Strümpell's familial spastic paraplegia: an electrophysiological demonstration of selective central distal axonopathy

Three patients with autosomal dominant Strümpell's familial spastic paraplegia (SFSP) were evaluated by means of somatosensory evoked potentials (SEPs) from upper and lower limb and determination of sural nerve conduction velocity. Findings of normal sural nerve conduction but reduced amplitude and poor definition of SEPs with normal latencies on peroneal nerve stimulation support a pattern of central nervous system degeneration characterized by a selective involvement of centrally directed axons within the gracile fasciculi.     

Use of SEPs to localize degeneration in a rare polyneuropathy: Studies on polyneuropathy associated with pigmentation,hypertrichosis, edema,and plasma cell dyscrasia

Peripheral and central nerve conduction were studied in five patients who had polyneuropathy associated with pigmentation, hypertrichosis, edema, and plasma cell dycrasia by using the short-latency somatosensory evoked potential (SEP) to electrical stimulation of the median nerve at the wrist. The clavicular component N9 was markedly reduced inamplitude, and its latency was moderately prolonged. The interpeak latency from N9 to the cervical component N13 was significantly prolonged, indicating a conduction delay in the dorsal root. The interpeak latency from N13 to the cortical component N20 was normal, suggesting normal central conduction. These Physiological findings were consistent with the pathological findings, which showed degeneration of axons and segmental demyelination and remyelination in the sural nerve and extensive segmental demyelination and remyelination in the dorsal root but normal posterior columns of the spina cord. SEP is a noninvasive method of localizing the site of axon or myelin disorder in a peripheral neuropathy.     

亚急性脊髓混合变性的17例临床特征和诊断

目的评价亚急性脊髓混合变性（ＳＣＤ）的临床特征及电生理和磁共振成像的诊断价值。方法回顾分析了１７例ＳＣＤ患者的临床表现。结果发现全部ＳＣＤ患者发病由维生素Ｂ１２缺乏引起，胃大部切除术是一个主要病因，肢体感觉异常和深感觉减退是ＳＣＤ最常见的症状和体征，１２例合并周围神经损害，５例合并植物神经损害，体感诱发电位有极高的敏感性，磁共振成像可以明确脱髓鞘的部位。结论电生理和磁共振检查对ＳＣＤ的诊断和治疗起重要作用     

Short latency somatosensory evoked potentials following the peripheral nerve stimulation of lower extremities in children

We have evaluated the short latency somatosensory evoked potentials (SSEPs) following peroneal and posterior tibial nerve stimulation in 27 normal children and adults, and then applied SSEPs examination following peroneal nerve stimulation to 6 children with neurological deficits. Features of the evoked potentials following peroneal nerve stimulation in normal children were almost similar to those in adults, but we found several points characteristic in children; a higher incidence of evoked potentials and a clearer appearance of "standing potential" at the lower thoracic vertebral level than in adults. Spinal afferent conduction velocity reached at a maximum at 3-4 years of age. The SSEPs following peripheral nerve stimulation in lower extremities are useful in pediatric neurology to determine the level of the spinal lesion, to reveal the distribution and pathophysiology of the spinal dysfunction, and to analyze the process of the disease progression.     

Somatosensory evoked potentials in syringomyelia.

The two types of upper limb somatosensory evoked potential abnormality observed in nine patients with syringomyelia were reduced amplitude or absent cervical potentials and an abnormal central conduction time. Although this pattern of abnormalities resembles that observed in other intrinsic spinal cord lesions, it differs from peripheral nerve diseases and cervical radiculopathy in which the central conduction time is normal.     

Spinal somatosensory evoked potentials in hereditary spastic paraplegia.

Cervical somatosensory evoked potentials elicited by median nerve stimulation were recorded from 18 cases of hereditary spastic paraplegia. Motor and sensory nerve conduction in the median nerve was normal in each. In one third of the patients no spinal evoked potential was detectable. In the remainder the amplitude of the evoked potential was reduced in comparison with a control series; the latency was not significantly different. These changes suggest that a selective degeneration of the centrally directed axons derived from the dorsal root ganglion cells occurs in this disorder. The findings are discussed in relation to previous reports on the pathological appearances.     

Adult metachromatic leukodystrophy: neurophysiologic findings

The visual and somatosensory evoked potentials were delayed in two cases of the adult form of metachromatic leukodystrophy. Brainstem auditory evoked potentials were normal. The conduction velocity along peripheral nerves was 50% slowed in one case and near normal in the other. The findings are compatible with demyelination in the central and peripheral nervous systems. The diagnosis of metachromatic leukodystrophy should be considered in cases of early dementia, with or without psychosis or other neurologic deficits, in which evoked potentials are delayed and peripheral nerve conduction is slowed.     

Evoked potentials in cerebrotendinous xanthomatosis and effect induced by chenodeoxycholic acid.

Evoked potentials are reported in 10 patients with cerebrotendinous xanthomatosis, eight of whom had peripheral neuropathy. Four subjects showed delayed N13 to N20 interpeak latencies for arm somatosensory evoked potentials, and five showed moderately prolonged I to III and I to V interpeak latencies of brain-stem auditory evoked potentials. Six of seven patients showed marked delay and desynchronization of visual evoked potentials. All five patients undergoing transcutaneous magnetic stimulation of the motor cortex presented greatly delayed central motor conduction time, especially of the lower limbs. After treatment with chenodiol (750 mg/d for at least 2 years), there was a significant improvement in nerve conduction velocities, N13 to N20 interpeak latencies, and visual evoked potential latencies. Brain-stem auditory evoked potentials remained unchanged.     

Peripheral and central somatosensory nerve conduction defects in Friedreich's ataxia.

Somatosensory evoked potentials were recorded over the clavicle, cervical spine, mastoid processes and the hand area of the contralateral somatosensory cortex to median nerve stimulation in 22 cases of Friedreich's ataxia. There was a marked attenuation of the clavicular potential, but little evidence of delay of this or the major cervical component. A dispersed and delayed cortical response was therefore suggestive of slowed conduction in central pathways. The cortical response was shown to be mediated by peripheral fibres with normal conduction velocity between stimulation sites at the wrist and the elbow.     

Evoked potentials in HIV infection]

The study of the literature data on the multimodal evoked potentials in HIV infected patients shows many abnormalities as well in asymptomatic subjects without AIDS as in AIDS subjects with or without neurological signs. Visual evoked potentials (VEPs) reveal prolonged P100 wave latency in 22% of HIV asymptomatic subjects and in 26% of HIV symptomatic subjects; brainstem auditory evoked potentials (BAEPs) reveal an increase of the interpeak latency I-V in 16% of asymptomatic subjects and in 32% of symptomatic subjects; somatosensory evoked potentials (SEPs) by median nerve stimulation reveal prolonged central conduction time in 6% of asymptomatic subjects and in 11% of symptomatic subjects; somatosensory evoked potentials (SEPs) by tibial nerve stimulation reveal prolonged central conduction time in 4% of asymptomatic subjects and in 45% of symptomatic subjects; motor evoked potentials (MEPs) by magnetic stimulation reveal prolonged central motor conduction time in 46% of asymptomatic subjects.     

Electrophysiological studies in cerebrotendinous xanthomatosis.

Seven patients with cerebrotendinous xanthomatosis (CTX) were studied by electrophysiological techniques. The percentages of abnormalities detected in nerve conduction studies and electroencephalograms were 28.6% (two patients) and 100%, respectively. All patients showed prolonged central conduction times in short latency somatosensory evoked potentials (SSEPs) by tibial nerve stimulation but normal SSEPs by median nerve stimulation. Brain stem auditory evoked potentials and visual evoked potentials were abnormal in three (42.9%) and four patients (57.1%), respectively. These electrophysiological parameters were correlated with the ratio of serum cholestanol to cholesterol concentration. The results of SSEPs suggest that the polyneuropathy in CTX is caused by distal axonopathy affecting longer axons before shorter axons (central-peripheral distal axonopathy).     

Sensory conduction study in chronic sensory ataxic neuropathy.

Sensory conduction was studied in six patients with chronic sensory ataxic neuropathy of an idiopathic type and associated with Sjögren's syndrome. Motor nerve conduction velocities were normal in most cases, but sensory nerve potentials could not be evoked in a routine peripheral nerve conduction study. Cortical and cervical somatosensory evoked potentials (SEPs) and evoked potentials from Erb's point were barely recorded by median nerve stimulation at the wrist. When the median nerve was stimulated at more proximal points, clear potentials were recorded from Erb's point, but cortical SEPs were still hardly elicited. Thus the sensory nerves are centrally and peripherally involved in this condition, and the involvement is more prominent in the distal portion in the peripheral nerve. These findings suggest that central-peripheral distal axonopathy is a process involved in this illness and that the dorsal root ganglia may be primarily involved, in accord with previous pathological studies.     

A study of peripheral cervical and cortical evoked potentials and afferent conduction times in the somatosensory pathway

Somatosensory evoked potentials were recorded from Erb's point (N9), the cervical spine (N14) and the scalp (N20) in 47 volunteer patients to establish the normal impulse conduction time between these recording sites. Either the ulnar or the median nerve or both were stimulated percutaneously, and pure sensory as well as mixed sensorimotor nerve fibres were used. No significant differences in either the N9-N14 or N14-N20 conduction times were found for different sets of peripheral stimuli. The N9-N14 conduction time evidently reflects impulse propagation in the proximal part of the brachial plexus, the cervical roots and the dorsal column. Cross-correlation analysis, however, suggested that the main contribution to this conduction time is a central one, probably the dorsal column. The N14-N20 conduction time represents a pure central conduction time probably between the dorsal column nuclei and the cortex. While the amplitudes, morphologies and latencies of the somatosensory evoked responses N9, N14 and N20 varied significantly, the N9-N14 and N14-N20 conduction times were fairly constant. The results indicate that diagnostic use of the somatosensory evoked potentials based exclusively on the response latencies can be very misleading, both when latencies are normal and when pathologically delayed. In such cases the N9-N14 and N14-N20 conduction times can be conclusive, and we suggest that these times should be included in all SEP tests.     

Evaluation of the evoked potentials in various acquired polyneuropathies (Guillain-Barré syndrome and chronic recurrent polyneuropathy). Preliminary report

In 15 patients with acquired polyneuropathy (Guillain-Barré syndrome and chronic recurrent polyneuropathy) the conduction velocity was measured in the peripheral nerves of the upper and lower extremities, the latency of the F wave was determined, and the somatosensory evoked potentials were assessed stimulating the median enerve and posterior tibial nerve. The abnormalities were assessed in the parameters of the obtained somatosensory evoked potentials comparing them with the changes of F wave and the velocity of conduction in peripheral nerves. The sensitivity and usefulness of these methods in acquired polyneuropathies are discussed.     

Peripheral and central conduction abnormalities in diabetes mellitus

OBJECTIVES: To investigate peripheral and central somatosensory conduction in patients with diabetes. METHODS: The authors recorded sensory nerve action potentials and 5-channel somatosensory evoked potentials (SEPs) with noncephalic reference after median nerve stimulation in 55 patients with diabetes and 41 age- and height-matched normal subjects. The authors determined onset or peak latencies of the Erb's potential (N9) and the spinal N13-P13 and the cortical N20-P20 components, and obtained the central conduction time (CCT) by onset-to-onset and peak-to-peak measurements. RESULTS: Both onset and peak latencies of all SEP components were prolonged in patients with diabetes. The mean onset CCT in the diabetic group was 6.3 +/- 0.5 msec (mean +/- SD)-significantly longer than that in the control group (6.1 +/- 0.2 msec)-whereas no significant difference was found in the peak CCT. The amplitudes of N9 and N13-P13 components (but not N20-P20) were significantly smaller in the diabetic group. The peripheral sensory conduction velocity was also decreased in the diabetic group, but there was no significant correlation between peripheral conduction slowing and the onset of CCT prolongation. CONCLUSIONS: Diabetes affects conductive function in the central as well as peripheral somatosensory pathways. The CCT abnormality does not coincide with lowering of the peripheral sensory conduction. The current results do not favor a hypothesis that a central-peripheral distal axonopathy plays an important role in development of diabetic polyneuropathy.     

Electrophysiologic features of abetalipoproteinemia: functional consequences of vitamin E deficiency

We performed electrophysiologic testing in 10 patients with abetalipoproteinemia (ABL). Peripheral nerve studies implied an axonal disorder. Visual evoked potentials demonstrated prolonged P100 latency in three patients and abnormal electroretinograms in six. Somatosensory evoked potentials indicated dorsal column dysfunction in eight patients. Brainstem auditory evoked potentials were normal. Findings were consistent with the known neuropathology of ABL and of experimental vitamin E deficiency. Stabilization or improvement in electrophysiologic findings occurred with vitamin E supplementation. Neurophysiologic tests document retinal, central somatosensory and peripheral nerve lesions in vitamin E deficiency and provide an objective indication of response to treatment.     

Cerebral and spinal somatosensory evoked potentials in children with CNS degenerative disease

Spinal and cerebral somatosensory evoked potentials to peroneal nerve and median nerve stimulation were recorded in 17 children with CNS degenerative disease and compared with similar potentials obtained in a group of age-matched normal control subjects. Spinal potentials were increased in duration over caudal cord segments and were poorly defined or absent over the rostral cord in some patients. In 12 patients the conduction velocity of the spinal response was slow over spinal cord segments. However, conduction velocity over peripheral nerve and cauda equina was normal in all patients. The scalp recorded evoked potentials to both median and peroneal nerve stimulation which arise in neural structures rostral to the brain stem were absent in 14 patients. Cerebral responses and certain spinal potentials were greatly increased in amplitude in one patient with myoclonus. This study demonstrates that these methods permit an evaluation of the entire neuraxis from peripheral nerve to cerebral cortex and that they may be helpful in the evaluation of patients with diffuse or multifocal disease of the nervous system.     

Denervation in hemiplegic muscles

This study examined the frequency of denervation activity in hemiplegic muscles in relation to the size and location of the central lesion. We studied 20 patients, 14 with major unilateral cerebral infarctions in the middle cerebral or internal carotid territories; four with a single lacune in the pons, internal capsule, or thalamus; and two with precentral infarcts. Using somatosensory evoked potentials, motor conduction studies, and assessments of conduction across the plexus and roots, we detected no conduction abnormalities on the affected side. Fibrillation was common in both groups, especially in distal and intermediate muscles. The distribution of the fibrillation and the normal conduction studies suggested that trauma of peripheral nerves was not a factor. Although the normal conduction studies and pattern of fibrillation activity do not exclude peripheral nerve trauma as the cause of the fibrillation, we suggest that transsynaptic degeneration is a reasonable alternative explanation.     

Electrophysiological studies in the assessment of polyneuropathies

In many cases, one encounters great difficulties in finding causes of polyneuropathies among some 100 etiologies. However, in current practice, the diagnostic span is not so large. At this point, it is usual to get some aid from electrophysiologic tests in order to determine the nature of the peripheral nerve disorder. Examination with needle electrodes is mainly useful to detect fibrillation potentials or positive sharp waves which are indicative of an acute or subacute axonal neuropathy in which the process of degeneration is more important than the capacities of regeneration. Studies of sensory and motor nerve conduction velocities is of a more important utility to separate the different types of peripheral neuropathies: axonopathies in which nerve conduction velocities are normal or slightly decreased but in which muscular evoked potentials and sensory potentials are reduced, myelin disorders in which nerve conduction velocities are markedly decreased and in which finding of conduction blocks allows to individualize two forms, motor and sensory neuronopathies, where the pure lesion of the motor or sensory cell bodies correlate with the normality of sensory and motor pathways respectively.     

Multimodality evoked potentials in motor neuron disease

We performed median and tibial nerve somatosensory evoked potentials (SEPs), pattern-shift visual evoked potentials (PSVEPs), and brain-stem auditory evoked potentials (BAEPs) on 27 patients with motor neuron disease (MND). Median and tibial nerve SEPs were abnormal in 8 (30%) of 27 and 3 (14%) of 21 patients tested, respectively. Central and peripheral abnormalities were recorded in the absence of spondylosis. As a group, patients with MND and no evidence of cervical spondylosis had normal conduction to Erb's point following median nerve stimulation, but conduction times beyond this point were prolonged. The PSVEPs and BAEPs were within normal limits in all patients, excluding abnormalities attributable to other disease, but the group P100 latency was significantly prolonged in the group with MND. The BAEPs were normal in the group with MND. This study provides neurophysiological evidence of sensory system involvement in MND.