What happened, in summary

A 39-year-old Chinese woman who had never smoked was diagnosed with EGFR L858R-positive lung adenocarcinoma after a chest X-ray unexpectedly showed an opacity. Soon afterward, partial seizures led to brain imaging, which found at least nine metastases and established stage IVB disease. She began erlotinib 150 mg daily, together with dexamethasone and phenytoin for neurologic symptoms. About five weeks later, elevated liver enzymes led to a temporary stop in erlotinib and a switch from phenytoin to brivaracetam. During that interruption, she developed facial twitching, loss of taste, and severe weakness on both sides of her face, leaving her unable to close her eyes and causing speech difficulty and drooling. MRI findings supported leptomeningeal spread involving both facial nerves. Erlotinib was restarted, but the facial palsy persisted. She was then changed to osimertinib. Within one week, facial strength began to improve, and by two weeks her facial movement and taste were nearly normal. Imaging after two and six months showed marked improvement in the facial nerve lesions and reduction of other brain metastases. At 15 months, seizures returned and three smaller brain lesions had grown, although the facial weakness had not recurred.