Assessing ulnar neuropathy at the elbow using magnetoneurography.

OBJECTIVE: To measure neuromagnetic fields of ulnar neuropathy patients at the elbow after electrical stimulation and evaluate ulnar nerve function at the elbow with high spatial resolution. METHODS: A superconducting quantum interference device magnetometer system recorded neuromagnetic fields of the ulnar nerve at the elbow after electrical stimulation at the wrist in 16 limbs of 16 healthy volunteers and 21 limbs of 20 patients with ulnar neuropathy at the elbow. After artifact removal, neuromagnetic field signals were processed into current distributions, which were superimposed onto X-ray images for visualization. RESULTS: Based on the results in healthy volunteers, conduction velocity of 30 m/s or 50% attenuation in current amplitude was set as the reference value for conduction disturbance. Of the 21 patient limbs, 15 were measurable and lesion sites were detected, whereas 6 limbs were unmeasurable due to weak neuromagnetic field signals. Seven limbs were deemed normal by nerve conduction study, but 5 showed conduction disturbances on magnetoneurography. CONCLUSIONS: Measuring the magnetic field after nerve stimulation enabled visualization of neurophysiological activity in patients with ulnar neuropathy at the elbow and evaluation of conduction disturbances. SIGNIFICANCE: Magnetoneurography may be useful for assessing lesion sites in patients with ulnar neuropathy at the elbow.

Assessing carpal tunnel syndrome with magnetoneurography.

OBJECTIVE: To measure the neuromagnetic fields of carpal tunnel syndrome patients after electrical digital nerve stimulation and evaluate median nerve function with high spatial resolution. METHODS: A superconducting quantum interference device magnetometer system was used to record neuromagnetic fields at the carpal tunnel after electrical stimulation of the middle digital nerve in 10 hands of nine patients with carpal tunnel syndrome. The patients were diagnosed based on symptoms (numbness, tingling, and pain) supported by a positive Phalen or Tinel sign. A novel technique was applied to remove stimulus-induced artifacts, and current distributions were calculated using a spatial filter algorithm and superimposed on X-ray. RESULTS: In 6 of the 10 hands, the amplitude of the inward current waveform attenuated to <70% or the nerve conduction velocity was <40 m/s. The results of conventional nerve conduction studies were normal for two of these six hands. All four hands that could not be diagnosed by magnetoneurography had severe carpal tunnel syndrome superimposed on peripheral neuropathy secondary to comorbidities. CONCLUSIONS: Technical improvements enabled magnetoneurography to noninvasively visualize the electrophysiological nerve activity in carpal tunnel syndrome patients. SIGNIFICANCE: Magnetoneurography may have the potential to contribute to the detailed diagnosis of various peripheral nerve disorders.

Visualization of electrical activity in the cervical spinal cord and nerve roots after ulnar nerve stimulation using magnetospinography.

OBJECTIVE: To establish a method for magnetospinography (MSG) measurement after ulnar nerve stimulation and to clarify its characteristics. METHODS: Using a 132-channel magnetoneurography system with a superconducting quantum interference device, cervical MSG measurements were obtained for 10 healthy volunteers after stimulation of the ulnar nerve at the elbow and the wrist, and neural current distribution was calculated and superimposed on the cervical X-ray images. RESULTS: Neuromagnetic signals were obtained in all participants after applying the stimulus artifact removal algorithm. The measured magnetic field intensity after elbow stimulation was about twice that after wrist stimulation. Calculated neural currents flowed into the intervertebral foramina at C6/7 to T1/2 and propagated cranially along the spinal canal. The conduction velocity from the peak latency of inward currents at C5-C7 was 73.4 ± 19.6 m/s. CONCLUSIONS: We successfully obtained MSG measurements after ulnar nerve stimulation. The neural currents flowed into the spinal canal from more caudal segments after ulnar nerve stimulation compared with median nerve stimulation, and these MSG measurements were effective in examining the spinal tracts at C5/6/7. SIGNIFICANCE: This is the first report on the use of MSG to visualize electrical activity in the cervical spinal cord and nerve root after ulnar nerve stimulation.

Evaluation of neural activity by magnetospinography with 3D sensors.

OBJECTIVE: Magnetospinography (MSG) has been developed for clinical application and is expected to be a novel neurophysiological examination. Here, we used an MSG system with sensors positioned in three orthogonal directions to record lumbar canal evoked magnetic fields (LCEFs) in response to peripheral nerve stimulation and to evaluate methods for localizing spinal cord lesions. METHODS: LCEFs from the lumbar area of seven rabbits were recorded by the MSG system in response to electrical stimulation of a sciatic nerve. LCEFs and lumbar canal evoked potentials (LCEPs) were measured before and after spinal cord compression induced by a balloon catheter. The lesion positions were estimated using LCEPs and computationally reconstructed currents corresponding to the depolarization site. RESULTS: LCEFs were recorded in all rabbits and neural activity in the lumbar spinal cord could be visualized in the form of a magnetic contour map and reconstructed current map. The position of the spinal cord lesion could be estimated by the LCEPs and reconstructed currents at the depolarization site. CONCLUSIONS: MSG can visualize neural activity in the spinal cord and localize the lesion site. SIGNIFICANCE: MSG enables noninvasive assessment of neural activity in the spinal canal using currents at depolarization sites reconstructed from LCEFs.

Visualization of electrophysiological activity at the carpal tunnel area using magnetoneurography.

OBJECTIVE: To establish a noninvasive method to measure the neuromagnetic fields of the median nerve at the carpal tunnel after electrical digital nerve stimulation and evaluate peripheral nerve function. METHODS: Using a vector-type biomagnetometer system with a superconducting quantum interference device, neuromagnetic fields at the carpal tunnel were recorded after electrical stimulation of the index or middle digital nerve in five healthy volunteers. A novel technique for removing stimulus-induced artifacts was applied, and current distributions were calculated using a spatial filter algorithm and superimposed on X-ray. RESULTS: A neuromagnetic field propagating from the palm to the carpal tunnel was observed in all participants. Current distributions estimated from the magnetic fields had five components: leading and trailing components parallel to the conduction pathway, outward current preceding the leading component, inward currents between the leading and trailing components, and outward current following the trailing component. The conduction velocity and peak latency of the inward current agreed well with those of sensory nerve action potentials. CONCLUSION: Removing stimulus-induced artifacts enabled magnetoneurography to noninvasively visualize with high spatial resolution the electrophysiological neural activity from the palm to the carpal tunnel. SIGNIFICANCE: This is the first report of using magnetoneurography to visualize electrophysiological nerve activity at the palm and carpal tunnel.

Novel functional imaging technique for the brachial plexus based on magnetoneurography.

OBJECTIVE: To visualize neural activity in the brachial plexus using magnetoneurography (MNG). METHODS: Using a 124- or 132-channel biomagnetometer system with a superconducting quantum interference device, neuromagnetic fields above the clavicle and neck region were recorded in response to electrical stimulation of the median and ulnar nerves in five asymptomatic volunteers (four men and one woman; age, 27-45 years old). Equivalent currents were computationally reconstructed from neuromagnetic fields and visualized as pseudocolor maps. Reconstructed currents at the depolarization site and compound nerve action potentials (CNAPs) at Erb's point were compared. RESULTS: Neuromagnetic fields were recorded in all subjects. The reconstructed equivalent currents propagated into the vertebral foramina, and the main inflow levels differed between the median nerve (C5/C6-C7/T1 vertebral foramen) and the ulnar nerve (C7/T1-T1/T2). The inward current peaks at the depolarization site and CNAPs showed high linear correlation. CONCLUSIONS: MNG visualizes neural activity in the brachial plexus and can differentiate the conduction pathways after median and ulnar nerve stimulations. In addition, it can visualize not only the leading and trailing components of intra-axonal currents, but also inward currents at the depolarization site. SIGNIFICANCE: MNG is a novel and promising functional imaging modality for the brachial plexus.

Surgical treatment of mucous cysts on fingers without skin excision.

Mucous cysts on the fingers are commonly treated by excision followed by a rotation flap or skin graft. However, such procedures require skin donors or large incisions. Therefore, a less invasive procedure is needed. Here, we report a surgical treatment method that does not require the excision of the cyst. A skin flap was made around the cyst and raised; the pedicle of the cyst was then electrodesiccated or ligated, and the contents of the cyst were evacuated. If the pedicle could not be clearly identified, the backside of the flap was electrodesiccated to break the connection between the cyst and the distal interphalangeal joint. The skin flap was replaced and sutured. The flaps became almost normal during the follow-up period. No complications or recurrences occurred in any of the six cases that were treated. Our procedure appears to be an effective and less-invasive treatment for mucous cysts of the fingers.