neurologist has sent a patient for nerve conduction studies (NCS) and has received the report, but what does it mean? We hope to remove some of the mysteries that may surround NCS. The techniques and how they are affected by disease are described in general terms. These principles can be applied to specific conditions discussed elsewhere. We also discuss the numerous pitfalls that may be encountered with NCS. Understanding these basic concepts will allow you to get the most from your clinical neurophysiology department. NCS are only part of a complete peripheral neurophysiological examination (PNE) and are frequently accompanied by a needle electromyogram (EMG). The combination of both techniques and those detailed in other articles in this issue are often required for a complete diagnostic study. The process of choosing the appropriate tests is the responsibility of the clinical neurophysiologist (CN) and not the referring doctor and is planned as a dynamic series of steps designed to answer specific questions about nervous system function raised by the clinical picture. ABBREVIATIONS c Clinical neurophysiologists can employ a confusing number of terms and abbreviations. Box 1 lists the ones we use frequently.

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The single fiber needle electrode (SFNE), which is designed to isolate single muscle fiber action potentials, has played an important role in the diagnosis of myasthenia gravis (MG). However, the concentric needle electrode (CNE) has been recently adopted by some workers to study neuromuscular instability in MG, and reference data have also been obtained in healthy subjects. In this study we wanted to establish whether data acquired using the SFNE is comparable to that obtained using the CNE when studying patients with MG. We established reference data for our laboratory using the CNE for orbicularis oculi (OO) and extensor digitorum communis (EDC). We compared data from 24 MG patients using both SFNE and CNE and found no significant differences in mean jitter values for either muscles. We correlated the neurophysiological data obtained by either electrode with various clinical assessments, the ice pack test, OO and EDC strength measurement, and MGFA classification of disease, and we found no significant relation. We compared discomfort scores for the two needle electrodes for each muscle and found that the discomfort scores for CNE are significantly lower (P = 0.0004). We conclude that the CNE is a useful alternative electrode for studying single fiber potentials, but more reference data from normal control subjects is desirable. Muscle Nerve, 2008.

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We present the clinical features and growth and development of a child with a 45,XX,der(5)t(5;18)(pl5;qll.2),-18 karyotype. She had microcephaly, prominent, posteriorly rotated ears, short palpebral fissures with an upward slant, a wide nasal bridge, a thin upper lip, and a short neck. In addition, she had complex congenital heart disease. Although there has been delay in growth and development, she has shown progress in both areas. (JMed Genet 1998;35:865-867) Keywords: cri du chat; 5p-; 18p-; tetralogy of Fallot Prenatal diagnostic testing provides information that can be used to predict potential problems for an affected child. The situation becomes more complex, however, when a fetus is found to have an anomaly that has not been described previously. In this report we will discuss the clinical features of a child born after amniocentesis showed a 45,XX,der(5) t(5;18)(p15;ql 1.2),-18 karyotype.

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Neurophysiology is a useful investigation to assess peripheral nerve injury. It consists of nerve conduction studies and electromyography, providing information on anatomical distribution of the lesion (pre/postganglionic, single/multiple nerves), whether the lesion is primarily demyelinating or axonal, and whether the lesion is in continuity, as well as the overall prognosis.