Utility of visual evoked potentials using hemifield stimulation and several check sizes in the evaluation of suspected multiple sclerosis

One hundred and eleven patients with suspected multiple sclerosis (64 possible, 47 probable) and 16 with a definite diagnosis of MS were evaluated with pattern-reversal visual evoked potentials (VEPs), employing monocular full-field checks subtending 7′, 14′ and 28′ of visual angle, and right and left hemifield 28′ checks. Thirty-seven patients (29%) had a completely normal study. Sixty-six patients (52%) had abnormal responses to full-field 28′ checks, and in 13 (10%) of these, additional abnormalities were found in one or more of the other test conditions, which indicated the presence of an additional site of dysfunction in the visual pathway. Twenty-four patients (19%) with ‘normal’ full-field 28′ response had abnormalities in one or more of the other test conditions; these included prolonged latency to small size (7′ and 14′) full-field checks, abnormal responses in homonymous hemifields, and abnormal responses limited to a hemifield of one eye. Thus, the use of several check sizes and hemifield stimulation not only increases the sensitivity of VEPs in the evaluation of patients with suspected demyelinating disease, but enhances the capability of the VEP to demonstrate more than one area of visual system impairment.     

Diagnostic role of brain-stem auditory evoked potentials in neurobrucellosis

Evoked potential audiometry and brain-stem auditory evoked potentials were evaluated in 15 patients with systemic brucellosis in whom brucella meningitis was suspected clinically. In 8 patients cerebrospinal fluid (CSF) was abnormal with high brucella titre, and evoked potentials were abnormal in all of them. In 7 patients the CSF was normal and evoked potentials were also normal. Brain-stem auditory evoked potential abnormalities were categorised into 4 types: (1) abnormal wave I, (2) abnormal wave V, both irreversible, (3) prolonged I–III interpeak latencies, and (4) prolonged I–V interpeak latencies, both reversible. These findings are of important diagnostic value and correlate well with the clinical features, aetiopathogenesis and final outcome.     

Delayed visual evoked potentials are independent of pattern orientation in macular disease

Visual evoked potentials (VEPs) and contrast sensitivity (CS) were studied in patients affected by maculopathy. VEP delays and CS reduction were demonstrated in each affected eye. In distinction to patients affected by multiple sclerosis (MS), in maculopathy patients VEP latency is independent of the orientation of the grating stimulus. It is proposed that stimulating with more than one pattern orientation is useful in the differential diagnostic use of VEPs.     

Brain-stem auditory evoked potentials (BAEPs) and magnetic resonance imaging (MRI) in a case of facial myokymia

The case of a 37-year-old woman with facial myokymia is reported. Magnetic resonance imaging (MRI), electromyography (EMG) and brain-stem auditory evoked potentials (BAEPs) supported the clinical diagnosis of suspected multiple sclerosis (MS). MRI showed a single area of abnormal signal in the pontine region. The authors discuss the possible relationship between the brain-stem lesion and the electrophysiological abnormalities demonstrated by BAEPs and the EMG of facial muscles.     

Morphological measurement of the SEP using a dynamic time warping algorithm

A dynamic time warping technique was created to align the components of digitally high-pass (300 Hz–2500 Hz) filtered somatosensory evoked potentials evoked by median nerve stimulation recorded with a bipolar cephalic montage. A cost function was assigned related to the amount of warping necessary to match a standard wave derived from 24 normal subjects. Its value ranged from 0.525 to 2.456 (mean 1.305±0.501). This contrasted with a mean of 5.089±4.277 (range 0.701–13.972) derived from 25 patients with definite (n = 24) or possible (n = 1) multiple sclerosis chosen on the basis of having few or no clinical abnormalities at the time of testing. Fourteen (56%) of the patients had cost functions that were 3 or more S.D.s above the normal mean as compared to 3 (12%) having prolonged latency of the N19 peak. When used in combination, the cost function and latency yielded 60% abnormalities; 5 times higher than latency measurement alone.     

Evoked potential findings in Behçet's disease. Brain-stem auditory,visual, and somatosensory evoked potentials in 44 patients

We studied 54 patients with Behçet's disease, 41 males and 13 females, mean age 28 years. Forty-four patients had auditory brain-stem evoked potential (BAEP) recordings, 39 had pattern reversal visual evoked potentials (VEP), 27 had median nerve somatosensory evoked potential (SEP) recordings, and 25 tibial nerve SEPs. BAEPs were abnormal in 16 patients (52%) with neurological manifestations and in 4 (31%) without, because of decreased amplitude of wave V, prolonged I–III or III–V interpeak latencies, or uncertain/absent waves III and/or V. Eleven patients (40%) with neurological symptoms and 3 patients (25%) without, had abnormal VEPs. Absent potentials, decreased amplitude, with or without prolonged P100 latency, were found in 75% of the cases, the rest had prolonged P100 latency only. Median SEPs were abnormal in 8 patients (38%) with neurological manifestations. Four patients (21%) had abnormal tibial SEPs. Decreased amplitude with or without mild slowing in central conduction was the predominant SEP abnormality. SEPs were normal in all patients without neurological symptoms. In total, 84% of patients with, and 38% of patients without, neurological symptoms had abnormalities of one or more EP modality.When used cautiously, EP studies in Behçet's disease might be helpful to separate neuro-Behçet from other disorders with similar symptomatology, to disclose subclinical CNS involvement, to evaluate and monitor CNS disease activity, and to provide objective measures of treatment response.     

Electrophysiological Analysis of Transmission Via Spinal Pathways After Vertebral Trauma

Complex electrophysiological examination of the state of spinal neuronal mechanisms was carried out in patients after complicated vertebral trauma (n = 52). Electromyographic responses of the muscles of the upper and lower limbs evoked by stimulation of the peripheral nerves, effects of magnetic stimulation (MS) of the brain cortex (transcranial MS, TMS) and spinal roots, and somatosensory evoked potentials (SSEPs) were recorded. Partial disorders of the motor functions of the lower limbs were observed in 21 patients. Subjects with complete absence of movements of the limbs demonstrated two variants of the patterns of electrophysiological phenomena. In 21 patients, evoked potentials were entirely absent, while reduced MS-evoked motor responses (MS MRs) and SSEPs could be observed in 10 subjects. The presence of these potentials was indicative of partial preservation of the cerebrospinal pathways after damage to the spinal cord. Thus, estimation of the results of complex electrophysiological examination allows one to objectively verify the state and dynamics of transmission via the spinal pathways, to make justified the tactics of treatment, and to estimate the efficacy of the measures directed toward recovery of the lost functions of spinal mechanisms.     

The value of ulnar somatosensory evoked potentials (SEPs) in cervical myelopathy

In 57 patients with clinical signs and surgical documentation of compressive myelopathy, ulnar nerve somatosensory evoked potentials (SEPs) were more sensitive (with 74% abnormal) than either median or tibial nerve SEPs. The most frequent abnormalities were reduced or absent neck evoked responses and prolonged central conduction time. All subjects who had an SEP abnormality were identified by combined tibial and ulnar SEPs. Median nerve SEP added no additional information. Normal ulnar and tibial nerve SEPs were also able to exclude major cord damage in patients with cervical radiculopathy but little evidence of myelopathy.     

Interweaving and overlapping of evoked potentials

The refractory effect of one stimulus upon the response to a closely following stimulus in a different modality is much less than upon the response to a stimulus in the same modality. It is therefore far more efficient to record responses to stimuli in different modalities concurrently than to record each one separately. We evaluated 2 techniques for concurrent recording. Interweaving involves recording the response to one stimulus in the intervals between recording responses to other stimuli. Overlapping occurs when two or more responses are at times being simulateneously recorded. Interweaving and overlapping reduced the time required to record auditory brain-stem responses, short-latency somatosensory evoked potentials and pattern-reversal visual evoked potentials by a factor of 3 over the time required to record each response separately. Overlapping caused no significant change in the evoked potentials. Depending upon the actual timing schedule, interweaving may distort the evoked potentials if later parts of the response to one stimulus override the evoked potential to a following stimulus. Filtering and randomization of stimulus timing may attenuate the effects of these overriding potentials.     

Brain-stem somatosensory dysfunction in a case of long-standing left hemispherectomy with removal of the left thalamus: a nasopharyngeal and scalp SEP study

We have studied median nerve somatosensory evoked potentials (SEPs) in a patient who had undergone early surgical removal of the left cerebral hemisphere and left thalamus. Stimulation of the right side evoked normal latency P9, P11 and P13 potentials at scalp as well as at nasopharyngeal (NP) leads, while P14 and N18 potentials were absent. These SEP abnormalities, that have been described previously in cervico-medullary lesions and in comatose patients with upper brain-stem involvement, suggest that in our patient the removal of the left thalamus has caused retrograde degeneration of the cuneate-thalamic projections. Moreover, this study confirms that P13 and P14 potentials have different generators.     

Event-related auditory evoked potentials and multiple sclerosis

Long latency event-related auditory evoked potentials, particularly the P300 wave, constitute an objective electrophysiological index of cognitive function. For this reason, these potentials have been studied in a series of 101 patients with multiple sclerosis (MS), classified according to McAlpine's criteria into definite, probable and possible cases. The patients were also classified as depressed or non-depressed according to the DSM-III and Research Diagnostic Criteria. They were also subjected to a battery of psychometric tests.In the patient population the N200 and P300 latencies were increased, as were the P200 latencies, when compared with a control population. This electrophysiological pattern had previously been observed in other conditions characterised by subcortical lesions. Partial correlations (at constant disease duration) between the disability score and the cognitive deficit were found to be significant. Patients with an increased P300 latency had a greater disability and the P300 latency was significantly correlated with the duration of the illness.The N200 and P300 latencies were increased in depressed MS subjects, but this increase did not reach the level of significance. Depression was more frequent in the more severely handicapped patients. This suggests that the origin of the depression seen in multiple sclerosis is only partly organic, and that it is one of the factors contributing to the subcortical cognitive deficit in multiple sclerosis.Progressive forms of the disease exhibited the most profound cognitive deficit, and the most marked increase in P300 latency.     

Sensory and cognitive evoked potentials in a case of congenital hydrocephalus

We studied auditory and visual evoked potentials in D.W., a patient with congenital stenosis of the cerebral aqueduct. Head CT scans revealed marked hydrocephalus with expanded ventricles filling more than 80% of the cranium and compressing brain tissue to less than 1 cm in thickness. Despite the striking neuroanatomical abnormalities, however, the patient functioned well in daily life and was attending a local community college at the time of testing.Evoked potentials provided evidence of preserved sensory processing at cortical levels. Pattern reversal visual evoked potentials had normal latencies and amplitudes. Brain-stem auditory evoked potentials (BAEPs) showed normal wave V latencies. Na and Pa components of middle-latency AEP had normal amplitudes and latencies at the vertex, although amplitudes at lateral electrodes were larger than at the midline.In contrast to the normal sensory responses, long-latency auditory evoked potentials to standard and target tones showed abnormal P3 components. Standard tones (probability 85%), evoked NN1 components with normal amplitudes (−3.7 μV) and latencies (103 msec), but also elicited large P3 components (17 μV, latency 305 msec) that were never observed following frequent stimuli in control subjects. Target stimuli (probability 15%) elicited P3s in D.W. and controls, but P3 amplitudes were enhanced in D.W. (to more than 40 μV) and the P3 showed an unusual, frontal distribution. The results are consistent with a subcortical sources of the P300. Moreover, they suggest that the substitution of controlled for automatic processes may help high-functioning hydrocephalics compensate for abnormalities in cerebral structure.     

Preleukemic syndromes.

Acute nonlymphocytic leukemia (ANLL) is preceded by a hematologic illness representing the "preclinical" stages of the disease in many patients. This "preclinical stage" or preleukemic stage is difficult to recognize by conventional hematologic morphologic techniques. A prospective study was carried out to determine whether cytogenetic studies would be helpful in the recognition of preleukemic states and whether the presence of cytogenetic abnormalities would have prognostic significance. A study of 284 patients with suspected preleukemia has yielded 62 patients with progression to overt ANLL. Cytogenetic abnormalities were found in 30% of suspected preleukemic patients, whereas 53% of the patients progressing to acute leukemia had cytogenetic abnormalities. These studies show that the presence of cytogenetic abnormalities aid in the recognition of preleukemia but are not specific for early leukemia. Patients with cytogenetic abnormalities are more likely to develop overt ANLL. Banded chromosome studies demonstrated cytogenetic abnormalities in the preleukemic phase in 13 of 26 patients. A variety of clonal chromosomal abnormalities were observed.     

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 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.     

Three-dimensional human pattern visual evoked potentials. II. Multiple sclerosis patients

Pattern visual evoked potentials were obtained from 46 patients with definite relapsing/remitting multiple sclerosis, using both a conventional 5-channel occipital array and a 3-D recording technique consisting of three bipolar derivations approximating the three dimensions of space. These three orthogonal wave forms were displayed as a 3-D Lissajous trajectory for each subject. Two of the 15 patients with completely normal conventional pattern VEPs had abnormalities of the orientation of the B-C curvilinear segment of the 3-D pattern VEPs. Delays in the first major occipital positive component (P100) were evident using both techniques; the correlation between P100 latency and the latency of the corresponding trajectory apex was r = 0.99 (P < 0.01). Post-chiasmal MRI abnormalities were associated with 3-D VEP orientation abnormalities. Three-dimensional pattern VEPs are moderately more sensitive than conventional pattern VEPs at detecting dysfunction posterior to the optic chiasm in demyelinating disease and do not require the use of eccentric fixation to do so.     

Tongue-muscle-controlling motoneurons in the Japanese toad: topography,morphology and neuronal pathways from the ‘snapping-evoking area’ in the optic tectum

As a step to clarifying the neural bases for the visually-guided prey-catching behavior in the toad, special attention was paid to the flipping movement of the tongue. Tongue-muscle-controlling motoneurons were identified antidromically, and their topographical distribution within the hypoglossal nucleus, the morphology, and the neuronal pathways from the optic tectum including the 'snapping-evoking area' (see below) to these motoneurons were investigated in paralyzed Japanese toads using intracellular recording techniques. The morphology of motoneurons innervating the tongue-protracting or retracting muscles (PMNs or RMNs respectively) was examined by means of intracellular-staining (using HRP/cobaltic lysine) and retrograde-labeling (using cobaltic lysine) methods. Both PMNs and RMNs showed an extensive spread of the branching trees of dendrites; 4 dendritic fields were distinguished: lateral/ventrolateral, dorsal/dorsolateral, medial, and in some motoneurons, contralateral dendritic fields, although there was a tendency for the dorsal/dorsolateral dendritic field to be less extensive in the PMNs than in the RMNs. The axons of both PMNs and RMNs arose from thick dendrites, ran in a ventral direction without any axon-collaterals branching off, and then entered the hypoglossal nerve. The PMNs and RMNs were distributed topographically within the hypoglossal nucleus; the RMNs were located rostrally within the nucleus, whereas the PMNs were located more caudally within it. In about 3/4 of the RMNs tested, depolarizing potentials [presumably the excitatory postsynaptic potentials (EPSPs)], on which action potentials were often superimposed, were evoked by electrical stimuli applied to the nerve branch innervating the tongue protractor. These EPSPs were temporally facilitated when the electrical stimuli were applied at short intervals (10 ms). Both PMNs and RMNs showed hyperpolarizing potentials (IPSPs) in response to single electrical stimuli of various intensities (10-200 microA) applied to the 'snapping-evoking area' (lateral/ventrolateral part of the optic tectum) on either side. These IPSPs were facilitated after repetitive electrical stimulations at short intervals (10 ms) and of weaker intensities (down to 10 microA); i.e., a temporal facilitation of the IPSPs was observed. On the other hand, large and long-lasting EPSPs which prevailed over the underlying IPSPs were evoked after repetitive electrical stimulations (a few pulses or more) at short intervals (10 ms) and of stronger intensities (generally 90 microA or more); thus, a temporal facilitation of the EPSPs was also observed.(ABSTRACT TRUNCATED AT 400 WORDS)     

Electrophysiologic identification and evaluation of stylohyoid and posterior digastricus muscle complex.

PURPOSE: To identify the function of stylohyoid and posterior digastricus (STH-PD) muscle complex by the EMG techniques. METHODS: Unaffected sides of the faces of 30 patients with facial paralysis or hemifacial spasm were investigated. A concentric needle electrode was inserted to the STH-PD muscle complex and another concentric needle electrode was inserted to the orbicularis oris (OO) muscle. Simultaneous recording were obtained from two muscles using electrical stimulation (ES) (in 25 cases) and magnetic coil stimulation (MS) (in 15 cases); and both in 10 cases. Afterwards, the function of STH-PD was studied such as whistling, lip pursing, swallowing, jaw opening and closing. RESULTS: (1) The motor latency of compound muscle action potential (CMAP) of the STH-PD muscle was shorter than that of OO. (2) When the facial nerve was stimulated more distally than the stylomastoid foramen, the CMAP elicited from the STH-PD muscle complex immediately disappeared. (3) Ipsilateral MS was able to elicit the motor evoked potential (MEP) from STH-PD either at intracranially (half of cases) or at the extracranially. While OO muscle was always stimulated intracranially by MS. (4) The STH-PD muscle complex could not be basically recruited by the mimicry except lip pursing. The main recruitment were provided by swallowing and jaw opening. Cortical MS were facilitated during swallowing (5) Late reflex responses appeared in the STH-PD muscle complex during infraorbital-trigeminal and facial nerve ES. CONCLUSION: The STH-PD muscle complex is identified electrophysiologically. Although it is innervated by the facial nerve, its functions are mainly related with jaw opening and oropharyngeal swallowing. However, it is activated by the lip pursing.     

Auditory responses in the torus semicircularis of the cane toad, Bufo marinus. I. Field potential studies

Field potentials have been recorded in the torus semicircularis of the toad, Bufo marinus, in response to brief tones presented in the free field. The amplitude of the potentials varied with the frequency of the stimulus and location of the electrode along the rostro-caudal axis of the torus. All frequencies in the auditory range evoked largest potentials when the stimulus was located in the contralateral auditory field. Potentials evoked by low to mid frequencies were largest when the stimulus was located near the line orthogonal to the long axis of the animal. For progressively higher frequencies, the optimal stimulus position was progressively more anterior in the contralateral field. In animals in which one eighth nerve had been sectioned, field potentials evoked by tones of low to mid frequency were less sensitive to changes in stimulus direction than in normal animals. However, the directional sensitivity of field potentials evoked by mid to high frequencies was similar in monaural and normal animals. These observations suggest that binaural neural integration is important in determining the directional sensitivity of field potentials in the torus evoked by low to mid frequencies but not for potentials evoked by mid to high frequencies.     

Effects of localized pontine lesions on auditory brain-stem evoked potentials and binaural processing in humans

Objectives and mehtods: Four sets of measurements were obtained from 11 patients (44–80 years old) with small, localized pontine lesions due to vascular disease: (1) Monaural auditory brain-stem evoked potentials (ABEPs; peaks I to VI); (2) Binaural ABEPs processed for their binaural interaction components (BICs) in the latency range of peaks IV to VI; (3) magnetic resonance imaging (MRI) of the brain-stem; and (4) psychoacoustics of interaural time disparity measures of binaural localization. ABEPs and BICs were analyzed for peak latencies and interpeak latency differences. Three-channel Lissajous' trajectories (3-CLTs) were derived for ABEPs and BICs and the latencies and orientations of the equivalent dipoles of ABEP and BICs were inferred from them.Results: Intercomponent latency measures of monaurally evoked ABEPs were abnormal in only 3 of the 11 patients. Consistent correlations between sites of lesion and neurophysiological abnormality were obtained in 9 of the 11 patients using 3-CLT measures of BICs. Six of the 11 patients had absence of one or more BIC components. Seven of the 11 had BICs orientation abnormality and 3 had latency abnormalities. Trapezoid body (TB) lesions (6 patients) were associated with an absent (two patients with ventral-caudal lesions) or abnormal (one patient with ventral-rostral lesions) dipole orientation of the first component (at the time of ABEPs IV), and sparing of this component with midline ventral TB lesions (two patients). A deviant orientation of the second BICs component (at the time of ABEPs V) was observed with ventral TB lesions. Psychoacoustic lateralization in these patients was biased toward the center. Rostral lateral lemniscus (LL) lesions (3 patients) were associated with absent (one patient) or abnormal (two patients) orientation of the third BICs component (at the time of ABEPs VI); and a side-biased lateralization with behavioral testing.Conclusions: These results indicate that: (1) the BICs component occurring at the time of ABEPs peak IV is dependent on ventral-caudal TB integrity; (2) the ventral TB contributes to the BICs component at the time of ABEPs peak V; and (3) the rostral LL is a contributing generator of the BICs component occurring at the time of ABEP peak VI.     

The role of upper limb somatosensory evoked potentials in the management of cervical spondylotic myelopathy: preliminary data

We studied upper limb somatosensory evoked potentials (SEPs) in 11 patients with MRI and clinical evidence of cervical spondylotic myelopathy (CSM), before and after cervical open-door laminoplasty. SEP studies before surgery revealed two main types of abnormality, the first characterized by the isolated loss of the spinal N13 response, reflecting the dysfunction of dorsal horn cervical cells in 4 patients. The second combined abnormalities of both spinal N13 and scalp far-field P14 potential, suggesting the involvement of both dorsal horn cells and dorsal columns at the cervical level in 7 patients. After surgery, N13 recovered in 9 patients, while P14 abnormalities remained unchanged. Clinical recovery, evaluated by means of the Japanese Orthopaedic Association (JOA) disability scale, was accompanied by SEP improvement. Moreover, this improvement was more pronounced in patients with isolated loss of the N13 than in patients with combined abnormalities of the N13 and scalp P14 response. Our data strongly suggest that upper limb SEPs can be useful in monitoring the effectiveness of surgery, as well as in selecting before surgery patients who are likely to have a better postsurgical outcome.