Unilateral facial nerve paralysis following prolonged weekly paclitaxel therapy: a rare case of cranial neurotoxicity with diagnostic challenges

Paclitaxel is a widely used chemotherapeutic agent for the treatment of breast cancer. While peripheral neuropathy is a well-recognized dose-limiting toxicity of paclitaxel, cranial nerve involvement remains exceptionally rare. We report a case of unilateral facial nerve palsy in a breast cancer patient receiving standard-dose paclitaxel therapy, highlighting the diagnostic challenges in distinguishing drug-induced neurotoxicity from other aetiologies. A 43-year-old woman with metastatic breast cancer developed left facial nerve paralysis after 12 months of weekly paclitaxel treatment (80 mg/m²). Contrast-enhanced cranial Magnetic Resonance Imaging (MRI) demonstrated bilateral cranial nerve VII enhancement, creating diagnostic uncertainty between leptomeningeal metastasis, paclitaxel-induced neuritis, and idiopathic Bell’s palsy. Paclitaxel was discontinued, and corticosteroid therapy was initiated. Clinical and radiological improvement at follow-up strongly supported a drug-related aetiology. This case illustrates the diagnostic complexity of facial nerve palsy in cancer patients receiving neurotoxic chemotherapy. The overlapping clinical and radiological features between drug-induced cranial neurotoxicity, leptomeningeal disease, and idiopathic causes present significant diagnostic challenges. Clinicians should maintain a high degree of suspicion for rare chemotherapy-related cranial neuropathies while pursuing comprehensive differential diagnosis, including infectious aetiologies and metastatic disease.