and arc lengths, and microcollimation can similarly improve the isodose gradients from linac units. In both instances, the dosimetric advantages occur along selected aspects of the target perimeter border. However, the more frequent use of multiple isocentred 'shots' on the gamma unit achieves greater conformity indices for more complex target volumes, but at the expense of steeper internal dose gradients. We studied two patients with tumours close to or arising from radiosensitive special sensory nerves (optic and cochlear) to compare and contrast fine tuning of the two technologies. In a previously irradiated patient with a pituitary adenoma, the dose gradient achieved at the rostral margin, adjacent to the optic chiasma, was steeper on the gamma unit (due to the concentration of small collimator shots rostrally and beam blocking), which was therefore the dosimetrically preferred technique. In contrast, the vastly smaller internal dose gradient (11% for linac/X-knife versus 100% for Gamma Knife) and the ability to fractionate on the X-knife system, gave a large dosimetric advantage to the X-knife plan in the treatment of an acoustic neuroma, where the intracanalicular component of the cochlear nerve traversed the target volume. This advantage also pertains to the cochlear ramus of the internal auditory (labyrinthine) artery and the facial nerve. Our published work on X-knife radiosurgery of acoustic neuroma has documented improvement of hearing after therapy and may be relevant in this regard. That there are advantages in physical dose distribution and fractionation, producing a reduction in the biological dose in normal tissue, argues for the use of linac technology in acoustic neuromas. Craniopharyngiomas enveloping the optic nerve/chiasma will similarly be better treated by the linac X-knife system. It is apparent that different radiosurgery systems may be indicated in particular neuro-oncological situations.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
5/159. Cavernous angioma of the internal acoustic meatus--case report.A 39-year-old female presented with an intrameatal cavernous angioma manifesting as hearing loss and tinnitus in the right ear which progressed over 8 months. Magnetic resonance (MR) images revealed an intrameatal lesion as ultra-high intensity, nearly as bright as cerebrospinal fluid, on the T2-weighted images, and isointensity on the T1-weighted images. Computed tomography (CT) showed the mass accompanied by stippled patterns of calcification. The patient underwent surgery under a diagnosis of calcified acoustic neurinoma. Histological studies were compatible with cavernous angioma. Intrameatal cavernous angioma is a rare disease which requires differential diagnosis from the more common neurinoma or meningioma in this location. Intrameatal lesion with ultra-high intensity on T2-weighted MR imaging and stippled patterns of calcification on CT is more likely to be cavernous angioma than acoustic neurinoma. These neuroimaging features are important information in deciding the treatment strategy.- - - - - - - - - - ranking = 0.0053786631179875keywords = spinal (Clic here for more details about this article) |
6/159. Miniaturised ultrasonic aspiration handpiece for increased applicability.OBJECTIVE: At present, ultrasonic aspiration is routinely used in several fields of surgery, especially in brain and spinal micro-surgery for tumour removal. In order to broaden the access to difficult surgical sites, it is important to design highly miniaturised but still efficient handpieces. The internal resonant system, always made of high-grade materials, must be optimally dimensioned. Normally this is done semi-empirically, by successively improving the design during many iterative test steps. This method however involves several additional difficulties when the degree of miniaturisation increases. For example, small transducer weights exacerbate heat-dissipation problems and make design optimisation important. methods: To resolve these problems we have produced modelling software that makes it possible to simulate and automatically tune each individual interacting section of the design before it is actually manufactured, thereby assuring optimal efficiency. RESULTS: Using a new mini-handpiece, designed via the software, two cases of dissection of acoustic neurinomas were successfully performed. CONCLUSION: Using conventional physical steps for improving ultrasonic aspiration handpieces, several problems arise when the grade of miniaturisation increases, due to increasing demands. We have designed computer software for handpiece simulation. Using this model it has been possible to manufacture a highly efficient miniaturised handpiece.- - - - - - - - - - ranking = 0.0053786631179875keywords = spinal (Clic here for more details about this article) |
7/159. meningioma of the internal auditory canal with extension into the vestibule.Meningiomas account for approximately 18 to 19 per cent of all brain tumours. Although they can arise in numerous locations, meningiomas of the internal auditory canal (IAC) are rare. Most tumours that originate in the IAC are schwannomas of the VIIIth cranial nerve (acoustic neuromas). We report a case of a meningioma which appears to originate from the IAC and extends into the vestibule. The clinical findings and the radiographical features of meningiomas of the IAC are similar to those of acoustic neuromas. Pre-operative differentiation between acoustic neuromas and meningiomas of the IAC may be difficult.- - - - - - - - - - ranking = 5keywords = canal (Clic here for more details about this article) |
8/159. Focal amyotrophy in neurofibromatosis 2.Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterised by bilateral vestibular schwannomas and other CNS tumours including meningiomas and spinal schwannomas. Occasionally, peripheral neuropathy occurs in these patients but this is the first report of focal amyotrophy. Clinical, electrophysiological, and imaging data from four NF2 patients seen at a specialist neurofibromatosis clinic over a 4 year period are described in whom symptomatic focal amyotrophy preceded the diagnosis of NF2. Two presented with wasting and weakness of a single muscle group, several years before NF2 was diagnosed. In one patient a mononeuritis multiplex was the presenting feature of NF2, and in one patient focal wasting and weakness developed after the diagnosis of NF2 was made. In none of the four cases could a focal peripheral nerve or root neurofibroma be identified despite extensive imaging with MRI, and the limitations of neuroimaging for identifying a structural cause in patients with NF2 with a focal peripheral nerve lesion is discussed. It is likely that NF2 may affect peripheral nerve structures in a manner distinct from a compressive schwannoma.- - - - - - - - - - ranking = 0.0053786631179875keywords = spinal (Clic here for more details about this article) |
9/159. Lesions of the internal auditory canal and cerebellopontine angle in an only hearing ear: is surgery ever advisable?OBJECTIVE: To define the indications for surgery in lesions of the internal auditory canal (IAC) and cerebellopontine angle (CPA) in an only hearing ear. STUDY DESIGN: Retrospective case series. SETTING: Tertiary referral center. patients: Seven patients with lesions of the IAC and CPA who were deaf on the side opposite the lesion. Five patients had vestibular schwannoma (VS), and one each had meningioma and progressive osseous stenosis of the IAC, respectively. The opposite ear was deaf from three different causes: VS (neurofibromatosis type 2 [NF2]), sudden sensorineural hearing loss, idiopathic IAC stenosis. INTERVENTION(S): Middle fossa removal of VS in five, retrosigmoid resection of meningioma in one, and middle fossa IAC osseous decompression in one. MAIN OUTCOME MEASURE: Hearing as measured on pure-tone and speech audiometry. RESULTS: Preoperative hearing was class A in four patients, class B in two, and class C in one. Postoperative hearing was class A in three patients, class B in one, class C in two, and class D in one. CONCLUSIONS: Although the vast majority of neurotologic lesions in an only hearing ear are best managed nonoperatively, in highly selected cases surgical intervention is warranted. Surgical intervention should be considered when one or more of the following circumstances is present: (1) predicted natural history of the disease is relatively rapid loss of the remaining hearing, (2) substantial brainstem compression has evolved (e.g., large acoustic neuroma), and/or (3) operative intervention may result in improvement of hearing or carries relatively low risk of hearing loss (e.g., CPA meningioma).- - - - - - - - - - ranking = 5keywords = canal (Clic here for more details about this article) |
10/159. Cavernous haemangioma of the internal auditory canal.Cavernous haemangiomas are rare lesions of the cerebello-pontine angle that can mimic the more commonly occurring vestibular schwannoma. A case report involving a patient with a cavernous haemangioma of the internal auditory canal (IAC) highlights this as a diagnostic possibility for lesions of the IAC by comparing and contrasting the clinical and radiological findings with the more commonly occurring vestibular nerve and facial schwannomas. Symptoms such as hearing loss and facial paralysis that are disproportionate to the size of the lesion or fluctuate with hormonal changes such as those seen in pregnancy are suggestive of haemangioma. Radiological imaging demonstrating a lesion enhancing with gadolinium and containing areas of calcification is also suggestive of haemangioma. It is important to consider the possible diagnosis of haemangioma as early recognition of this entity may improve the chances of preserving the functional integrity of the facial nerve.- - - - - - - - - - ranking = 5keywords = canal (Clic here for more details about this article) |
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