Sensory and motor axonal excitability testing in early diabetic neuropathy.

OBJECTIVE: The aim of the present study was to gain insight into the pathophysiology of diabetic polyneuropathy (DPN) and examine the diagnostic value of sensory and motor axonal excitability testing. METHODS: One hundred and eleven type 2 diabetics with and without DPN (disease duration: 6.36 ±â€¯0.25 years) and 60 controls were included. All participants received a thorough clinical examination including Michigan Neuropathy Screening Instrument (MNSI) score, nerve conduction studies (NCS), and sensory and motor excitability tests. Patients were compared by the likelihood of neuropathy presence, ranging from no DPN (17), possible/probable DPN (46) to NCS-confirmed DPN (48). RESULTS: Motor excitability tests showed differences in rheobase and depolarizing threshold electrotonus measures between NCS-confirmed DPN group and controls but no changes in hyperpolarising threshold electrotonus or recovery cycle parameters. Sensory excitability showed even less changes despite pronounced sensory NCS abnormalities. There were only weak correlations between the above motor excitability parameters and clinical scores. CONCLUSIONS: Changes in excitability in the examined patient group were subtle, perhaps because of the relatively short disease duration. SIGNIFICANCE: Less pronounced excitability changes than NCS suggest that axonal excitability testing is not of diagnostic value for early DPN and does not provide information on the mechanisms.

MScanFit motor unit number estimation and muscle velocity recovery cycle recordings in diabetic polyneuropathy.

OBJECTIVE: Motor Unit Number Estimation (MUNE) methods may be valuable in tracking motor unit loss in diabetic polyneuropathy (DPN). Muscle Velocity Recovery Cycles (MVRCs) provide information about muscle membrane properties. This study aimed to examine the utility of the MScanFit MUNE in detecting motor unit loss and to test whether the MVRCs could improve understanding of DPN pathophysiology. METHODS: Seventy-nine type-2 diabetic patients were compared to 32 control subjects. All participants were examined with MScanFit MUNE and MVRCs in anterior tibial muscle. Lower limb nerve conduction studies (NCS) in peroneal, tibial and sural nerves were applied to diagnose large fiber neuropathy. RESULTS: NCS confirmed DPN for 47 patients (DPN + ), with 32 not showing DPN (DPN-). MScanFit showed significantly decreased MUNE values and increased motor unit sizes, when comparing DPN + patients with controls (MUNE = 71.3 ± 4.7 vs 122.7 ± 3.8), and also when comparing DPN- patients (MUNE = 103.2 ± 5.1) with controls. MVRCs did not differ between groups. CONCLUSIONS: MScanFit is more sensitive in showing motor unit loss than NCS in type-2 diabetic patients, whereas MVRCs do not provide additional information. SIGNIFICANCE: The MScanFit results suggest that motor changes are seen as early as sensory, and the role of axonal membrane properties in DPN pathophysiology should be revisited.

Diagnosis and prevalence of diabetic polyneuropathy: a cross-sectional study of Danish patients with type 2 diabetes.

BACKGROUND AND PURPOSE: Diabetic polyneuropathy (DPN) is a common complication of diabetes. Using the Toronto criteria for diabetic polyneuropathy and the grading system for neuropathic pain, the performance of neuropathy scales and questionnaires were assessed by comparing them to a clinical gold standard diagnosis of DPN and painful DPN in a cohort of patients with recently diagnosed type 2 diabetes. METHODS: A questionnaire on neuropathy and pain was sent to a cohort of 5514 Danish type 2 diabetes patients. A sample of 389 patients underwent a detailed clinical examination and completed neuropathy questionnaires and scales. RESULTS: Of the 389 patients with a median diabetes duration of 5.9 years, 126 had definite DPN (including 53 with painful DPN), 88 had probable DPN and 53 had possible DPN. There were 49 patients with other causes of polyneuropathy, neuropathy symptoms or pain, 10 with subclinical DPN and 63 without DPN. The sensitivity of the Michigan Neuropathy Screening Instrument questionnaire to detect DPN was 25.7% and the specificity 84.6%. The sensitivity of the Toronto Clinical Neuropathy Scoring System, including questionnaire and clinical examination, was 62.9% and the specificity was 74.6%. CONCLUSIONS: Diabetic polyneuropathy affects approximately one in five Danish patients with recently diagnosed type 2 diabetes but neuropathic pain is not as common as previously reported. Neuropathy scales with clinical examination perform better compared with questionnaires alone, but better scales are needed for future epidemiological studies.

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method - MScanFit MUNE.

OBJECTIVE: Detection of motor involvement in diabetic polyneuropathy (DPN) by nerve conduction studies (NCS) does not occur until there is substantial loss of motor units, because collateral reinnervation maintains compound muscle action potential (CMAP) amplitude. Motor unit number estimation (MUNE) methods may therefore be more sensitive. This study was undertaken to test whether the novel method, MScanFit MUNE (MScan) can detect motor involvement in DPN despite normal NCS. METHODS: Fifty-two type-2 diabetic patients and 38 healthy controls were included. The median nerve was examined in all participants using standard NCS and a detailed CMAP scan, used for MScan. Additional lower extremity NCS in patients were used for DPN diagnosis. RESULTS: Of 52 diabetic patients, 21 had NCS-defined DPN while lower extremity NCS were normal in 31 patients. MScan motor unit number and size showed higher sensitivity and incidence of abnormality than motor NCS parameters, and a similar sensitivity to sensory NCS. CONCLUSIONS: MScan is able to detect motor axonal damage at times when collateral reinnervation limits NCS changes. SIGNIFICANCE: MScan is a sensitive method to detect motor involvement in DPN, which our data suggests is present as early as sensory.

The utility of motor unit number estimation methods versus quantitative motor unit potential analysis in diagnosis of ALS.

OBJECTIVE: To compare the diagnostic utility of motor unit number estimation (MUNE) methods to motor unit potential (MUP) analysis in amyotrophic lateral sclerosis (ALS). METHODS: Twenty-five patients (1 definite, 11 probable, 9 possible ALS and 4 progressive muscular atrophy) and 22 healthy controls were prospectively included. Quantitative MUP analysis and three MUNE methods; Multiple Point Stimulation MUNE (MPS), Motor Unit Number Index (MUNIX) and MScanFit MUNE (MScan) were done in abductor pollicis brevis muscle. The sensitivities were compared by McNemar chi-square test. MUNE, MUP and revised ALS Functional Rating Scale (ALSFRS-R) parameters were correlated by regression analysis. RESULTS: The sensitivities of MPS (76%) and MScan (68%) were higher than MUP duration (36%) and amplitude (40%) in detecting motor unit loss (p < 0.05). MUNE methods increased the categorical probability from possible to probable ALS in 4 patients (16%). There was only significant correlation between ALSFRS-R and MScan (r = 0.443, p = 0.027) among the electrophysiological tests. MUNE methods did not correlate to MUP parameters. CONCLUSIONS: MUNE methods are more sensitive in showing abnormality than MUP analysis. SIGNIFICANCE: MUNE methods, in particular MScan, may have the potential to be implemented in the clinical practice for diagnosis and follow-up of neuromuscular disorders particularly ALS.

Memantine (a N-methyl-D-aspartate receptor antagonist) in the treatment of neuropathic pain after amputation or surgery: a randomized, double-blinded, cross-over study.

UNLABELLED: Evidence has accumulated that the N:-methyl-D-aspartate receptor system plays a role in continuous and particularly, in stimulus-evoked pain after nerve injury. We examined, in a randomized, double-blinded, cross-over fashion, the analgesic effect of memantine (a N:-methyl-D-aspartate receptor antagonist) in a group of patients with chronic pain after surgery. We randomized 19 patients to receive either memantine or placebo in the first 5-wk treatment period. A washout period of 4 wks was followed by another 5-wk treatment period with the opposite drug. The dosage of drug was increased from 5 to 20 mg/d. Pain was recorded daily, with the use of a 0-10 numeric rating scale. Before and at the end of each treatment period, pain and sensitivity were also assessed by using the McGill Pain Questionnaire, allodynia to touch, brush and cold, wind-up-like pain, and thresholds to mechanical stimuli (pressure and von Frey hair). A total of 15 patients (12 amputees and three patients with other nerve injuries) completed the study. There was no difference between memantine and placebo on any of the outcome measures. We conclude that memantine at a dosage of 20 mg/d does not reduce spontaneous or evoked pain in patients with nerve injury pain. IMPLICATIONS: In a randomized, double-blinded and cross-over study, the analgesic effect of memantine (a drug which reduces the excitability of sensitized neurons in the dorsal horn) was examined in 19 patients with chronic pain after nerve injury.