Neurophysiological localisation of ulnar neuropathy at the elbow: Validation of diagnostic criteria developed by a taskforce of the Danish Society of clinical neurophysiology.

OBJECTIVE: This study validates consensus criteria for localisation of ulnar neuropathy at elbow (UNE) developed by a taskforce of the Danish Society of Clinical Neurophysiology and compares them to the existing criteria from the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). The Danish criteria are based on combinations of conduction slowing in the segments of the elbow and forearm expressed in Z-scores, and difference between the segments in m/s. Examining fibres to several muscles and sensory fibres can increase the certainty of the localisation. METHODS: Diagnostic accuracy for UNE was evaluated on 181 neurophysiological studies of the ulnar nerve from 171 peer-reviewed patients from a mixed patient-group. The diagnostic reference standard was the consensus diagnosis based on all available clinical, laboratory, and electrodiagnostic information reached by a group of experienced Danish neurophysiologists. RESULTS: The Danish criteria had high specificity (98.4%) and positive predictive value (PPV) (95.2%) and fair sensitivity (76.9%). Compared to the AANEM criteria, the Danish criteria had higher specificity (p<0.001) and lower sensitivity (p=0.02). CONCLUSIONS: The Danish consensus criteria for UNE are very specific and have high PPV. SIGNIFICANCE: The Danish criteria for UNE are reliable and well suited for use in different centres as they are based on Z-scores.

Effect of intrathecal bupivacaine on somatosensory evoked potentials following dermatomal stimulation.

The effect of spinal anesthesia with 3.6 +/- 0.1 ml (mean +/- SEM) of 0.5% bupivacaine on early (less than 150 msec) somatosensory evoked potentials (SEPs) with electrical stimulation of the L1 and S1 dermatomes was examined in 12 patients. The mean level of sensory analgesia (pinprick) was T8,9 +/- 1.0 (+/- SEM) and the mean degree of motor blockade was 1.3 +/- 0.1 (Bromage scale). Intrathecal bupivacaine significantly (P less than 0.05) decreased the amplitude of all SEP components after stimulation of the L1 dermatome and most components during stimulation of the S1 dermatome. Intrathecal bupivacaine also increased the latency of SEPs (P less than 0.05) of both dermatomes. The L1 SEP disappeared in 7 and the S1 SEPs in 5 of the 12 patients during neural blockade. In three patients the SEPs disappeared at both locations. Sensory thresholds increased significantly during blockade. We found no correlation between decrease of amplitude and degree of motor blockade or level of sensory analgesia. Thus, intrathecal plain bupivacaine has a strong depressant effect on the neural afferent transmission as assessed by SEPs. However, despite clinically effective blockade as assessed by pinprick and motor blockade nerve potentials after nociceptive stimulation within the area of sensory block were often able to pass to the cerebral cortex.

Effect of long-term implanted nerve cuff electrodes on the electrophysiological properties of human sensory nerves.

During a long-term implantation (307 days) of a tripolar split cuff electrode around the palmar digital nerve to the radial side of the left index finger, branching off the median nerve in a medullary lesioned C6 patient, the physiological state of the nerve was intensively monitored. The resulting sensory nerve action potential (SNAP) amplitude was recorded, using both near-nerve electrodes and the implanted cuff electrode. The SNAP amplitude declined within 10 days to approximately 50% of the first SNAP cuff amplitude measured on Day 2 after implantation and recovered to the initial amplitude within 3 months. The SNAP amplitude measurements made with near-nerve electrodes were consistent with the cuff results; the SNAP conduction velocity (CV) recorded by the near-nerve electrodes and the cuff electrode was constant during the whole implantation period. This is in agreement with the results from two other patients: one with a cuff implanted around the sural nerve, and the other with a cuff implanted around a branch of the tibial nerve. These results and animals studies show that the cuff electrode is an electrically stable neural-electrical transducer.

Effect of epidural bupivacaine on somatosensory evoked potentials after dermatomal stimulation.

The effect of lumbar epidural analgesia with plain bupivacaine, 0.5%, on early (less than 0.5 sec) somatosensory evoked potentials (SEP) to electrical stimulation of the T-10, L-1, and S-1 dermatomes and the posterior tibial nerve was examined in eight patients. A decrease of the cortical amplitude and an increase in latency were seen, most pronounced at the L-1 level, but with only minor effect on the S-1 dermatome. No correlation was found between segmental level of analgesia and decrease in amplitude of the evoked potentials. Thus despite clinically adequate surgical anesthesia, the neural pathways as assessed by SEP were incompletely blocked except at the L1 dermatome near the epidural injection site.

Effect of extradural morphine on somatosensory evoked potentials to dermatomal stimulation.

The effect of the extradural (L2-3) administration of morphine 6 mg on early (less than 0.5 s) somatosensory evoked cortical potentials (SEP) to electrical stimulation of the L1- and S1-dermatomes was examined in eight patients. Extradural morphine did not influence SEP amplitude. SEP latency did not change, except for a minor increase in the latencies of the onset and the P2 components following S1 stimulation.

Prevention of cerebral palsy in motor risk infants by treatment ad modum Vojta. A controlled study.

The proposal by V. Vojta in 1974 to prevent development of cerebral palsy in "motor risk" infants by special treatment has been investigated in 11 Danish and 10 Swedish babies and compared with 30 control infants with similar risk, who were not given Vojta treatment. We found a tendency for "uncomplicated" cerebral palsy cases to accumulate in the control group, although the difference was non-significant on 1 5% level. Further controlled studies must be completed before it is possible to accept the prophylactive treatment of cerebral palsy recommended by Vojta.