Early Hints of Metagenome Next‐Generation Sequencing and Copy Number Variations Analysis: An Occult Case of Leptomeningeal Metastasis With Rapid Cognitive Decline

Early detection and treatment are critical for improving the prognosis of patients with leptomeningeal metastasis. However, heterogeneous clinical manifestations, non-specific imaging, and limited sensitivity of cerebrospinal fluid cytology posed challenges to identifying leptomeningeal metastasis in the early stage. Here we reported a case of lung adenocarcinoma complaining of rapid cognitive decline, whose magnetic resonance imaging showed interstitial brain edema. Under the circumstances of negative cerebrospinal fluid cytology, metagenome next-generation sequencing and copy number variations analysis were applied, which indicated leptomeningeal metastasis and was confirmed in the subsequent cytology.