Segmental Comparative Electrophysiological Study Of Chronic Demyelinating Neuropathies

Objective:To clarify the electrophysiologic characteristics of chronic inflammatory demyelinating polyneuropathy(CIDP), hereditary neuropathy with liability to pressure palsies(HNPP) and Charcot-Marie- Tooth disease typel (CMT1), identify their electrophysiological characteristics of demyelinating in different nerve segments.Methods:From December 2006 to February 2009, theses three groups of patients and one group of healthy control subjects described below were recruited:29 patients diagnosed as CIDP,18 patients clinically diagnosed as HNPP,28 patients consistent with the standard of CMT1 and 22 subjects of healthy controls, all patients and healthy controls matched in age, sex and height. We registed clinical data of the patients.Then, motor nerve conduction studies of upper limb, terminal latency index (TLI) and modified F ratio (MFR) of median nerve and ulnar nerve were conducted.Results:1. CIDP group, HNPP group and CMT1 group showed the existence of signifcant differences in DML, CMAP, MNCV and F-wave compare to the control group. manifested as:prolonged distal motor latencies (DML), reduced compound muscle action potential (CMAP), reduced motor nerve conduction velocities (MNCV), prolonged F-wave latencies or unrecordable F-wave.These results suggest that the primary pathological changes in nerves of CIDP, HNPP and CMT1 is demyelination.2. TLI of median nerve in HNPP group was 0.25 (0.21-0.26), TLI of median ulnar nerve in HNPP group was 0.32 (0.29-0.35). TLI of median and ulnar nerve in HNPP group was significantly reduced in comparison with CIDP group, CMT1 group and normal control group. Indicate that the demyelination is more severe in the distal segment than the middle segment of the nerve in HNPP group.3. MFR of median nerve in CIDP group was 2.11 (1.75-2.48), MFR of ulnar nerve in CIDP group was 4.00(3.27-4.92).The comparison of median nerve MFR between HNPP group, CMT1 group and control group showed no significant difference. The ulnar nerve MFR were significantly higher in CIDP group compare to HNPP group,CMT1 group and control group. Indicate that the demyelination in the proximal segment is more server than in the distal segment in ulnar nerve in CIDP, whereas demyelination in the proximal and distal segment in median nerve is uniform.Suggest that proximal accentuate demyelination is predominant in ulnar nerve in CIDP.4. We draw the receiver operator characteristic curve (ROC) of ulnar nerve MFR values, The area under curve (AUC) was 0.8231. In this study the cut off point of ulnar nerve MFR was 3.75. The diagnostic sensitivity was 61.5%, specificity was 100%. MFR≥3.75 was observed in 8 out of 13(61.5%) of the ulnar nerves in CIDP group. In HNPP group and normal control group, no MFR≥3.75 was recorded in ulnar nerve. In CMT1 group, MFR≥3.75 was recorded in 1 out of 17(5.9%)ulnar nerves. These results suggest that ulnar nerve MFR as a single test for the distinction between normal and HNPP patients has moderate diagnostic value. When the ulnar nerve MFR≥3.75, the possibility of CIDP patients is rather high.5. A significant correlation was found between ulnar nerve MFR and age in this group in CIDP group(r=-0.8635, P= 0.0001). The ulnar nerve MFR is not correlated with age in the control group.Suggest CIDP patients' MFR value decreases with aging. In CIDP group median nerve MFR was not correlated with height. In median and ulnar nerve, There were neither correlation between TLI and height nor between TLI and age in HNPP group.6. CIDP patients were divided into two subgroups, the subgroup with less upper limbs muscle strength and the subgroup with less lower limbs muscle strength. Two subgroups were compared.This study enrolled a total number of 29 CIDP patients:11 patients had less upper limbs muscle strength compare to lower limbs, 11 patients had less lower limbs muscle strength compare to upper limbs.7 patients had symmetrical limb muscle strength. Two subgroups showed no significant difference in the median nerve and ulnar nerve in DML, CMAP, MNCV, F wave latency, TLI and MFR. These results could not suggest different muscle strength in upper or lower limbs can result in variance of distribution or severity of demyelination in CIDP.Conclusion:1. TLI as a stable test in the segmental electrophysiological examination of peripheral nerve is characterized by its convenience and its facility, It can also compare demyelination in the distal nerve segment with the middle nerve segment,with no increasing of the stimulation point or the time of electrophysiological examination. Provides electrophysiological evidence for the distally accentuated demyelination of nerves in HNPP; provides clues for the further study of pathogenesis of HNPP.Helped the differential diagnosis of HNPP and CIDP.2. MFR as a stable test in the segmental electrophysiological examination of peripheral nerve is characterized by its convenience and its facility, It provides a new method for the evaluation of demyelinating conditions including Erbs point to anterior horn cells, and it can compare demyelination in the proximal nerve segment versus distal nerve segment,with no increasing of the stimulation point or the time of electrophysiological examination. Provides electrophysiological evidence for the proximally accentuated demyelination of nerves in CIDP; provides clues for the further study of pathogenesis of CIDP. Not only helped the diagnosis of CIDP,but also the differential diagnosis of HNPP and CIDP.