Using ultrasonography we found multiple sites with nerve enlargement along the course of the brachial plexus, median, ulnar, and radial nerves in the majority of 21 patients with multifocal motor neuropathy. Sonography and electrophysiologic studies showed more abnormalities than expected on purely clinical grounds. Moreover, sonography revealed nerve enlargement without clinical or electrophysiologic abnormalities.

Multifocal motor neuropathy (MMN) is characterized by a slowly progressive, asymmetric weakness of the limbs without sensory loss. The arms are usually affected to a greater extent than the legs, and distal muscles more than proximal muscles. The distribution of electrophysiological abnormalities and its correlation with weak muscle groups in MMN have not been investigated systematically. The aim of the present study was to assess whether electrophysiological abnormalities have a preferential or random distribution, whether electrophysiological abnormalities in a nerve correlate with weakness in the innervated muscles, and whether these results are relevant for the development of optimal electrodiagnostic protocols. We compared the pattern of weakness and electrophysiological abnormalities in 39 patients with a lower motoneuron syndrome and a positive response to intravenous immunoglobulins. All patients underwent an extensive standardized electrophysiological examination. Electrophysiological evidence of demyelination was found more often in the nerves of the arms and was distributed randomly over lower arm, upper arm and shoulder segments. Electrophysiological evidence of axonal loss presented more frequently in longer nerves, occurring most often in the leg nerves. For the arm nerves, it is possible that the length dependence of axonal loss is due to the random distribution of demyelinating lesions that lead to axonal degeneration. Weakness was associated with features of demyelination and axonal loss in the nerves of the arm, and with features of axonal loss in leg nerves. However, a substantial number (approximately one-third) of electrophysiological abnormalities were found in nerves innervating non-weakened muscles. These results imply that in MMN, conduction block is most likely to be found in long arm nerves innervating weakened muscles, but if conduction block cannot be detected in these nerves, the electrophysiological examination should be extended to other arm nerves including those innervating non-weakened muscles.

Clinical, laboratory and electrodiagnostic studies are the mainstay in the diagnosis of polyneuropathy. An accurate etiological diagnosis is of paramount importance to provide the appropriate treatment, prognosis and genetic counselling. High resolution sonography of the peripheral nervous system allows nerves to be readily visualized and to assess their morphology. Ultrasonography has brought pathophysiological insights and substantially added to diagnostic accuracy and treatment decisions amongst mononeuropathies. In this study the literature on its clinical application in polyneuropathy is reviewed. Several polyneuropathies have been studied by means of ultrasound: Charcot-Marie-Tooth, hereditary neuropathy with liability to pressure palsies, chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, multifocal motor neuropathy, paraneoplastic polyneuropathy, leprosy and diabetic neuropathy. The most prominent reported pathological changes were nerve enlargement, increased hypo-echogenicity and increased intraneural vascularization. Sonography revealed intriguingly different patterns of nerve enlargement between inflammatory neuropathies and axonal and inherited polyneuropathies. However, many studies concerned case reports or case series and showed methodological shortcomings. Further prospective studies with standardized protocols for nerve sonography and clinical and electrodiagnostic testing are needed to determine the role of nerve sonography in inherited and acquired polyneuropathies.

Background: Multifocal motor neuropathy (MMN) is characterised by asymmetrical weakness and muscle atrophy, in the arms more than the legs, without sensory loss. Despite a beneficial response to treatment with intravenous immunoglobulins (IVIg), weakness is slowly progressive. Histopathological studies in MMN revealed features of demyelination and axon loss. It is unknown to what extent demyelination and axon loss contribute to weakness. Unlike demyelination, axon loss has not been studied systematically in MMN. Aims/Methods: To assess the independent determinants of weakness in MMN, 20 patients with MMN on IVIg treatment were investigated. Using a standardised examination in each patient, muscle strength was determined in 10 muscles. In the innervating nerve of each muscle, axon loss was assessed by concentric needle electromyography, and conduction block or demyelinative slowing by motor nerve conduction studies. Multivariate analysis was used to assess independent determinants of weakness. Results: Needle electromyography abnormalities compatible with axon loss were found in 61% of all muscles. Axon loss, and not conduction block or demyelinative slowing, was the most significant independent determinant of weakness in corresponding muscles. Furthermore, axon loss and conduction block were independently associated with each other. Conclusion: Axon loss occurs frequently in MMN and pathogenic mechanisms leading to axonal degeneration may play an important role in the outcome of the neurological deficit in patients with MMN. Therapeutic strategies aimed at prevention and reduction of axon loss, such as early initiation of treatment or additional (neuroprotective) agents, should be considered in the treatment of patients with MMN.

Brachial plexus sonography could complement MRI in the diagnostic work-up of patients with suspected CIDP and MMN. Our results indicate that combined imaging studies may add value to the current diagnostic consensus criteria for chronic inflammatory neuropathies.

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The diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) is based on clinical and laboratory results and on features of demyelination found in nerve conduction studies. The criteria that are currently used to reveal demyelinative slowing in CIDP have several limitations. These criteria were only determined in lower arm and lower leg nerve segments, were not defined with respect to nerve temperature, and the relationship with distal compound muscle action potential (CMAP) amplitudes is unclear. The aim of our study was to determine criteria for demyelinative slowing for lower arm and leg segments as well as for upper arm and shoulder segments at a temperature of 37 degrees C, and to assess whether criteria have to be modified when the distal CMAP is decreased. Included were 73 patients with lower motor neuron disease (LMND), 45 patients with CIDP and 36 healthy controls. The arms and legs were warmed in water at 37 degrees C for at least 30 min prior to an investigation and thereafter kept warm with infrared heaters. The proposed criteria for demyelinative slowing were based on the maximum conduction slowing that may occur as a consequence of axonal degeneration and consisted of the upper boundary (99%) or the lower boundary (1%) of conduction values in LMND. In LMND, the maximum conduction slowing was different for arm and leg nerves and for segments within the arm nerves. Moreover, distal motor latency and motor conduction velocity were slower in nerves with distal CMAP amplitudes below 1 mV than in nerves with distal CMAP amplitudes above 1 mV. For these reasons, separate criteria were proposed for arm nerves, for leg nerves and for different segments within arm nerves, and more stringent criteria were proposed for distal motor latency and motor conduction velocity when the distal CMAP amplitude was below 1 mV. The diagnostic yield in CIDP was assessed using the nerve, and not the patient, as the unit of measurement. Thus, whether demyelinative slowing was present was determined for each nerve. Compared with other criteria, our criteria increased the specificity without affecting sensitivity. We conclude that the present criteria, based on the maximum slowing that may occur as a result of axonal degeneration, allow more accurate detection of demyelinative slowing in CIDP compared with other criteria. It should be emphasized that the proposed criteria can only be applied if the method of warming in water at 37 degrees C for at least 30 min is adopted.

On the basis of their data, the authors suggest that CSDs play a minor role, if any, in the acute pathophysiology of SAH. Administration of Mg++ reduces the cerebral lesion volume that is present during the acute period after SAH. The neuroprotective value of Mg++ after SAH may, in part, be explained by a reduction in the duration of the ID of brain cells.