Hi there, my name is Xiaomeng Li and I'm a fourth year resident at University of Washington in Seattle. My case report is about the localization of a sciatic nerve tumor using electrodiagnostic studies. Our patient, whom I saw late last December, was a 41-year-old female marathoner whose past medical history only included idiopathic neutropenia treated with filgrastim. She came to our EMG clinic after developing new onset right calf cramping and pain, followed by foot drop. This weakness worsened over a two-week period and she began to have difficulty climbing stairs and standing from seated. During this time, she had already interfaced with medical care several times, receiving an ultrasound DVT that was negative and a lumbar MRI that was also unremarkable. She presented to us at about three weeks after symptom onset. On physical exam, there was subtle weakness with knee flexion and extension, as well as overt weakness at the ankle in all directions. There was reduced sensation to light touch at the S1 dermatome and reduced or absent PIMPRIC at L4-5 dermatomes. Electrodiagnostic testing showed normal nerve conduction studies for bilateral fibular motor to EDB, bilateral tibial motor to AH, and bilateral serosensories. Her needle studies showed abnormal recruitment in her tibialis anterior, medial head of the gastroc, tibialis posterior, flexor digitorum longus, and peroneus longus, as well as some signs of membrane instability in several of these muscles. Findings were consistent with either L5-S1 radiculopathies or a sciatic mononeuropathy. These findings helped the patient's clinicians obtain an MRI of the thigh 11 days later, which revealed a large sciatic nerve mass, discovered to be diffuse large B-cell lymphoma after biopsy. This patient was connected with oncology, who started her on both chemotherapy and radiation. A repeat MRI of her thigh was obtained July of this year, after six months of treatment, and the sciatic nerve mass was much smaller. For my discussion, I would like to talk about the diagnosis of neurolymphomatosis, or NL, which is defined as peripheral nerve infiltration by cancer cells of a hematologic origin, most frequently B-cell non-Hodgkin's lymphoma. The syndrome is thought to be uncommon, though it's unclear how uncommon it is due to its challenging diagnosis. One study looking at NL between 2013 and 2015 estimated the prevalence to be around 0.2% in non-Hodgkin's lymphoma. Interestingly, NL can present in all sorts of ways, including plexopathies, mononeuropathies, polyneuropathies, radiculopathies, and even cranial nerve palsies. There's currently no literature that characterizes what standard electrodiagnostic findings are to be expected when looking for NL. One study attempted to characterize electrodiagnostic findings in lymphoma generally, which did include but was not exclusive to NL, and reported a wide range of findings, including demyelinating and or axonal injuries affecting sensory and or motor nerves, and findings could present as a mononeuropathy, polyneuropathy, or radiculopathy. In conclusion, electrodiagnostic studies can be useful for lesion localization when used within the appropriate timeframe. This diagnosis is rare, but perhaps this case report will add peripheral nerve tumor to your list of differential diagnoses. Thank you for your attention. I want to thank my attending, Dr. Kate Delaney, for helping me with this case and this poster presentation.

sciatic nerve tumor

electrodiagnostic studies

neurolymphomatosis

diffuse large B-cell lymphoma

localization of nerve tumors