Respuesta evocada auditiva de tronco en el schwannoma del VIII par: correlación anatomofisiológica y funcional. Nuestra experiencia

INTRODUCTION

Schwannomas are tumors charasteristically originated from the nerve sheath. They expande eccentrically from the nerve promoting a disturbance in the neural function either due to vascular compresion or to the effect of the tumor itself on the nerve, disturbance that can be evidenced with the Auditory-evoked Brainstem Response (ABR), fact that constituted the base for their diagnosis in the past. The new radiological techniques developed over the last decades have made possible an earlier diagnosis, and therefore changed their prognosis in terms of nerve function. Diagnosis is more certain today with these techniques so it could seem that ABR may not have any longer a role in the management of this condition.

OBJECTIVE

To describe the most frequent ABR patterns in those patients suffering from acoustic schwannoma related to the size of the tumour and the remanent audition thresholds, and to determine the value of this test in our practice.

MATERIAL AND METHODS

We describe the ABR features found in our series of 72 patients. Whose diagnosis was done between 1997 and 2003 in relation to the size of the tumour and the residual auditory function.

RESULTS AND CONCLUSIONS

ABR has a good sensibility for detection of acoustic schwannoma. This sensibility decreases in small-sized tumours, specially in intracanalicular ones. ABR patterns do not relate to the size of the tumour but they do to the auditory function. The authors defend ABR to be a very valuable test due to the information and accesibility they provide.

[Facial nerve tumours]

INTRODUCTION

Tumours originating in the facial nerve are extremely rare and their therapeutic approach requires the aid of specialists from a number of disciplines.

AIMS

Our aim was to analyse the cases treated in our centre over a five-year period.

PATIENTS AND METHODS

All the subjects submitted to surgical interventions to treat facial nerve tumours between January 1992 and December 1996 were evaluated retrospectively. Data recorded from all patients included age, sex, side affected, time prior to diagnosis, presenting symptom and symptoms observed at the time of diagnosis, previous history of disorders affecting the facial nerve and associated neurological symptoms. We also noted the location of the lesion, the surgical technique used, pathology findings, post-operative complications, length of post-operative stay in hospital, facial sequelae and surgical repair procedures used on the facial nerves involved in the intervention.

RESULTS

Six cases, with a mean age of 29 years (range: 16-46 years), were treated. Three of the patients were males (50%). Symptoms of the disease included facial palsy (4), neurosensory hypoacusis (1) and tinnitus (1). All six individuals (100%) had alterations affecting facial functioning in the course of the disease. The pathological diagnosis was schwannoma in four cases and hemangioma in the other two. Neural grafts were carried out in three patients and some kind of deficit was observed at the end of the follow-up in all the cases.

CONCLUSIONS

Facial nerve tumours are very infrequent. An early diagnosis is needed to diminish the facial sequelae following surgery performed to treat this clinical entity.

A rare case of cellular schwannoma involving the trigeminal ganglion

Cellular schwannomas rarely involve the cranial nerves, being more common in the spinal and peripheral nerves. A rare case of cellular schwannoma involving the gasserian ganglion, a hitherto unreported site, that extended infratentorially to present as a cerebellopontine angle tumor is reported. It is important to recognize that cellular schwannomas can histologically mimic malignant peripheral nerve sheath tumors because of their high cellularity and mitotic activity, but they are relatively benign tumors with a tendency to recur but not metastasize.

Subfrontal Schwannoma Without Hyposmia-Case Report-

A 44-year-old man presented with a rare subfrontal schwannoma with headache. He had undergone radiation therapy for a pineal lesion 30 years previously, but the histology was not verified. On admission, neurological examination revealed no focal deficits including hyposmia. Computed tomography demonstrated a mass measuring 5 x 3 cm in the right anterior cranial fossa. Magnetic resonance imaging revealed a heterogeneously enhanced mass with multiple cysts. The tumor, which was clearly separable from the surrounding normal brain, was totally resected through a right frontal craniotomy. There was no adhesion between the tumor and the olfactory groove or cribriform plate. The frontal base dura was suspected to be the tumor attachment. The patient was discharged without hyposmia. Histological examination revealed a typical pattern of schwannoma consisting of Antoni type A and type B. Immunohistochemical staining was positive for S-100 protein but negative for epithelial membrane antigen. Subfrontal schwannoma not associated with the olfactory groove or cribriform plate is extremely rare. The operative findings and absence of hyposmia suggest that the meningeal branch of the trigeminal nerve was the origin of the tumor. However, the possibility of radiation-induced reactive Schwann cells cannot be excluded.

Facial Nerve Tumors

OBJECTIVE

To evaluate the surgical results in primary facial nerve (FN) tumors.

STUDY DESIGN

Retrospective case review.

SETTING

Private neuro-otological and skull-base tertiary referral center.

PATIENTS

Twenty eight consecutive patients affected by primary FN tumors that underwent surgery between December 1990 and February 2001.

INTERVENTIONS

The lesions were removed through a variety of surgical approaches, depending on tumor location and extension, as well as preoperative hearing. In one case, partial removal was performed.

MAIN OUTCOME MEASURES

Preoperative and postoperative FN function; preoperative and postoperative hearing level; and postoperative complications.

RESULTS

Based on histologic examination, tumors were distributed as follows: 18 schwannomas, six hemangiomas, two meningiomas, and two neurofibromas. Tumor location varied, with lesions distributed along the entire length of the nerve. Facial dysfunction was the most frequently recorded symptom, followed by hearing loss. Only five patients presented a preoperative grade 1 facial function. In the remaining patients of the group, the facial deficit lasted from 2 to 120 months, with a mean of 31.2 months. Anatomic integrity of the nerve was preserved in 4 cases; all others required a nerve interruption followed by reconstruction using a sural nerve graft. The complications recorded were: one cerebrospinal fluid leak, one postoperative retraction pocket, and one external auditory canal wall resorption requiring a surgical revision. Preoperative hearing remained unchanged in 8 out of the 15 patients in whom a hearing preservation procedure was attempted. In 25 cases, a follow-up of equal to or longer than 1 year was available, with the FN functions: two grade 1, eight grade 3, nine grade 4, three grade 5, and three grade 6. Patients with a preoperative deficit lasting more than 1 year demonstrated the worst recovery.

CONCLUSIONS

Primary FN tumors are rare lesions that include different histologic types. FN deficit represents the most common symptom, but it is not present in all cases. A conservative strategy is often adopted in presence of a normal preoperative facial function. When surgical management is selected, the decision on surgical approach to use depends on tumor size and location, as well as on preoperative hearing. FN integrity may be spared in rare occasions, but more frequently nerve reconstruction is required. Final facial function recovery is mainly dependent on the preoperative presence of FN deficit and its duration.

[Gamma knife radiosurgery for trigeminal schwannomas]

OBJECTIVE

To evaluate the role of gamma knife (GK) in the treatment of trigeminal schwannomas.

METHODS

From June 1994 to June 2000, 38 patients with trigeminal schwannoma treated with GK radiosurgery were reviewed. GK was the primary treatment modality in 30 cases and followed microsurgery in 8 cases. Of the 38 tumors, 12 had small cysts within the tumors, the rest were solid. The mean diameter of the 38 tumors was 32 mm (range: 16 approximately 48 mm) and the tumors ranged in volume from 2 to 33 cm(3) (with a mean mean volume of 9 cm(3)). The maximum dose irradiated to tumor was 20 to 33 Gy (mean: 26 Gy), the tumor margin dose ranged from 11 to 15 Gy (mean: 13 Gy).

RESULTS

35 patients had been followed for 26 to 98 months (mean: 65 months). 20 had been followed more than 60 months. Mild numbness or diplopia relieved completely in 12 patients after GK treatment. Improvement of neurological deficits was seen in 11, unchanged dysfunction or slightly worsening of trigeminal nerve deficits in 9. Three patients had mild worsened symptoms at different time because of tumor progression. Tumor growth control: tumor disappeared after GK treatment was observed in 5 cases from 18 to 36 months after, a marked decrease in volume was observed in 24 cases, unchange in 2 cases and increase in 3 cases at 5, 26, and 60 months after respectively. One patient with resolved symptom refused to have MRI examination for more than 6 years. Of the three increased tumors, one recurrent malignant schwannoma elapsed 26 months after GK treatment. The second was a small tumor and started to progress 5 years after, but after second GK treatment, the tumor decreased again. The third was large tumor and was subtotally removed through surgery because of tumor swelling 5 months after. At last follow-up, the residual tumor remained stable. The control rate of the 35 tumors was 91% (32/35).

CONCLUSION

Small and middle-size trigeminal schwannomas are the best candidates for GK radiosurgery. The control dose is 13 to 14 Gy.

Neurofibromatosis 2: two case reports

Our study presents two cases of neurofibromatosis 2 (NF2) that have been diagnosed at the Ear, Nose, and Throat Department of Hradec Králové (Czech Republic). The first case involved a young man with a history of sudden hearing loss accompanied by tinnitus on the left side. The diagnosis of NF2 was made, and an operation for left acoustic neuroma was performed. Looking toward the future, the acoustic neuroma on the right side should be resolved as well. The second case concerned a woman (the mother of our patient 1) examined at the same Ear, Nose, and Throat Department in 1980, after 4 years of gait instability and progressive loss of hearing and tinnitus on the right side. Computed tomography scan detected a bilateral expansion in the pontocerebellar angles, and a large tumor on the right side was removed. The patient is deaf and has facial palsy without progression of symptomatology during long-term follow-up. These two cases document the rare but serious hereditary disease of NF2. Its most frequent first presentation is acoustic neuroma; further, benign tumors of the nervous system and juvenile cortical cataract also are often detected. The variability of number, location, and biological behavior of tumors associated with NF2 require an individual patient treatment approach, long-term follow-up, and insertion of appropriate hearing aids. Important also is a genetic examination to exclude pathological NF2 genes in the first-degree relatives of the affected individuals.

Pathological laughter in a patient with trigeminal neurinoma

We present a 47-year-old woman with a long history of anxiety and a more recent history of shock-like facial pain and episodes of laughter without any motivation. She could not explain the laughing bursts and did not have a sense of mirth preceding it. On neurological examination she presented a VI nerve palsy and trigeminal hypoesthesia (V2 and V3) on the right side. Magnetic resonance imaging exhibited a large cystic lesion on the right middle fossa causing significant compression on the brain stem. A frontoorbitozygomatic and pretemporal combined approach was performed. During intra and extradural exploration a large tumor was found on the trigeminal nerve. The whole lesion was resected, revealing to be a neurinoma on pathological exhamination. She maintained a VI nerve palsy but had complete remission of the unmotivated laughing episodes during the one year follow up.

[Diagnostic image (86). A man with thirst and diplopia]

A 71-year-old man was thirsty, had bone pains and a double vision. Multiple myeloma with hypercalcemia was diagnosed. One tumour in the clivus turned out to be compressing the left N. abducens.

Abducens nerve schwannoma: a case report and review of the literature

BACKGROUND

Schwannomas of the abducens nerve are extremely rare tumors; only 10 cases have been reported so far. The tumor may be located within the cavernous sinus (CS) or more commonly at the prepontine region. Patients usually present with VIth cranial nerve paresis.

CASE DESCRIPTION

We report a case of a 42-year-old male patient who presented with headache, vertigo, and hearing deficit, but no symptoms or signs related to a VIth cranial nerve impairment. Computed tomography and magnetic resonance imaging showed a large mass with a ring-like contrast enhancement in the prepontine area. Surgical treatment, via a simple retrosigmoid suboccipital approach, revealed a schwannoma originating from the VIth cranial nerve at its prepontine portion. Postoperative histological examination confirmed the diagnosis of schwannoma, and the patient had only a VIth cranial nerve palsy, which resolved during long-term follow-up.

CONCLUSIONS

Abducens schwannomas are rare tumors, representing less than 1% of all intracranial schwannomas in our clinic and about 13% of oculomotor nerve schwannomas reported in the literature. These lesions can be mainly divided into tumors originating from the intracavernous portion of the VIth cranial nerve or more commonly from the cisternal part of the nerve, leading to a lesion in the prepontine region. In such cases, with no invasion of the cavernous sinus, radical tumor resection with preservation of the abducens nerve can be performed via a simple suboccipital retrosigmoid approach.

Trigeminal schwannomas: removal of dumbbell-shaped tumors through the expanded Meckel cave and outcomes of cranial nerve function

OBJECT

As in patients with vestibular schwannomas, advances in surgical procedures have markedly improved outcomes in patients with trigeminal schwannomas. In this article the authors address the function of cranial nerves in a series of patients with trigeminal schwannomas that were treated with gross-total surgical removal. The authors emphasize a technique they use to remove a dumbbell-shaped tumor through the expanded Meckel cave, and discuss the advantage of the extradural zygomatic middle fossa approach for total removal of tumor and preservation or improvement of cranial nerve function.

METHODS

Within an 11-year period (1989-2000), 25 patients (14 female and 11 male patients with a mean age of 44.4 years) with benign trigeminal schwannomas were surgically treated by the senior author (O.A.) with the aim of total removal of the tumor. Three patients had undergone previous surgery elsewhere. Trigeminal nerve dysfunction was present in all but two patients. Abducent nerve paresis was present in 40%. The approach in each patient was selected according to the location and size of the lesion. Nineteen tumors were dumbbell shaped and extended into both middle and posterior fossae. All 25 tumors involved the cavernous sinus. The zygomatic middle fossa approach was particularly useful and was used in 14 patients. The mean follow-up period was 33.12 months. In patients who had not undergone previous surgery, the preoperative trigeminal sensory deficit improved in 44%, facial pain decreased in 73%, and trigeminal motor deficit improved in 80%. Among patients with preoperative abducent nerve paresis, recovery was attained in 63%. Three patients (12%) experienced a persistent new or worse cranial nerve function postoperatively. Fifth nerve sensory deficit persisted in one of these patients, sensory and motor dysfunction in another, and motor trigeminal weakness in the third patient. In all patients a good surgical outcome was achieved. One patient died 2 years after treatment from an unrelated cause. In three patients the tumors recurred after an average of 22.3 months.

CONCLUSIONS

Preservation or improvement of cranial nerve function can be achieved through total removal of a trigeminal schwannoma, and skull base approaches are better suited to achieving this goal. The zygomatic middle fossa approach is particularly helpful and safe. It allows extradural tumor removal from the cavernous sinus, the infratemporal fossa, and the posterior fossa through the expanded Meckel cave.

Transtemporal facial nerve schwannoma without facial nerve paralysis

Facial schwannoma is a relatively rare but well documented lesion, presenting either as a mass or with facial nerve symptoms. In this report, an extensive facial schwannoma, extending from the brain stem to the periphery with minimal facial nerve symptoms and normal facial function is presented.

Visual pathway tumors and hydrocephalus

The authors evaluated the impact of hydrocephalus on the clinical picture of children with visual pathway tumor (VPT) with or without neurofibromatosis (NF). Charts of children with VPT treated in the authors' center since 1985 were retrospectively reviewed, and those with hydrocephalus were selected and summarized. Thirty-five children with VPT were found, of whom 20 had NF. Hydrocephalus was found in 4 children with NF (20%) and in 5 without NF (33.3%). In 6 of the children, ventricular dilatation with signs of acute increased intracranial pressure already existed at the time of diagnosis and the hydrocephalus was shunted at this time. In the other 3 children, all with NF, the hydrocephalus resulted from slowly developing aqueductal stenosis, leading in 2 to severe visual acuity deterioration. The results suggest that in children with VPT and NF, hydrocephalus, and especially hydrocephalus resulting from aqueductal stenosis, is more frequent than in the general population of NF patients, and less frequent than in VPT patients without NF. The possibility of the indolent development of hydrocephalus should be borne in mind while following children with NF. The optic nerve, when already involved with a glioma, is more vulnerable to increased pressure. Thus, in children with VPT and NF, any ventricular dilatation should lead to a consideration of early shunting.

Pathological laughter as a presenting symptom of massive trigeminal neuromas: report of four cases

OBJECTIVE AND IMPORTANCE

This is a report of four cases of huge trigeminal neuromas that presented with the principle symptom of pathological laughter (PL).

CLINICAL PRESENTATION

All four patients were male and were in either the third or fourth decade of life. In addition to PL, there were neurological deficits related to trigeminal nerve, brainstem, and cerebellar dysfunctions.

INTERVENTION

All tumors were radically excised via a lateral basal temporal approach. The PL was cured immediately after surgery.

CONCLUSION

PL sometimes precedes other neurological manifestations and may be a useful localizing sign. The clinical and radiological features in our cases suggest that PL is a result of extra-axial compression of the pons and adjoining neural structures.

[Monitoring of the auditory stem evoked potentials in removal of tumors of the posterior cranial fossa]

The material of intraoperative monitoring of the acoustic stem evoked potentials (ASEP) in 9 patients with tumors of the stem and in 28 patients with the parastem localization was analyzed. It was shown that changes in the amplitude of ASEP rather than latency were the decisive factor in the assessment of the functional state of the brain stem. It was found that even the pronounced changes of the bioelectrical activity recorded during the excision of the tumor could be reversible after a change of the strategy of the operative intervention and/or after performing the necessary therapeutic measures. An important test of favorable prognosis of the postoperative course is considered to be the normalization of brain activity, ASEP included, at the final stages of the operation.

Audiovestibular findings prior to and after acoustic neuroma surgery

We performed a retrospective study of 131 patients who underwent microsurgical removal of statoacoustic neuroma at the University of Wuerzburg. Our goal was to evaluate objective audiovestibular findings prior to and after surgery. Our analysis focused on the evaluation of quantitative parameters in speech and pure-tone audiometry and on the reactivity of the vestibular system.

Surgical findings in idiopathic trigeminal neuropathy mimicking a trigeminal neurinoma

Idiopathic trigeminal neuropathy is a benign disorder where the main clinical feature is facial numbness limited to the territory of one or more divisions of the trigeminal nerve, persisting for a few weeks to several years and in which no underlying disease can be identified. The case of a 37-year-old man with a brief history of sensory and motor trigeminal symptoms who showed magnetic resonance imaging (MRI) findings consistent with a small trigeminal neurinoma is reported. The patient was operated on but no tumour could be found during surgery and a biopsy was taken from the portio major. Pathological diagnosis was chronic non granulomatous inflammatory reaction with areas of coagulation necrosis. Control MRI showed complete resolution of the trigeminal abnormalities. It is concluded that in patients with MRI findings suggestive of a small trigeminal schwannoma, benign idiopathic trigeminal neuropathy should also be considered in the differential diagnosis. A conservative approach with sequential MRI studies may avoid an unnecessary surgical exploration.

Sympathectomy does not affect the early ectopic discharge from myelinated fibres in ferret inferior alveolar nerve neuromas

Ectopic neural activity from damaged axons is thought to contribute to the development of sensory disorders following nerve injury. Here we have studied the role of sympathetic fibres in the generation or potentiation of this abnormal activity by determining the effect of predegenerating these fibres. Twelve adult ferrets were used in the study and six of them underwent sympathectomy by removal of the left superior cervical ganglion. Electrophysiological recordings were made from myelinated axons in fine filaments dissected from the inferior alveolar nerve, 3 days after it had been ligated further distally, and the level of spontaneous activity and mechanical sensitivity was determined. There was no significant difference between the level or characteristics of spontaneous activity, or the level of mechanical sensitivity, in the two groups of animals. We conclude that, in this animal model, the absence of sympathetic nerve fibres does not affect the development or characteristics of ectopic neural activity in the early period following nerve injury.

Prognostic value of the pattern electroretinogram in cases of tumors affecting the optic pathway

BACKGROUND

Tumors compressing the optic pathway may lead to irreversible loss of vision which may be detected by the pattern electroretinogram (PERG) because of its relation to ganglion cell function.

METHODS

Eyes of 19 patients were tested shortly before and 5-10 days after tumor surgery. Visual acuity, the 30-deg visual field and the transient and steady-state pattern reversal ERG were measured.

RESULTS

Using patterns of 1.5 x 1.2 deg there was a good correlation between the change of pre- and post-surgical visual performance and most of the pattern ERG amplitudes. For all variables tested--P50, N95- and steady-state amplitude--there was a critical value beyond which the visual outcome could be bad or favorable, whereas patients showing higher amplitudes always remained stable or improved after surgery.

CONCLUSION

The positive correlation between pattern ERG amplitudes and the post-surgical outcome in the case of tumors affecting the optic pathway may be helpful in predicting the outcome for these patients.

Preoperative electroneurography (ENoG) in parotid surgery: assessment of facial nerve outcome and involvement by tumor--a preliminary study

BACKGROUND

Facial electroneurography (ENoG) is an established and reliable method for assessing neural degeneration in various conditions affecting the facial nerve. The facial nerve may be subclinically involved by parotid tumors, but estimating such involvement preoperatively may be difficult when facial function is normal. The hypothesis that preoperative ENoG: (1) can detect subclinical facial nerve degeneration as a measure of involvement by parotid tumors and (2) can predict facial nerve function following parotidectomy was prospectively evaluated in the present study.

METHODS

Twenty-two patients undergoing parotidectomy for tumors were tested preoperatively with ENoG, and their facial nerve function was graded pre- and postoperatively (House-Brackmann system). Eight patients had malignant tumors and 14 benign tumors.

RESULTS

In patients with malignant tumors, lower percentage of preoperative ENoG response indicated nerve involvement that was not evident on clinical examination and correlated significantly (p = .035) with postoperative facial nerve dysfunction. Preoperative ENoG reduction of greater than 80% was found in all patients whose facial nerve was infiltrated by tumor. In 14 patients with benign tumors, preoperative ENoG results had no correlation with postoperative facial function.

CONCLUSIONS

In malignant tumors, even when facial function is clinically intact, a low preoperative ENoG response may predict facial nerve involvement by the tumor. The lower the preoperative ENoG response, the poorer is the expected postoperative facial nerve function. There was no such correlation in benign parotid tumors.

Hemifacial spasm caused by a hemangioma at the geniculate ganglion: case report

OBJECTIVE AND IMPORTANCE

Hemifacial spasm is rarely caused by facial nerve lesions in the temporal bone. Intratemporal facial nerve hemangiomas may initially present as facial spasm.

CLINICAL PRESENTATION

A 30-year-old woman developed right hemifacial spasm. Physicians observed slight weakness on the right side of her face, in addition to the hemifacial spasm, but routine radiological examinations did not detect any abnormal findings along the course of the facial nerve. Although the patient underwent neurovascular decompression, the spasm persisted postoperatively. Two years after surgery, the right facial palsy progressed. Concurrently, the hemifacial spasm diminished. High-resolution computed tomography demonstrated a small mass lesion expanding the cortex of the right petrosal bone involving the geniculate ganglion of the facial nerve.

INTERVENTION

The patient underwent a second craniotomy through a subtemporal extradural route, and the tumor was completely removed. A pathological examination demonstrated a cavernous hemangioma.

CONCLUSION

Routine radiological examinations may fail to detect small intratemporal facial nerve hemangiomas, particularly at the geniculate ganglion. Therefore, when physicians encounter atypical facial spasm, the intratemporal portion of the facial nerve should be carefully examined using high-resolution computed tomography.

Management of vestibular schwannomas (acoustic neuromas): auditory and facial nerve function after resection of 120 vestibular schwannomas in patients with neurofibromatosis 2

OBJECTIVE

Vestibular schwannomas (VSs) affect young patients with Neurofibromatosis 2 (NF-2) and cause very serious problems for hearing, facial expression, and brain stem function. Our objective was to determine a therapy concept for the right timing and indication of neurosurgical therapy.

METHODS

In 1000 consecutive VS resections, 120 tumors in 82 patients with NF-2 were surgically treated by the same surgeon (MS) at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. The mean age of the patients was 27.5 years. Sixty tumors were surgically treated in 41 male patients, and 60 tumors were surgically treated in 41 female patients. Bilateral tumor resection was performed in 38 patients (76 operations, after previous partial surgery in 15 cases elsewhere), and unilateral operations were performed in 44 patients, 5 of whom had undergone ipsi- or contralateral surgery that was performed elsewhere. The operative and clinical findings are evaluated and compared with the data of patients without NF-2.

RESULTS

In 105 cases, complete tumor resections were achieved. In 15 cases, deliberate subtotal resections were performed. These were for brain stem decompression in 4 cases and for hearing preservation in the last hearing ear in 11 cases, with successful preservation in 8 of the 11. Pre- and postoperative hearing rates were higher in male than in female patients (70% in male versus 65% in female patients before surgery and 40.5 versus 31%, respectively, after surgery). Hearing was preserved in 29 of 81 ears (36%). The rate of preservation was 24% in cases of large tumors and 57% in cases of small tumors (<30 mm). Twenty-one of 82 patients (26%) were bilaterally deaf before surgery. Twenty-five patients had uni- or bilateral hearing after surgery (i.e., 41 % of those with preoperative hearing or 30.5% of the whole group). Anatomic facial nerve preservation was achieved in 85%. The facial nerve was reconstructed intracranially at the cerebellopontine angle by sural grafting in 17 cases and by hypoglossal-facial reanimation in 5. Two deaths occurred 1 and 3 months postsurgically as a result of malignant tumor growth with brain stem dysfunction and respiratory problems. In summary, for patients with NF-2, the presentation ages are lower, tumor progression is faster, the chances of anatomic and functional nerve preservation are lower, the chances of good outcomes are best when surgery is performed early and when there is good preoperative hearing function, and the danger of sudden hearing loss is higher. The chances and danger often differ from side to side among individual patients.

CONCLUSION

The indication and the timing of tumor resections are in some respects different from normal VS handling and are dependent on the tumor extension and related necessity of brain stem decompression and on the auditory function. As an optimal goal, completeness of resection with functional cochlear nerve preservation is formulated, and as an acceptable compromise, subtotal microsurgical resection with functional cochlear nerve preservation in the last hearing ear is suggested.

Improvement in visual function in an eye with a presumed optic nerve sheath meningioma after treatment with three-dimensional conformal radiation therapy

The treatment of optic nerve sheath meningiomas (ONSM) is controversial. Radiation therapy has been used with some success in patients with progressive visual loss. We report a case of visual improvement in a patient with an optic nerve sheath meningioma and progressive visual field loss, treated with conformal radiotherapy.

[The role of cervical input in vestibular compensation]

The role of proprioceptive input from cervical receptors in vestibular compensation was investigated. Vibratory stimulation to the dorsal neck muscle was given to patients with unilateral vestibular lesions. The length of the displacement of the center of gravity, maximum sway length, and sway area increased markedly during vibratory stimulation to the dorsal neck. In patients in whom compensation had been achieved, a position vector to the side of the lesion increased and the center of gravity moved to the side of the lesion. From these results, it can be speculated that cervical input plays an important role in the process of vestibular compensation.

Twelfth-nerve palsy. Analysis of 100 cases

OBJECTIVE

To describe the causes and characteristics of hypoglossal nerve palsy.

DESIGN

A review of 26 years of personal experience in a large public hospital.

RESULTS

Twelfth-nerve palsies usually appear as signs rather than symptoms. Tumors, predominantly malignant, produced nearly half of the palsies (49 cases), while gunshot wounds made trauma (12) the second most common cause. Stroke (6), hysteria (6), multiple sclerosis (6), surgery (5), Guillain-Barré neuropathy (4), and infection (4) together accounted for about one third of the patients.

CONCLUSION

Twelfth-nerve palsy proved to be an ominous sign, with only 15% of patients experiencing complete or nearly complete recovery.