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Remote tentorium meningioma causing sudden sensorineural deafness
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Surgical Neurology 70 (2008) 312 – 318 www.surgicalneurology-online.com
Meningioma
Remote tentorium meningioma causing sudden sensorineural deafness☆ Dirk De Ridder, MD, PhD a,⁎, Tomas Menovsky, MD, PhD a , Carl Van Laer, MD b , Paul Van de Heyning, MD, PhD b Departments of
a
Neurosurgery, and bENT, University Hospital Antwerp, 2650 Edegem, Belgium Received 28 December 2006; accepted 16 April 2007
Abstract
Background: Sudden sensorineural deafness is a well-known symptom mostly of unknown etiology. Case Description: A case of sudden sensorineural deafness is reported to be caused by a small, remote, ipsilateral tentorial meningioma not compressing the vestibulocochlear nerve or auditory tract. Surgical resection of the meningioma immediately restored the patient's hearing. Conclusion: The authors hypothesize that the sudden sensorineural deafness resulted from a growing meningioma inducing a neurovascular compression of the vestibulocochlear nerve, the vertebral artery already being in close relationship with the vestibulocochlear nerve in the premorbid phase. Resection of the meningioma allows for an autodecompression of this vascular conflict resulting in hearing restoration. © 2008 Elsevier Inc. All rights reserved.
Keywords:
Microvascular compression; Meningioma; Neurovascular compression; Overcrowding; Sudden sensorineural deafness
1. Introduction Sudden sensorineural deafness is a symptom with an incidence in the United States of 1.5/100.000 [13]. Treatment for idiopathic sudden sensorineural deafness does not seem to surpass the spontaneous recovery rate (25–68%) seen in the natural history [10,14,33], though steroids [33] and hyperbaric oxygen treatment [14] might be beneficial in selected patients. Possible causes of sudden sensorineural deafness are viral and autoimmune disease, Ménière disease, trauma, vestibular schwannoma, multiple sclerosis, perilymphatic fistula, vascular disorders [8], and MVC [28,31,37]. Reports of meningiomas causing deafness are usually related to cerebellopontine tumors with direct compression of the vestibulocochlear nerve [19,27]. To our knowledge, no reports have been published on tumors at a distance from the cochlea, vestibulocochlear nerve, or auditory tract causing ipsilateral sudden sensorineural deafness. Abbreviations: AICA, anterior inferior cerebellar artery; BAEP, brainstem auditory evoked potentials; CISS, constructive in steady state; ENG, electronystagmography; CNS, central nervous system; IPL, interpeak latencies; MRI, magnetic resonance imaging; MVC, microvascular compression; 3D, 3-dimensional. ☆ Disclosure statement: The authors have not received any financial support in preparation of this submission. ⁎ Corresponding author. Tel.: +32 3 821 3336; fax: +32 3 825 2428. E-mail address: [email protected] (D. De Ridder). 0090-3019/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2007.04.014
The authors present a case of immediate restoration of hearing after resection of a small ipsilateral tentorial meningioma in the posterior fossa. 2. Case report 2.1. History A 68-year-old woman presented with a sudden sensorineural deafness in the right ear associated with a nonpulsatile tinnitus. There was no vertigo or aural fullness. Noise trauma or other possible etiologies for her hearing loss could not be found. Except for a breast tumor, which was surgically removed 2 years ago and postoperatively irradiated, the patient never had other major pathologies. 2.2. Clinical examination Micro-otoscopy was normal, Weber test lateralized to the left, and Rinne test was positive on the left and negative on the right. 2.3. Functional studies and imaging Tone audiometry demonstrated an asymmetric hearing deficit, with hearing thresholds at 110 dB on the right side and normal thresholds on the left side. Tympanometry showed normal middle ear pressures and acoustic
D. De Ridder et al. / Surgical Neurology 70 (2008) 312–318
admittance on both sides with intact ipsi- and contralateral stapedius reflex curve. Electronystagmographic analysis revealed a discrete hypofunctioning of the right side with normal central compensation. Transtympanic electrocochleography gave no arguments for endolymphatic hydrops. Serology and autoimmune testing were within reference range except for positive antinuclear (1/320) and cytoplasmatic (1/160) antibodies. Brainstem auditory evoked potentials could not be obtained due to the hearing deficit. Hyperbaric oxygen treatment was initiated consisting of a 5-day, 10-treatment sessions combined with intravenous corticosteroids administration, resulting in an improvement of 30 dB (Fig. 1A). Magnetic resonance imaging examination of the brain revealed an ipsilateral tentorial meningioma or a metastasis of the tentorium (Fig. 2A, B). On the thin-slice CISS images,
313
a microvascular conflict of the vestibulocochlear nerve could be assumed (Fig. 3). 2.4. Operation The patient was operated 1 week after termination of the hyperbaric oxygen therapy via a right-sided lateral suboccipital infratransverse sinus approach. A Simpson I resection was achieved consisting of a microscopically complete resection plus focal resection of the tentorium at the tumor base. Microscopic pathology confirmed the diagnosis of meningotheliomatous meningioma. 2.5. Postoperative course The postoperative course was uneventful. Two days post surgery, the patient noted that she answers the phone holding
Fig. 1. Audiogram depicting the hearing evolution. Upper figure: an improvement of 25 dB is achieved by hyperbaric oxygen treatment followed by a more dramatic improvement of 60 dB after meningioma removal. Lower figure: contralateral hearing status during same period.
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3. Discussion
Fig. 2. Preoperative MRI examination. Axial (A) and coronal (B) fat saturated T1-weighted MRI images after gadolinium-enhancement demonstrating a small tentorial meningioma remote from the auditory nerve or tract.
it in her right, that is, previously deaf, ear. She mentioned her hearing returning to almost normal. A high pitch nonpulsatile tinnitus remained present however. Her subjective findings were confirmed by audiometry. The hearing thresholds were improved to 30 versus 80 dB preoperatively (Fig. 1). The BAEPs at this stage demonstrated an absence of peak II and an interaural difference of 0.26 milliseconds. Interpeak latencies III-V were within reference range on both sides (Fig. 4A). Three months after surgery, the tinnitus had disappeared. Hearing thresholds have improved a further 10 dB and were almost symmetrical (Fig. 1). The BAEPs have normalized, that is, peak II has returned and the IPL I-III difference has become 0.1 milliseconds (Fig. 4B). After 6 months, MRI examination showed no contact of the blood vessels with the vestibulochochlear nerve (Fig. 5).
Sudden sensorineural deafness is a well-known clinical entity mostly of unknown origin. Sensorineural deafness resulting from infratentorial pathology can be caused by cochlear lesions, cranial nerve lesions, and brainstem pathology. At the level of the brainstem, the auditory tract follows a bilateral trajectory so brainstem lesions causing only unilateral deafness are extremely rare. Trying to explain sudden sensorineural deafness from a cochlear lesion in a patient with ipsilateral posterior fossa tentorial meningioma is almost impossible. Hence, only a cochlear nerve involvement seems plausible. In our patient, MRI demonstrated a possible MVC (Fig. 3). We hypothesize this MVC to be the cause for her sudden hearing loss. We base this hypothesis on 3 abnormal test results. Firstly, an MVC is seen on the preoperative MRI scanning (Fig. 3). As vascular compressions of the vestibulocochlear nerve are also found in many asymptomatic patients [17,30] (12.5% and 21.5%, respectively), we realize that this is not a sufficient argument. This discrepancy between the presence of a nerve compression and absence of symptoms is also noticed in trigeminal neuralgia (14%) [12] and even in herniated lumbar disks (36% nerve compressions without sciatica) [1], where this is not considered an argument to doubt about the pathophysiological importance of the neural compression. Secondly, the patient's postoperative BAEPs are highly suggestive for this hypothesis. Møller's criteria (Table 1) for MVC of the vestibulocochlear nerve are positive in this patient. An ipsilateral decrease in peak II is noted in this patient. Schwaber and Hall [32] found such a decrease in the amplitude of peak II in 57% of his patients who have cochleovestibular compression syndrome. Prolongation of the interpeak I-III latency occurred more frequently (66%), and although not longer than 2.3 milliseconds in this patient (2.14 milliseconds), we did find an interaural difference of more than 0.2 milliseconds (0.26 milliseconds), which is considered pathological. Peak II recurred 3 months after surgery, and the IPL I-III difference returned to normal (0.1 milliseconds). The returning of peak II and normalization of the IPL I-III difference coincides with the clinical disappearance of the postoperative ipsilateral tinnitus, probably relating to remyelinization of the affected nerve. A third argument is based in the ENG abnormalities. Because the vestibular component of the vestibulocochlear nerve is usually also involved in the compression, the discrete ipsilateral hypofunctioning of the labyrinth also fits the hypothesis of compression of the vestibulocochlear nerve. What is the relation between the neurovascular conflict and the meningioma that can explain the clinical evolution noted in this patient? We assume that the close anatomical relationship between the vertebral artery and the vestibulocochlear nerve was already present before the meningioma arose but was asymptomatic at that stage. The postoperative
D. De Ridder et al. / Surgical Neurology 70 (2008) 312–318
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Fig. 3. Preoperative MRI examination. Axial T2-weighted high-resolution CISS images through the cerebellopontine angle demonstrating a microvascular conflict of the right vestibulocochlear nerve.
MRI scan with high resolution CISS weighted images and 3D reconstruction clarifies the neurovascular anatomy clearly (Fig. 5). The delineating line between the vestibulocochlear nerve and vertebral artery highly suggests that no conflict is present anymore. In our patient, the growing meningioma decreased the available space for blood vessels and cranial nerves and can thus induce an MVC. Trigeminal neuralgia is reported to occur in posterior fossa tumors, both ipsilaterally [2,4,29] and contralaterally [9,11,16,18]. Many different pathophysiological mechanisms for this contralateral trigeminal neuralgia are proposed, such as direct trigeminal tract compression at the level of the brainstem [3], trigeminal nerve compression by the brainstem against the dura [26] or against the sharp edge of the dural foramen [23], or trigeminal nerve compression by an artery [6,11,35]. Ogasawara et al [24] described a relief of a tic convulsif secondary to the surgical removal of an ipsilateral large tentorial meningioma. The authors hypothesize the posteriorly located tumor displaces the brainstem directly, which results in secondary neurovascular compression of the fifth and seventh nerve, similar to the view shared by Ehni [7], Haddad and Taha [11], and Snow and Fraser [35]. Recently, it has been stated that for an MVC to become symptomatic, the compression has to be at the level of the CNS segment because this part of the cranial nerve is most sensible to microtrauma such as MVC [6]. The CNS segment of the VIIIth nerve is the longest in the posterior fossa with an average of 8.3 mm [15,34,36], that is, the whole cisternal part of the vestibulocochlear nerve. The other cranial nerves have a CNS segment that is a lot shorter; in the trigeminal nerve, it is 2.6 mm; in the facial nerve, 1.7 mm; and in the glossopharyngeal nerve, 1.2 mm. Therefore, the probability of a vascular compression to become symptomatic in the vestibulocochlear nerve is higher than in the facial nerve and
glossopharyngeal nerve as described before [6]. Vascular compression of the cochlear nerve is known to cause sudden sensorineural deafness that can be reversible if operated quickly [37]. Therefore, the immediate clinical improvement after surgery is most likely the result of an autodecompression of the VIIIth nerve. Sensorineural deafness due to “classical” MVC and subsequent improvement in hearing after microvascular decompression have been described by several authors recently [5,25,31]. Hearing impairment that occurs together with symptoms of vascular compression of the vestibular nerve, the intermediate nerve, or facial nerve is more likely to be caused by vascular contact with the auditory nerve, especially if it is frequency specific. For example, Moller and Moller [21] noted that some patients with a hemifacial spasm had hearing loss that occurred in narrow frequency ranges at low and mid-frequencies. De Ridder et al [5] reported on 31 patients who underwent microvascular decompression operations of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were substracted from postoperative audiograms obtained 2 years after microvascular decompression. Of the 31 patients studied, 19 had improvements of 5 dB or more at one or more frequencies postoperatively, and 15 patients had improvements of 10 dB or more. Three patients had improvements of 25 dB or more postoperatively. The postoperative hearing improvement was frequency-specific and related to the anatomical location of the vascular contact on the auditory nerve. The improvement of hearing became diluted when the differences between pre-and postoperative hearing thresholds were averaged over all audiometric frequencies. They concluded that decompression should be performed early, before BAEP changes become noticeable.
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Fig. 5. Postoperative MRI. Axial T2-weighted high-resolution CISS images demonstrating anatomical relationship between the right vestibulocochlear nerve and the AICA. Because a thin line can be revealed between the nerves and AICA, we conclude that there is no microvascular conflict.
VIII complex and the pons was observed, and postoperatively, the patient experienced a gradual return of useful hearing. Okamura et al [25] have shown that hearing improvement of more than 5 dB was achieved in 64% of patients in whom they performed microvascular decompression for cochlear symptoms (tinnitus and hearing loss). High-resolution heavily T2-weighted MRI images (CISS) has a high sensitivity and specificity for demonstrating MVCs. Newer techniques, involving 3D MRI reconstructing techniques, seem to be even more promising in locating the exact site of compression of the cochlear nerve. Correlation between the exact site of vascular compression and specific
Fig. 4. Preoperative BAEPs. Absence (A) and recurrence (B) of peak II as a diagnostic sign for MVC of the right vestibulocochlear nerve.
Rosseau et al [31] report on a patient with sudden sensorineural hearing loss who was found to have a megadolichoectasia vertebrobasilar system causing compression of the ipsilateral cranial nerves VII-VIII. The patient was treated conservatively for 4 months, during which time no hearing returned. He then underwent microvascular decompression of the affected nerves. At surgery, marked compression of the cranial nerves VII-
Table 1 Criteria for abnormal BAEPs in disabling positional vertigo (cochleovestibular compression syndrome) according to Møller [20] Wave I-III interval difference Wave I-III interval difference Wave II amplitude Contralateral wave III-V interval difference Contralateral wave III-V interval difference Ipsilateral wave I-III absolute interval Contralateral wave III-V absolute interval
N0.2 ms N0.16 ms if low or absent wave II b33% contralateral side N0.2 ms N0.16 ms if low or absent wave II N2.3 ms N2.2 ms
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frequency hearing loss, using this 3D imaging technique, is being verified [22]. 4. Conclusion Sudden sensorineural deafness can be caused by even a small tentorium meningioma by reducing the available space in the posterior fossa, resulting in an increased likelihood of vascular compression, especially if a close anatomical relationship was already present before the meningioma arose. Removing the meningioma surgically can result in a dramatic improvement of the auditory function by autodecompression of the cochlear nerve. This should alert surgeons to consider urgent surgery in the case of sudden sensorineural deafness if associated with space occupying lesions of the posterior fossa. Acknowledgments We thank Marina Pieters for assistance in preparing this manuscript. References [1] Boden S, Davis D, Dina T, et al. Magnetic resonance scans of the lumbar spine in asymptomatic patients. J Bone Joint Surg 1990;72A:403-8. [2] Bullit E, Tew JM, Boyd J. Intracranial tumors in patients with facial pain. J Neurosurg 1986;64:865-71. [3] Charbonnel A, Colas J, Baron F. Méningiome de l'angle pontocérébelleux. Névralgie trigéminale croisée. Interêt de la radiographie et de l' examen vestibulaire instrumental. Rev Oto-Neuro-Ophthalmol 1951;23:460-9. [4] Cheng TM, Cascino TL, Onofrio BM. Comprehensive study of diagnosis and treatment of trigeminal neuralgia secondary to tumors. Neurology 1993;43:2298-302. [5] De Ridder D, Ryu H, De Mulder G, et al. Frequency specific hearing improvement in microvascular decompression of the cochlear nerve. Acta Neurochir (Wien) 2005;147:495-501. [6] De Ridder D, Møller A, Verlooy J, et al. Is the root entry/exit zone important in microvascular compression syndromes? Neurosurgery 2002;51:427-33. [7] Ehni G. False localizing signs in intracranial tumors. Report of a patient with left trigeminal palsy due to a right temporal meningioma. Arch Neurol Psychiatry 1950;64:692-8. [8] Fitzgerald DC, Mark AS. Sudden hearing loss: frequency of abnormal findings on contrast-enhanced MR studies. AJNR Am J Neuroradiol 1998;19:1433-6. [9] Grigoryan YA, Onopchenko CV. Persistent trigeminal neuralgia after removal of contralateral posterior cranial fossa tumor. Report of two cases. Surg Neurol 1999;52:56-60. [10] Guyot JP, Thielen K. Evolution of sudden deafness without treatment. [in French]Schweiz Med Wochenschr Suppl 2000;116:93-6. [11] Haddad FS, Taha JM. An unusual cause for trigeminal neuralgia/ contralateral meningioma of the posterior fossa. Neurosurgery 1990;26:1033-8. [12] Hamlyn P. Neurovascular relationships in the posterior cranial fossa, with special reference to trigeminal neuralgia. 2. Neurovascular compression of the trigeminal nerve in cadaveric controls and patients with trigeminal neuralgia: quantification and influence of method. Clin Anat 1997;10:380-8. [13] Hughes GB, Freedman MA, Haberkamp TJ, et al. Sudden sensorineural hearing loss. Otolaryngol Clin North Am 1996;29:393-405.
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[14] Lamm K, Lamm H, Arnold W. Effect of hyperbaric oxygen therapy in comparison to conventional or placebo therapy or no treatment in idiopathic sudden hearing loss, acoustic trauma, noise-induced hearing loss and tinnitus. A literature survey. Adv Otorhinolaryngol 1998;54:86-99. [15] Lang J. Uber Bau, Länge und Gefässbeziehungen der zentralen und peripheren Strecken der intrazisternalen Hirnnerven. Zentralblatt für Neurochirurgie 1982;43:217-58. [16] Maatsuura N, Kondo A. Trigeminal neuralgia and hemifacial spasm as false localizing signs in patients with a contralateral mass of the posterior cranial fossa. Report of three cases. J Neurosurg 1996;84:1067-71. [17] Makins AE, Nikolopoulos TP, Ludman C, et al. Is there a correlation between vascular loops and unilateral auditory symptoms? Laryngoscope 1998;108:1739-42. [18] Mase G, Zorzon M, Capus L, et al. Trigeminal neuralgia due to contralateral meningioma of the posterior cranial fossa. J Neurol Neurosurg Psychiatry 1994;57:1010. [19] Matthies C, Carvalho G, Tatagiba M, et al. Meningiomas of the cerebellopontine angle. Acta Neurochir Suppl (Wien) 1996;65:86-91. [20] Møller MB. Controversy in Meniere's disease: results of microvascular decompression of the eighth nerve. Am J Otol 1988;9:60-3. [21] Moller MB, Moller AR. Audiometric abnormalities in hemifacial spasm. Audiology 1985;24:396-405. [22] Nowe V, De Ridder D, Van de Heyning P, et al. Does the location of a vascular loop in the cerebellopontine angle explain pulsatile and nonpulsatile tinnitus? Eur Radiol 2004;14:2282-9. [23] O'Connell JEA. Trigeminal false localizing signs and their causation. Brain 1978;101:119-42. [24] Ogasawara H, Oki S, Kohno H, et al. Tentorial meningioma and painful tic convulsif. Case report. J Neurosurg 1995;82:895-7. [25] Okamura T, Kurokawa Y, Ikeda N, et al. Microvascular decompression for cochlear symptoms. J Neurosurg 2000;93:421-6. [26] Paillas JE, Pellet W, Janny P, et al. L'atteinte contre-latérale des nerfs craniens au cours des tumeurs de la fosse postérieure. [in French]Rev Neurologique 1969;121:452-64. [27] Pensak ML, Glasscock III ME, Josey AF, et al. Sudden hearing loss and cerebellopontine angle tumors. Laryngoscope 1985;95:1188-93. [28] Portmann M, Dauman R, Aran JM. Audiometric and electrophysiological correlations in sudden deafness. Acta Otolaryngol 1985;99:363-8. [29] Puca A, Meglio M. Typical trigeminal neuralgia associated with posterior cranial fossa tumors. Ital J Neurol Sci 1993;14:549-52. [30] Reisser C, Schuknecht H. The anterior inferior cerebellar artery in the internal auditory canal. Laryngoscope 1991;101:761-6. [31] Rosseau GL, Jannetta PJ, Hirsch B, et al. Restoration of useful hearing after microvascular decompression of the cochlear nerve. Am J Otol 1993;14:392-7. [32] Schwaber MK, Hall JW. Cochleovestibular nerve compression syndrome: I. Clinical features and audiovestibular test findings. Laryngoscope 1992;102:1020-9. [33] Schweinfurth JM, Parnes SM, Very M. Current concepts in the diagnosis and treatment of sudden sensorineural hearing loss. Eur Arch Otorhinolaryngol 1996;253:117-21. [34] Skinner HA. Some histologic features of the cranial nerves. Arch Neurol Psychiatry 1931;25:356-60. [35] Snow RB, Fraser RAR. Cerebello-pontine angle tumor causing contralateral trigeminal neuralgia: a case report. Neurosurgery 1987;21:84-6. [36] Tarlov IM. Structure of the nerve root. 1. Nature of the junction between the central and the peripheral nervous system. Arch Neurol Psychiatry 1937;37:555-83. [37] Wahlig JB, Kaufmann AM, Balzer J, et al. Intraoperative loss of auditory function relieved by microvascular decompression of the cochlear nerve. Can J Neurol Sci 1999;26:44-7.
Surgical Neurology 70 (2008) 312 – 318 www.surgicalneurology-online.com
Meningioma
Remote tentorium meningioma causing sudden sensorineural deafness☆ Dirk De Ridder, MD, PhD a,⁎, Tomas Menovsky, MD, PhD a , Carl Van Laer, MD b , Paul Van de Heyning, MD, PhD b Departments of
a
Neurosurgery, and bENT, University Hospital Antwerp, 2650 Edegem, Belgium Received 28 December 2006; accepted 16 April 2007
Abstract
Background: Sudden sensorineural deafness is a well-known symptom mostly of unknown etiology. Case Description: A case of sudden sensorineural deafness is reported to be caused by a small, remote, ipsilateral tentorial meningioma not compressing the vestibulocochlear nerve or auditory tract. Surgical resection of the meningioma immediately restored the patient's hearing. Conclusion: The authors hypothesize that the sudden sensorineural deafness resulted from a growing meningioma inducing a neurovascular compression of the vestibulocochlear nerve, the vertebral artery already being in close relationship with the vestibulocochlear nerve in the premorbid phase. Resection of the meningioma allows for an autodecompression of this vascular conflict resulting in hearing restoration. © 2008 Elsevier Inc. All rights reserved.
Keywords:
Microvascular compression; Meningioma; Neurovascular compression; Overcrowding; Sudden sensorineural deafness
1. Introduction Sudden sensorineural deafness is a symptom with an incidence in the United States of 1.5/100.000 [13]. Treatment for idiopathic sudden sensorineural deafness does not seem to surpass the spontaneous recovery rate (25–68%) seen in the natural history [10,14,33], though steroids [33] and hyperbaric oxygen treatment [14] might be beneficial in selected patients. Possible causes of sudden sensorineural deafness are viral and autoimmune disease, Ménière disease, trauma, vestibular schwannoma, multiple sclerosis, perilymphatic fistula, vascular disorders [8], and MVC [28,31,37]. Reports of meningiomas causing deafness are usually related to cerebellopontine tumors with direct compression of the vestibulocochlear nerve [19,27]. To our knowledge, no reports have been published on tumors at a distance from the cochlea, vestibulocochlear nerve, or auditory tract causing ipsilateral sudden sensorineural deafness. Abbreviations: AICA, anterior inferior cerebellar artery; BAEP, brainstem auditory evoked potentials; CISS, constructive in steady state; ENG, electronystagmography; CNS, central nervous system; IPL, interpeak latencies; MRI, magnetic resonance imaging; MVC, microvascular compression; 3D, 3-dimensional. ☆ Disclosure statement: The authors have not received any financial support in preparation of this submission. ⁎ Corresponding author. Tel.: +32 3 821 3336; fax: +32 3 825 2428. E-mail address: [email protected] (D. De Ridder). 0090-3019/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2007.04.014
The authors present a case of immediate restoration of hearing after resection of a small ipsilateral tentorial meningioma in the posterior fossa. 2. Case report 2.1. History A 68-year-old woman presented with a sudden sensorineural deafness in the right ear associated with a nonpulsatile tinnitus. There was no vertigo or aural fullness. Noise trauma or other possible etiologies for her hearing loss could not be found. Except for a breast tumor, which was surgically removed 2 years ago and postoperatively irradiated, the patient never had other major pathologies. 2.2. Clinical examination Micro-otoscopy was normal, Weber test lateralized to the left, and Rinne test was positive on the left and negative on the right. 2.3. Functional studies and imaging Tone audiometry demonstrated an asymmetric hearing deficit, with hearing thresholds at 110 dB on the right side and normal thresholds on the left side. Tympanometry showed normal middle ear pressures and acoustic
D. De Ridder et al. / Surgical Neurology 70 (2008) 312–318
admittance on both sides with intact ipsi- and contralateral stapedius reflex curve. Electronystagmographic analysis revealed a discrete hypofunctioning of the right side with normal central compensation. Transtympanic electrocochleography gave no arguments for endolymphatic hydrops. Serology and autoimmune testing were within reference range except for positive antinuclear (1/320) and cytoplasmatic (1/160) antibodies. Brainstem auditory evoked potentials could not be obtained due to the hearing deficit. Hyperbaric oxygen treatment was initiated consisting of a 5-day, 10-treatment sessions combined with intravenous corticosteroids administration, resulting in an improvement of 30 dB (Fig. 1A). Magnetic resonance imaging examination of the brain revealed an ipsilateral tentorial meningioma or a metastasis of the tentorium (Fig. 2A, B). On the thin-slice CISS images,
313
a microvascular conflict of the vestibulocochlear nerve could be assumed (Fig. 3). 2.4. Operation The patient was operated 1 week after termination of the hyperbaric oxygen therapy via a right-sided lateral suboccipital infratransverse sinus approach. A Simpson I resection was achieved consisting of a microscopically complete resection plus focal resection of the tentorium at the tumor base. Microscopic pathology confirmed the diagnosis of meningotheliomatous meningioma. 2.5. Postoperative course The postoperative course was uneventful. Two days post surgery, the patient noted that she answers the phone holding
Fig. 1. Audiogram depicting the hearing evolution. Upper figure: an improvement of 25 dB is achieved by hyperbaric oxygen treatment followed by a more dramatic improvement of 60 dB after meningioma removal. Lower figure: contralateral hearing status during same period.
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3. Discussion
Fig. 2. Preoperative MRI examination. Axial (A) and coronal (B) fat saturated T1-weighted MRI images after gadolinium-enhancement demonstrating a small tentorial meningioma remote from the auditory nerve or tract.
it in her right, that is, previously deaf, ear. She mentioned her hearing returning to almost normal. A high pitch nonpulsatile tinnitus remained present however. Her subjective findings were confirmed by audiometry. The hearing thresholds were improved to 30 versus 80 dB preoperatively (Fig. 1). The BAEPs at this stage demonstrated an absence of peak II and an interaural difference of 0.26 milliseconds. Interpeak latencies III-V were within reference range on both sides (Fig. 4A). Three months after surgery, the tinnitus had disappeared. Hearing thresholds have improved a further 10 dB and were almost symmetrical (Fig. 1). The BAEPs have normalized, that is, peak II has returned and the IPL I-III difference has become 0.1 milliseconds (Fig. 4B). After 6 months, MRI examination showed no contact of the blood vessels with the vestibulochochlear nerve (Fig. 5).
Sudden sensorineural deafness is a well-known clinical entity mostly of unknown origin. Sensorineural deafness resulting from infratentorial pathology can be caused by cochlear lesions, cranial nerve lesions, and brainstem pathology. At the level of the brainstem, the auditory tract follows a bilateral trajectory so brainstem lesions causing only unilateral deafness are extremely rare. Trying to explain sudden sensorineural deafness from a cochlear lesion in a patient with ipsilateral posterior fossa tentorial meningioma is almost impossible. Hence, only a cochlear nerve involvement seems plausible. In our patient, MRI demonstrated a possible MVC (Fig. 3). We hypothesize this MVC to be the cause for her sudden hearing loss. We base this hypothesis on 3 abnormal test results. Firstly, an MVC is seen on the preoperative MRI scanning (Fig. 3). As vascular compressions of the vestibulocochlear nerve are also found in many asymptomatic patients [17,30] (12.5% and 21.5%, respectively), we realize that this is not a sufficient argument. This discrepancy between the presence of a nerve compression and absence of symptoms is also noticed in trigeminal neuralgia (14%) [12] and even in herniated lumbar disks (36% nerve compressions without sciatica) [1], where this is not considered an argument to doubt about the pathophysiological importance of the neural compression. Secondly, the patient's postoperative BAEPs are highly suggestive for this hypothesis. Møller's criteria (Table 1) for MVC of the vestibulocochlear nerve are positive in this patient. An ipsilateral decrease in peak II is noted in this patient. Schwaber and Hall [32] found such a decrease in the amplitude of peak II in 57% of his patients who have cochleovestibular compression syndrome. Prolongation of the interpeak I-III latency occurred more frequently (66%), and although not longer than 2.3 milliseconds in this patient (2.14 milliseconds), we did find an interaural difference of more than 0.2 milliseconds (0.26 milliseconds), which is considered pathological. Peak II recurred 3 months after surgery, and the IPL I-III difference returned to normal (0.1 milliseconds). The returning of peak II and normalization of the IPL I-III difference coincides with the clinical disappearance of the postoperative ipsilateral tinnitus, probably relating to remyelinization of the affected nerve. A third argument is based in the ENG abnormalities. Because the vestibular component of the vestibulocochlear nerve is usually also involved in the compression, the discrete ipsilateral hypofunctioning of the labyrinth also fits the hypothesis of compression of the vestibulocochlear nerve. What is the relation between the neurovascular conflict and the meningioma that can explain the clinical evolution noted in this patient? We assume that the close anatomical relationship between the vertebral artery and the vestibulocochlear nerve was already present before the meningioma arose but was asymptomatic at that stage. The postoperative
D. De Ridder et al. / Surgical Neurology 70 (2008) 312–318
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Fig. 3. Preoperative MRI examination. Axial T2-weighted high-resolution CISS images through the cerebellopontine angle demonstrating a microvascular conflict of the right vestibulocochlear nerve.
MRI scan with high resolution CISS weighted images and 3D reconstruction clarifies the neurovascular anatomy clearly (Fig. 5). The delineating line between the vestibulocochlear nerve and vertebral artery highly suggests that no conflict is present anymore. In our patient, the growing meningioma decreased the available space for blood vessels and cranial nerves and can thus induce an MVC. Trigeminal neuralgia is reported to occur in posterior fossa tumors, both ipsilaterally [2,4,29] and contralaterally [9,11,16,18]. Many different pathophysiological mechanisms for this contralateral trigeminal neuralgia are proposed, such as direct trigeminal tract compression at the level of the brainstem [3], trigeminal nerve compression by the brainstem against the dura [26] or against the sharp edge of the dural foramen [23], or trigeminal nerve compression by an artery [6,11,35]. Ogasawara et al [24] described a relief of a tic convulsif secondary to the surgical removal of an ipsilateral large tentorial meningioma. The authors hypothesize the posteriorly located tumor displaces the brainstem directly, which results in secondary neurovascular compression of the fifth and seventh nerve, similar to the view shared by Ehni [7], Haddad and Taha [11], and Snow and Fraser [35]. Recently, it has been stated that for an MVC to become symptomatic, the compression has to be at the level of the CNS segment because this part of the cranial nerve is most sensible to microtrauma such as MVC [6]. The CNS segment of the VIIIth nerve is the longest in the posterior fossa with an average of 8.3 mm [15,34,36], that is, the whole cisternal part of the vestibulocochlear nerve. The other cranial nerves have a CNS segment that is a lot shorter; in the trigeminal nerve, it is 2.6 mm; in the facial nerve, 1.7 mm; and in the glossopharyngeal nerve, 1.2 mm. Therefore, the probability of a vascular compression to become symptomatic in the vestibulocochlear nerve is higher than in the facial nerve and
glossopharyngeal nerve as described before [6]. Vascular compression of the cochlear nerve is known to cause sudden sensorineural deafness that can be reversible if operated quickly [37]. Therefore, the immediate clinical improvement after surgery is most likely the result of an autodecompression of the VIIIth nerve. Sensorineural deafness due to “classical” MVC and subsequent improvement in hearing after microvascular decompression have been described by several authors recently [5,25,31]. Hearing impairment that occurs together with symptoms of vascular compression of the vestibular nerve, the intermediate nerve, or facial nerve is more likely to be caused by vascular contact with the auditory nerve, especially if it is frequency specific. For example, Moller and Moller [21] noted that some patients with a hemifacial spasm had hearing loss that occurred in narrow frequency ranges at low and mid-frequencies. De Ridder et al [5] reported on 31 patients who underwent microvascular decompression operations of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were substracted from postoperative audiograms obtained 2 years after microvascular decompression. Of the 31 patients studied, 19 had improvements of 5 dB or more at one or more frequencies postoperatively, and 15 patients had improvements of 10 dB or more. Three patients had improvements of 25 dB or more postoperatively. The postoperative hearing improvement was frequency-specific and related to the anatomical location of the vascular contact on the auditory nerve. The improvement of hearing became diluted when the differences between pre-and postoperative hearing thresholds were averaged over all audiometric frequencies. They concluded that decompression should be performed early, before BAEP changes become noticeable.
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Fig. 5. Postoperative MRI. Axial T2-weighted high-resolution CISS images demonstrating anatomical relationship between the right vestibulocochlear nerve and the AICA. Because a thin line can be revealed between the nerves and AICA, we conclude that there is no microvascular conflict.
VIII complex and the pons was observed, and postoperatively, the patient experienced a gradual return of useful hearing. Okamura et al [25] have shown that hearing improvement of more than 5 dB was achieved in 64% of patients in whom they performed microvascular decompression for cochlear symptoms (tinnitus and hearing loss). High-resolution heavily T2-weighted MRI images (CISS) has a high sensitivity and specificity for demonstrating MVCs. Newer techniques, involving 3D MRI reconstructing techniques, seem to be even more promising in locating the exact site of compression of the cochlear nerve. Correlation between the exact site of vascular compression and specific
Fig. 4. Preoperative BAEPs. Absence (A) and recurrence (B) of peak II as a diagnostic sign for MVC of the right vestibulocochlear nerve.
Rosseau et al [31] report on a patient with sudden sensorineural hearing loss who was found to have a megadolichoectasia vertebrobasilar system causing compression of the ipsilateral cranial nerves VII-VIII. The patient was treated conservatively for 4 months, during which time no hearing returned. He then underwent microvascular decompression of the affected nerves. At surgery, marked compression of the cranial nerves VII-
Table 1 Criteria for abnormal BAEPs in disabling positional vertigo (cochleovestibular compression syndrome) according to Møller [20] Wave I-III interval difference Wave I-III interval difference Wave II amplitude Contralateral wave III-V interval difference Contralateral wave III-V interval difference Ipsilateral wave I-III absolute interval Contralateral wave III-V absolute interval
N0.2 ms N0.16 ms if low or absent wave II b33% contralateral side N0.2 ms N0.16 ms if low or absent wave II N2.3 ms N2.2 ms
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