Fulminant inflammatory neuropathy mimicking cerebral death.

We report a case of a 44-year-old woman who developed rapidly progressive tetraparesis followed by respiratory failure and abolition of brainstem reflexes. Electrodiagnostic studies excluded the possibility of cerebral death and confirmed the diagnosis of acute motor-sensory axonal neuropathy. The initial fulminant course of the disease was followed by slow recovery to independence in daily activities.

Occurrence of A-waves in F-wave studies of healthy nerves.

A-waves are compound muscle action potentials that follow the M-wave with a constant shape and latency; usually they are detected during F-wave studies. A large reference value database for F-wave parameters from the median, ulnar, peroneal, and tibial nerves was collected from 121-196 subjects aged 14 to 95 years without known pathology involving the studied nerves. From this material, we studied retrospectively the occurrence of A-waves. To be included, an A-wave had to be clearly discriminated from the baseline in at least 8 of 20 traces with a jitter of less than 0.5 ms. A-waves occurred in 25% of the tibial nerves studied and 14% of the peroneal nerves but in only 2% of median and ulnar nerves. In the peroneal and tibial nerves, the frequency of A-waves increased with age, suggesting that A-waves may be related to normal age-related mild neuropathic changes of alpha motor neurons. Thus, A-waves are frequently found in lower-extremity nerves in healthy subjects and less commonly in upper-extremity nerves. Their presence must therefore be interpreted with caution and cannot be taken as necessarily indicative of abnormality.

Reference values of F wave parameters in healthy subjects.

OBJECTIVE AND METHODS: A large reference value database for F wave parameters was constructed with data from 121 to 196 healthy subjects; the age range of the subjects was 14-95 years. We studied the following parameters: minimum F wave latency (FMINLAT), mean F wave latency (FMEANLAT), maximum F wave latency (FMAXLAT), number of F waves/20 stimuli (FNUMBER) and F wave dispersion (FDISP=FMAXLAT-FMINLAT). The median, ulnar, peroneal and tibial nerves were studied. RESULTS: Height explains almost half of the FMINLAT variability. The F wave latency increases with height in the arms by 0.2 ms/cm and in legs 0.4 ms/cm. The effect of age on F wave latency in the arms is relatively small, only 0.03 ms/year; and in the legs age increases the FMINLAT by 0.1 ms/year. Gender does not affect FMINLAT in a systematic way. The peroneal nerve has slightly longer FMINLAT than the tibial nerve, while the FNUMBER is higher in the tibial nerve than the peroneal nerve. The differences between the ulnar and median nerve are slight. There is a very high correlation between all 3 latency parameters (FMINLAT, FMAXLAT and FMEANLAT), but no correlation between FDISP and FNUMBER and the other parameters. Side to side comparisons reveals no significant differences in any of the parameters except for the median nerve FMINLAT and FMEANLAT, which is 0.2 ms longer on the right than left. If side difference of more than 2 standard deviation is taken as the upper limit for normal, the side difference in arms is 1.4 ms and in legs 3 ms. In repeated studies the interexaminer variability is small; the correlation coefficient between the different F parameters is high (P>0.6 in arms and P>0.7 in legs). In the arms the upper limit for a significant difference of FMINLAT on repeated studies in the median nerve is 1.0 and 1.7 ms for the ulnar nerve. In the legs, FMINLAT for the peroneal nerve is 2.6 ms and for the tibial nerve is 2.1 ms. CONCLUSIONS: This large reference value database can be used not only to evaluate single measurements in relation with height and age, but also to compare right and left side and changes over time at repeated studies.