Internal auditory canal metastasis - Acta Otorhinolaryngologica Italica
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Internal auditory canal metastasis - Acta Otorhinolaryngologica Italica
ACTA OTORHINOLARYNGOL ITAL 24, 78-82, 2004 Internal auditory canal metastasis Le metastasi del condotto uditivo interno M. FALCIONI, E. PICCIRILLO, G. DI TRAPANI, G. ROMANO, A. RUSSO Gruppo Otologico, Piacenza-Roma, Italy Key words Tumours of the ear • Internal auditory canal neoplasms • Metastasis Summary Parole chiave Tumori dell’orecchio • Neoplasie del condotto uditivo interno • Metastasi Riassunto This report deals with 3 cases of internal auditory canal metastasis, an extremely rare lesion, few cases having been reported in the international literature. Since pre-operative diagnosis is fundamental in the planning of a correct therapeutic strategy, it is important that the neurotologist be aware of the possibility of their occurrence in this particular area. Metastasis can occur unilaterally as well as bilaterally; the latter being the case in 1 of the patients described herein. Correct pre-operative diagnosis is particularly difficult in patients in whom the primary tumour has not been detected at the time of identification of the lesion in the internal auditory canal. The only characteristic, specific of metastasis, is the presence of multifocal cerebral lesions. However, these were detected in only 1 of the present cases. On the contrary, in cases of a single metastasis, both magnetic resonance imaging and computed tomography usually fail to show any distinctive feature when compared to the most common tumours of the internal auditory canal (vestibular schwannomas and meningiomas). Bilateral metastases can also be misdiagnosed as neurofibromatosis type 2. Clinical data that should alert the clinician are: rapidly progressive sensorineural hearing loss, followed by onset of progressive facial nerve weakness. Radiotherapy and/or chemotherapy are the two main treatment modalities, while surgical removal is reserved for selected cases of a single metastasis. Albeit, due to the paucity of specific radiological and clinical characteristics, surgical removal is often necessary to reach the correct diagnosis, as occurred in 2 of the present patients. In questo lavoro sono riportati 3 casi di lesioni metastatiche a livello del condotto uditivo interno. Si tratta di lesioni estremamente rare, con pochissimi casi riportati nella letteratura internazionale; tuttavia è importante che il neurotologo sia a conoscenza della possibilità dell’insorgenza di lesioni metastatiche a questo livello, in quanto la diagnosi preoperatoria è fondamentale per la pianificazione di una corretta strategia terapeutica. Le metastasi possono manifestarsi sia mono che bilateralmente; questa ultima eventualità si è verificata in 1 dei nostri 3 casi. Il raggiungimento di una corretta diagnosi preoperatoria è spesso difficile, soprattutto nei pazienti in cui il tumore primitivo è sconosciuto al momento dell’identificazione della lesione a livello del condotto uditivo interno. L’unica caratteristica specifica delle metastasi è la presenza di lesioni multifocali a livello cerebrale. Tuttavia tali lesioni erano presenti in 1 caso soltanto tra i nostri pazienti. Al contrario in caso di metastasi singole sia la TC che la RMI generalmente non evidenziano caratteristiche distintive rispetto alle più comuni lesioni del condotto uditivo interno (neurinomi dell’acustico e meningiomi). Anche le metastasi bilaterali possono essere confuse con casi di neurofibromatosi tipo 2. Il dato clinico che deve allertare il medico è l’insorgenza di un’ipoacusia rapidamente progressiva a cui si associa in successione un deficit del nervo facciale. La radioterapia e/o la chemioterapia rappresentano le due principali modalità di trattamento, mentre la rimozione chirurgica è riservata a casi selezionati di metastasi singole. Tuttavia a causa della rara presenza di caratteristiche cliniche o radiologiche specifiche delle metastasi l’exeresi chirurgica è spesso richiesta per il raggiungimento della corretta diagnosi, come accaduto in 2 dei nostri casi. Introduction agnosis is fundamental for correct planning of the therapeutic strategy. However, in the majority of cases, diagnosis may be extremely demanding, since metastasis may present clinical and radiological features indistinguishable from other lesions of the IAC and CPA. In the present report, 3 patients diagnosed with metastasis in the IAC, at our centre, between 1987 and 2002, are described. Internal auditory canal (IAC) and cerebellopontine angle (CPA) metastases are extremely rare lesions and account, according to Brackmann and Bartels 1, for 0.2% of all CPA neoformations. Although very rare, the neurotologist should take into consideration the possibility of secondary metastatic deposits in these areas, since the pre-operative di- 78 INTERNAL AUDITORY CANAL METASTASIS Case reports CASE N. 1 A 53-year-old female who came to our attention in March 1999 complaining of sudden left hearing loss (HL), progressive right-sided sensorineural HL and progressive left facial nerve (FN) weakness over the last 5 months. In July 1997, the patient had a total hysterectomy for a squamous cell carcinoma (SCC) of the uterine cervix followed by adjunctive chemotherapy. Clinical evaluation showed negative otoscopy bilaterally with a complete FN palsy on the left side. Audiometric evaluation revealed a dead ear on the left side and a right-sided sensorineural HL (mean PTA 40 dB, SDS 60%). Cerebral MRI showed the presence of a bilateral IAC lesion (Fig. 1). Both lesions were hypointense on T1 and hyperintense on T2 sequences, with a homogeneous enhancement after gadolinium infusion. The clinical and radiological evaluation was highly suspicious of a bilateral IAC metastasis, with the only other possible diagnosis being neurofibrobatosis type 2. In order to confirm the diagnosis, in agreement with the patient, it was decided to remove the left-sided lesion through an enlarged translabyrinthine approach (March 22, 1999). During surgery, the facial nerve was found to be considerably infiltrated by the tumour and had to be resected. Frozen section biopsy results revealed a metastatic SCC. Surgery was then concluded with total removal of the lesion without FN reconstruction. The patient, discharged on the third post-operative day without any further complications, was referred to a Department of Oncology where she underwent stereotactic radiotherapy for the other lesion and the area of surgical removal. In the meantime, a rightsided FN palsy developed. No other metastases were discovered. The patient underwent serial radiological follow-up and, 16 months after surgery, there was no recurrence on the operated site; however, the contralateral lesion grew into the CPA, infiltrating the midbrain and producing a marked perifocal oedema (Fig. 2). In addition, a new lesion, at the level of the corpus callosum, was discovered. The patient’s conditions progressively deteriorated until she was bedridden and died in August 2001, 30 months after surgical removal of the left-sided metastasis. CASE N. 2 A 50-year-old female who came to our attention in January 2001, complaining of vertigo spells, rightsided tinnitus and HL of 1 year’s duration. In addition, a rapidly progressing right FN weakness had appeared over the last month. Otoscopic examination was negative, bilaterally. On clinical examination, the FN deficit on the right side was classified as 79 Fig. 1. Cerebral MRI with gadolinium, axial section: bilateral IAC lesions with minimal CPA extension. Fig. 2. Post-operative cerebral MRI with gadolinium, axial section: growth of the lesion with brainstem infiltration and oedema. Absence of signs of contralateral recurrence. House Brackmann grade III. Audiometric evaluation showed a dead ear, on the right side, and normal hearing, on the left. At MRI, a lesion filling the IAC was clearly visible, with lateral extension to the geniculate ganglion and inner ear. This lesion was hypointense on T1 and hyperintense on T2 sequences, with a homogeneous enhancement after gadolinium infusion (Figs. 3, 4). Clinical history was negative for any previous neoplastic disease. The tumour was removed January 31st, 2001, through a transotic approach, in order to control the entire lesion from the IAC to the geniculate ganglion. Intraoperatively, the FN was found involved in the intracanalicular, intra-labyrinthine and geniculate ganglion areas. The lesion showed infiltration of all the components of the VII-VIII nerve bundle; however, since total removal was easily achieved, no intra-operative histological examination was required. The intra-cysternal segment of the nerve appeared intact M. FALCIONI, ET AL. differentiated epithelial malignant neoplasm”. The patient was then sent to the Department of Oncology in order to locate the primary lesion, which was a lung tumour. Despite chemotherapy, the patient died 8 months after surgery. CASE N. 3 A 71-year-old male patient came to our attention complaining of progressive left-sided HL and tinnitus of 2 months’ duration. History was positive for otalgia and unsteadiness. Clinical examination was negative, but audiological tests showed a left-sided sensorineural HL (PTA 55dB). The patient underwent cerebral MRI that revealed an IAC lesion, with a hypointense signal on T1 and T2 sequences, and enhancement after gadolinium infusion (Fig. 5). Three other small enhanced areas were also present in the brain, 2 in the frontal lobe and 1 in the left temporal lobe, the latter showing a surrounding area of oedema (Fig. 6). The radiological examination strongly suggested the presence of plurimetastatic lesions. Fig. 3. Cerebral MRI with gadolinium, axial section: IAC lesion with vestibule involvement. Fig. 5. Cerebral MRI with gadolinium, coronal section: IAC lesion. Fig. 4. Cerebral MRI with gadolinium, axial section: enhancement of geniculate ganglion area. and thus reconstruction, by means of a sural nerve graft, was accomplished. The patient was sent home on post-operative day 5. Definitive histological examination revealed “poorly Fig. 6. Cerebral MRI with gadolinium, axial section: other metastatic location at level of temporal lobe. 80 INTERNAL AUDITORY CANAL METASTASIS Total body CT scan located the primary tumour in the prostate and revealed the presence both of bony and lung metastases. In the meantime, the HL progressed to anacusis and ipsilateral FN weakness (grade III) appeared. Two months after attempted chemotherapy, the patient died from intra-cerebral haemorrhage. Discussion IAC metastases are very rare lesions accounting for only a small fraction (1.6%) of the IAC tumours submitted to surgery at our center between 1987 and 2002 (107 vestibular schwannomas, 10 meningiomas, 5 haemangiomas and 1 lipoma). Both unilateral and bilateral IAC metastases have been reported in the literature 2-4. As with other sites, IAC metastases can occur in patients in whom the primary lesion has already been detected or may present as the first sign of the disease. However, the presence of a malignant tumour, in the clinical history of a patient with an IAC lesion, strongly suggests the presence of metastasis. Breast, lung, prostate, kidney and colon are reported to be the most common sites of the primary lesion 2 3 5. IAC and APC are rarely involved by spreading of melanomas and lymphomas 3 6. When the metastasis is the first sign of the disease, correct pre-operative diagnosis may be particularly demanding. In fact, the symptoms and radiological aspect may be completely non specific and common to every IAC and CPA lesion. The main features that should alert the otoneurosurgeon are: rapid progression of hearing loss 2 3 5 7 and the frequent association with facial weakness. In fact, the most common tumours of the IAC (vestibular schwannomas and meningiomas) present, in the majority of cases, with slow progressive hearing loss or with a sudden hearing loss, and only, in few instances, they cause a FN deficit. On the contrary the latter is often found in the presence of metastasis, appears a short time after the onset of hearing loss, and shows rapid progression to complete palsy. Schwannomas and hemangiomas of the FN nerve are the lesions frequently responsible for facial palsy. However, in these cases, progression of the FN weakness is usually very slow. In 2 of our cases, a fast deterioration of hearing loss was observed, while in the third case, affected by bilateral metastases, the hearing loss appeared suddenly, on one side, and progressively on the other. FN deficit quickly deteriorated in all 3 cases and occurred a few weeks after the onset of the hearing loss. In the majority of the cases, cerebral MRI with gadolinium fails to distinguish between metastasis and other neoformations of the IAC 6. 81 When bilateral IAC lesions are present, neoplastic spread should be suspected, with the neurofibromatosis type 2 being the only possible alternative diagnosis. Albeit, the simultaneous presence of other intra-parenchymal cerebral lesions is diagnostic for neoplastic spread. The main neuro-radiological characteristics of cerebral metastases are parenchymal infiltration and perifocal oedema. In the case of IAC metastases, these radiological signs are evident only when the mass extends to the CPA, as in the final progression, in one of our cases. When the lesion is limited to the IAC, it is very difficult to distinguish the metastasis from a benign tumour since they present the same neuro-radiological features (hypo-iso intensity in T1, slight hyper-intensity in T2, gadolinium enhancement). Radiological signs reported in the literature, such as slight and dyshomogeneous enhancement, after gadolinium infusion, are very difficult to detect 8. For this reason, it is not uncommon for the diagnosis of IAC metastasis to be made only during or after the operation, as in 2 of our cases. High resolution CT scan, as for the other diseases confined to the IAC and CPA, does not provide any additional details, useful for the diagnosis. The only exceptions are the cases with extension into the Fallopian canal, where CT scan can confirm and visualize the extension through enlargement of the Fallopian canal itself. Again, the radiological features are similar to those of an intrinsic tumour of the FN, with no specific features of the metastasis. Once the diagnosis of IAC metastasis is made, treatment has to be arranged with an oncologic centre. When bilateral or multiple metastasis are present, radiotherapy combined with chemotherapy is the treatment of choice. In selected cases of an isolated single metastasis, surgical removal may be indicated. It should be stressed that, regardless of the treatment modality, survival of these patients is often in the range of a few months. Only one case with a 5-year survival 9 has been reported in the literature. Conclusions IAC metastases are very rare lesions in which diagnosis may be extremely difficult. Except in the presence of multifocal lesions, neither MRI nor CT scan are able to elicit distinctive features. The clinical sign that must alert the ENT specialist is the presence of a rapidly progressive HL combined with the onset of a FN deficit with a fast evolution. Treatment is based mainly upon stereotactic radiotherapy combined with chemotherapy, while surgery is reserved only for selected cases presenting a single metastasis. However, surgical removal is often necessary in order to reach the correct diagnosis. M. FALCIONI, ET AL. References 1 2 3 4 5 Brackmann DE, Bartels LJ. Rare tumors of the cerebellopontine angle. Otolaryngol Head Neck Surg 1980;88:555-9. Moloy PJ, del Junco R, Porter RW, Brackmann DE. Metastasis from an unknown primary presenting as a tumor in the internal auditory meatus. Am J Otol 1989;10:297-300. Shinogami M, Yamasoba T, Sasaki T. Bilateral isolated metastases of malignant melanoma to the cerebellopontine angle. 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Le Chevalier TL, Smith FP, Caille P, Constants JP, Rodesse JG. Site of primary malignancies in patients presenting with cerebral metastasis. A review of 120 cases. Cancer 1985;56:880-2. Arriaga MA, Lo WWM, Brackmann DE. Rare tumors of the cerebellopontine angle. Arch Otolaryngol Head Neck Surg 1995;121:1052-6.