Here, we present a 73-year-old female with a history of gastric high-grade B-cell lymphoma presenting initially to Cancer Rehabilitation Clinic with a three-month history of right shin and dorsal foot numbness, right foot drop, and balance impairment. So notably, she'd been diagnosed with lymphoma only six months earlier, and she was in the midst of chemotherapy and reported losing about 40 to 50 pounds since diagnosis. She couldn't recall an inciting event or trauma, and she'd reported that her weakness and numbness were steadily worsening. Physical examination was notable for a 0 out of 5 strength with right ankle dorsiflexion and big toe extension, along with decreased sensation in the web space between the right first and second toes. Given her foot drop, she was prescribed an AFO and referred for electrodiagnostic testing. So on electrodiagnostic testing, nerve conduction studies showed focal conduction slowing and partial conduction block of the right fibular nerve across the fibular head. So as you can see, this is most apparent when you look at recording the fibular nerve from the tibialis anterior muscle on the right, where you can see a decrease in amplitude when you're recording at the fibular head versus at the popliteal fossa. And also, you could see that the right superficial peroneal or superficial fibular sensory nerve action potential amplitude was 4, which is less than half of that on the left. And also, there are just reduced fibular compound muscle action potential amplitudes at the right tibialis anterior muscle and extensor digitorum brevis muscles. On electromyography, fibrillation potentials were noted in the right tibialis anterior, peroneus longus, and extensor hallucis brevis muscles, suggesting subacute denervation. There are also enlarged motor unit action potentials that were visualized in the right tibialis anterior and peroneus longus muscles. So the constellation of these findings were diagnostic of an incomplete common fibular neuropathy localizing to the fibular head. And that's consistent with a Slimmer's palsy, given the patient's history. So fortunately, upon follow-up with her cancer rehabilitation physician after the electrodiagnostic studies were performed, the patient had reported marked improvement of her symptoms, and she did not need an AFO brace. She aimed to gain weight, and she no longer needed an assistive device with ambulation. So the key here is that fibular neuropathy is the most frequent mononeuropathy in the lower extremity, and it's most often going to happen in the fibular neck. So this can classically result in weakness with ankle dorsiflexion and result in foot drop due to deep peroneal nerve involvement, and likely foot eversion weakness due to involvement of the superficial peroneal nerve. Patients can demonstrate a steppage gait where they're going to have to bring their knee up higher so their foot can clear the floor. Fibular neuropathies themselves are typically traumatic in origin, and you can have stretching or compression of the nerve, which would be pretty common in the patient's history. You're also thinking about prolonged squatting. I think the classic case is a strawberry picker. And as seen in this patient's case, weight loss can absolutely be a cause of the neuropathy itself. So with weight loss, this can be in the setting of dieting, bariatric surgery, or just the setting of the patient's chemo regimen and their response to that. The neuropathy in this case was likely due to increased susceptibility to mechanical irritation at the proximal head of the fibula due to decreased fat around the peroneal nerve. So electrodiagnostic studies can specifically demonstrate axonal damage, demyelination, or both, as was evidenced in this patient's particular case. In conclusion, the differential for foot drop is indeed very broad. It can include anything from radiculopathy, lumbosacral plexopathy, peripheral neuropathy, vitamin deficiencies, and metabolic disorders, including diabetes. However, particularly as it pertained to this patient, who had a history of malignancy of high grade, B-cell lymphoma, and weight loss, 40 to 50 pounds, it's certainly important to consider slimmer's palsy as the underlying cause of foot drop.

case study

gastric high-grade B-cell lymphoma

numbness

foot drop

balance impairment