1. At this point in time, is there evidence of spinal cord involvement in this case and, if so, at what level?
No
2. Is there evidence of dorsal or ventral root involvement or spinal nerve involvement in this case, and, if so, what is the level(s) of the involvement?
No. The patient’s motor and sensory signs and symptoms do not follow a specific dermatomal or myotomal pattern.
3. Concerning the patient’s new left lower limb signs and symptoms, is there evidence of plexus or peripheral nerve involvement in this case, and, if so, how would you differentiate between the two? What evidence is there to support one or the other site of lesion in this case?
Yes. The patient’s signs and symptoms suggest partial involvement of two specific terminal peripheral nerves of the left sacral plexus, the tibial and common fibular (peroneal) nerves, while sparing other nerves of the plexus (e.g., more proximal nerves of the plexus). (see below)
4. Indicate the level of the neurologic lesions in this case and the structures involved by the pathologic process.
Numbness and tingling of the dorsal surface of the first 4 digits and corresponding area of the dorsum of the foot and the mild weakness of ankle dorsiflexion and extension of the great toe suggest a lesion of the left common fibular (peroneal) nerve, involving both the superficial and deep fibular (peroneal) nerves.
Numbness and tingling of the plantar surface of the first 4 digits and corresponding area of the sole of the foot and the mild weakness of ankle plantar flexion suggest a lesion of the left tibial nerve.
The lack of sensory signs and symptoms involving the lateral border of the foot, fifth digit, and more proximal regions of the left lower leg indicates sparing of the sural nerve and the branches that contribute to its formation.
5. Concerning the patient’s new left lower limb signs and symptoms, where is the anatomical location of the pathologic process leading to this patient’s condition?
Once again, the history and clinical examination suggest a multifocal process involving two peripheral nerves (i.e., multiple mononeuropathies or mononeuritis multiplex).
Her common fibular (peroneal) neuropathy appears to be localized to the popliteal fossa, distal to the branch to the short head of the biceps femoris muscle, or to the region near the head of the fibula where the nerve winds around the neck of the fibula, passes deep to the fibularis (peroneus) longus muscle, and divides into the superficial fibular (peroneal) and deep fibular (peroneal) nerves. This is a common site of compression of the fibular (peroneal) nerves.
Her tibial neuropathy most likely is also localized to the popliteal fossa, since the plantar flexors of the ankle are mildly weak. The most likely location for pressure on the nerve is as it passes under the tendinous arch of the soleus muscle.
6. In general, what type of pathological process do you think is involved in this case?
Once again, the most likely pathological process in this setting is a compression or pressure neuropathy; although a specific mechanism of compression is less clear than in the upper limb. However, as before, multiple mononeuropathies can also be due to amyloid or tumor infiltration and ischemic, infectious, or inflammatory processes such as diabetes, leprosy, sarcoidosis, vasculitis, and autoimmune diseases.
7. What diagnostic procedure(s) would you undertake at this point?
Click here for images.
