Analysis of F-wave in metabolic neuropathies: a comparative study in uremic and diabetic patients

Sonographic evaluation of the peripheral nerve in diabetic patients: the relationship between nerve conduction studies, echo intensity, and cross-sectional area

OBJECTIVE

Early detection of nerve dysfunction is important to provide appropriate care for patients with diabetic polyneuropathy. The aim of this study was to assess the echo intensity of the peripheral nerve and to evaluate the relationship between nerve conduction study results and sonographic findings in patients with type 2 diabetes mellitus.

METHODS

Thirty patients with type 2 diabetes (mean +/- SD, 59.8 +/- 10.2 years) and 32 healthy volunteers (mean, 53.7 +/- 13.9 years) were enrolled in this study. The cross-sectional area (CSA) and echo intensity of the peripheral nerve were evaluated at the carpal tunnel and proximal to the wrist (wrist) of the median nerve and in the tibial nerve at the ankle.

RESULTS

There was a significant increase in the CSA and hypoechoic area of the nerve in diabetic patients compared with controls (wrist, 7.1 +/- 2.0 mm(2), 62.3% +/- 3.0%; ankle, 8.9 +/- 2.8 mm(2), 57.6% +/- 3.9%; and wrist, 9.8 +/- 3.7 mm(2), 72.3% +/- 6.6%; ankle, 15.0 +/- 6.1 mm(2), 61.4% +/- 5.3% in controls and diabetic patients, respectively; P < .05). Cross-sectional areas were negatively correlated with reduced motor nerve conduction velocity and delayed latency.

CONCLUSIONS

These results suggest that sonographic examinations are useful for the diagnosis of diabetic neuropathy.

Sonographic evaluation of the median nerve in diabetic patients: comparison with nerve conduction studies

OBJECTIVE

Diabetes mellitus is becoming a major cause of premature disability in Japan, and peripheral neuropathy is a common complication of diabetes. The aim of this study was to evaluate the relationship between the results of nerve conduction studies (NCS) and the size of the nerve determined by sonography in diabetic patients.

METHODS

Twenty diabetic patients (mean age +/- SD, 57.1 +/- 13.6 years) and 20 healthy volunteers (mean, 61.1 +/- 8.9 years) were enrolled in this study. Patients' wrists that had symptoms of carpal tunnel syndrome were not included in the study; those that were included had negative Phalen test results. We then divided the patients into 2 groups (patients with and without diabetic symmetric polyneuropathy [DPN]). The cross-sectional area (CSA) was measured in the carpal tunnel 5 cm proximal to the wrist and elbow joint of the median nerve.

RESULTS

There was a significant increase in the CSA in patients with DPN in the carpal tunnel compared with the control participants (P < .01) and patients without DPN (P < .01). The CSA in the carpal tunnel showed a significant correlation with the motor nerve conduction velocity (r = -0.473).

CONCLUSIONS

The CSA of the median nerve in the carpal tunnel of patients with DPN is greater than that in patients without DPN and healthy individuals and correlates with NCS.

F-waves: neurophysiology and clinical value

This review deals with F responses, which are late responses obtained by supramaximal stimulation of virtually all the motor and mixed peripheral nerves. They are recorded over a muscle innervated by the stimulated nerve. The first description of F-waves was published in the fifties. Their neurophysiological mechanisms have been abundantly discussed in the literature leading to a current consensus, whereby F-waves are considered as antidromic responses produced by a pool of motoneurons activated by peripheral nerve stimulation. In the first part of this review, the neurophysiological mechanisms of F-waves as well as the distinction between these and H reflexes are described from a historical point of view. Other late responses are intentionally not reported; nevertheless A-waves are discussed since they are frequently ill-described in a number of conditions. Stimulation and recording procedures as well as F-wave parameters analysis are detailed, with emphasis on measures most useful for clinical purposes. A rigorous F-wave recording method is mandatory for reliable and meaningful analyses. Physiological factors, which influence F-waves such as ageing, drugs and sleep, must be known and their effects discussed. Also, as maturation is an important factor in clinical neurophysiology, data on F-wave ontogenesis are reviewed and discussed. Finally, the different F-wave alterations described so far in the literature, in either peripheral or central disorders, are listed and commented. It is emphasised that F-waves are particularly useful for the diagnosis of polyneuropathies at a very early stage and for the diagnosis of proximal nerve lesions. F-wave recording is indeed one of the rare methods in routine examination allowing at the same time the functional assessment of motor fibres on their proximal segment, and contributing to the evaluation of motoneuronal excitability.

Various aspects of F-wave values in a healthy population

OBJECTIVE

To characterize various aspects of F-wave in a healthy population and establish normative data for future clinical use.

METHODS

A total of 100 healthy volunteers underwent sensory and motor nerve conduction studies of the ulnar and tibial nerves, including F waves elicited by 32 stimuli.

RESULTS

The F-wave measurements (mean +/- SD for ulnar vs tibial nerve) consisted of persistence (83 +/- 19 vs 97 +/- 5%), minimum, mean and maximum latencies (26.5 +/- 2.1, 28.1 +/- 2.2, and 30.4 +/- 2.3 vs 47.0 +/- 4.1, 49.6 +/- 4.4, and 52.5 +/- 4.4 ms), minimum, mean and maximum F-wave conduction velocities (FWCV) (55.0 +/- 2.7, 60.0 +/- 2.3, and 64.0 +/- 3.0 vs 49.0 +/- 2.9, 52.2 +/- 3.1, and 55.5 +/- 3.4 m/s), chronodispersion (3.9 +/- 0.9 vs 5.5 +/- 1.4 ms), mean amplitude (347 +/- 152 vs 384 +/- 148 microV) and mean duration (8.6 +/- 2.9 vs 13.0 +/- 4.5 ms). Additional measures, registered by electronic averaging, included latency (27.4 +/- 2.3 vs 48.6 +/- 4.7 ms), duration (9.6 +/- 2.2 vs 16.4 +/- 4.2 ms), and amplitude (299 +/- 156 vs 208 +/- 116 microV).

CONCLUSIONS

The use of a height nomogram serves well as an acceptable means to adjust F latencies for the limb length. In addition to the commonly used minimal latency, maximal FWCV, and persistence, clinically relevant measures with a narrow variability includes mean and maximal latencies, chronodispersion, and mean duration. In particular, mean latency obtained with 10 stimuli gave accurate results either for group or individual analysis.

SIGNIFICANCE

The data help establish an adequate manner of recording F-wave latencies in clinical evaluation.

A comparison between different parameters in F-wave studies

Ulnar nerve F-waves were studied in 23 healthy volunteers and 27 diabetic patients. Latencies and chronodispersion were analyzed in each group. In the diabetic group all the parameters were normal in 14 patients (52%) and in 13 (48%) at least one parameter was altered. In these patients the most frequently altered parameter was the maximum latency (92%), followed by mean latency (85%), minimum latency (54%) and chronodispersion (54%). These findings suggest that maximum and mean latencies are better parameters to be analyzed in ulnar F-wave studies than minimum latency.

The effects of zenarestat, an aldose reductase inhibitor, on peripheral neuropathy in Zucker diabetic fatty rats

We studied the effects of zenarestat, an aldose reductase inhibitor (ARI), on peripheral neuropathy in Zucker diabetic fatty (ZDF) rats, an animal model of type 2 diabetes. ZDF rats and their lean rats counterparts were fed a sucrose-containing diet, and zenarestat was given orally once a day for 8 weeks. Motor nerve conduction velocity (MNCV), F-wave minimal latency (FML), and sorbitol concentrations in the sciatic nerve were measured. In ZDF control rats, a remarkable accumulation of sorbitol, a delay in FML, and a slowing of MNCV were observed compared with lean rats. At a dose of 3.2 mg/kg, zenarestat had no significant effect on the delay in FML and the slowing of MNCV, although the sorbitol accumulation in the sciatic nerve was partially inhibited in ZDF rats. On the other hand, 32 mg/kg zenarestat treatment improved these nerve dysfunctions in ZDF rats, along with a reduction of nerve sorbitol accumulation almost to the level of lean rats. These data showed that zenarestat improved diabetic peripheral neuropathy in ZDF rats, a type 2 diabetes model, providing evidence for the therapeutic potential of zenarestat for the treatment of diabetic neuropathy.

F-wave-duration in diabetic polyneuropathy

The diagnostic sensitivity of F-wave duration (Fdur) in diabetic polyneuropathy was analyzed. Some patients had abnormal Fdur values with normal minimum F latencies (Fmin). The incidence of abnormality for tibial and peroneal Fdur was somewhat more common than for Fmin in cases of suspected mild or early phase polyneuropathy. Fdur may provide additional diagnostic information in certain cases, particularly those in which there is mild polyneuropathy.

F-wave latency, the most sensitive nerve conduction parameter in patients with diabetes mellitus

In this study we examined the diagnostic sensitivity of minimal F-wave latency, F-wave persistence, motor nerve conduction velocity (MCV), and amplitude of the compound motor action potential (CMAP) of the median, ulnar, tibial, and peroneal nerves, and of sensory conduction velocity (SCV) and sensory nerve action potential (SNAP) amplitude of the sural nerve in 82 diabetic patients. For the median, ulnar, and tibial nerves the Z scores of the minimal F-wave latency were significantly larger than those of the MCV, and for all four motor nerves the Z scores of the minimal F-wave latency were significantly larger than those of the amplitude of the CMAP. The Z scores of the peroneal minimal F-wave latency exceeded those of peroneal MCV, sural SCV, and sural SNAP. F-wave persistence did not differ significantly from the reference values. In conclusion, minimal F-wave latency is the most sensitive measure for detection of nerve pathology and should be considered in electrophysiological studies of diabetic patients.

Case Forum

A 62-year-old Man with Numbness, Tingling, Weakness in the Lower Extremities and Difficulty in Walking