Intraexaminer Variability of Nerve Conduction Study in Healthy Person

BACKGROUND: Nerve conduction study (NCS) is an objective and quantitative test in evaluating peripheral nerve disorders. Several physiological and technical factors are well known to influence the results of NCS, which can be controlled and regulated by standardization of environment and through the process to make range of normality. However, most electromyographers do not pay much attentions about inter- and intra-examiner variabilities, and there are only a few and incomplete reports on these topics. We examined the intra-examiner variability of NCS on the basis of periods of practice. METHODS: Twenty-eight electromyographers were divided into two groups: residents and neurologist-technicians. All, having variable NCS training periods, have performed NCS on one of other 27 electromyographers ten times within two weeks where each study was made once a day. RESULTS: Coefficient of variation and external quotient increased according to the following order - nerve conduction velocities (NCV), terminal latencies (TL), and amplitudes of compound action potentials (AMP). There were significant differences between the two groups in NCV and TL, but no statistical difference in AMP. CONCLUSIONS: Our results suggest that errors from intra-examiner variability should be considered when interpreting NCS and that those electromyographers who have enough training should perform NCS.

The usefulness of standardization of the nerve conduction study in the diagnosis and follow up of the demyelinating polyneuropathy

BACKGROUND: Nerve conduction study is an objective and quantitative diagnostic method for the diagnosis and follow-up study of polyneuropathy. Sometimes it is hard to interpret the nerve conduction study, because there are many segmental variables to test and uneven distribution of abnormalities in polyneuropathy. And there can be some interpersonal differences in the interpreting the results. It is obvious that one objective and quantitative value that represents the many segmental variables is helpful for the clinical interpretation and follow?up of polyneuropathy. METHODS: We evaluated 242 normal subjects and 71 patients with demyelinating polyneuropathy to find out a standardized representative value, distinguishing patients from normal subjects. The standardized representative value was made by combination of the some standardized segmental variables which showed marked differences between two groups. We evaluated the clinical usefulness of this value by comparing the sequential changes of this value with the clinical course. RESULTS: Statistically significant differences were present in each segmental value of the nerve conduction study between the groups of patients and normal persons. The diagnostic sensitivity of the segmental value was in range of 25.7%-81.8% in case of 2SD criteria. The diagnostic sensitivity of each functional standardized value - average of the segmental standardized values of same nature - was in range of 54.1%-89.9% in case of 2SD criteria. Using 3SD criteria the sensitivity was reduced to 20.9%-81.1%, more in sensory and mixed nerve than motor nerve. By combination of these functional standardized values, the diagnostic sensitivity could increase up to 79.1%-93.2% on 3SD criteria. CONCLUSION: The best combination which represents the NCV study is the average of the motor nerve terminal latency, the motor nerve conduction velocity, and the ratio of conduction block with 93.2% sensitivity and 100% specificity. This representative value well reflects the clinical course of patient in follow-up studies.

Renal Tubular Acidosis Mimicking Guillain Barre Syndrome

The typical attacks of hypokalemic periodic paralysis come on during sleep or at late night. The patients usually awaken to find mild or severe weakness of the limbs and the attacks evolve over minutes to several hours. Once established, the weakness lasts a few several hours in most cases. However, our two patients due to the hypokalemia of renal tubular acidosis showed more prolonged, progressive courses of flaccid, hyporeflexic motor weakness. Especially one patient also showed slowed motor nerve conduction velocities which were normalized after potassium correction of one day. So we initially mistook the motor weakness for Guillian Barre Syndrome.

Renal Tubular Acidosis Mimicking Guillain Barre Syndrome

The typical attacks of hypokalemic periodic paralysis come on during sleep or at late night. The patients usually awaken to find mild or severe weakness of the limbs and the attacks evolve over minutes to several hours. Once established, the weakness lasts a few several hours in most cases. However, our two patients due to the hypokalemia of renal tubular acidosis showed more prolonged, progressive courses of flaccid, hyporeflexic motor weakness. Especially one patient also showed slowed motor nerve conduction velocities which were normalized after potassium correction of one day. So we initially mistook the motor weakness for Guillian Barre Syndrome.

Solitary Plasmacytoma associated with Peripheral Neuropathy

Solitary plasmacytoma, in contrast to the disseminated neoplastic proliferation of plasma cells with marked infiltration of multiple organ system in multiple myeloma, is plasma cell neoplasm of a single focus occuring either in bone or soft tissue. The association between a solitary plasmacytoma and peripheral neuropathy is rare, and it is a progressive sensorimotorneuropathy, with a raised CSF protein and mixed demyelination and axonal loss in nerve biopsy. Localized radiotherapy indeed proves to be effective of not only arresting the progress of the neuropathy but also allowing a degree of recovery. We experienced a 55-year-old male with a solitary plasmacytoma and peripheral neuropathy confirmed by the radiologic studies, immunohistochemical stain of nasopharyngeal mucosa biopsy and sural nerve biopsy, which has loss of myelinated fiber and axonal degeneration. Until now, the reported cases are very rare in Korea, so we presented a case of solitary plasmacytoma associated with peripheral neuropathy.

CT Findings in Eclampsia

Eclampsia is characterized by hypertension. Proteinuria, edema. And seizures or mental changes after the 20th week of gestation. The incidence of abnormal CT findings in eclamptic patients are reported in 29%-21% previously, according to authors. In many previous reports, abnormal CT findings in eclamptic patients were usually bilateral. Symmetrical and non-enhancing hypodensities with mass effect at posterio; parts of cerebral hemispheres. We anal!zed the abnormal CT findings and clinical findings of 16 eclamptic Korean women and the following results were obtained. 1. There were three patterns of abnormal CT findings: low density pattern(13 cases). High density hemorrhagic pattern(3 cases). And a pattern of generalized cerebral edema(one case). 2. Low density lesions. Which could be found within 24 hours after development of neurologic symptoms or signs were usually bilateral (9/13) and symmetrical (6/9). 3. The usual location of low density lesions was around basal ganglia rather than posterior parts of cerebral hemispheres. The major clinical symptom of basal ganglia lesions was mental change rather than visual symptoms of lesions of posterior parts of cerebral hemispheres. 4. Within 2 weeks. The characteristic low density lesions on CT scans were markedly diminished or disappeared, which run parallel with neurological symptoms. 5. The cases with definite neurological deficits revealed the corresponding CT abnormalities, but the patient with sezure showed variable CT abnormalities.

Two Fatal Cases due to Porphyric Peripheral Neurophathy

We report two cases of porphyric peripheral neuropathy in a 19-year-old male with variegate porphyria and in a 39 year-old male with intermittent acute prophyria. Clinically, there were sensory, motor disturbance and autonomic symptoms including decreased sweating, urinary and sphinctor distrubances. Variegate porphyria showed facial diplegia and positive family history inherited by autosomal dominent trait. Intermittent acute porphyria was combined-with SIADH. Both cases were expired due to respiratory failure. Nerve conduction studies were carried out in two cases and both cases showed slow motor, sensory nerve conductlon velocity ,and significant low CMAPs(Compound Muscle Action Potentials). Sural nerve biopsy was carried out in a variegate prophyria compared with one normal control. Decreased large myelinated fibers was found. In nerve fiber teased study. 8.5% of nerve fibers showed axonal degenration and only 2.3% of the segmental demyelination. There findings are suggesting that the porphyric neuro might be the axonal type.and severe neuropathy in a sign of poor prognosis.

Cliaical Characteristics of Benign Focal Amyotrophy

A discription is given of 24 patients with the benigen focal amyotrophy; Nineteen had upper-limb and five had lower-limb involvement. The characteristic clinca! Features were insidious onset in the second and third decades, male predominance. Sporadic occurance, wasting and weakness confined to one limb, relatively good prognosis and absence of involvement of the cranial nerves, cerebrum, brainstem, and sensory syetem. The nerve conduction studies, electromyographic pattems, somatosensory evoked potential studies, and CTMM or MR findings suggested anterior horn cell disorders. In nine cases we were able to demonstrate focal atrophy in the lower cervical cord limited to the ipsilateral anterior horn region, and two cases segmental cord atrophy in the lower cervical cord in MR or CTMM studies. The benign focal amyotrophy, for which no causes been described, is benign and self-limiting, unlike most motor neuron diseases.

Cliaical Characteristics of Benign Focal Amyotrophy

A discription is given of 24 patients with the benigen focal amyotrophy; Nineteen had upper-limb and five had lower-limb involvement. The characteristic clinca! Features were insidious onset in the second and third decades, male predominance. Sporadic occurance, wasting and weakness confined to one limb, relatively good prognosis and absence of involvement of the cranial nerves, cerebrum, brainstem, and sensory syetem. The nerve conduction studies, electromyographic pattems, somatosensory evoked potential studies, and CTMM or MR findings suggested anterior horn cell disorders. In nine cases we were able to demonstrate focal atrophy in the lower cervical cord limited to the ipsilateral anterior horn region, and two cases segmental cord atrophy in the lower cervical cord in MR or CTMM studies. The benign focal amyotrophy, for which no causes been described, is benign and self-limiting, unlike most motor neuron diseases.

A Case of Cervical cord Tumor with Focal Myokymic Discharge in Intrinsic Hand Muscles

Myokymic discharge is a train of motor unit potentials that occur spontaneously, recur regularly, and sometimes may be associated with clinical myokymia. We report a 39-years-old male with progressive muscle weakness and atrophy of right upper extremity, who revealed focal myokymic discharges in the intrinsic hand muscles where no denervation was evident on EMG study. The cervical CTMM and MRI study showed a large cervical cord tumor at C3-C6 spine level. Postoperative pathological diagnosis of the tumor was anaplastic astrocytoma.