Paraneoplastic Polyneuritis Cranialis Associated With Breast Carcinoma: A Case Report

Paraneoplastic neurological syndromes (PNSs) are rare immune-mediated disorders that occur as remote manifestations of malignancy and may precede the diagnosis of the underlying cancer.Polyneuritis cranialis is an uncommon neurological condition characterized by the involvement of multiple cranial nerves and rarely occurs as a paraneoplastic manifestation of breast carcinoma.Recognition of this association is important as neurological symptoms may represent the first clue to an occult malignancy.A 107-year-old female patient was referred from the eye clinic with progressive left eye pain, partial ptosis, ophthalmoplegia, and facial weakness.Neurological examination demonstrated involvement of the left third, sixth, and seventh cranial nerves.Initial neuroimaging and routine investigations were unremarkable.Further evaluation revealed an elevated carcinoembryonic antigen level, prompting comprehensive malignancy screening.Computed tomography of the chest identified a left breast lesion, and subsequent ultrasound-guided biopsy confirmed poorly differentiated invasive breast carcinoma (NST, Grade III).A diagnosis of paraneoplastic polyneuritis cranialis associated with breast carcinoma was possible.However, extensive workup had to be done to exclude other vascular, neoplastic, and immune causes of polyneuritis cranialis.While the patient was undergoing specific imaging and laboratory testing, she was treated with intravenous immunoglobulin, with subsequent partial neurological improvement.Although breast cancer is a recognized cause of PNSs, cranial nerve predominance is uncommon.Previously reported cases revealed brainstem and cerebellar syndromes as known paraneoplastic presentations associated with breast cancer.Autoantibody production seems to be the suspected cause of such manifestations, such as anti-Yo and anti-Ri antibodies.The current available management includes treating the underlying malignancy, in combination with immunotherapy.Unexplained presentations with cranial polyneuropathy should be considered alarming for the presence of an occult malignancy and should therefore be investigated thoroughly.Paraneoplastic polyneuritis cranialis may represent a very early manifestation of occult malignancy and precede the eventual diagnosis of cancer.Clinicians should maintain a high index of suspicion for an underlying malignancy in patients presenting with unexplained progressive cranial neuropathies.Early recognition, comprehensive cancer screening, and timely immunomodulatory treatment may improve neurological outcomes and facilitate earlier oncological management.