Marcel Souffrant, MD
Resident Physician
Rutgers/Kessler Institute of Rehabilitation
Newark, New Jersey, United States
Sharon Ong, MD
Attending Physician
Orthopedic Physicians Alaska
Anchorage, Alaska, United States
We present a 41-year-old female presenting with several months of right sided low-back pain radiating into the right anterior hip and buttocks after a motor vehicle accident, and acute onset, new, left foot drop. MRI findings revealed multilevel degenerative changes from L4-S1, an L4-5 spondylolisthesis, facet arthropathy with moderate canal stenosis and bilateral foraminal stenosis. She was referred by neurosurgery for electrodiagnostic evaluation, which showed isolated severe axonal left deep fibular mononeuropathy and acute denervation changes in the left tibialis anterior and extensor hallucis longus. She did not recall any direct pressure over the lateral leg but endorsed being in several uncomfortable positions and prolonged, flat-footed, deep squats while shearing sheep, the previous day.
Discussions:
Fibular neuropathy is the most common entrapment neuropathy of the lower extremities and is often implicated in cases of foot drop, particularly in instances of rapid weight loss, prolonged leg-crossing, and repetitive squatting. The vulnerability of the fibular nerve can be attributed to its anatomical route: it hugs the fibular neck in the ‘fibular tunnel’, at the aponeurosis of the soleus and fibularis longus, and exits through the anterior intermuscular septum as the deep fibular nerve. It is additionally vulnerable to damage due to its paucity of vascularization. Unlike the tibial nerve which has extensive vaso nervorum supply, the common fibular nerve receives asymmetric and limited collateral blood flow.
Conclusions:
In this case, the patient’s day spent shearing sheep in awkward squat positions, likely led to a stretch-related injury. Given multiple confounding factors, including degenerative lumbar spine changes, a motor vehicle collision, and a prolonged clinical course, this was difficult to elucidate. Electrodiagnostic testing was crucial in distinguishing the presence of an L5 radiculopathy that would have otherwise led to spinal surgery, versus an isolated fibular mononeuropathy, which eventually self-resolved without need for surgery.
