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PubMed2005

Mobile phone use and risk of acoustic neuroma: results of the Interphone case-control study in five North European countries.

There is public concern that use of mobile phones could increase the risk of brain tumours. If such an effect exists, acoustic neuroma would be of particular concern because of the proximity of the acoustic nerve to the handset. We conducted, to a shared protocol, six population-based case-control studies in four Nordic countries and the UK to assess the risk of acoustic neuroma in relation to mobile phone use. Data were collected by personal interview from 678 cases of acoustic neuroma and 3553 controls. The risk of acoustic neuroma in relation to regular mobile phone use in the pooled data set was not raised (odds ratio (OR) = 0.9, 95% confidence interval (CI): 0.7-1.1). There was no association of risk with duration of use, lifetime cumulative hours of use or number of calls, for phone use overall or for analogue or digital phones separately. Risk of a tumour on the same side of the head as reported phone use was raised for use for 10 years or longer (OR = 1.8, 95% CI: 1.1-3.1). The study suggests that there is no substantial risk of acoustic neuroma in the first decade after starting mobile phone use. However, an increase in risk after longer term use or after a longer lag period could not be ruled out.

Case-Control Studies↗

PubMed1982

[Polymodal sensory input in command neurons of snails].

Putative command neurones of snail's escape behaviour reacted with excitatory postsynaptic potentials and spikes to tactile, vestibular, light-off and thermal stimuli evoking behavioural escape reactions. Presented data confirm the command function of identified neurones. No monosynaptic connections have been revealed between intracellularly recorded primary cells of the statocyst and command neurones, but it has been shown that command neurones reacted to strong stimulation of the acoustic nerve. Presence of second-order sensory neurones in the vestibular pathway was assumed.

Acoustic Stimulation↗

PubMed1982

Acoustic tumour detection with early auditory evoked potentials and neuroradiological methods.

A total of 43 patients with surgically identified acoustic neuromas were tested. Results of early auditory evoked potentials (EAEP) and of neuroradiological methods were analysed. Abnormal EAEPs were observed in all patients. In 73% of the cases the EAEP indicated the retrocochlear site of the lesion; in 27%, however, the results did not localize the exact site of the lesion owing to a lack of waves I, II and III due to a pronounced hearing loss. Neuroradiological procedures provided an indication of the site and extent of the tumour. The number of true positives was 21 of 29 cases with polytomography of the petrous bone, 23 of 28 with computed tomography and in all cases when pontine angle cisternography and computed tomography combined with gas cisternography were performed. The EAEPs provide a screening-test for acoustic tumour detection at an early stage. Wave abnormalities indicative of a lesion at the acoustic nerve should lead to a neuroradiological investigation and are particularly valuable in cases with small intracanalicular tumours.

Adult↗

PubMed2000

Sporadic unilateral vestibular schwannoma with islets of meningioma: case report.

OBJECTIVE AND IMPORTANCE: Vestibular schwannomas with meningioma islets have been rarely reported in the literature; they have been observed only among patients with neurofibromatosis Type II. We present a case of a sporadic mixed tumor in a patient without neurofibromatosis Type II that was not suspected before surgery. CLINICAL PRESENTATION: A 59-year-old female patient presented with clinical signs of progressive loss of hearing. Her family history did not include evidence of neurological diseases. Magnetic resonance imaging scans revealed a typical unilateral vestibular schwannoma. INTERVENTION: The tumor presented with invasion of the surrounding arachnoid membrane, as well as Cranial Nerves VII and VIII. Preservation of the facial nerve with complete removal of the tumor was not possible. Therefore, Cranial Nerve VII reconstruction was performed. CONCLUSION: The concomitant occurrence of schwannomas and meningiomas infiltrating the arachnoid membrane might be related to poor clinical outcomes for patients with neurofibromatosis Type II, with respect to preservation of facial and acoustic nerves. Among sporadic schwannomas, this phenomenon is extremely rare.

Female↗

PubMed1992

The bony crescent sign--a new sign of facial nerve schwannoma.

Schwannomas of the facial nerve are rare slowly growing lesions that have a predilection for the geniculate ganglion. Radiological evaluation is important in their diagnosis and in the assessment of their extent. In our series of 4 cases the facial nerve schwannoma was seen on high resolution CT as a soft tissue mass bounded anteriorly by a thin rim of bone. This bony crescent sign is a previously undescribed sign of facial nerve schwannoma which appears on the basis of this small series to be strongly indicative of the presence of this tumour. Schwannomas are relatively uncommon intracranial tumours. They most commonly involve the acoustic nerve followed in frequency by the trigeminal nerve. Other cranial nerves are rarely involved. Facial nerve schwannomas occurring within the petrous temporal bone are very rare. Their diagnosis may be missed prospectively even when appropriate CT scans are performed. Even in retrospect the site of abnormality may be difficult to identify, especially if there is an associated middle ear mass such as a cholesteatoma. Lesions occurring in the petrous area are all rare. The differential diagnosis includes cholesterol granuloma, epidermoid, carotid aneurysm and, very rarely, primary and secondary bone tumours. We describe a new sign associated with facial nerve schwannoma on CT, that of a bony crescent. Recognition of this sign makes those tumours arising in the region of the geniculate ganglion easy to diagnose prospectively.

Adolescent↗

PubMed1996

[Electrocochleography by extra- and transtympanic methods: the results in a group of normal subjects].

Electrocochleography (ECoG) is an electrophysiologic approach to the study of hearing. In ECoG, electrical activity that originates within the cochlea or the auditory nerve is recorded. ECoG represents an evoked or stimulus dependent measure. The electrical potentials which can be analyzed in ECoG are: the cochlear microphonic potential (CM), the summating potential (SP) and the acoustic nerve potential (AP). Two major types of electrocochleography electrodes can be used, transtympanic and extratympanic. Transtympanic ECoG is performed by inserting a long needle electrode, placed through the tympanic membrane onto the promontory. Extratympanic ECoG is recorded by using electrodes placed within the external meatus near the tympanic membrane. At the ENT Department of the University of Parma, ECoG was performed in 10 normal hearing subjects (4 males and 6 females. Their ages ranged from 21 to 29 years (mean 26 years). All subjects underwent ECoG recording simultaneously with extratympanic and transtympanic technique.

Adult↗

PubMed2001

[Speech perception ability in a patient with a 8-channel auditory brainstem implant].

Auditory brainstem implant (ABI) is a central prosthesis that directly stimulates the cochlear nucleus in the brainstem for those who have interrupted auditory nerves and cannot benefit from the cochlear implantation. Speech perception in a recipient of the Nuclues 8 channel ABI, the first in Japan, is reported. A 25-year-old man with bilateral acoustic nerve tumors postlingually deafened due to tumor resection received auditory sensations with 5 channels. The correct answer using a coding strategy, SPEAK, was 35% for 5 vowels and 36% for 5 monosyllables. The use of ABI also improved his lip-reading ability on monosyllables and open-set words. This indicated that he benefited from ABI, although it was limited. Even after 1 year and 3 months of follow-up, he had no serious side effects such an infection or implant rejection.

Adult↗

PubMedDate not supplied

[Subarachnoid hemorrhage in acoustic neuroma].

A 32-year-old patient is reported with two subarachnoid bleedings occurring at an interval of 5 years. The cause of bleeding was a richly vascularized neurinoma of the acoustic nerve with focal necrosis. Operation was successful.

Adult↗

PubMed1983

Intratemporal schwannoma of the facial nerve.

Two patients with schwannomas that originated from the region of the geniculate ganglion of the facial nerve are reported. They presented with progressive facial nerve paralysis and variable disturbance of hearing. Computed tomograms demonstrated a mass lesion eroding the temporal bone (petrous portion) and extending into the middle fossa. The treatment consisted of complete excision of the tumor, and a hypoglossal-facial nerve anastomosis. Computed tomography should be performed on all patients with facial palsy of a progressive nature. Early diagnosis and surgical treatment of facial schwannoma should permit preservation of function of the facial and the acoustic nerves.

Adult↗

PubMed1989

Facial nerve recovery after acoustic neuroma removal.

A retrospective analysis of 76 patients who underwent acoustic neuroma removal is reported. Facial nerve function prior to surgery and tumour size are assessed with respect to final facial nerve recovery and the need for surgical rehabilitation. Both pre-operative facial weakness and tumour size greater than 2.5 cm. are shown to be predictive factors of poor facial nerve recovery. Multiple surgical rehabilitative procedures are often required when inadequate function and/or cosmetic results are obtained. Primary nerve repair and facial-hypoglossal anastomosis give better rehabilitative results than dynamic and static procedures. The association of tumour size greater than 2.5 cm. with increased risk of poor facial recovery re-emphasizes the need to detect and remove acoustic neuromas at an early stage.

Adolescent↗

PubMed1987

Angioma of the cerebellopontine cistern simulating acoustic neurinomas.

We report a cryptic angioma associated with a cisternal hematoma confined to the cerebellopontine cistern occurring in a 29-year-old woman. The angioma was related to the acoustic nerve. The cisternal hematoma appeared to have increased in size gradually with repeated hemorrhages from the angioma. The location of the lesion, in conjunction with the gradual size increase of the cisternal hematoma, resulted in the lesion simulating acoustic neurinomas radiologically as well as neurologically.

Adult↗

PubMed1976

Reversible deafness as model of pressure damage to the VIIIth nerve.

Frequency-specific compound action potentials (CAP) of the VIIIth nerve were registered in patients in which surgery confirmed retrocochlear pathology. A different pathologic behaviour of threshold latency was encountered for 2 and 4 kHz CAP, respectively. This was due to the question of whether transmission of neural information by the acoustic nerve's fibres was blocked completely by retrocochlear pathology or not. A totally reversible hearing loss in a case of cystic arachnitis can offer a reasonable explanation.

Action Potentials↗

PubMed2004

Delayed facial nerve paresis following acoustic neuroma resection and postoperative vasoactive treatment.

OBJECT: Delayed facial nerve paresis is a well known clinical phenomenon following acoustic neuroma surgery, typically occurring early during the postoperative course. The clinical course of the delayed facial nerve paresis and intraoperative electromyographic (EMG) signals were evaluated in a subgroup of patients who underwent vasoactive treatment for preservation of hearing and developed secondary deterioration after termination of treatment. METHODS: Between 1990 and 2001 seven patients were identified who received vasoactive treatment for preservation of hearing and developed a delayed facial nerve paresis after termination of medication. Intraoperative facial nerve EMG activity was analyzed in six patients. RESULTS: All patients developed a delayed facial nerve paresis between 2-5 days following termination of a 10 day treatment consisting of HES and nimodipine. Medication was re-initiated and the facial nerve paresis improved in all patients. In two patients intraoperative EMG signals revealed "A-trains" waveform patterns, which are highly suggestive for an immediate postoperative facial nerve paresis, whereas in four patients no pathognomonic EMG patterns could be recorded. CONCLUSIONS: The delayed onset of a facial paresis following termination of vasoactive treatment points to a disturbed microcirculation of the nerve as the main pathophysiological feature. Two groups could be identified on the basis of intraoperative EMG activity. In one group with presence of "A-trains" medication apparently masked the onset of an immediate postoperative facial nerve deficit. Four patients without "A-trains" did not develop a typical delayed facial nerve paresis during vasoactive treatment, but thereafter. The time lag between termination of treatment and onset of a delayed palsy points to a protective effect due to improved microcirculation.

Adult↗

PubMed1976

[Topodiagnostic ERA results at a female patient with multiple sclerosis in the brainstem (author's transl)].

At a female patient suffering from multiple sclerosis with demyelinisation mainly in the pontine and mesencephalic tegmentum, the five early potentials consisting of the compound action potential of the acoustic nerve (Pot. I) and the four brainstem potentials (Pot. II-V) as well as the slow evoked vertex-potential were registered. The threshold behaviour, the characteristic curve and the latency curve of all potentials were obtained, and thereby damages of the central acoustic pathways found out. A topodiagnostic is tried by means of the alterations of the peripheral and central ERA, and by means of the informations described in the literature. A control registration, carried out four weeks later, demonstrated an improvement of the diagnosis.

Audiometry↗

PubMed1991

[Multiple nerve root tumors and neurofibromatosis: contribution of magnetic resonance imaging].

Three patients (two females and one male) with radiculospinal neurologic involvement secondary to different forms of neurofibromatosis are reported. The first two met the diagnostic criteria for NF-1, although case 2 had a posterior fossa meningioma, which is an uncommon finding in this group. The male patient had an apparently sporadic NF-2, with bilateral acoustic nerve neurinoma, multiple meningioma, multiple radicular neurinoma and an intraspinal tumor apparent in magnetic resonance imaging. In the three cases the whole central nervous system was evaluated with gadolinium-enhanced magnetic resonance imaging. A great number of radicular tumors, many of which were asymptomatic, were detected. In spite of the severity of the clinical features, the three patients showed a dramatic improvement after the surgical removal of the symptomatic tumors. The use of magnetic resonance is encouraged, owing to its high resolution and safety, for the assessment of incidence, character and localization of tumors in neurofibromatosis and to establish a good clinico-lesional correlation before surgery. This technique may help to a better understanding of the spectrum of abnormalities in each type of neurofibromatosis, thus facilitating the evaluation of this complex condition.

Adult↗

PubMed1981

Estrogen receptors in acoustic neurilemmomas.

Acoustic neurilemmomas are more frequent, larger, and more vascular in women, and such lesions have a rapidly progressive clinical course in pregnant women; these findings suggest that the growth of these neoplasms may bear a relationship to certain hormone levels. Tissues from 8 patients with acoustic neurilemmoma (3 men and 5 women) were studied by a new fluorescent steroid histochemical technique to detect the presence of estrogen receptors in or on neoplastic cells. Estrogen receptor protein has also been found in meningioma cells in women. Neurilemmoma of the acoustic nerve is the second neoplasm of the central nervous system in which such receptors have been demonstrated.

Adult↗

PubMed1997

Glycinergic and GABAergic inputs affect short-term suppression in the cochlear nucleus.

Most cochlear nucleus (CN) neurons exhibit short-term response suppression to a second stimulus in a paired-pulse (click), forward-masking, paradigm. The magnitude of suppression, which appears to be greater than that observed in acoustic nerve, is dependent on the temporal separation and/or relative intensities of the two stimuli. Recent evidence suggests that inhibitory circuitry ending on CN neurons may mediate this response suppression. Using extracellular recordings from single CN neurons, suppression was evaluated using a forward-masking paradigm. Responses to paired acoustic clicks (i.e., a 'masker' followed by an identical 'probe' click) were measured while the time interval between the masker and probe was varied systematically. The role of inhibitory circuitry in forward-masking in the CN was assessed by pharmacologic manipulation of the GABA(A) and glycine(I) (strychnine-sensitive) receptors. Blockade of glycinergic or GABAergic receptors by iontophoretic application of the antagonists, strychnine and bicuculline methiodide, decreased the effects of forward-masking by shortening recovery times of the probe response in 2/3 of the neurons tested. Conversely, agonist application (glycine, and GABA or muscimol) increased the magnitude of suppression and delayed recovery of the probe response relative to control values. These findings suggest that known circuits releasing glycine and/or GABA mediate short-term response suppression in some CN neurons.

Acoustic Stimulation↗

PubMed1998

Comparison of response amplitude versus stimulation threshold in predicting early postoperative facial nerve function after acoustic neuroma resection.

OBJECTIVE: This study aimed to better predict the early postoperative facial nerve (FN) function after acoustic neuroma (AN) resection. STUDY DESIGN: This study was a prospective series. SETTING: The surgery was conducted in a tertiary referral center. PATIENTS: A total of 44 patients undergoing AN resection with cranial nerve monitoring were observed for at least 1 year after surgery. MAIN OUTCOME MEASURES: The predictive value of amplitude of the FN stimulus response on the early postoperative FN function was measured. RESULTS: Cranial nerve monitoring in AN surgery was used to obtain the stimulation threshold and facial electromyograph response amplitudes to FN stimulation proximal and distal to the tumor at 0.2 V above threshold. Thirty-eight of forty-four patients studied had a low postresection threshold (< or = 0.1 V). Of these (10), 26% sustained a postoperative FN dysfunction of House-Brackmann (HB) grades 3-6. In an effort to improve the predictive value from cranial nerve monitoring, the response amplitude to suprathreshold stimulation was compared with the threshold and FN function. Eighty-nine percent of patients with an amplitude of > or =200 microV had a grade 1-2 early postoperative FN function, whereas only 41% of patients with < 200 microV had a grade 1-2 early postoperative FN function (p = 0.00035). Eighty-eight percent of patients with both a low threshold and high amplitude had a grade 1-2 early postoperative FN function, whereas the remaining 12% of patients had a grade 3-6 FN function (p = 0.0032). The false-positive rate of threshold alone in predicting a grade 1-2 FN function was 26% compared to 12% for low threshold and high amplitude combined. CONCLUSIONS: The use of FN threshold and amplitude together is superior to threshold alone as a predictor of early postoperative FN function.

Adolescent↗