Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA. ![]() 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. When the cochlear nerve enters the brainstem, it innervates or supplies nerve signals to the cochlear nuclei located at the pontomedullary junction (where the pons and medulla of the brainstem meet). The differentiation between benign and malign lesions in the CPA and IAC is important, as it requires diverse treatment protocols. It's within the internal auditory canal that the cochlear nerve trunk joins the vestibular nerve to form cranial nerve VIII. 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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