# Bannwarth Syndrome in a Patient With Early-Stage Breast Cancer: An Atypical Manifestation of Lyme Neuroborreliosis

## TL;DR

A breast cancer patient showed neurological symptoms initially thought to be cancer-related but was diagnosed with a rare Lyme disease complication called Bannwarth syndrome.

## Contribution

Highlights Bannwarth syndrome as a rare but important differential diagnosis in oncology patients with neurological decline.

## Key findings

- Neurological decline in oncology patients may be due to immune-mediated disorders like Bannwarth syndrome.
- Lyme neuroborreliosis can present as Bannwarth syndrome with lymphocytic meningoradiculitis.
- Inflammatory cerebrospinal fluid findings should prompt consideration of immune-mediated or infectious causes.

## Abstract

Neurological symptoms in breast cancer patients can arise from metastasis, medication side effects, or underlying neurodegenerative conditions. When imaging is inconclusive, the more uncommon immune-mediated neuropathies should be considered. Guillain-Barré syndrome and Lyme neuroborreliosis are two immune-mediated conditions that share neurological findings. This case involves a 72-year-old Caucasian female who presented with early-stage invasive ductal carcinoma with neuroendocrine features and gradual bilateral upper extremity weakness and paresthesia. Surgery was uncomplicated, but in the subacute postoperative period, the patient developed progressive worsening of neck and scapular pain, left upper extremity weakness, right-hand paresthesia, and decreased right-hand dexterity. Cervical spine MRI and CT scans of the head and neck areas were insignificant. Leukocytosis, mild hyponatremia, and elevated C-reactive protein were found on laboratory workup. The initial differential diagnosis included paraneoplastic syndromes; however, given the inconclusive imaging, immune-mediated neuropathies, including Lyme neuroborreliosis, were prioritized. A lumbar puncture established the diagnosis of Lyme neuroborreliosis presenting as Bannwarth syndrome, also known as lymphocytic meningoradiculitis. Acute or subacute neurological decline in oncology patients should prompt consideration of paraneoplastic and infectious immune-mediated neurological disorders. Despite its rarity in the United States, Bannwarth syndrome should be considered as a paraneoplastic neuropathy mimic, especially with inflammatory cerebrospinal fluid findings.