CSF dissemination of EGFR-mutant lung cancer present as cranial nerve injury and masticator muscle denervation: a case report and literature review.

Lung cancer with central nervous system metastases are troublesome clinical scenarios. Rare and diagnostically challenging presentations with subtle image findings may delay diagnosis. We report one case with advanced non-small cell lung cancer. A 48-year-old female present with chewing difficulty, diplopia and facial asymmetry. Magnetic resonance imaging of the brain revealed edematous swelling and abnormal enhancement over bilateral masticator muscles, and faint enhancement over origins of cranial nerves near brainstem. Therefore, masticator muscle denervation related to cranial nerve injury was diagnosed. Symptomatic and disease control was achieved after double dose osimertinib which provide novel insights in the treatment of EGFR-mutant lung cancer with cranial nerve involvement. Chewing difficulty is an exceptional clinical presentation in lung cancer and may lead to delayed diagnosis in case of unawareness. In addition, radiological detectable bilateral masticator muscle denervation is rarely seen and has not been published in the field of lung cancer.