Test-retest and time dependent variation and diagnostic values of vibratory sensation determined by biothesiometer and the Rydel-Seiffer tuning fork.

BACKGROUND AND AIMS: Polyneuropathy is a common neurological disorder with many potential causes. An essential part in screening, diagnosis, and follow-up evaluation of polyneuropathy is testing of the sensory function including vibratory sensation. The graduated Rydel-Seiffer tuning fork and the biothesiometer have been developed to quantify vibratory sensation through detection thresholds. The aim of this study is to compare the vibration detection thresholds determined by the two instruments regarding intraindividual temporal changes, interindividual variation in healthy subjects and comparison of the diagnostic value in patients with a clinical suspicion of polyneuropathy. METHODS: Ninety-four healthy subjects, 98 patients with and 97 patients without a diagnosis of polyneuropathy were included. Quantitative sensory testing including biothesiometry, structured clinical examination, and nerve conduction studies were performed three times during 52 weeks in healthy subjects and once in patients. RESULTS: There were no significant changes over time for neither the Rydel-Seiffer tuning fork nor the biothesiometer, and both had larger between-subject variation than within-subject variation. Relative intertrial variability was largest for the biothesiometer. Diagnostic value (sensitivity, specificity, positive predictive value, and negative predictive value) was moderate for both methods (Rydel-Seiffer tuning fork: 58%, 74%, 70%, 64%; biothesiometer: 47%, 77%, 68%, 59%). INTERPRETATION: The Rydel-Seiffer tuning fork and the biothesiometer have a low test-retest and time dependent variation. They perform almost equally as diagnostic tools in patients with suspected polyneuropathy with a tendency toward better performance of the tuning fork.

Oxaliplatin Neuropathy: Predictive Values of Skin Biopsy, QST and Nerve Conduction.

BACKGROUND: Oxaliplatin-induced peripheral neuropathy negatively affects the quality of life for patients with gastrointestinal cancers and may cause neuropathic pain. Measures of peripheral nerve structure or function, such as intraepidermal nerve fiber density (IENFD) during treatment could reduce neuropathy severity through individualized dose reduction. OBJECTIVE: The aim was to evaluate the predictive values of IENFD, quantitative sensory testing (QST), and nerve conduction studies (NCS) for significant neuropathy and neuropathic pain. METHODS: Fifty-five patients were examined prospectively before, during, and six months following treatment using skin biopsies, QST and NCS. Clinically significant neuropathy six months after treatment was defined as reduced Total Neuropathy Score of more than five and neuropathic pain was assessed according to International Association for the Study of Pain criteria. RESULTS: Thirty patients had a clinically significant neuropathy, and 14 had neuropathic pain. Vibration detection threshold (VDT) before treatment was correlated with clinically significant neuropathy six months after treatment (OR 0.54, p = 0.01) and reductions in cold detection threshold (CDT) after 25% of treatment (OR 1.38, p = 0.04) and heat pain threshold (HPT) after 50% of treatment (OR 1.91, p = 0.03) with neuropathic pain. Cut off values of 5 for baseline VDT and changes of more than -0.05 °C and -0.85 °C in CDT and HPT were estimated. Sensitivity and specificity was low to moderate. There was no correlation between changes in IENFD or NCS and significant neuropathy or neuropathic pain. CONCLUSIONS: Vibration detection thresholds and thermal detection thresholds may be useful for prediction of clinically significant and painful neuropathy, respectively. However, low to moderate sensitivity and specificity may limit the predictive value in clinical practice.

Asymptomatic loss of intraepidermal nerve fibers with preserved thermal detection thresholds after repeated exposure to severe cold.

Background: Cold-induced peripheral neuropathy has been described in individuals exposed to severe cold resulting in pain, hypersensitivity to cold, hyperhidrosis, numbness, and skin changes. Nerve conduction studies and thermal detection thresholds are abnormal in symptomatic patients, and intraepidermal nerve fiber density (IENFD) in skin biopsies is reduced. Case presentation: A 41-year-old male was included as a healthy subject in a study of the spontaneous variability of quantitative sensory testing (QST), nerve conduction studies (NCS), and IENFD. Unexpectedly, IENFD was significantly reduced, whereas the rest of the examination was normal except for reduced vibration detection threshold. The results were confirmed at follow-up examination. The subject had been repeatedly exposed to severe cold resulting in short lasting numbness and paresthesia while living in the eastern part of Greenland and the northern part of Norway. Conclusion: Loss of intraepidermal nerve fibers caused by exposure to severe cold may be asymptomatic, and their function assessed by thermal detection thresholds may be preserved. This case illustrates that QST and IENFD are complementary tests and that subclinical cold-induced peripheral neuropathy may be prevalent in subjects living in or near polar regions which could have implications for the recruitment of healthy subjects.