a- d Patient 1: a 6-month-old girl presenting with congenital deafness has bilateral congenital malformations of the labyrinth on CT. The endolymphatic duct is connected to the saccule and courses through a bony canal-the vestibular aqueduct-to form the endolymphatic sac in the posterior fossa (Figs. The vestibule harbours the oval window the stapes footplate is attached to the oval window. The vestibular system is located posterior to the cochlea and contains the vestibule with the saccule and utricle and three semicircular canals which are oriented perpendicular to each other. The cochlea is connected to the middle ear by the round window. The modiolus containing the spiral ganglion can, however, be visualised in the centre of the cochlea. The scala media, containing the organ of Corti and filled with endolymph, cannot be visualised separately with current imaging systems. These scalae are connected to each other at the apical tip of the cochlea (helicotrema) and they contain perilymph. Within each turn the cochlea is divided into the scala tympani and scala vestibuli by the osseous spiral lamina. The normal cochlea consists of two-and-a-half turns separated by interscalar septae. The inner ear comprises the cochlea, the vestibular system and the endolymphatic duct and sac. The display slice thickness should not exceed 1.5 mm. Contiguous or overlapping sections from the superior most mastoid air cells to the stylomastoid foramen should be obtained with the gantry angle parallel to the infraorbital-meatal line. With multidetector CT, images can be reconstructed in any desired plane, obviating the need for direct coronal scanning. Temporal bone CT should consist of both axial and coronal images. MRI will render supplementary information on the fine intralabyrinthine structures. CT forms an ideal means to evaluate the bony details of the otic capsule and labyrinth and will also allow evaluating the course of the facial nerve canal and eventual associated anomalies of middle ear structures and the external auditory canal. In patients requiring anaesthesia, these exams should be planned in one session. These techniques render complementary information. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.Imaging of the inner ear is performed with computed tomography (CT) and/or magnetic resonance imaging (MRI). For the developmental research the left-right asymmetry might be a field of research. For the physician this differentiation represents a clinical and radiological challenge. The differentiation between benign and malign lesions in the CPA and IAC is important, as it requires diverse treatment protocols. In view of the sparse literature on treatment of single intracanalicular metastases, the review is broadened to the current treatment recommendations of single brain metastases. We address the issue of a possible regulation of CPA lesion laterality by asymmetrically expressed genes. The discussion focuses on the incidence of extra-axial CPA and IAC lesions with their clinical presentations and their radiological findings. The patient was treated with intrathecal chemotherapy. MRI showed an increase of the residual tumor and meningeosis carcinomatosa, and cerebrospinal fluid (CSF) examination was positive for tumor cells. The patient's condition deteriorated gradually. The investigations for the primary tumor site were all negative. Histological examination revealed blennogenic cylindrical adenocarcinoma. Due to progressive headaches and dizziness, the patient underwent a left transtemporal craniotomy with subtotal tumor resection.
The follow-up MRI showed an unchanged pattern of contrast enhancement. Magnetic resonance imaging (MRI) showed an extra-axial mass most likely representing a left-sided vestibular schwannoma with characteristic contrast enhancement in the IAC. He presented 8 months later with left-sided tinnitus, progressive hearing loss, and attacks of vertigo. Cranial computed tomography scan revealed bilateral nonspecific periventricular and subcortical vascular lesions. We provide a review of uncommon lesions in the IAC and describe to our knowledge the first instance of a primary adenocarcinoma.Ī 60-year-old man presented with nausea and vomiting. Intracanalicular metastases of adenocarcinoma are documented, but a primary adenocarcinoma remains unreported. Despite the relatively frequent occurrence of multiple primary tumors, namely, 10% of intracranial tumors, metastasis is a rare occurrence within the internal auditory canal (IAC) and cerebellopontine angle (CPA).
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