The objective of this study is to evaluate the degree of symptom improvement and the change of electrophysiological and ultrasonographic findings after sonographically guided local steroid injection using an in-plane ulnar approach in carpal tunnel syndrome (CTS).Seventy-five cases of 44 patients diagnosed with CTS were included and evaluated at baseline and at 4 and 12 weeks after injection. All patients received injection with 40 mg of triamcinolone mixed with 1 mL of 1% lidocaine into the carpal tunnel using an in-plane Ultrasound (US)-guided ulnar approach, out-plane US-guided approach, and blind injection. For clinical evaluation, we used the Boston Carpal Tunnel Questionnaire (BCTQ) and electrophysiological tests. The ultrasonographic findings were also evaluated with regard to cross-sectional area and the flattening ratio of the median nerve.Subjective symptoms measured by BCTQ and median nerve conduction parameters showed significant improvement at 4 weeks in the in-plane ulnar approach group compared with the out-plane ulnar approach and blind injection. This improvement was still observed at 12 weeks. The flattening ratio and cross-sectional area of the median nerve showed a more significant decrease with the in-plane ulnar approach than with the out-plane ulnar approach and blind injection (P < 0.05).US-guided local steroid injection using an in-plane ulnar approach in the CTS may be more effective than out-plane or blind injection.

We report two cases of subacute combined degeneration (SCD) caused by nitrous oxide (N2O) gas intoxication, which is rarely reported in Korea. Two patients recreationally inhaled N2O gas daily for several months. They presented with paresthesia of limbs, voiding difficulty, and gait disturbance. The initial vitamin B12 levels were normal or decreased, but homocysteine levels of the two patients were increased. Magnetic resonance imaging of the cervical spine showed T2-weighted hyperintensity in the bilateral dorsal columns of the cervical spinal cord. Electromyography and somatosensory evoked potential tests for both patients suggested posterior column lesion of the spinal cord combined with sensorimotor polyneuropathy. According to these findings, we concluded that the two patients had SCD. The patient’s symptoms partially improved after cessation of N2O gas inhalation and the receiving of vitamin B12 supplementation therapy. As the incidence of recreational N2O gas inhalation is increasing in Korea, physicians must be alert to the N2O induced SCD in patients presenting with progressive myelopathy.