Electrophysiologic Identification of the Cochlear Nerve Fibers during Cerebellopontine Angle Surgery

Colletti, Vittorio; Fiorino, Francesco

doi:10.3109/00016489309135895

Cited by 24 publications

(10 citation statements)

References 17 publications

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“…Therefore the surgeon cannot be sure which manipulation during the tumour dissection has caused the loss of BAEPs. The direct monitoring of the cochlear nerve (CNAP) may warn the surgeon earlier [7,42]. But it is not able to explain, which manipulation really had caused the worsening of the potentials.…”

Section: Introductionmentioning

confidence: 99%

Influence of blood supply, thermal and mechanical traumata on hearing function in an animal model

Braun

Richter

1996

Acta neurochir

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Even with modern neurosurgical techniques preservation of functional hearing in acoustic neurinoma surgery is still impossible in a large number of cases. Due to the necessity of averaging the brainstem auditory evoked potentials (BAEP) this monitoring is not a real time measurement. Therefore the surgeon cannot be sure which manipulation during the tumour dissection has caused the loss of the BAEPs. The direct monitoring of the cochlear nerve (CNAP) may warn the surgeon earlier. But it is not able to explain, which manipulation has caused the worsening of the potentials. A loss of the waves after coagulation of a vessel next to the cochlear nerve may be the result of the heat or of the disturbance of the blood supply. Potentially harmful to cochlear nerve function may be the interruption of inner ear blood supply, thermal or mechanical traumata. Experimental studies are rare to nonexistent. We therefore tested selectively each trauma for its influence on the BAEPs in an animal model. In New Zealand rabbits a lateral craniectomy of the posterior fossa was performed. Care was taken not to retract the cerebellum or to open the inner ear system, because both factors might disturb the BAEPs. Each step of the operation was followed by BAEP recording. After reaching the internal auditory canal, the cerebellopontine angle of 6 animals was exposed to heated water with definitive increasing temperature. The BAEPs did not react significantly until 71 degrees C was reached and protein coagulation started. In the second group, the internal auditory artery of 6 rabbits was compressed with a microdissector for 3 minutes. Subsequently the BAEPs disappeared in all animals. In the last group a constant pressure of 10 g was applied to 6 cochlear nerves for 1 minute consistently causing the loss of the BAEPs. The results are statistically significant (p = 0.03). We therefore concluded that the blood supply of the inner ear is of the upmost importance for cochlear nerve function. Mechanical manipulation should be minimized whereas thermal traumatization of the nerve is only critical when the nerve itself is coagulated.

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Section: Introductionmentioning

confidence: 99%

Influence of blood supply, thermal and mechanical traumata on hearing function in an animal model

Braun

Richter

1996

Acta neurochir

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“…A particular feature of the RS-TM approach is the unique possibility it affords of performing real-time intraoperative monitoring by means of direct recording of CNAPs and FNAPs. [14][15][16][17][18][19] Instantaneous information on the function of the cochlea and the cochlear and facial nerves is obtained with these techniques, and insights into the mechanisms of hearing and facial nerve impairment are therefore available during surgery. [14][15][16][17][18][19] The information provided by intraoperative monitoring has thus helped refine surgical techniques directed toward the preservation of cranial nerve function.…”

Section: Discussionmentioning

confidence: 99%

“…Otoacoustic emissions and electrocochleography (EcoG) were used in the early stages but were soon abandoned because of poor reliability in the results obtained with these techniques. 8 The intraoperative auditory monitoring technique has been reported in previous articles [14][15][16][17][18] and will be only briefly outlined here. The ear undergoing the operation is stimulated by rarefaction click stimuli at 31/s, generated by applying 100-micron rectangular electric pulses through a lightweight set of earphones (such as those used with portable cassette players or radios).…”

Section: Methodsmentioning

confidence: 99%

Intraoperative Monitoring for Hearing Preservation and Restoration in Acoustic Neuroma Surgery

Colletti¹,

Fiorino²,

Carner³

et al. 2000

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Su rgeryHearing preservation during AN surgery is one of the most intriguing and interesting aspects of the otoneurosurgeon's work.Advances in diagnostic testing enabling audiologists and neuro-otologists to diagnose a higher proportion of patients with small ANs are probably the most important factors underlying the progressive increase in hearing preservation rates. The application of neurophysiological intraoperative monitoring methods and the consequent refinement of surgical techniques are additional important factors that have increased hearing preservation rates.The challenge facing the neuro-otologist today is all the more stimulating as a result of the incredible progress achieved in hearing restoration in the only hearing ear in patients with AN or in patients with NF2. Most of these patients cannot be rehabilitated using a traditional cochlear implant when the auditory nerves are no longer intact after surgery. The multichannel ABI electrically stimulates the auditory system at the level of the cochlear nuclei, providing partial restoration of auditory function. 1-6 An additional theoretical indication for ABI is total deafness in patients with head trauma or cochlear nerve aplasia. A critical role in the decision to 187 Skull

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“…Proper identification and respect for CN and vascular structures, preservation of the inner ear, and early detection of cochlear and/or neural damage are the prerequisites for hearing preservation. 4,10,11,[15][16][17][18][19][20] Auditory brainstem responses (ABRs) have been utilized in AN surgery to establish correlations between surgical maneuvers and damage to cochlear structures and postoperative hearing, the aim being to identify and avoid dangerous surgical maneuvers.21-24 ABRs, however, require a considerable length of time (at least 1 to 2 min) for reliable responses to be obtained and interpreted. To analyze each individual maneuver in a more specific and detailed way, enabling the surgeon to correlate causes and effects of damage, a real-time recording technique is needed.…”

Section: Discussionmentioning

confidence: 99%

Iatrogenic Impairment of Hearing During Surgery for Acoustic Neuroma

Colletti¹,

Fiorino²,

Sacchetto³

1996

Skull Base

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The decision to attempt hearing preservation during acoustic neuroma (AN) surgery has a dramatic impact on the choice of surgical approach. The translabyrinthine route, which has been in use for many years by otoneurosurgeons, has helped to reduce the mortality and morbidity rates. According to many authors, this is the technique of choice in subjects with poor preoperative hearing function, that is, greater than 50 dB or 70 dB in pure-tone average (PTA) and/or less than 70% or 50% in speech discrimination score (SDS).'-5 In patients with serviceable hearing, the retrosigmoid or middle fossa routes are preferred. '-5 Our group is intensely involved in functional otosurgical procedures and particularly in hearing preservation during AN surgery. To this end we selected the retrosigmoid-transmeatal approach, as it presents a series of advantages such as adequate control of bleeding in the cerebellopontine angle (CPA) and the possibility of monitoring hearing function by means of direct recording of cochlear nerve action potentials (CNAPs).5-0 TWhis method of monitoring is particularly suitable for investigating the mechanisms of auditory damage in AN and during AN surgery. The derived potentials are of large amplitude and are easily visualized on an oscilloscope either directly or after averaging a few responses. They provide rapid information on the function of the cochlear nerve (CN) and the cochlea. They also furnish a unique opportunity to investigate auditory physiology and pathophysiology in humans.11-13During surgery of the posterior fossa, CNAPs have proven to be sensitive in detecting damage to the periph-153

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Electrophysiologic Identification of the Cochlear Nerve Fibers during Cerebellopontine Angle Surgery

Cited by 24 publications

References 17 publications

Influence of blood supply, thermal and mechanical traumata on hearing function in an animal model

Influence of blood supply, thermal and mechanical traumata on hearing function in an animal model

Intraoperative Monitoring for Hearing Preservation and Restoration in Acoustic Neuroma Surgery

Iatrogenic Impairment of Hearing During Surgery for Acoustic Neuroma

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