Clinical Reasoning: A 65-Year-Old Woman With Cancer History and Wrist Drop.

Wrist drop is a common presentation in neurology. To localize the lesion, clinicians can focus on testing finger extension, elbow flexion with semipronated forearm, and elbow extension among other muscle groups and identifying dermatomes of numbness. Once the lesion is localized, electrophysiology or imaging can guide to an underlying etiology. Here, we describe a case that illustrates the importance of using a stepwise approach to diagnose the etiology of wrist drop in a patient with a cancer history. A 65-year-old woman with diffuse large B-cell lymphoma in remission presented with new onset wrist drop, severe pain, numbness, and tingling concerning for peripheral nerve injury. Imaging findings from PET, venous ultrasound, nerve conduction velocity study, and MRI were conflicting favoring deep venous thrombosis, cancer recurrence, or peripheral nerve sheath tumor. A biopsy was ultimately required to confirm the diagnosis.