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Somatosensory evoked potential results predict the likelihood of nonawakening from coma with a high level of certainty. Adults in coma from hypoxic-ischemic encephalopathy with absent somatosensory evoked potential responses have <1% chance of awakening.

No abstract

The combination of an absent N1 peak and elevated CKBB performs better than either alone in predicting nonawakening after cardiac arrest. Prolonged or absent N3 latency may increase sensitivity. These results should be interpreted with caution given the small number of patients and the possibility of a self-fulfilling prophecy.

It is important to have strong predictors of outcome in traumatic neuropathies so that appropriate management can be instituted early. Our objective in this study was to evaluate the prognostic value of electrodiagnostic studies in traumatic radial neuropathy. In this retrospective study, 33 of 67 subjects with traumatic radial neuropathy met the inclusion criteria. Good outcome was defined as grade 3 or higher strength on the Medical Research Council scale in wrist extensors. Compound muscle action potential (CMAP) responses from extensor indicis proprius (EIP) predicted prognosis: 92% of subjects with a recordable CMAP had a good outcome; and 65% of those with an absent response had a good outcome. Recruitment in brachioradialis was also predictive: 92% of those with full, central, or reduced recruitment had a good outcome; 67% of those with discrete recruitment had a good outcome; and only 33% of those with absent recruitment had a good outcome. Studies performed more than 3 months after injury produced more prognostic certainty than those performed earlier. We conclude that electrodiagnostic studies produce useful prognostic information in traumatic radial neuropathy. It is noteworthy, however, that 65% of subjects with an absent radial CMAP (suggesting complete or nearly complete axon loss) still have a good outcome.

The combined sensory index (CSI), the sum of three latency differences, median‐ulnar across the palm (palmdiff), median‐ulnar to the ring finger (ringdiff), and median‐radial to the thumb (thumbdiff), has higher sensitivity and reliability for carpal tunnel syndrome than individual tests. The objective in this study was to develop an approach that minimizes testing but maximizes accuracy. We retrospectively studied 300 hands. There were endpoints for individual tests that confidently predicted the CSI; for ranges between these endpoints, further testing was required. These ranges were: palmdiff 0–0.3 ms; ringdiff 0.1–0.4 ms; and thumbdiff 0.2–0.7 ms. One may use a strategy in which more tests are performed when results are in these ranges. This approach can allow accurate diagnosis with fewer tests when values are extreme, yet uses the greater diagnostic power of more tests when values are midrange. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 1880–1882, 2000

There is debate regarding how best to utilize ulnar motor nerve conduction velocity (MNCV) to identify ulnar neuropathy at the elbow (UNE). We used receiver operator characteristic (ROC) curves to compare absolute across-elbow MNCV with MNCV difference between elbow and forearm segments (VDIF) when recording from abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles. Also, we determined how their utility was impacted by low amplitudes of compound muscle action potentials (CMAPs). We studied 85 subjects with UNE and 77 subjects with carpal tunnel syndrome but without clinical evidence of UNE. The UNE group was divided into three subgroups based on CMAP amplitude. At 95% specificity, MNCV sensitivities were 80% at ADM and 77% at FDI, and VDIF sensitivities were 51% at ADM and 38% at FDI. The ROC curves showed MNCV to be superior to VDIF across all amplitude subgroups; however, confidence intervals overlapped when amplitude was high.

The combined sensory index (CSI) is a useful electrodiagnostic tool, but it was not known if the CSI can be correlated with clinical outcome following carpal tunnel decompression. The objective of this study was to examine the association between the CSI and symptom relief from pain and parasthesiae following surgical intervention. Retrospective chart review was performed on 272 patients, diagnosed with carpal tunnel syndrome by electrodiagnostic criteria, who proceeded to undergo open or endoscopic carpal tunnel release with postoperative follow-up at an academic medical center between 1996 and 2006. The CSI demonstrated statistical significance (P = 0.03) for correlation with resolution of pain and parasthesiae following carpal tunnel decompression. Patients with a CSI of 2.5-4.6 had the best prognosis for resolution of pain and parasthesiae following surgical intervention. Median compound muscle action potential (CMAP) amplitude and median motor latency were also associated with resolution of parasthesiae, but not pain. The CSI effectively establishes correlation with clinical outcomes following surgical intervention for carpal tunnel syndrome, and thus a range of optimal outcomes (CSI between 2.5 and 4.6) can also be established.