Cranial Mononeuropathy as the First Sign of Intracranial Metastases

In 13 cases of malignant disease the sign of intracranial metastases was a mononeuropathy of either the fifth or twelfth cranial nerve. Postmortem examination was performed in all patients, and in each instance there was meningeal or cranial nerve root sheath infiltration by tumor. The cranial nerve syndromes were partially reversible with X-ray treatment and chemotherapy. None of the patients had the clinical or laboratory characteristics of "carcinomatosis of the meninges." It is concluded that even subtle cranial mononeuropathy in a patient with an active malignancy elsewhere in the body is most likely due to direct tumor invasion of intracranial contents and is not an indirect or nonmetastatic manifestation of a distant malignancy. The relationship to "carcinomatosis of the meninges" is discussed.