A case of rotational restriction of the forearm due to abnormal configuration of pronator quadratus muscle.

We present a case of rotational restriction of the forearm due to abnormal configuration of the pronator quadratus muscle. A 20-year-old man developed right wrist joint pain on pitching of a baseball game and thereafter displayed rotational disorder of the forearm. Magnetic resonance imaging (MRI) revealed a space-occupying lesion from the volar side of the radius to the dorsal side of the ulna. The lesion was iso-hyperintense on T1-weighted (T1W) images and showed a mixed pattern of high intensities on T2-weighted (T2W) images. His symptoms were immediately reduced after removal of the mass. Histological examination showed that the mass contained much skeletal muscle and revealed myxoid degeneration of striated muscles. We assumed that his pronator quadratus muscle had been a divided form of deep layer and superficial layer tissue, possibly congenitally. We supposed that the deep layer had degenerated due to chronic stimulation and had extended around to the dorsal side of the ulna, which caused rotational restriction from the resulting impaired distal radioulnar joint. To our knowledge, there has been no similar case reported in the literature.

Characteristics of the electrophysiological activity of muscles attached to the transverse carpal ligament in carpal tunnel syndrome.

The main cause of carpal tunnel syndrome (CTS) remains unknown. Stiffness of the subcutaneous area of the volar aspect of the carpal tunnel is present in many patients and suggests that the stiffness of muscles attached to the transverse carpal ligament is increased. We performed an electrophysiological study to investigate muscle activities and to clarify whether the stiffness of muscles attached to the transverse carpal ligament is involved in the pathogenesis of CTS. The subjects of this study included 16 patients with early CTS showing no motor dysfunction. Both thenar muscles (opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis) and hypothenar muscles (opponens digiti minimi, abductor digiti minimi, flexor digiti minimi brevis) were investigated. Surface electrodes were placed on each muscle, and maximum voluntary contractions with the thumb and little finger in opposition were maintained for 3 seconds in all patients and in 7 control subjects. Electromyographs were subjected to fast Fourier transform analysis, and the root mean square (RMS) and the mean power frequency (MPF) were determined for each muscle. The RMS of the opponens pollicis was significantly less in hands affected by CTS (292.8 µV) than in healthy hands (405.9 µV). The RMS did not differ between affected hands and healthy hands for the other 2 thenar muscles but did differ significantly for the hypothenar muscles. The MPF did not differ between affected hands and healthy hands for any muscle. The results show that electrophysiological differences are present among muscles innervated by the median nerve and that hypothenar muscles originally unrelated to median nerve dysfunction are also affected in early CTS. These results suggest that modulation of muscles attached to the transverse carpal ligament is involved in the pathogenesis of CTS.

Clinical usefulness of assessing lumbar somatosensory evoked potentials in lumbar spinal stenosis. Clinical article.

OBJECT: The aim of this retrospective study was to evaluate the clinical usefulness of assessing lumbar somatosensory evoked potentials (SSEPs) in central lumbar spinal stenosis (LSS). METHODS: The latencies of lumbar SSEPs were recorded in 40 patients with central LSS, including 16 men and 24 women. The mean age of the patients was 67.3 +/- 7.4 years. The diagnosis was LSS in 23 cases and LSS associated with degenerative spondylolisthesis in 17 cases. The average duration of symptoms was 43.8 +/- 51.2 months. Twenty-two cases had bilateral and 18 cases had unilateral leg symptoms. Thirty-seven cases were associated with neurogenic intermittent claudication and the mean walking distance of patients with this condition was 246.8 +/- 232.7 m. The mean Japanese Orthopedic Association scale score, as well as the visual analog scale (VAS) scores of low-back pain, leg pain, and numbness, were 16.5 +/- 3.5, 6.0 +/- 2.5, 6.9 +/- 2.1, and 7.8 +/- 2.2, respectively. The minimal cross-sectional area of the dural sac on MR imaging was 0.44 +/- 0.21 cm(2). Thirty-nine cases of cervical spondylotic myelopathy without lumbar and peripheral neuropathy were chosen as the control group. RESULTS: The latencies of lumbar SSEPs in patients with LSS and in the control group were 23.0 +/- 2.0 ms and 21.6 +/- 1.9 ms, respectively. There was a statistically significant difference between the LSS and control groups (p < 0.05). The latency of lumbar SSEPs was significant correlated with the VAS score of leg numbness (p < 0.05). The latency of lumbar SSEPs in LSS was clearly delayed when the VAS score of leg numbness was > or = 8 (p < 0.05). CONCLUSIONS: Lumbar SSEPs are able to detect neurological deficit in the lumbar area effectively, and they can reflect part of the subjective severity of sensory disturbance (numbness) in LSS. Both lumbar SSEPs and VAS scores of leg numbness may be useful for clinical evaluation in patients with LSS.

Clinical value of motor evoked potentials with transcranial magnetic stimulation in the assessment of lumbar spinal stenosis.

The objective of this study was to evaluate the clinical usefulness of assessing motor evoked potentials (MEP) in lumbar spinal stenosis (LSS). Twenty-three LSS patients were enrolled. The preoperative data of MEP latency (MEPLT), clinical symptoms, Japanese Orthopaedic Association (JOA) scores for low back pain, visual analogue scale (VAS) for back pain, leg pain and numbness, walking distance and the minimal cross-sectional area (mCSA) of the dural sac were evaluated. The mean MEPLT was 42.1 +/- 2.8 ms. Fourteen patients had bilateral leg symptoms. The mean walking distance and mCSA were 302.1 +/- 302.8 m and 0.4 +/- 0.2 cm(2), respectively. The mean JOA score and VAS scores for back pain, leg pain and numbness were 15.9 +/- 4.8, 6.0 +/- 2.9, 7.7 +/- 1.9 and 7.3 +/- 3.0, respectively. MEPLT was related to the walking distance, limb symptoms and the VAS for numbness. MEPLT was significantly delayed in patients who showed a walking distance less than 500 m. MEP is useful in LSS assessment. It can reflect the subjective severity of motor disturbance and predict the neurological deficit prior to appearance.