ABSTRACT
We developed a cochlear nerve action potential (CNAP) monitoring technique using a
microdissector and compared the results of CNAP and auditory brainstem response (ABR)
monitoring. Thirty-six patients underwent vestibular schwannoma resection via the
retrosigmoid approach to preserve hearing. Both CNAP with the microdissector and surface
ABR were recorded during the operation. We used the microdissector as an intracranial
electrode for CNAP monitoring. The CNAP waveform was classified into four types: triphasic,
biphasic, positive, and flat. At the completion of the tumor resection, the triphasic
waveform was observed in 11 patients and the biphasic waveform was observed in 11
patients. Hearing function was preserved in all of them, although it was preserved
in only two patients with other CNAP waveform types. The prognostic value of CNAP
is significantly higher than that of ABR. We found that although CNAP with a microdissector
does not provide real-time monitoring, with the classification of waveforms it can
be used as predictable tool for postoperative hearing more accurately than ABR.
KEYWORDS
cochlear nerve action potential - microdissector - auditory brainstem response - vestibular
schwannoma
REFERENCES
- 1
Tucker A, Slattery III W H, Solcyk L, Brackmann D E.
Intraoperative auditory assessments as predictors of hearing preservation after vestibular
schwannoma surgery.
J Am Acad Audiol.
2001;
12(9)
471-477
- 2
Abramson M, Stein B M, Pedley T A, Emerson R G, Wazen J J.
Intraoperative BAER monitoring and hearing preservation in the treatment of acoustic
neuromas.
Laryngoscope.
1985;
95(11)
1318-1322
- 3
Danner C, Mastrodimos B, Cueva R A.
A comparison of direct eighth nerve monitoring and auditory brainstem response in
hearing preservation surgery for vestibular schwannoma.
Otol Neurotol.
2004;
25(5)
826-832
- 4
Schmerber S, Lavieille J P, Dumas G, Herve T.
Intraoperative auditory monitoring in vestibular schwannoma surgery: new trends.
Acta Otolaryngol.
2004;
124(1)
53-61
- 5
Jackson L E, Roberson Jr J B.
Acoustic neuroma surgery: use of cochlear nerve action potential monitoring for hearing
preservation.
Am J Otol.
2000;
21(2)
249-259
- 6
Nedzelski J M, Chiong C M, Cashman M Z, Stanton S G, Rowed D W.
Hearing preservation in acoustic neuroma surgery: value of monitoring cochlear nerve
action potentials.
Otolaryngol Head Neck Surg.
1994;
111(6)
703-709
- 7
Rowed D W, Nedzelski J M, Cashman M Z, Stanton S, Harrison R V.
Cochlear nerve monitoring during cerebellopontine angle operations.
Can J Neurol Sci.
1988;
15(1)
68-72
- 8
Linden R D, Tator C H, Benedict C, Charles D, Mraz V, Bell I.
Electrophysiological monitoring during acoustic neuroma and other posterior fossa
surgery.
Can J Neurol Sci.
1988;
15(1)
73-81
- 9
Zappia J J, Wiet R J, O'Connor C A, Martone L.
Intraoperative auditory monitoring in acoustic neuroma surgery.
Otolaryngol Head Neck Surg.
1996 l;
115(1)
98-106
- 10
Samii M, Matthies C.
Management of 1000 vestibular schwannomas (acoustic neuromas): surgical management
and results with an emphasis on complications and how to avoid them.
Neurosurgery.
1997;
40(1)
11-21
- 11
Samii M, Matthies C.
Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve–preservation
and restitution of function.
Neurosurgery.
1997;
40(4)
684-694
- 12
Samii M, Gerganov V, Samii A.
Improved preservation of hearing and facial nerve function in vestibular schwannoma
surgery via the retrosigmoid approach in a series of 200 patients.
J Neurosurg.
2006;
105(4)
527-535
- 13
Møller A R, Jannetta P J.
Compound action potentials recorded intracranially from the auditory nerve in man.
Exp Neurol.
1981;
74(3)
862-874
- 14
Roberson Jr J B, Jackson L E, McAuley J R.
Acoustic neuroma surgery: absent auditory brainstem response does not contraindicate
attempted hearing preservation.
Laryngoscope.
1999;
109(6)
904-910
- 15
Hoehmann D.
Pre- and postoperative hearing thresholds and brainstem responses in patients with
acoustic neuroma: follow-up study using the middle fossa approach.
Am J Otol.
1991;
12(3)
172-178
- 16
Colletti V, Fiorino F G, Mocella S, Policante Z.
ECochG, CNAP and ABR monitoring during vestibular schwannoma surgery.
Audiology.
1998;
37(1)
27-37
- 17
Sekiya T, Iwabuchi T, Kamata S, Ishida T.
Deterioration of auditory evoked potentials during cerebellopontine angle manipulations.
An interpretation based on an experimental model in dogs.
J Neurosurg.
1985;
63(4)
598-607
- 18
Rosenberg S I, Martin W H, Pratt H, Schwegler J W, Silverstein H.
Bipolar cochlear nerve recording technique: a preliminary report.
Am J Otol.
1993;
14(4)
362-368
- 19
Tani T, Ushida T, Yamamoto H, Okuhara Y.
Waveform changes due to conduction block and their underlying mechanism in spinal
somatosensory evoked potential: a computer simulation. Technical note.
J Neurosurg.
1997;
86(2)
303-310
- 20
Colletti V, Fiorino F G.
Advances in monitoring of seventh and eighth cranial nerve function during posterior
fossa surgery.
Am J Otol.
1998;
19(4)
503-512
- 21
Colletti V, Bricolo A, Fiorino F G, Bruni L.
Changes in directly recorded cochlear nerve compound action potentials during acoustic
tumor surgery.
Skull Base Surg.
1994;
4(1)
1-9
Noritaka AiharaM.D. Ph.D.
Department of Neurosurgery, Nagoya City University Medical School
Kawasumi 1, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
Email: aihara@med.nagoya-cu.ac.jp
