The usefulness of minimal F-wave latency and sural/radial amplitude ratio in diabetic polyneuropathy

Polyneuropathy and the sural/radial sensory nerve action potential ratio in primary Sjögren's syndrome

Objectives: Polyneuropathy is the most common neurological complication in primary Sjögren's syndrome (pSS). A ratio of sural nerve and superficial radial nerve sensorial action potential amplitudes (SRARs) of <0.4 is an indicator for early axonal neuropathy. We evaluated the polyneuropathies and SRARs in pSS patients.Method: Fifty-two female patients who were diagnosed with pSS according to the European-American Consensus Criteria and 45 healthy controls were enrolled. Nerve conduction studies were performed to diagnose polyneuropathy. Sensory axonal polyneuropathy was diagnosed in three patients, so SRARs were compared in 49 patients and 50 healthy controls.Results: Fifty-two patients with pSS underwent nerve conduction tests. The sural sensory nerve action potential (SNAP) was <6 µV in threepatients and they were diagnosed with sensory axonal neuropathy. SRARs were evaluated in 49 female patients, with a mean age of 51.98 ± 10.79 years and 50 healthy controls with a mean age of 50.52 ± 12.55 years. The mean disease duration was 7.59 ± 6.17 years. The SRAR values were different between the patient and control groups. SRAR was <0.4 in 20.4% of the patient group and <0.4 in 6% of the control group. The SRAR value was not statistically different within the patient group based on anti-Ro and anti-La.Discussion: The potential for neurological involvement in patients with pSS who have no signs or injury should be evaluated because nervous system involvement in pSS is a negative prognostic factor. SRAR in patients with pSS can be used as a marker for the early detection of axonal neuropathy.

Double-Shock Stimulation of the Superficial Radial Nerve Compared With Standard Medial Plantar Nerve Conduction in the Early Detection of Asymptomatic Diabetic Neuropathy: A Pilot Study

PURPOSE

Diabetes mellitus is a major public health problem. Diabetic polyneuropathy (DP) is one of the most common complications of diabetes mellitus. The early detection of DP is very important for timely treatment of symptoms and preventative foot care.

METHODS

Participants were sorted into 3 age- and sex-matched groups: 20 "healthy" individuals; 21 diabetic patients without DP symptoms, "asymptomatic"; and 24 diabetic patients suffering from symptoms consistent with DP, "symptomatic." All study participants had normal results on conventional nerve conduction studies. All groups underwent both medial plantar mixed nerve conduction (as a single-shock stimulation technique) and superficial radial nerve conduction (double-shock stimulation) measurements. Interstimulus intervals of 2 to 8 ms were used to record sensory nerve action potentials (SNAP) 1 and SNAP 2 for both stimuli.

RESULTS

We found statistically significant decreases in medial plantar NAPs' amplitude and conduction velocity, and SNAP1/SNAP2 ratios between the three groups, especially at smaller interstimulus intervals.

CONCLUSIONS

Both medial plantar mixed nerve conduction and double-shock superficial radial nerve stimulation are reliable methods for the early detection of asymptomatic DP. However, the medial plantar mixed nerve technique is easier and less time-consuming.

Electrophysiologic testing in diabetic neuropathy

Electrophysiologic studies provide objective data concerning nerve and muscle function. This information enables the diagnosis of disease states and monitoring of disease progression. This chapter describes the changes in electrophysiologic function in both prediabetes and diabetes and discusses the utility of this testing in patients with diabetes. Both the strengths and limitations of electrophysiology are discussed.

Comparison of the accuracy of monofilament testing at various points of feet in peripheral diabetic neuropathy screening

BACKGROUND

Diabetic Peripheral Neuropathy is one of the most prevalent complications of diabetes mellitus. The development and progression of such complications are responsible for much of the morbidity and mortality. The purpose of this study was to evaluate the effectiveness of Semmes-Weinstein monofilament ten gram in 3, 4, eight and ten points in the screening of diabetic peripheral neuropathy in patients with diabetes mellitus.

METHODS

In a descriptive correlational design, 150 patients with diabetes mellitus were selected using convenience sampling. All patients were evaluated for sensory neuropathy using ten gram Semmes-Weinstein Monofilaments and questionnaire on neuropathy symptoms. In the next phase, nerve conduction velocity was examined. The most common subjective symptoms were paresthesia of both feet, pain in feet, burning sensation in the extremities and numbness in the extremities.

RESULTS

The results showed that the sensitivity of Monofilament in three and four points were 35.9 to 53.8 present and 38.5 to 51.3 percent respectively. Specificity of Monofilament the same points, were 73.9 to 84.7 and 73 to 87.4 percent respectively. Monofilament sensitivity at eight and ten points were 38.5 to 61.5 and 64.1 to 30.8 percent respectively. Also, specificity of the same points were 77.5 to 95.5 and 64 to 89.2 percent respectively. It was revealed that the difference sensitivity and specificity of Monofilament in three and four points with sensitivity and specificity in eight and ten point is not statistically significant.

CONCLUSIONS

This study showed that Semmes-Weinstein monofilament can easily use as a simple and inexpensive device for screening. Since increasing the number of points it was not significantly difference. Therefore, we suggest that screening for diabetic peripheral neuropathy, especially in large populations to avoid wasting time on Monofilament application, areas like three or four points eight and ten points could be used.

Motor neuropathy

In distal symmetric sensorimotor polyneuropathy (DSPN) in diabetes, involvement of the motor system is rarely seen. Using dynamometry, substantial weakness at the ankle and knee has been found in type 1 and type 2 diabetic patients. The muscle weakness is found only in diabetic patients with DSPN, and is closely related to signs and severity of DSPN. In long-term follow-up studies, neuropathic patients have accelerated loss of muscle strength. Studies using MRI have shown that muscle weakness is paralleled by muscular atrophy within the feet and lower legs and in follow-up studies this atrophy is accelerated compared to healthy controls and non-neuropathic patients. In large-scale studies of diabetic subjects, lower muscle quality has been found, which indicates that even with preserved muscle strength diabetes per se causes lower strength per unit striated muscle. Muscle weakness causes slower movements of the feet and legs, unstable gait, and more frequent falls. Furthermore, weakness is also an independent risk factor for the development of foot ulcers. Training may improve strength, postural stability, and walking performance; however, this still needs to be studied including patients with various degrees of DSPN.

COMPARATIVE NEUROPHYSIOLOGICAL STUDY FOR THE DIAGNOSIS OF MILD POLYNEUROPATHY IN PATIENTS WITH DIABETES MELLITUS AND GLUCOSE INTOLERANCE

This article evaluates diagnostic sensitivity of minimal F-wave latency, sural/radial amplitude ratio (SRAR), dorsal sural/radial amplitude ratio (DSRAR), sympathetic skin response (SSR), and R-R interval variability (RRIV) for detecting early polyneuropathy in patients with glucose intolerance and diabetic patients. F-wave latencies were more prolonged in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). SRAR was lower, SSR latency was more prolonged, and RRIV was lower in diabetic patients with abnormal nerve conduction studies than healty controls (p < .001). SSR latency was more prolonged and RRIV was lower in diabetic patients with normal nerve conduction studies than healty controls (p < .01, p < .05, respectively). DSRAR was lower in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). DSRAR was also lower in patients with glucose intolerance than control subjects (p < .01). DSRAR was the most sensitive and specific test in either of diabetic patients with normal nerve conduction studies (sensitivity 66%, specificity 90%) and diabetic patients with abnormal nerve conduction studies (sensitivity 100%, specificity 90%). DSRAR is the most reliable method for detection of early nerve pathology. Patients with glucose intolerance might have subclinical neuropathy that can be demonstrated with DSRAR analysis.

Femoral nerve involvement in diabetics

BACKGROUND AND PURPOSE

In this study, the conduction of the femoral nerve has been evaluated in diabetic patients without clinical signs of femoral nerve involvement and in a group of healthy subjects.

METHODS

Forty-eight patients have been included in the study. Patients have been examined in terms of neuropathy and their neuropathy scores have been calculated. In addition to the nerve conduction studies have been performed. The findings of the diabetic patients have been compared with those of the 26 healthy volunteers.

RESULTS

There has been a statistically significant difference between diabetics and the healthy volunteers in the control group in terms of both femoral nerve motor latency and amplitude. The femoral latencies of patients have significantly been related to the total neuropathy score. A significant difference between diabetic patients without polyneuropathy and the controls was observed with respect to their femoral latencies.

CONCLUSION

In our study, femoral nerve conduction abnormalities have been determined in diabetics who clinically did not have femoral nerve involvement. It has been observed that these abnormalities become more evident as the polyneuropathy of the patients becomes more serious. Our study has shown that femoral nerve conductions may increase the sensitivity of the diagnosis of polyneuropathy.

Treatment of symptomatic diabetic peripheral neuropathy with the protein kinase C beta-inhibitor ruboxistaurin mesylate during a 1-year, randomized, placebo-controlled, double-blind clinical trial

OBJECTIVE

The aim of this study was to assess the effects of ruboxistaurin (RBX) mesylate on nerve function and sensory symptoms in patients with diabetes mellitus (DM) and diabetic peripheral neuropathy (DPN).

METHODS

Patients were enrolled in a multinational, randomized, Phase II, double-blind, placebo-controlled parallel-group trial comparing 32 mg/d or 64 mg/d RBX with placebo for 1 year. DPN was identified by abnormal measurable vibration detection threshold (VDT) and verified by abnormal neurologic examination and nerve electrophysiology measures. Baseline patient characteristics (eg, sex, type of DM, age, body mass index, glycosylated hemoglobin, and duration of DM and DPN) were measured. The primary end point was the change in VDT. Secondary end point measures included effects of RBX versus placebo on Neuropathy Total Symptom Score-6 (NTSS-6), neurologic examination, electrophysiologic nerve conduction studies, Neuropathy Impairment Score, Clinical Global Impressions, and safety. A post-hoc analysis was performed on patients with less severe DPN (sural sensory nerve action potential > or =0.5 microV and NTSS-6 total score >6).

RESULTS

Two hundred five patients were assessed: 66 were assigned to the RBX 32 mg/d group, 71 to the RBX 64 mg/d group, and 68 to the placebo group. The demographic and baseline characteristics of the treatment groups were well matched between the RBX 32 mg/d, RBX 64 mg/d, and placebo groups: mean (SD) age, 45.6 (8.41) years; 122 (60%) men, 83 (40%) women; 110 (54%) with type 1 DM, 95 (46%) with type 2 DM; mean (SD) duration of DPN, 3.4 (4.21) years. The RBX 32 mg/d group had slightly more patients with type 1 DM (P = 0.05). Eighty-three patients had clinically significant symptoms at baseline (defined as NTSS-6 total score >6: RBX 32 mg/d, n = 22; RBX 64 mg/d, n = 26; placebo, n = 35); 122 patients had NTSS-6 total scores < or =6. No treatment differences were observed for change in VDT. Among the 83 patients with significant symptoms at baseline, there was a reduction from baseline at 12 months in the NTSS-6 total score in the RBX 32 mg/d (P = NS) and RBX 64 mg/d (P = 0.015) groups compared with placebo. In a subgroup of patients with clinically significant symptoms and less severe DPN (n = 50), there was a significantly greater reduction in the NTSS-6 total score with RBX 64 mg/d (P = 0.006 vs placebo). Furthermore, in these patients, there was a statistically significant improvement in VDT for both RBX 32 mg/d (P = 0.012) and RBX 64 mg/d (P = 0.026) compared with placebo.

CONCLUSIONS

RBX appeared to be well tolerated in the patients with DPN who participated in this study. Overall, changes in VDT and NTSS-6 total scores did not differ among treatment groups at end point. However, RBX treatment appeared to be of benefit for the subgroup of patients with less severe symptomatic DPN by relieving sensory symptoms and improving nerve fiber function, as indicated by reductions in VDT and NTSS-6 total score.

Sural sensory action potential identifies diabetic peripheral neuropathy responders to therapy

Identifying patients with diabetic peripheral neuropathy (DPN) amenable to therapy is a challenge. To determine whether the amplitude of the sural sensory nerve action potential (sural SNAP) reflects the severity of DPN, an analysis was performed on 205 patients with DPN, identified by an abnormal vibration detection threshold (VDT), who were enrolled in a multinational clinical trial investigating ruboxistaurin (RBX) mesylate. Nerve conduction velocity and response amplitude and latency were measured and compared. VDT was significantly lower in those with preserved sural SNAPs (n = 128) than in those in whom they were absent (n = 77; 21.5 vs. 22.7 JND units, P = 0.002). Thus, preserved sural SNAP denoted less severe DPN. Logistic regression analyses evaluating baseline characteristics, HbA(1c), and baseline symptom scores identified only DPN duration as a factor that might contribute to the presence of sural SNAP (P = 0.004; OR = 0.896). For patients with abnormal VDT, preserved sural SNAP identifies a patient population with less severe DPN who may respond to therapeutic intervention in clinical trials.

Sural/radial nerve amplitude ratio: Reference values in healthy subjects

The sural/radial nerve amplitude ratio (SRAR) has been proposed as a sensitive indicator of early-stage axonal polyneuropathy. However, previous studies did not take into account the effect of sex differences or different calculating methods. To obtain reference values and information on the variability of the SRAR in daily practice, we measured amplitudes of sural and superficial radial sensory nerve action potentials in 106 healthy adults, correlated them with epidemiological variables, and calculated the SRAR in several ways. Our results show that the SRAR is a robust measure, independent of age, weight, sex, or method of calculation. The use of bilateral measurements is recommended. The cut-off value (5th percentile) of 0.2 in these healthy subjects is much lower than found previously, especially compared to defining cut-off values by comparing patients with matched controls. Further study is needed to establish the clinical value of this SRAR in the early detection of axonal polyneuropathies.

Diabetic neuropathy: a review emphasizing diagnostic methods

Diabetic sensorimotor polyneuropathy (DSP) is the most common complication of diabetes. In order to manage DSP effectively, it is necessary to formulate an accurate diagnosis and monitor subjects regularly. This review of important aspects of the diagnosis of DSP starts with a conceptual framework that includes elements of DSP epidemiology, pathophysiology, and therapy. The emphasis of the review is to present our current understanding of diagnostic methods for DSP including their utility and limitations. Screening for DSP in the diabetes clinic can be achieved successfully using simple clinical tests. Clinical neurophysiological methods are necessary to exclude other diagnoses, stage severity, and monitor the course of DSP. Novel investigative techniques are highly promising, but their usefulness in the clinic setting remains limited at this time. This article presents an overview of diagnostic methods for DSP.

Electrophysiologic measures of diabetic neuropathy: mechanism and meaning

Whole nerve electrophysiologic procedures afford a battery of measures that can provide a noninvasive and objective index of the onset and progression of diabetic polyneuropathy (DPN). Advances in physiologic procedures, digital hardware, and mathematical models have allowed assessment of activity in slower conducting fibers, as well as measures that reflect changes in refractory periods and threshold excitability. These expanded options can augment standard measures of maximal conduction velocity and compound amplitude and greatly enhance the sensitivity of whole nerve measure to both structural (e.g. demyelination) and "nonstructural" (e.g. redistribution of ion channels) deficits associated with DPN. The mechanisms underlying the physiologic events in DPN are multifactorial and their sequence in complex, with different mechanisms contributing to change at overlapping, but distinct points in the progression. Factors influencing early change in velocity may differ from those contributing to chronic deficits and these mechanisms may also differ in their response to various putative therapies. This review attempts to summarize the pattern of whole nerve electrophysiologic change associated with DPN, outlines the strengths and limitations of the various measures that are feasible, and discusses the specific impact of know pathophysiologic mechanisms on these end points.