Digital nerve action potentials in healthy subjects, and in carpal tunnel and diabetic patients
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Abstract:
A technique is described for stimulating and recording from nerves in the finger using surface electrodes. A decrease in amplitude and velocity was found with increasing age. In control subjects the digital potential was approximately one and a half times larger than the potential recorded at the wrist. In patients with carpal tunnel syndrome there was some reduction in amplitude and velocity of the digital potential, but the changes were more marked at the wrist. In diabetic patients more uniform changes were found in the two segments. The technique was particularly useful in enabling conduction velocity to be calculated in the digital nerves when no potential could be recorded at the wrist.Keywords:
Digital nerve
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Neuroradiology
Entrapment Neuropathy
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Carpal tunnel syndrome is one of the most common entrapment neuropathies and is caused by median nerve compression as it traverses the carpal tunnel. Marked enlargement of the median nerve in the setting of carpal tunnel syndrome.
Entrapment Neuropathy
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Carpal tunnel syndrome (CTS) is a common compression neuropathy of the median nerve in the wrist. Early diagnosis of CTS is essential for selecting treatment options and assessing prognosis. The current diagnosis of CTS is based on the patient's clinical symptoms, signs, and an electromyography (EMG) test. However, they have some limitations. Recently, ultrasound has been adopted as an adjunct diagnostic tool for electromyography (EMG). Ultrasound is a non-invasive and cost-effective technique. It provides a dynamic display of morphological changes in the median nerve and an assessment of CTS etiology such as tenosynovitis, mass compression, and tendon disease. This study aimed to investigate the value of conventional ultrasound and real-time shear wave elastography (SWE) in evaluation of median neuropathy in patients with carpal tunnel syndrome (CTS) before and after surgery.First, the Boston Carpal Tunnel Questionnaire (BCTQ) was administered to patients with CTS. All subjects were measured at three levels: the distal 1/3 of the forearm, the carpal tunnel inlet, and the distal carpal tunnel using conventional ultrasound and SWE. Median nerve parameters were examined in patients with CTS 1 week after surgery.The cross-sectional area (CSA) and stiffness of the median nerve at the carpal tunnel inlet and distal carpal tunnel were significantly higher in patients with CTS than in healthy controls (p < 0.001). The CSA and stiffness of the median nerve at the carpal tunnel inlet were statistically significantly significantly between pre- and postoperative patients with CTS (p < 0.001). The CSA and stiffness of the nerve in patients with CTS had a positive correlation with electrophysiology severity.Conventional ultrasound and elastography are valuable in the diagnosis of CTS and are useful in the clinical assessment of patient's nerve recovery after operation.
Tenosynovitis
Entrapment Neuropathy
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Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy caused by impairment of the median nerve due to compression as it passes through the carpal tunnel. The current gold standard in diagnosing CTS and nerve damage is by electrophysiological nerve conduction study (NCS). However, 10 to 25% of NCS results are falsely negative. Moreover, NCS remains an expensive and time-consuming procedure for patients. Ultrasonography serves as a real-time, well-tolerated, portable, and noninvasive tool for assessing the carpal tunnel. This study aims to assess the role of high-frequency ultrasound of the median nerve at the wrist in evaluating CTS and correlate with NCS to determine whether sonography can be used as an alternative to NCS in diagnosing and grading CTS.
Entrapment Neuropathy
Nerve conduction study
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Objective: Reports of nerve conduction studies following treatment for carpal tunnel syndrome are uncommon. To better understand the improvement of median nerve after release of compression over wrist in carpal tunnel syndrome patients, we studied the recovery from preoperative to postoperative period using neurophysiological methods.
Design: prospective, early postoperative intervals neurophysiological investigations
Materials and methods: From March 1999 to March 2000, seventeen carpal tunnel syndrome patients received minimal invasive carpal tunnel release surgery in Kaohsiung Veterans General Hospital. We compared the data of median nerve motor and sensory distal latencies, motor nerve conduction velocity, amplitudes of motor and sensory action potentials between preoperative and postoperative period.
Results: We found the following: (1) The preoperative motor latency, sensory distal latency, and sensory amplitude of the median nerve of the carpal tunnel syndrome patients showed significantly abnormal in comparison with those of the normal groups. (2) The minimal invasive carpal tunnel release produced constant good result in carpal tunnel syndrome patients. (3) The median motor latency significantly improved 4wk after minimal invasive carpal tunnel release, but it took at least 8 wk for the median motor latency recovery back to normal. (4) The median sensory latency and amplitude significantly improved and back to normal since 8 wk after the operation.
Conclusions: Minimal invasive carpal tunnel release is a useful method in treating carpal tunnel syndrome. The recovery of the median motor and sensory on the electrophysiological point of views is not apparent until 8 wk after operation.
Sensory nerve
Motor nerve
Neurophysiology
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Although controversial, recent studies have demonstrated advantages of sonographic techniques in the diagnosis of carpal tunnel syndrome (CTS). The purpose of this study was to assess the utility of median nerve ultrasonography in the diagnosis of CTS in Iranian patients.Ninety patents with clinically suspected CTS were studied. Based on gold standard electromyography/nerve conduction velocity studies, wrists with CTS were divided into three groups on the basis of severity of CTS, ie, mild, moderate, and severe. In addition, both sides of the wrist were examined using sonography. Transverse images of the median nerve were obtained and median nerve cross-section areas were measured at three levels, ie, immediately proximal to the carpal tunnel inlet, at the carpal tunnel inlet, and at the carpal tunnel outlet. Furthermore, flexor retinaculum thickness was evaluated.The mean age of the studied patients was 48.52 ± 12.17 years. Median values of the median nerve cross-section at the carpal tunnel inlet, carpal tunnel outlet, and proximal carpal tunnel significantly differed between the wrists with and without CTS (P < 0.05). Comparisons between the CTS groups (mild, moderate, and severe) and non-CTS wrists demonstrated that the median cross-sections of median nerve at the carpal tunnel inlet, carpal tunnel outlet, and inlet proximal carpal tunnel were significantly greater in the severe CTS group than in the other three groups (P < 0.05). The results showed that the median nerve cross-section at the three levels of carpal tunnel could only fairly differentiate severe CTS from other cases.The present study demonstrated that median nerve ultrasonography cannot replace the gold standard test (nerve conduction velocity) for the diagnosis of CTS because of low overall sensitivity and specificity, although it might provide useful information in some patients.
Retinaculum
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Forty-seven men with numbness and paresthesiae in their hands after long-term occupational exposure to vibrating hand-held tools were examined neurophysiologically and clinically. The vibration thresholds of the finger tips were assessed and fractionated neurography of the median nerve motor and sensory fibres carried out. They were compared with control groups of healthy subjects and patients with idiopathic carpal tunnel syndrome. The patients exposed to vibration had major increases in their finger vibration thresholds, shown with both the Goldberg-Lindblom vibrameter and the Lundborg vibrogram. They also had a moderately increased motor distal latency at the wrist, but significantly less than patients with idiopathic carpal tunnel syndrome. Similar changes were seen in the sensory conduction velocities from finger to wrist. Measurement of fractionated conduction velocity across the carpal tunnel showed a bimodal distribution; one group of patients exposed to vibration had a significant reduction in conduction velocity similar to that in the genuine carpal tunnel syndrome, and one group had no localised affection at the carpal tunnel, suggesting more distal dysfunction at the level of palm or finger, or at the receptor level. A careful neurophysiological assessment of these cases is necessary before treatment is planned. It is particularly important to confirm median nerve damage at the wrist level if the carpal tunnel ligament is to be sectioned.
Sensory nerve
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Carpal tunnel syndrome (CTS) is the most common and widely known of the entrapment neuropathies in which the body's peripheral nerves are compressed. Common symptoms of CTS involve the hand and result from compression of the median nerve within the carpal tunnel. In general, CTS develops when the tissues around the median nerve irritate or compress on the nerve along its course through the carpal tunnel, however often it is very difficult to determine cause of CTS. Proper treatment (conservative or surgical) usually can relieve the symptoms and restore normal use of the wrist and hand.
Entrapment Neuropathy
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We investigated the changes in MRI T2 mapping values in subjects with carpal tunnel syndrome (CTS) compared to healthy controls.We enrolled 71 patients with CTS and 26 healthy controls. Median nerve T2 values were measured at the distal carpal tunnel, hamate bone, proximal carpal tunnel, and forearm levels. These were compared between patients and controls and correlated with median nerve cross-sectional area (CSA) and nerve conduction measurements.The mean T2 values at the proximal carpal tunnel levels were higher in the CTS group (56.7 ms) than in the control group (51.2 ms, P = .02) and also were higher than at the distal carpal tunnel (51.0 ms, P < .001) and forearm levels (47.6 ms, P < .001). T2 values were not significantly associated with CSA or nerve conduction measurements.T2 mapping of the carpal tunnel provides qualitative information on median nerve pathology but does not reflect CTS severity.
Nerve conduction study
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