Meningeal carcinomatosis occurs when cancer cells diffusely infiltrate the cerebrospinal cavity and form metastatic foci . Particularly, meningeal carcinomatosis within the internal auditory canal (IAC) is relatively rare and its prognosis is very poor [8, 10]. Chang and Michaelidis reviewed some literature regarding meningeal carcinomatosis of the IAC and reported that 52.9% of 102 cases were bilateral. They also reported that the lung (21.2%), skin (18.6%), and breast (16.7%) were the sites of primary origin in bilateral cases and that the rate of co-occurring sites of metastatic disease present in cases of meningeal carcinomatosis within IAC was over 60% [10, 11]. Other studies reported that the incidence of meningeal carcinomatosis in gastric cancer is 0.1 ~ 0.69% [4,5,6,7]. Despite the fact that tumor markers remained high in this case, CT could not detect the recurrence in the whole body. Therefore, meningeal carcinomatosis within IAC was considered to be the first recurrence site for this patient.
In general, meningeal carcinomatosis shows several symptoms such as hearing loss, headache, nausea, vertigo, etc. When a cranial nerve symptom appears, the II, III, VII, and VIII cranial nerves are injured, and the VII and VIII cranial nerves are particularly injured . It was reported in the mechanism of onset that cancer cells infiltrate the cerebrospinal fluid, the cerebrospinal fluid stagnates in the basal cistern and the cerebellopontine angle, and the cancer cells easily spread in that area . Other diseases that exhibit the bilateral hearing loss and vestibulopathy are shown in primary and metastatic brain tumor, neurofibromatosis II, Guillain-Barré syndrome, Fisher syndrome, etc . In this case, after the appearance of symptoms related to the VIII nerves, the VII neuropathy appeared rapidly. However, no characteristic family history or rash findings were observed, and no prior suspected infection of Guillain-Barré syndrome or Fisher syndrome was observed. Therefore, primary brain tumor, metastatic brain tumor, or brain infraction was suspected.
Enhanced MRI is reported to be very effective in diagnosing meningeal carcinomatosis. Some studies reported that the sensitivity of enhanced MRI for meningeal carcinoma is approximately 70% and is more effective than enhanced CT, the sensitivity of which is approximately 30% [13, 14]. Additionally, to obtain a definitive diagnosis, CSF test is the most effective. CSF protein is increased in 75%, CSF pressure is increased in 50%, and glucose decrease in CSF is observed in 40% of cases [15, 16]. However, the positive rate of cerebrospinal fluid in the initial test is approximately 45–50% and CSF tests should be performed multiple times if meningeal carcinomatosis is suspected [15, 16]. In this case, enhanced MRI revealed the neoplastic lesion filling the bilateral internal auditory canal and CSF test showed class V (adenocarcinoma). Meningeal carcinomatosis due to gastric cancer was confirmed.
No standard treatment has been clearly defined for the management of meningeal carcinomatosis. The treatment for meningeal carcinomatosis is aimed at restraining or improving the neurological symptom and extending the survival. The main treatment for meningeal carcinomatosis is chemotherapy. However, drug delivery into the intrathecal cavity is reported to be difficult with systemic chemotherapy due to blood–brain barrier [17, 18]. Therefore, the intrathecal chemotherapy with Methotrexate or Cytarabine or whole brain irradiation is often attempted in patients with stable general condition or stable performance status . Rapid introduction of the intrathecal chemotherapy is reported to be effective in alleviating the neurological symptom . However, no large-scale study has evaluated its efficacy, and further studies on the administration period are necessary. In this case, his condition and performance status rapidly got worse after confirmed diagnosis. Therefore, the intrathecal chemotherapy or whole brain irradiation could not be introduced and the symptom could be reduced to the end.
The prognosis of meningeal carcinomatosis is very poor and the average survival period after diagnosis is reported to be approximately one month in untreated patients, two months in refractory patients and the duration of survival time depends on the primary tumor . Our patient died approximately two months after the symptom onset and about one month after the confirmed diagnosis.