Multiple Cranial Neuropathies as the Presenting Sign in a Patient with Metastatic BRAF-Mutated Lung Adenocarcinoma with Leptomeningeal Involvement

Leptomeningeal carcinomatosis accounts for only 4% of cases of multiple cranial neuropathies. Here, we report the case of a patient who presented with multiple synchronous cranial neuropathies. After treatment for neuroborreliosis and broad infectious workup, endobronchial ultrasound-guided mediastinal lymph node biopsy confirmed a diagnosis of metastatic BRAF-mutated lung adenocarcinoma with leptomeningeal involvement. To our knowledge, this is the first reported case of metastatic BRAF-driven lung adenocarcinoma with leptomeningeal disease at diagnosis. In this case, the presence of leptomeningeal carcinomatosis at diagnosis, not as a late manifestation of heavily pretreated disease, alludes to a possible association between leptomeningeal involvement and BRAF-mutated non-small cell lung cancer.