role of ultrasonography and intra-nerve ratio (new electrophysiological test) in increasing diagnostic sensitivity of ulnar nerve entrapment at the elbow

Ulnar nerve entrapment (UNE) at the elbow is the second most common entrapment neuropathy in the upper extremity. Because of its superficial position at the elbow,The clinical picture ranges from intermetittent parasthesia in the fourth and fifth digits to complete sensory loss in the ulnar nerve distibusion with atophy and weakness of the ulnar muscles .The aim of this work was to verify the usefulness of the IN-RATIO test and the ultrasonography in increasing the diagnostic sensitivity of the UNE at the elbow.from this study we found that :1- In UNE diagnosis electrophysiological evaluations is crucial for localizing nerve damage at the elbow and for assessing the degree of nerve involvement, but it may not reveal milder nerve lesions.2-The American Assaciation of Electrodiagnostic medicine (AAEM) criteria are useful and allow the neurophysiological diagnosis of UNE.3- According to fascicular organization of peripheral nerves, if in UNE patients the fibres to FDI are more damaged than the fibres to ADM, the IN-RATIO can reveal a relative slowing of FDI-CV compared to ADM-CV in the segment across the elbow.4- Evaluation of IN-RATIO increases the sensitivity of diagnosis up to 66.7%.5-Evaluation of maximum crosss sectional area inceases the sensitivity to 87.9% but with specificity of 76.8%.6- Evaluation of the IN-RATIO and CSA-MAX increase the sensitivity of diagnosing of the UNE to 90.9%.Conclusionfrom this study we concluded that:• IN-RATIO is a useful neurophysiological parameter to increase sensitivity of diagnosing the patients with clinical UNE.• When IN-RATIO is positive and FDI-CV and ADM-CV across the elbow are within the normal range, the patient may be classified as having a ‘‘minimal UNE”.• Fibres to FDI have a higher susceptibility to damage than fibres to ADM.• Ultasonography can be confirmed as being accurate in the diagnosis of UNE.• Maximum CSA of the ulnar nerve at the elbow is the most important ultrasonographic finding.• There is a good correlation between the IN-RATIO and the CSA-max• Evaluation of the IN-RATIO and CSA-MAX increase the sensitivity of diagnosing of the UNE to 90.9%.