Assistant Professor Temple University Philadelphia, Pennsylvania
Case Diagnosis: 68-year-old female with Stage I Breast Cancer and Stage III Diffuse Large B-Cell Lymphoma developed low back pain after intrathecal methotrexate treatment and was found to have diffuse thickening of the cauda equina nerve roots on MRI and severe primary axonal and motor polyneuropathy affecting the upper and lower extremities on EMG/NCS suspected from intrathecal methotrexate toxicity.
Case Description or Program Description: A 68-year-old female with Stage I Breast Cancer and Stage III Diffuse Large B-Cell Lymphoma presented to clinic with one and a half years of low back pain. Patient also noted associated bilateral lower extremity weakness, especially with ankle dorsiflexion. Symptoms started after hospitalization while undergoing chemotherapy, including intrathecal methotrexate. On exam, she had 5/5 bilateral lower extremity strength except for 4/5 dorsiflexion worse on the right. Back pain was noted with oblique extension.
Setting: Academic Medical Center
Assessment/Results: Electrodiagnostic study performed showed severe mostly axonal sensory and motor peripheral polyneuropathy. MRI of the lumbar spine with contrast showed diffuse ropelike thickening of nerve roots of cauda equina with leptomeningeal intrathecal enhancement. PET scan did not show any new lesions. Labs were notable for an ESR elevated at 36, normal LDH, normal WBC and platelets, hemoglobin of 11.9, and an LP with cytology and flow negative from the CSF. Protein was elevated in the sample.
Discussion (relevance): The protein elevated in the CSF suggests inflammatory disorder possibly secondary to intrathecal methotrexate toxicity. Pathophysiology could involve direct toxicity with local folate deficiency with subsequent immune reaction. Neurology consulted and recommended treating symptomatically with therapy. If symptoms worsen, experimental IVIG followed by IV methylprednisolone can be considered.
Conclusions: Polyneuropathy caused by intrathecal methotrexate is a rare finding but can be treated if recognized early enough. It may be beneficial to further study the effects of intrathecal methotrexate and create treatment protocols for some of its adverse effects.