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PubMed2002

Current results of the surgical management of acoustic neuroma.

A retrospective analysis of 162 consecutive cases in 160 patients who underwent microsurgical resection of vestibular schwannomas between October 1995 and June 2001 was undertaken to compare the results with those of other treatment modalities. Patient hospital records, operative video pictures, neuroimaging studies, audiograms, and follow-up data were reviewed. The mean follow-up period was 24 months.There were 34 small (<1.5 cm), 92 medium (1.5-3 cm), and 36 (>3 cm) large tumors. Six were recurrent tumors. Gross total resection was accomplished in all 34 small tumors and 92 medium tumors but only in 50% of the large tumors. Among the 126 small and medium tumors, the facial nerve was saved anatomically in 124 patients. On long-term follow up, facial function was preserved in 94.4% of all patients. Anatomically, the cochlear nerve was preserved in 55.9% of the small and 20.7% of the medium tumors. Function was preserved (Gardner-Robertson class 1 and 2) in 25% of the small and in 19.4% of the medium tumors. Cerebrospinal leakage was present in 10.5%, meningitis in 9.9%, wound infection in 3.7%, and hematoma or contusion in 2.5%. Only one patient died (mortality rate 0.6%). Our data reflect that surgical removal should be the standard management for acoustic tumors, particularly for large and medium tumors, and can be accomplished with acceptable complication rates.

Journal Article↗

PubMed1996

Vestibular nerve section following previous mastoidectomy.

Vestibular neurectomy is an effective procedure in the management of vertigo due to active labyrinthine disease. Various approaches have been developed for selectively sectioning the vestibular nerve, in order to preserve serviceable hearing and avoid facial nerve injury. In patients who have a mastoid cavity, from previous surgery for chronic otitis media, the approach to the vestibular nerve has to be modified. Considerations taken into account are cavity infection, hearing status, and the presence of associated loud tinnitus. Vestibular or vestibulo-cochlear nerve section has been undertaken, by the senior author, in eight patients with a mastoid cavity from previous surgery for chronic otitis media. Translabyrinthine, retrosigmoid and middle fossa approaches have all been used; strategies for selection of each specific technique are considered, and the aetiology of post-chronic suppurative otitis media (CSOM) peripheral vestibular disease discussed.

Adult↗

PubMed1995

Microsurgical anatomy around the foramen of Luschka in relation to intraoperative recording of auditory evoked potentials from the cochlear nuclei.

Three cadaveric heads were dissected to investigate the microsurgical anatomy around the foramen of Luschka. It was found possible to place a recording electrode in proximity to the cochlear nuclei by inserting it in the lateral recess of the fourth ventricle through the foramen of Luschka. In operations of the cerebellopontine angle using the retromastoid approach, access to the foramen of Luschka and the lateral recess is obtained by retracting the biventral lobule of the cerebellum in a caudal-rostral direction under a caudal-rostral/medial field of vision. The craniectomy might need to be enlarged a few millimeters in the caudal direction. A wick electrode can be inserted in the lateral recess beneath the choroid plexus in a rostromedial direction and to a depth of approximately 3 to 5 mm from the foramen of Luschka without excessive retraction of the cerebellum. The optimum position for the recording electrode is in the triangle formed by the axis of the cochlear nerve and the glossopharyngeal nerve and by the lip of the foramen of Luschka. The caudal retromastoid approach is more suitable than the translabyrinthine technique for recording from the cochlear nuclei as well as for implantation of stimulating electrodes into the cochlear nuclei for use as hearing prostheses.

Cadaver↗

PubMed1996

Correlation of MRI, clinical, and electroneuronographic findings in acute facial nerve palsy.

Intratemporal enhancement of (Gd-DTPA) was investigated by an interleaved-overlapping magnetic resonance imaging (MRI) technique in 35 cases of acute facial palsy. In a reference group (normal facial function), enhancement was localized from the ganglion geniculi to the stylomastoid foramen. In cases of acute palsy, the facial nerve enhanced in the meatal fundus independent of etiology (idiopathic, herpetic, or traumatic). In 70% of those with Ramsay-Hunt syndrome, the vestibular and cochlear nerves, the labyrinth, and the sheets of the internal and external auditory canal additionally enhanced. No correlation was found between intensity, extension, and duration of the enhancement and the clinical, intraoperative, or electroneuronographic degree of the facial palsy. The pathogenesis of the Gd-DTPA enhancement of the facial nerve appears to be closely connected with the vascular supply of the fallopian canal and the permeability of the neural sheets.

Adolescent↗

PubMed2000

The prognostic value of promontory electric auditory brain stem response in pediatric cochlear implantation.

OBJECTIVE: To test the hypothesis that children with clear promontory electrically evoked auditory brain stem responses (prom-EABRs) would outperform, after cochlear implantation, children who had no prom-EABR preoperatively. DESIGN: A prospective study was undertaken on 47 implanted children assigning them to two groups (group A: 35 children with a clear wave e-V in the preoperative prom-EABR and group B: 12 children with no prom-EABR). Speech perception and speech intelligibility were assessed annually up to 3 yr after implantation with the IOWA sentence test (level A and level B), Connected Discourse Tracking, Categories of Auditory Performance, and Speech Intelligibility Rating. t-test and Mann-Whitney U test were used to compare the above outcome measures in the two groups. RESULTS: There was no statistically significant difference between the two groups on any of the outcome measures at any interval. Moreover, the small differences observed showed no consistent trend toward either group of children. Further analysis revealed that the outcomes have not been affected by possible confounding factors (age at implantation, duration of deafness, preoperative unaided pure-tone thresholds, and number of inserted electrodes). CONCLUSIONS: The results suggest that children with no prom-EABR performed at levels comparable with children who had clear promontory responses preoperatively. The prognostic value of prom-EABR is limited and absence of a prom-EABR is not, by itself, a contraindication for cochlear implantation. However, in selected cases (congenital malformations, cochlear nerve dysplasia or suspected aplasia, narrow internal auditory canal, etc.) the presence of a prom-EABR is a positive finding in the assessment of candidates for cochlear implantation as it confirms the existence of intact auditory neurones.

Audiometry, Pure-Tone↗

PubMedDate not supplied

Surgery of the internal acoustic meatus and the cerebello-pontine angle.

Tumoral and functional surgery of the cerebellopontine angle and the internal acoustic meatus has been performed in our department for more than 20 years. Acoustic neurinomas (700 cases operated to date) represent the great bulk of this surgery. Since 1985, we have drastically modified our approach to these tumors (220 cases). Large tumors are now dealt with, regardless of the patient's hearing, through a widened translabyrinthine approach. Small tumors with normal hearing are operated on through a suboccipital or a retrolabyrinthine approach depending on the tumoral extension in the internal acoustic meatus. The facial nerve function was preserved in 83% of the cases. Hearing was saved only 6 times in 45 attempts, despite 23 cases of apparent anatomical conservation of the cochlear nerve. Vestibular neurectomy, carried out through a middle cranial fossa or through a retrolabyrinthine approach, ameliorated vertigo in 95% of cases. The major operative risks are regressive facial paresis and secondary total deafness (10% of cases). Surgical treatment of facial hemispasm by neurovascular decompression is very effective, but not without risk. We now prefer to use botulin toxin therapy.

Cerebellar Neoplasms↗

PubMed1991

Effect of dexamethasone or HWA-138 in combination with antibiotics in experimental Haemophilus influenzae type b infection.

Modulation of the host's inflammatory response in bacterial meningitis may be beneficial. In this study, the effects of dexamethasone and HWA-138, an analog of pentoxifylline, on CSF cultures and cochlear inflammation in an infant rat model of Haemophilus influenzae type b were studied. Five-day-old infant rats were inoculated once intraperitoneally with 1 x 10(4) to 10 x 10(4) CFU of H. influenzae type b (strain 1406). Twenty-four hours later, infant rats were treated intraperitoneally with one dose of ampicillin (0.1 mg/g of body weight), cefotaxime (0.05 mg/g), or cefuroxime (0.05 mg/g) alone or in combination with one dose of dexamethasone (0.00015 mg/g) or HWA-138 (0.005 mg/g). Twenty-four hours after treatment with cefuroxime plus dexamethasone, animals had a significantly (P less than or equal to 0.04) greater incidence of bacteremia and meningitis (eight of nine animals) than that in animals of the other treatment groups. Overall, dexamethasone was associated with less inflammation (P less than 0.04) of the cochlear nerve compared with that from antibiotic treatment alone. In this model, when suboptimal antimicrobial therapy is administered, anti-inflammatory agents may be beneficial with respect to reducing cochlear inflammation. However, dexamethasone and cefuroxime lead to a higher rate of positive blood and cerebral spinal fluid cultures than cefuroxime alone.

Ampicillin↗

PubMed2006

Preservation of facial nerve function after postoperative vasoactive treatment in vestibular schwannoma surgery.

OBJECTIVE: Facial nerve paresis and hearing loss are common complications after vestibular schwannoma surgery. Experimental and clinical studies point to a beneficial effect of nimodipine and hydroxyethyl starch for preservation of cochlear nerve function. A retrospective analysis was undertaken to evaluate the effect of vasoactive treatment on facial nerve outcome. PATIENTS AND METHODS: Forty-five patients with vestibular schwannoma removal, intraoperative electromyographic monitoring, and postoperative deterioration of facial nerve function were evaluated. Twenty-five patients underwent vasoactive treatment consisting of nimodipine and hydroxyethyl starch for improvement of hearing outcome. Twenty patients did not receive such treatment. Facial nerve function was evaluated before and after surgery, as well as 1 year after the surgical procedure. Patients were comparable regarding age, tumor size, and preoperative facial nerve function. RESULTS: Long-term results of facial nerve function were significantly improved in those patients who experienced severe postoperative deterioration of facial nerve function and received vasoactive treatment as compared with patients who did not receive nimodipine and hydroxyethyl starch after surgery. Treated patients showed a significantly higher rate of complete recovery compared with patients without treatment. CONCLUSION: The study points to a potential effect of vasoactive treatment for facial nerve function after vestibular schwannoma surgery. In particular, patients with postoperative disfiguring facial nerve palsy clearly benefit from intravenous hydroxyethyl starch and nimodipine with respect to a long-term socially acceptable facial nerve function.

Adult↗

PubMed1991

Acoustic neuromas presenting as sudden hearing loss.

Progressive hearing loss is well known as a usually existing complaint in patients with acoustic neuromas. However, sudden hearing loss is also a relatively frequent condition in acoustic neuroma patients. In our review of 132 patients with surgically proven unilateral acoustic neuromas, 29 (22.0%) presented a history of sudden hearing loss. We investigated the clinical and audiological characteristics of these patients, and discuss the etiology of sudden hearing loss in patients with acoustic neuromas. The characteristics of patients with AN presenting sudden hearing loss were as follows: 1) a small tumor, 2) short duration after onset, 3) low incidences of vertigo, dizziness, facial and trigeminal nerve symptoms, 4) the trough type in the audiogram configuration, 5) normal caloric response. Based on the analysis of these results, we conclude that a conduction block of the cochlear nerve is likely to be the etiology of sudden hearing loss.

Adult↗

PubMed1990

[Vestibular efferent neurons of the guinea pig forming projections into the saccule].

The distribution of vestibular efferent neurons projecting to the saccule and efferent neurons transmitting axons to the acoustic nerve (cochlear efferent neurons) has been studied in guinea pig by comparison using the method of retrograde axonal transport of horseradish peroxidase. The saccular efferent neurons are revealed bilaterally in the subendymal granular fundus of the fourth ventricle of the brain and more laterally of the facial nerve genu, ipsilaterally in the small-celled reticular nucleus as well as in nuclei of the supraolivary complex: nucleus of lateral oliva and lateral nucleus of the trapezoid body. The cochlear efferent neurons are localized ipsilaterally in the reticular caudal nucleus of the bridge in the anteroventral cochlear nucleus and in nuclei of lateral and medial olivae. In the medial nucleus of the trapezoid body such neurons are found contralaterally. Thus, the regions of the vestibular saccular efferent neurons are partially overlapped with such of the cochlear efferent units. Possible participation of the vestibular efferent neurons of the saccule in the mechanism of the acoustic perception is discussed.

Animals↗

PubMed1991

Identification of point scores at stage 23 in the rat according to the system of scoring in the human embryo.

The 8-point scores, evidenced in the human embryo of stage 23, were analysed in the rat at the end of the embryonic period. Eleven OFA rat embryos-crown-rump length 16 mm, 16th postcoital day--were submitted to serial histological sections with graphic reconstruction. The 8 internal key structures, previously observed in man by O'Rahilly--i.e. the cornea, optic nerve, cochlear duct, adenohypophysis, vomeronasal organ, submandibular gland, metanephros and humerus--were readily recognizable. The identification of these anatomical features permits to determine the end of the embryonic period and to obtain a clear distinction between this and the fetal period. The similarity and the presence of the same organs in man and rats at this period of development permits to consider the rat as a good experimental model of teratology.

Animals↗

PubMedDate not supplied

Estimates of essential neural elements for stimulation through a cochlear prosthesis.

Electrical stimulation of afferent auditory pathways through electrodes placed within and outside of the cochlea were used to study stimulation and design parameters relevant to a cochlear prosthesis. In the acute guinea pig preparation, the tract response evoked in brachium of the inferior colliculus by electrical stimulation to an ear provided estimates of the effectiveness of various electrode placements. Stimulation between an electrode in the cochlea and a site along the eighth nerve was characterized by the lowest thresholds. Stimulation between intracochlear electrodes was somewhat less effective, and stimulation between external electrodes at the nerve, cochlear nucleus, or distant point was least effective. Thresholds, expressed as current, rose at approximately 6 dB per octave for stimulus frequencies from 1 kHz to 16 kHz. Thresholds below 10 microA rms were seen for optimal placements. These observations suggest that the neural elements being stimulated are the cell bodies of the spiral ganglion cells.

Afferent Pathways↗

PubMed2004

Hearing preservation with the transcrusal approach to the petroclival region.

OBJECTIVE: We studied the hearing results and outcomes after transcrusal craniotomy. STUDY DESIGN: We conducted a retrospective review. SETTING: This study was conducted at a tertiary care hospital. PATIENTS: We studied 10 consecutive patients, including two men and eight women, who underwent transcrusal craniotomy for petroclival masses or tumors. INTERVENTION: The intervention consisted of therapeutic removal of petroclival meningioma. MAIN OUTCOME MEASURE: The main outcome measure of this study was hearing preservation as measured by standard audiogram. RESULTS: There were six meningiomas, one eighth nerve schwannoma, one fifth nerve schwannoma, one chordoma, and one midbasilar artery aneurysm. Postoperative hearing was measured according to the AAOHNS criteria. Complications and further therapies were recorded. Postoperative hearing was measured in eight. The cochlear nerve was severed in one patient. One was unavailable for follow up. Eight patients retained hearing at or near preoperative levels, seven with SRT within 10 dB and speech discrimination within 10% of preoperative levels. Four patients presented with trigeminal symptoms, one with third nerve palsy and two with facial weakness. Postoperative deficits included fourth, sixth, seventh, and eighth nerve palsies in three patients. Complications included one wound infection, two cerebrospinal fluid leak, and two cases of meningitis, both of which were sterile. There were secondary procedures in five patients-three radiosurgery, two shunts, one tracheotomy, and one g-tube. CONCLUSIONS: Transcrusal craniotomy is a safe and effective approach to the petroclival region. Excellent hearing results can be expected with this technique.

Adult↗

PubMed2000

Connections of the facial and vestibular nerves: an anatomic study.

The facial and vestibulocochlear nerves emanate from the brain stem and then run parallel to each other within the internal auditory canal prior to their more peripheral distribution. Although anatomic connections between the facial and cochlear nerves have been described, reports outlining facial-vestibular anastomoses are few and may be found primarily in the non-English literature. The present study documents the existence of vestibulofacial neural connections as part of an anatomic dissection of 17 fresh human temporal bones.

Facial Nerve↗

PubMedDate not supplied

Role of biophysical specialization in cholinergic modulation in neurons of the ventral cochlear nuclei.

In contacting arrays of different types of neurons whose axons have differing targets in the brain stem, the auditory pathway is subdivided into parallel ascending pathways, each of which carries a different type of information. Several distinct arrays of neurons in the ventral cochlear nuclei have anatomical and biophysical specializations which enable them to extract differing facets of acoustic information and to convey it up the auditory pathway. T stellate cells have higher input resistances and have lower firing thresholds than bushy or octopus cells, enabling their firing to be modulated by small currents. Cholinergic currents, driven by neurons in the ventral nucleus of the trapezoid body that are likely to include medial olivocochlear efferents, excite T stellate cells, but have subtle effects on the firing of bushy cells, and have no detectable influence on octopus cells and D stellate cells. We suggest that cholinergic excitation of T stellate cells contributes toward shifting their acoustic dynamic ranges and increasing the encoding of spectral peaks in noisy conditions and in awake animals.

Acetylcholine↗

PubMed2005

[Anatomical references in auditory brainstem implant surgery].

UNLABELLED: The auditory brainstem implant (ABI) is an option for deaf patients who do not have the whole of their auditory pathways preserved. The surgery, because of its anatomical and functional complexity, requires specific training of the surgeon in an anatomy lab. AIM: To study the surgical anatomy of the surgery for auditory brainstem implant. STUDY DESIGN: Anatomic study. MATERIAL AND METHOD: In this exercise we dissected a fresh cadaver prepared with a dye solution injected into the arteries and intra-cranial veins. The location for the insertion of the electrode for the ABI has been studied through the translabyrinthine access. RESULTS: The surgical technique used for implanting the electrode of the brainstem is similar to that used in the removal of the schwannoma vestibular. The cochlear nucleus complex, composed of the ventral and dorsal cochlear nuclei is the location for placing the electrode. The ventral cochlear nucleus is the principal nucleus for transmission of neural impulses from the VIII par and form the main ascendant route of the cochlear nerve. Neither the ventral nor the dorsal nuclei are visible during surgery and their location depends on the identification of adjacent anatomical structures. CONCLUSION: The region for the implantation of the electrode in the auditory brainstem implant presents anatomical references that allow its easy identification during surgery.

Auditory Brain Stem Implants↗

PubMed1986

A systematic approach to the surgical management of acoustic neuroma.

Contemporary otomicrosurgical techniques have made total removal of acoustic tumor with preservation of the seventh and sometimes the eighth cranial nerves possible. The four approaches currently used in acoustic tumor surgery are the middle cranial fossa, the translabyrinthine, the suboccipital, and the combined translabyrinthine-suboccipital. This review examines the surgical results in the removal of more than 600 acoustic tumors and outlines a rationale for the choice of approach. Tumor size on computed tomographic scan and auditory reserve establish the parameters used in planning the surgical procedure. The translabyrinthine exposure is used most frequently followed by the combined translabyrinthine-suboccipital. The middle fossa and suboccipital approaches are used when preservation of hearing is attempted. Total removal of tumor was accomplished in more than 99% of patients with a mortality rate of less than 1%. Anatomic preservation of the facial nerve, which is directly related to tumor size, was achieved in more than 80% of patients. Preservation of hearing is unlikely when the tumor is larger than 2 cm; anatomic preservation of the cochlear nerve was successful in 73% of hearing preservation procedures.

Adolescent↗

PubMedDate not supplied

Postauricular (12 msec latency) responses to acoustic stimuli in patients with peripheral, facial nerve palsy.

The postauricular (12 msec latency) response to a loud click stimulation was investigated in 23 patients with facial nerve palsy. Of these patients 21 had an intracranial cause for the facial palsy and 2 had an extracranial cause. Only in those with the extracranial facial nerve damage could the response be obtained from both sides. When the nerve was damaged intracranially there was no response on the paralysed side. This seems to indicate that the posterior auricular muscle is the effector of the presumed sonomotor reflex arc involving the cochlea, cochlear nerve and nuclei, undetermined brainstem pathway, facial motor nucleus, facial nerve and the muscles supplied by it.

Acoustic Stimulation↗