PAN can affect almost any visceral organ, but it targets the peripheral nerves more often than other organ systems3, 18. So far, few studies focused on peripheral neuropathy due to PAN. Some of them concentrated on peripheral neuropathy in systemic vasculitis. According to our study, all PAN patients suffered asymmetric peripheral neuropathy at onset stage, which were in accord with mononeuropathy or multiplex mononeuropathy3,19. As the disease progress, multiple nerves were rapidly involved resulting in generalized symmetric polyneuropathy, just like previous studies on primary systemic vasculitis20–22. Fever is not part of the ACR diagnostic criteria nor the three indices proposed by the French Vasculitis Study Group (FVSG)23. Most patients with PAN develop organ involvement within weeks of developing fever24. In our study, 80% of patients had fever before the onset symptoms or as an accompanying symptom. Thus, PAN need to be kept in mind when patient with mononeuropathy or multiplex mononeuropathy presented weeks of fever.
In our study, the characteristics of peripheral neuropathy in PAN patients are consistent with asymmetric axonal neuropathy that has a predilection for the lower extremities, affects distal limbs more severely than proximal, and involves both motor and sensory nerves. Previous studies have shown that sensorimotor abnormalities on NCS and the presence of a pure axonal neuropathy were most consistent with pathologically confirmed vasculitis25, 26, which is consistent with our findings. The lower limb is the most susceptible to nerve injuries in PAN patients, since the high frequent of disease onset rate appeared at lower limb in the clinical data and the abnormal amplitudes of peroneal and sural nerve were detected in NCS. Despite the less rates of site of disease onset and abnormality of CMAP amplitude of median nerve, the mean values of CMAP amplitude of median nerve and SNAP amplitude of median and ulnar nerves were significantly declining, which are considered to exist subclinical changes in upper limbs of patients with PAN. Ulnar motor nerve was selectively spared in our result, which need to be further verified through enlarging the sample size of patients.
PAN can make arterial aneurysm and thrombosis in many organs, including brain27, heart28, kidney29, extremities30 etc., due to inflammatory lesions of the blood vessels and necrosis of the vessel wall. It’s associated with an increased risk of mortality, understanding the outstanding features of nerve conduction might enable us to quickly recognize PAN to start specific treatments as early as possible.
Our findings suggest that the asymmetric motor and sensory axonal neuropathy is the most common style, lower limbs are the most frequent site of involvement, and the severity of peripheral nerve involvement is more significant in the distal limb than in the proximal in patients with PAN of peripheral neuropathy onset. It is advisable for neurologists to consider PAN in the face of patients demonstrating above clinical and nerve conductive features as well as weeks of fever.