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.     

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.     

The assessment of severe head injury by short-latency somatosensory and brain-stem auditory evoked potentials

The relative prognostic value of short-latency somatosensory evoked potentials (SEPs) and brain-stem auditory evoked potentials (BAEPs) was assessed in 35 patients with post-traumatic coma. Analysis of the evoked potentials was restricted to those recorded within the first 4 days following head injury. Abnormal SEPs were defined as an increase in central somatosensory conduction time or an absence of the initial cortical potential following stimulation of either median nerve. Abnormal BAEPs were classified as an increase in the wave I-V interval or the loss of any or all of its 3 most stable components (waves I, III and V) following stimulation of either ear. SEPs reliably predicted both good and bad outcomes. All 17 patients in whom SEPs were graded as normal had a favourable outcome and 15 of 18 patients in whom SEPs were abnormal had an unfavourable outcome. Although abnormal BAEPs were associated with an unfavourable outcome in almost all patients (6 of 7), only 19 of 28 patients with normal BAEPs had a favourable outcome. The finding of normal BAEPs was therefore of little prognostic significance. These results confirm the superiority and greater sensitivity of the SEP in detecting abnormalities of brain function shortly after severe head trauma.     

肌萎缩侧索硬化患者可发生四肢体感诱发电位的变化

观察52例肌萎缩侧索硬化患者和30例健康人正中神经和胫后神经体感诱发电位变化,判断肌萎缩侧索硬化患者深感觉传导通路的功能状况。肌萎缩侧索硬化患者中,54%（28/52）出现体感诱发电位异常,且皆有下肢体感诱发电位异常。与健康对照者比较,近场皮质电位N20、P2、N2及中枢传导时间延长,可伴有波幅降低或者波形完全消失。表明54%肌萎缩侧索硬化患者体感诱发电位中四肢的中枢起源电位均发生明显异常,证实肌萎缩侧索硬化患者可伴有深感觉通路尤其是中枢深感觉传导障碍。     

Normal conduction in pathways traversing an asymptomatic multiple sclerosis plaque.

A 31-year-old woman developed right facial myokymia as the initial manifestation of multiple sclerosis (MS). An MRI scan revealed a focal signal abnormality confined to the left dorsolateral pontomedullary region. Brain-stem auditory evoked potentials (BAEPs), somatosensory evoked potentials (SEPs), and blink reflex (BR) failed to show a conduction abnormality through the left brain-stem lesion. Instead, BAEP and BR indicated a conduction defect in the right pons and EMG showed myokymic discharges in right facial muscles. Our findings provide rare documentation of normal conduction through a presumably asymptomatic MS plaque. The abnormal MRI signal likely represents tissue edema, rather than demyelination. This case demonstrates that physical findings in MS patients may correlate better with electrophysiological abnormalities than with MRI abnormalities.     

Somatosensory evoked potentials in amyotrophic lateral sclerosis.

Forty five patients with amyotrophic lateral sclerosis were investigated, by means of somatosensory evoked potentials, in order to detect the presence of subclinical sensory changes. Cervical SEPs from the median nerve and cortical SEPs from the median and tibial nerve were recorded, showing a delay of N13 and subsequent components; the latency of the first constant cortical potential was also increased in many patients. Only the SEPs from the tibial nerve showed a decrease of amplitude. These results suggest a pathological slowing of conduction along the central sensory pathways in amyotrophic lateral sclerosis.     

Multimodality evoked potentials in patients and carriers with adrenoleukodystrophy and adrenomyeloneuropathy

A combination of brain-stem auditory evoked potentials (BAEPs), short latency somatosensory evoked potentials (SEPs) and pattern reversal visual evoked potentials (VEPs), were studied in two patients with adrenoleukodystrophy (ALD) and one patient with adrenomyeloneuropathy (AMN), as well as in one female carrier of each of the respective diseases. Abnormalities in at least 1 of the 3 evoked potentials were found in every case, including the carriers of ALD and AMN. The two most common findings were prolongation of the I-V interval of the BAEP and the N13-N20 interval of the SEP. These abnormalities were recorded either alone or in combination in all 5 cases. This finding suggests delayed conduction time in the central sensory pathways in both diseases, probably due to demyelination. The remarkable result, which distinguished AMN from ALD, even in their respective carriers, was delay of the N9 latency of the SEP, indicating slowing in conduction velocity of the peripheral nerve. Multimodality evoked potentials are useful not only in raising the detection rate for abnormal findings, but also in providing additional information about the functional state of separate afferent pathways. It is also of value in detecting and differentiating the carriers of ALD and AMN.     

Cerebrotendinous xanthomatosis: 11-year treatment with chenodeoxycholic acid in five patients. An electrophysiological study

We report the electrophysiological follow-up of five cerebrotendinous xanthomatosis patients treated for 11 years with chenodeoxycholic acid (CDCA). Nerve conduction velocity (NCV) was reduced in three cases. P100 latency of visual evoked potentials was delayed in four cases, interpeaks I–III and I–V of brainstem auditory evoked potentials (BAEPs) was increased in two and interpeak N13–20 of upper limb somatosensory evoked potentials (SEPs) was slowed in one. After 4 months of therapy with CDCA, NCV was normal and did not show any significant change during the 11 years of observation. Central motor conduction time of motor evoked potentials (MEPs) and N24–P40 interpeak latency of lower limb SEPs were increased in five and four cases, respectively, in spite of 2/3-year treatment with CDCA. Improvement of evoked potentials, especially of MEPs and SEPs, was slower and continued over the whole 11-year period. The size of xanthomas slightly decreased in some patients during treatment and the clinical manifestations stabilized, avoiding progressive worsening, but there was no significant improvement in neurological deficit. Two sisters of patients who never took CDCA showed progressive worsening of clinical manifestations, upper limb SEPs and BAEPs.     

Middle latency auditory evoked potentials (MLAEPs) in (MS)

Middle latency auditory evoked potentials (MLAEPs) were studied in 30 definite multiple sclerosis (MS) patients in addition to brain-stem auditory evoked potentials (BAEPs). BAEP abnormalities were detected in 18 (60%) patients. MLAEPs were abnormal in 22 (73%) of them. In 15 patients BAEPs and MLAEPs were both abnormal. MLAEPs were found abnormal in 7 of the 12 patients with normal BAEPs. In 18 patients with abnormal BAEPs only 3 had normal MLAEPs. MLAEPs abnormalities are consistent with a rostral auditory pathway involvement. Therefore, they can be used in combination with BAEPs to examine the whole auditory system to improve the sensitivity.     

Multimodal evoked potentials in myotonic dystrophy (MyD).

By means of multimodal evoked potentials (EPs), we evaluated the central nervous system (CNS) involvement in 25 subjects suffering from myotonic dystrophy: brainstem auditory evoked potentials (BAEPs), middle-latency auditory evoked potentials (MLAEPs) and somatosensory evoked potentials (SEPs) from the upper limb were performed on all subjects, whereas only the 19 patients, whose clinical ocular abnormalities were slight, underwent pattern-electretinograms (PERGs) and pattern visual-evoked potentials (VEPs) in order to identify the site of lesion among visual pathways (retinal and/or retroretinal). PERGs were abnormal in 8/19 subjects, VEPs in 8/19 subjects (the two techniques were simultaneously abnormal in 8 eyes), BAEPs in 7/25 subjects, MLAEPs in 4/25 subjects (in one subject both BAEps and MLAEPs were abnormal) and SEPs were abnormal in 1/25 subjects. 13/25 of our subjects showed at least one EP that revealed a CNS involvement. The electrophysiological alterations were not correlated either with subject age or with disease duration. Multimodal EPs enabled us to demonstrate that CNS involvement in myotonic dystrophy is important and mainly affects the visual and auditory system.     

Somatosensory evoked potentials in the differential diagnosis between compression and amyotrophic srinal cord literal sclerosis

Spinal cord compression (SCC) often presents a similar clinical picture to amyotrophic lateral sclerosis (ALS). An early differential diagnosis is important because SCC is a potentially treatable clinical disorder. We carried out a longitudinal study of 43 patients with an initial diagnosis of ALS, in order to ascertain the percentage of patients with SCC, and to evaluate the usefulness of somatosensory evoked potentials (SEPs) in early diagnosis. Thirty-three patients had a final diagnosis of ALS and 8 of SCC. SEPs central conduction was abnormal in 3 ALS and 7 SCC patients, respectively (Fisher exact test, p < 0.05). We concluded that SEPs investigation is useful in the differential diagnosis between ALS and SCC patients with pure motor signs.     

Auditory brainstem evoked potentials in early-treated congenital hypothyroidism

To evaluate the effect of early treatment of congenital hypothyroidism on central nervous system development, auditory brainstem evoked potentials were determined in 32 patients with hyperthyrotropinemia diagnosed during neonatal screening. The patients included 27 with congenital hypothyroidism and 5 with transient hypothyroidism. Abnormal auditory brainstem evoked potential tracings were found in 8 patients (congenital hypothyroidism in 7 and transient hypothyroidism in 1). Four of these patients had increased peripheral conduction time (wave I prolongation), and the other 4 had increased central conduction time (wave III or V prolongation). The patients with abnormal auditory brainstem evoked potentials did not show increased initial manifestations, yet 6 of them had lower initial thyroxine levels. Specific auditory brainstem evoked potential abnormalities were found in 25% of early-treated patients with congenital hypothyroidism. The possible causal relationship between deviant auditory brainstem evoked potential patterns and later neurodevelopment demands further clarification. This study suggests the usefulness of auditory brainstem evoked potential assessment to provide information about electrophysiologic deviation of the auditory pathway in patients with early-treated congenital hypothyroidism.     

Neurophysiological evaluation of the central nervous impulse propagation in patients with sensorimotor disturbances

Motor evoked potentials (MEPs) to transcranial stimulation (TCS) and somatosensory evoked potentials to median nerve stimulation (MN-SEPs) were examined in 74 patients affected by multiple sclerosis (MS = 49 cases), amyotrophic lateral sclerosis (ALS = 9 cases), cervical cord lesions (7 cases), Parkinson's disease (PD = 5 cases), Huntington's chorea (HC = 2 cases), Wilson's disease (WD = 1 case), subacute combined degeneration (SCD = 1 case). MN-SEPs were altered in 38% of arms in MS with a higher incidence in clinically affected than in clinically 'silent' arms (= 77.8% vs. 27.5%). MEP alterations were found in 54% of examined arms, mostly because of a prolongation of the motor CCT. This index was invariably altered in the affected arms, whilst it was involved in 40% of the 'silent' ones. Twelve out of 18 arms displayed abnormal MEPs in ALS. These were mainly due to an absent response, even if moderate motor CCT prolongation and 'giant' MEPs were also encountered. MN-SEPs were altered in 3/18 arms. By recording MEPs from proximal and distal upper limb muscles, cues on the level of abnormal propagation were obtained in patients suffering from 'focal' lesions of the spinal cord. Combining SEP records enhanced the diagnostic yield in this field. Both MEPs and SEPs were normal in patients with PD and HC, whilst abnormally prolonged CCTs were found in the case with WD. MEP and SEP recording revealed central propagation abnormalities coupled to a severe clinical picture of the peripheral nerve involvement (as in the case of SCD).     

Evoked potentials in olivopontocerebellar atrophy

Pattern-reveral visual evoked potentials, far-field and cortical somatosensory evoked potentials, and auditory brainstem potentials were recorded in two patients with olivopontocerebellar atrophy. In one patient, visual evoked potentials exhibited prolonged latency and interocular latency differences in the absence of clinical visual dysfunction. Median and tibial nerve evoked cortical potentials were severely attenuated in the absence of somatosensory deficit or peripheral nerve slowing. The far-field somatosensory potentials, however, were well preserved. All components of the auditory brain-stem potentials had latencies within normal limits. In the other, more severely afflicted, patient, all visual, somatosensory, and auditory evoked potentials were abnormal.     

SEPs and CNS magnetic stimulation in syringomyelia.

Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) to transcranial and spinal stimulation from upper and lower limb muscles were elicited in 13 patients with syringomyelia. Seven had an associated Chiari type I anomaly. Diagnosis was confirmed by MRI. In 5 cases, SEPs and MEPs were performed before and after surgical treatment. Prolonged central motor conduction times or absent motor responses in upper or lower limbs were found in most patients. The greatest number of abnormalities was disclosed by measurement of CMCT followed by SEPs after tibial nerve stimulation. Two of 5 cases undergoing surgery improved clinically and showed reduction in CMCT after surgical treatment. Our study shows that MEPs were useful in the evaluation of neurophysiological status in syringomyelia patients, helping to estimate anterolateral spinal cord function.     

Evoked potential abnormalities in myotonic dystrophy

Past investigators have reported evidence of central nervous system involvement in myotonic dystrophy (MYD), including EEG abnormalities, ventricular enlargement, thalamic inclusion bodies, and impaired tests of cognitive function. Brain stem auditory evoked potentials have not been reported in myotonic dystrophy. We report the results of brain stem auditory (BAEP) and median nerve somatosensory (MSSEP) evoked potentials in 15 patients with MYD (9 males, 6 females, mean age = 35.8 +/- 11.4 years). BAEPs were abnormal in 53.3% (P less than 0.05). Four patients had abnormal wave I-III interwave latencies, 3 had abnormal wave III-V latencies, and 1 patient had both wave I-III and wave III-V latencies prolonged. MSSEPs were abnormal in 13.3% (P N.S.). Both patients showed a delay of the P15-N19 thalamic complex. Both patients had a normal clinical sensory examination and normal peripheral nerve conduction. No correlation was found between abnormal evoked potentials and patient age. A sex difference, however, was noted with 8/9 males having one or more abnormal evoked potentials compared with 0/6 females. Though our finding of abnormal MSSEPs was not statistically significant, both patients showed delay at the thalamic level, where pathology has been described. Abnormal ocular pursuit and sluggish pupillary reaction have implicated brain stem involvement in MYD. The abnormal BAEPs at the level of the pons and midbrain in this study provide neurophysiological evidence of brain stem pathology in MYD.     

Brain-stem auditory evoked potentials in children with brain-stem or cerebellar dysfunction

Brain-stem auditory evoked potentials (BAEPs) were recorded in 23 children who had signs of brain-stem or cerebellar dysfunction. In patients with brain-stem gliomas, BAEPs were abnormal in all except one, in whom involvement of the brain-stem auditory pathway was limited to the midbrain tectum. The BAEPs were normal in neuronal ceroid lipofuscinosis, but abnormal bilaterally in inheritable leukoencephalopathies. All patients with Leigh's encephalopathy had BAEP abnormalities; in two, abnormalities occurred before the appearance of lesions on computed tomographic scan. Patients with Friedreich's ataxia and giant axonal dystrophy had abnormal BAEPs, but the test was normal in a child with similar neurologic findings with vitamin E deficiency. Patients with diffuse metabolic encephalopathies had variable findings. Thus, BAEP abnormalities are nonspecific for various disease processes but are frequently seen in neoplastic and neurodegenerative diseases, with primary white matter or extensive brain-stem involvement.     

Cutaneous silent periods in intramedullary spinal cord lesions

OBJECTIVE: The neurophysiological assessment of intramedullary spinal cord lesions has been unsatisfactory. Previous studies in patients with syringomyelia suggest that testing of cutaneous silent periods (CSPs) may be useful to assess centromedullary lesions. METHODS: The authors studied nine patients with intramedullary spinal cord lesions of different etiologies. Eight patients with cervical lesions presented with hypalgesia, hypothermesthesia, or pain in at least one upper extremity; five of them had also upper limb weakness or sensory impairment. One patient with a thoracic lesion had normal upper limb function. The authors recorded CSPs in abductor pollicis brevis muscle following digit II and digit V stimulation. Somatosensory evoked potentials (SEPs) were obtained following median and tibial nerve stimulation. Motor evoked potentials (MEPs) were obtained in biceps brachii, abductor digiti minimi and tibialis anterior muscles following transcranial magnetic or electrical stimulation. RESULTS: CSP abnormalities were found in all patients with cervical lesions, but not in the patient with a thoracic lesion. Cortical median nerve SEPs had normal latencies in all patients, while tibial nerve SEPs, upper limb MEPs, and lower limb MEPs were delayed in five patients each. In one patient, abnormal CSP were the only neurophysiological finding. CSP abnormalities were associated with hypalgesia and hypothermesthesia in 95% of the studies. CONCLUSION: Upper extremity CSP testing is a sensitive neurophysiological technique for the assessment of cervical intramedullary lesions. In particular, abnormal CSPs are highly associated with spinothalamic dysfunction.     

3-2-04. Ultrasonographic evaluation of facial muscles in myathenia gravis

Vitamin B12 deficiency mainly affects the dorsal column. In this study, we investigated which part of the sensory pathway is affected in vitamin B12 deficiency using NCS and SEPs. We retrospectively reviewed EMG database of Teikyo University and Mitsui Memorial Hospital from 2008 to 2016, and enrolled patients who presented with sensory symptoms and/or gait disturbance, and whose serum B12 level was below 170 ng/ml. Enrolled were 17 patients. Spinal MRI demonstrated abnormalities in 4/17. NCS was abnormal in 3/15 patients for the sural nerve and in 5/12 patients for the median nerve. When NCS and peripheral segments of the SEPs were combined, conduction delay was detected in 12/15 patients for the lower limb and 8/13 patients for the upper limb. Delay of the central conduction was rarer, 3/15 patients in tibial SEPs. N9o to P13/14o segment in median SEPs was abnormal in 4/8 patients, although this is a mixture of the peripheral and central conductions. Vitamin B12 deficiency patients showed abnormalities of the peripheral nerve conduction more frequently than those of the central conduction. SEPs are useful in localizing the lesion along the sensory pathway, not only for CCT but for peripheral conduction.     

Clinical utility of trapezius muscle studies in the evaluation of amyotrophic lateral sclerosis.

Needle electromyography (EMG) and determining the motor evoked potential (MEP) of the genioglossus (tongue) are difficult to perform in evaluation of the craniobulbar region in patients with amyotrophic lateral sclerosis (ALS). Needle EMG and MEP determination in the upper trapezius were carried out in 17 consecutive ALS patients. The needle EMG parameters recorded included abnormal spontaneous activity and motor unit action potential morphology. An upper motor neuron lesion was presumed when either response to cortical stimulation was absent, or the central conduction time was delayed (>mean + 2 SD). Of the 12 patients with limb-onset ALS, using needle EMG, 11 were found to have abnormalities in the upper trapezius, and only five in the tongue. Three of the six patients with isolated limb involvement had abnormal MEP findings. In conclusion, electrophysiological studies of the upper trapezius are useful in ALS patients without bulbar symptoms.