[Radiotherapy for Alleviation of Paraparesis due to Leptomeningeal and Cauda Equina Metastasis of HER2-Positive Breast Cancer: A Case Report].

Leptomeningeal metastasis is a rare entity and its diagnosis is often difficult. Moreover, evidence-based therapeutic strategies have not yet been established. A 52-year-old woman presented with high fever and was diagnosed with bacterial meningitis at first examination;although her fever was alleviated, she experienced motor weakness in both of her lower extremities. Ga scintigraphy highlighted the hot-spot areas of the disease in the cranial bone. She was then transferred to our department. Open biopsy of the skull showed metastasis of the cancer. Chest CT results indicated right breast cancer and Gd-DTPA imaging showed obvious enhancement of the pia mater around the conus medullaris and cauda equina. However, cerebrospinal fluid(CSF)cytological examination did not show the presence of any positive cells;consequently, mastectomy was performed in the thoracic surgical department. The severity of paraparesis and pain in her legs increased;however, repeat MRI 1 month later showed no evidence of any change. Therefore, we performed biopsy of the cauda equina and arachnoid lesions. The pathological diagnosis was metastasis of breast cancer with positive human epidermal growth factor receptor 2(HER2)immunological staining. The results of a repeat cytological examination of the CSF during the surgery were negative. Local radiotherapy(25 Gy/5 Fr)as a monotherapy was selected for the patient, because her family did not approve of the combination of radiotherapy and chemotherapy. The severity of both paraparesis and limb pain decreased immediately after the radiotherapy.