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Cerebellopontine angle ganglionic hamartoma: case report.

Abstract

Cerebellopontine angle (CPA) ganglionic hamartomas are rare. We present a case of a 49-year-old woman who presented with left-sided hearing loss of more than 4 years' duration and vertigo since childhood. Magnetic resonance imaging revealed a mass on the intracanalicular segment of cranial nerve VIII on the left side, consistent with acoustic schwannoma. She opted for observation of the tumor. The patient returned 21 months after the initial evaluation with new-onset left facial weakness. At this time, a working diagnosis of facial nerve neuroma was made. The lesion was excised, and pathology confirmed a diagnosis of left-sided CPA ganglionic hamartoma. Otolaryngologists should be familiar with this uncommon tumor and include it in the differential diagnosis of CPA lesions.

Introduction

Acoustic neuromas account for 90% of cerebellopontine angle (CPA) lesions, with the other major primary tumors being meningiomas (3%), primary cholesteatomas (2.5%), and facial nerve schwannomas (1%). (1) Other CPA lesions are rare, with ganglionic hamartomas being among the rarest; only 11 cases have been reported. (2-10) We present a case of CPA ganglionic hamartoma in which the lesion was diagnosed preoperatively as a probable facial nerve neuroma.

Case report

A 49-year-old woman presented with left-sided hearing loss of more than 4 years' duration, occasional tinnitus, and vertigo. She had experienced vertigo since the age of 12 years, but the frequency of episodes had increased during the preceding year. She had no abnormal findings on physical examination.

All cranial nerve function was normal bilaterally with the exception of cranial nerve VIII. An audiogram revealed normal hearing on the right and mild to moderate sensorineural hearing loss (72% speech discrimination) on the left. Brainstem-evoked--response audiometry showed no signs of retrocochlear pathology. A 22% reduced left vestibular response and right-beating nystagmus were found on electronystagmography.

Electroneuronography (ENoG) demonstrated a 78% decreased facial response on the left. Probably because of the thickness and resiliency of the facial nerve, we have seen ENoG results showing as much as an 85% decrease in some patients who still had clinically normal facial function. Magnetic resonance imaging (MRI) revealed an enhancing 5 x 3-mm mass on the intracanalicular segment of cranial nerve VIII on the left, consistent with acoustic schwannoma (figure 1). Observation was recommendedinitially, with audiograms every 3 months and MRI every 6 months.

The patient returned 21 months after her initial evaluation with new-onset facial weakness on the left. The weakness was most prominent in her upper lip and nasolabial crease, and it was most pronounced when she spoke. Physical examination revealed a House/Brackmann grade I-II/VI palsy of the left facial nerve. Repeat ENoG revealed no change in electrical function when compared to the previous study. A working diagnosis of facial nerve neuroma was made, although the patient was informed that acoustic neuroma or other pathology could not be excluded.

The patient underwent a translabyrinthine excision of the lesion, which was located on a superior vestibular nerve, extending inferiorly to the area of the cochlear modiolus. The lesion was reflected medially, and an incision was made in the cerebellar dura. The lesion was larger than recognized on MRI and was followed to its medial extent of a few millimeters into the posterior fossa. Facial nerve function was preserved, but a House/Brackmann grade I-II/VI palsy was still evident 5 months postsurgically. Compression of the facial nerve by the tumor in the superior compartment of the internal auditory canal explained the preoperative and postoperative facial paresis.

Histologic evaluation of the lesion demonstrated normal myelinated axon fascicles separated by fibrous stroma and adipose tissue. Along the axons were multiple foci of mature ganglion cells with well-formed Nissl bodies in the peripheral cytoplasm. Foci of less mature ganglion cells also were identified. Immunohistochemical staining for synaptophysin, neurofilaments, and S-100 protein demonstrated a normal pattern of immunoreactivity. Furthermore, immunohistochemical staining for the tumor-proliferation marker MIB-1 revealed no positive cells. Based on the histologic examination, a diagnosis of left CPA ganglionic hamartoma was established (figure 2).

Discussion

The term hamartoma refers to a mass of abnormally arranged cells typically found in the surrounding tissue. (11) Such a lesion is believed to be a result of aberrant differentiation of tissue during embryonic development. Intracranial hamartomas can be subdivided into lipomatous and glioneuronal types. Lipomatous hamartomas are also known as lipomas and constitute less than 0.14% of CPA neoplasms. (4) Glioneuronal hamartomas are much rarer, with only 11 cases reported in the literature before the present case. (2-10)

Of the 11 patients whose cases were described in the previous reports, 2 were asymptomatic; the neoplasm was an incidental finding on autopsy in those 2 patients and in 1 additional patient (table). The remaining 9 patients presented with hearing loss on the affected side. Even when small, these firm tumors can compress cranial nerves VII and VIII and produce symptoms. Other symptoms include vertigo/disequilibrium, facial palsy, tinnitus, and headache.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Complete tumor excision was performed in most cases, with 1 partial resection to preserve the cochlear nerve. In 3 cases, partial resection of cranial nerves was performed to allow complete excision of the tumor. In one of these cases, the cochlear nerve was sacrificed; in another both the cochlear and vestibular nerves were sacrificed; and in the third case, the cochlear, vestibular, and facial nerves were sacrificed. In the case in which partial resection of the tumor was performed, the patient was doing well 1.5 years postoperatively, with no tumor regrowth. One patient who underwent complete tumor resection with preservation of cranial nerves suffered from facial nerve palsy, which improved over the first postoperative year. No other complications were reported.

Our patient presented initially with left-sided hearing loss, vertigo, and tinnitus with subsequent development of facial palsy. The tumor was situated on the superior vestibular nerve, which was sacrificed in favor of complete resection of the tumor. The postoperative course was uneventful, with no complications.

Complete resection of these tumorsis considered curative; however, only limited data are available regarding recurrence or regrowth following partial resection. In asymptomatic patients, surgical excision of the tumor may not be advisable because of the risks associated with resection, provided an accurate diagnosis can be established preoperatively, which is not common. (4) In the 11 previously reported cases and in the present case, no patient was accurately diagnosed preoperatively. Our patient was initially diagnosed with an acoustic neuroma, and the working diagnosis was changed to facial nerve neuroma when the studies were completed and her facial paresis occurred, but other pathology could not be excluded. Because of the progressive symptoms, surgical excision was deemed appropriate.

Ganglionic hamartomas remain challenging to differentiate preoperatively from other neoplasms of the CPA.

References

(1.) Brackmann DE, Arriaga MA. Extra-axial neoplasms of the posterior fossa. In: Cummings CW, ed. Otolaryngology Head & Neck Surgery. 4th ed. St. Louis: Mosby; 2005:1469-71.

(2.) Babin RW, Fratkin JD, Cancilla PA. Hamartomas of the cerebellopontine angle and internal auditory canal: Report of two cases. Arch Otolaryngol 1980;106(8):500-2.

(3.) Ho KL. Concurrence of ganglionic hamartoma and heterotopic neuroglial tissue in the cerebellopontine angle. Arch Pathol Lab Med 1981;105(8):438-9.

(4.) Palmer CA, Townsend JJ, Harnsberger HR, et al. Cerebellopontine angle glioneuronal hamartoma. Surg Neurol 1996;45(5):467-9.

(5.) Hung TY, Litofsky NS, Smith TW, Megerian CA. Ganglionic hamartoma of the intracanalicular acoustic nerve causing sensorineurai hearing loss. Am J Otol 1997;18(4):498-500.

(6.) Gonul E, Yetiser S, Tasar M, Ongoru O. Glioneural hamartoma of the VIIIth nerve. J Laryngol Otol 2006;120(1):70-3.

(7.) Goda M, Isono M, Karashima A, et al. Hamartoma in the internal auditory canal. J Clin Neurosci 2003;10(1):111-13.

(8.) Carvalho GA, Matthies C, Osorio E, Samii M. Hamartomas of the internal ausitory canal: Report of two cases. Neurosurgery 2003;52(4):944-8; discussion 948-9.

(9.) Apostolides PJ, Spetzler RF, Johnson PC. Ectomeshenchymal hamartoma (benign "ectomesenchymoma") of the VIIIth nerve: Case report. Neurosurgery 1995;37(6):1204-7.

(10.) Ajal M, Roche J, Turner J, Fagan P. Unusual lesions of the internal auditory canal. J Laryngol Otol 1998;112(7):650-3.

(11.) Kumar V, Faust N, Abbas A, eds. Robbins & Cotran Pathologic Basis of Disease. 7th ed. Philadelphia: Saunders; 2004:90.

Sidrah M. Ahmad, BS; Fernando Garcia, MD; Robert T. Sataloff, MD, DMA, FACS

From the Department of Otolaryngology-Head and Neck Surgery (Ms. Ahmad and Dr. Sataloff) and the Department of Pathology (Dr. Garcia), Drexel University College of Medicine, Philadelphia.

Corresponding author: Robert T. Sataloff, MD, 1721 Pine St., Philadelphia, PA 19103. E-mail: rtsataloff@phillyent.com
Table. Previously reported cases of cerebellopontine angle hamartoma

Author(s)                Pt.   Symptoms                Preop
                         age                           diagnosis

Babin et al, 1980 (2)    43    Decreased hearing       N/A
                               on right

                         36    None                    N/A

Ho, 1981 (3)             67    None                    N/A

Palmer et al, 1996 (4)   71    Intermittent vertigo    CPA tumor
                               and hearing loss

Hung et al, 1997 (5)     40    Progressive hearing     Intracanalicular
                               loss                    vestibular
                                                       schwannoma

Gonul et al, 2006 (6)    34    Unsteadiness and        Intracanalicular
                               hearing loss            vestibular
                                                       schwannoma

Goda et al, 2003 (7)     11    Progressive hearing     Intrameatal
                               loss and facial palsy   acoustic neuroma

Carvalho et al,          40    Progressive hearing     Intrameatal
2003 (8)                       loss and tinnitus       vestibular
                                                       schwannoma

                         39    Headache and            Intrameatal
                               progressive             vestibular
                               hearing loss            schwannoma

Apostolides et al,       35    Hearing loss            Intracanalicular
1995 (9)                                               vestibular
                                                       schwannoma

Ajal et al, 1998 (10)    15    Progressive             Acoustic neuroma
                               hearing loss and

Author(s)                Pt.   Affected   Findings
                         age     side

Babin et al, 1980 (2)    43       R       Ganglionic hamartoma
                                          involving intracranial
                                          portions of cochlear and
                                          vestibular nerves *

                         36       R       Ganglionic hamartoma
                                          in the CPA involving the
                                          Vlllth nerve *

Ho, 1981 (3)             67       R       Ganglionic hamartoma and
                                          heterotopic neuroglial
                                          tissue in the CPA near
                                          exit of Vlllth nerve *

Palmer et al, 1996 (4)   71       R       Ganglionic hamartoma
                                          involving the cochlear
                                          nerve

Hung et al, 1997 (5)     40       L       Ganglionic hamartoma
                                          involving the cochlear
                                          nerve

Gonul et al, 2006 (6)    34       L       Ganglionic hamartoma
                                          involving the Vlllth nerve

Goda et al, 2003 (7)     11       L       Ganglionic hamartoma
                                          involving cranial nerves
                                          (cochlear, vestibular, and
                                          facial nerves were
                                          indistinguishable)

Carvalho et al,          40       R       Ganglionic hamartoma
2003 (8)                                  involving both the cochlear
                                          and facial nerves

                         39       L       Ganglionic hamartoma
                                          involving the cochlear
                                          and vestibular nerves

Apostolides et al,       35       R       Ganglionic hamartoma
1995 (9)

Ajal et al, 1998 (10)    15       L       Ganglionic hamartoma
                                          involving Vlllth nerve

Author(s)                Pt.   Surgical
                         age   outcomes

Babin et al, 1980 (2)    43    N/A

                         36    N/A

Ho, 1981 (3)             67    N/A

Palmer et al, 1996 (4)   71    Complete resection
                               of tumor with
                               preservation of nerve ([dagger])

Hung et al, 1997 (5)     40    Complete tumor
                               resection with partial
                               resection of cochlear
                               nerve

Gonul et al, 2006 (6)    34    Complete resection
                               of tumor with
                               preservation of nerve

Goda et al, 2003 (7)     11    Complete tumor
                               resection with partial
                               resection of cochlear,
                               vestibular, and facial
                               nerves

Carvalho et al,          40    Partial resection of
2003 (8)                       tumor in favor of
                               preservation of nerves

                         39    Complete tumor
                               resection with partial
                               resection of cochlear
                               and vestibular nerves

Apostolides et al,       35    Complete resection of
1995 (9)                       tumor

Ajal et al, 1998 (10)    15    Complete resection of
                               tumor
                               loss of balance

* Incidental finding during autopsy.

([dagger]) Patient experienced a complication--facial nerve
palsy--which improved 1 year postoperatively.
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Title Annotation:ORIGINAL ARTICLE
Author:Ahmad, Sidrah M.; Garcia, Fernando; Sataloff, Robert T.
Publication:Ear, Nose and Throat Journal
Article Type:Clinical report
Geographic Code:1USA
Date:Mar 1, 2010
Words:1871
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