Peripheral late waves in patients with hereditary motor sensory neuropathy

Patents with different forms of hereditary motor sensory neuropathy (HMSN) were investigated. Peripheral late waves (PLWs) were recorded when determining F wave at supramaximal stimulation. We registered them most frequently in patients with demyelinating neuropathies (HMSN1--58% and HMSN3--100%) and in patients with HMSN2--24% and HMN--13%. In patients with HMSN1 and HMSN3 the peripheral late waves sometimes were more than one--two or three. They had a consistent appearance above a maximal threshold of stimulation, an invariable latency, amplitude and wave-form. Their latency times were in parallel with the M-response latency. These PLWs can be explained by collateral regeneration in case of axonal neuropathy. The ephaptic transmission might be taken in consideration when interpreting data from patients with demyelinating processes.