Underlying neuropathies combined with amyotrophic lateral sclerosis (ALS) cast doubt on the diagnosis of ALS when present.Abnormal sural nerve conductions were found in 3 patients with clinically definite ALS. Pathologically demyelinating, axonal, or vasculitic neuropathy was suggested respectively. High dose oral corticosteroid had no effect and clinical courses were deteriorating in all the patients.The causes of combined neuropathies were unclear. Possibility of direct consequence of ALS, concomitant neuropathies, or rare variants of ALS should be considered in these cases.

B a c k g r o u n d s: The pathway of the sural nerve (SN) is variable, but usually divided into medial and lateral suralbranches joining the posterior tibial nerve (PTN) and the peroneal nerve (PN). The sural nerve may be affected by PNpalsy. The frequency or the severity of SN involvement in peroneal palsy is not known. The purpose of the study is toinvestigate the frequency and the severity of the SN involvement by the peroneal nerve palsy.Methods: Total 85 patients were included with peroneal palsy. Amplitudes of distal peroneal, sural, and superficialperoneal nerves (SPN) were compared between normal and paralyzed sides. The frequency and severity of SN involvementby peroneal palsy were investigated.Results: Mean age was 48.4