Evoked Brainstem Potentials Research Articles

Clinicoradiological observation in three patients with suicidal hanging

Study design: A hospital-based clinical, radiological and neurophysiological study. Objectives: Hanging is a common mode of suicide in India, but there is paucity of MRI and neurophysiological findings in the context of clinical and neurological changes. We report the clinical, neurophysiological and MRI studies of three females who attempted suicide by hanging. Methods: All three patients who attempted hanging underwent detailed clinical, electroencephalographic, motor, somatosensory and brainstem-evoked potential and magnetic resonance imaging studies. Patients were clinically followed up for 6 months. Results: Their ages were 21, 26 and 35 years. They developed altered sensorium, decorticate posturing and had a wide variety of movement disorders. Patient no. 1 had the most severe illness and recovered by the seventh month while the others recovered earlier. MRI revealed hyperintense signal changes in the globus pallidus, caudate nucleus and thalamus in all patients and in the midbrain in one patient. Electroencephalography showed nonspecific slowing. Somatosensory, motor and brainstem-evoked potential studies were normal. Conclusion: Hanging leads to hypoxic brain damage resulting in signal changes mainly in the basal ganglia and thalamus and may be associated with transient movement disorders.

In vivo experiments in the cat with an implantable piezoelectric hearing aid transducer.

We have recently developed an implantable piezoelectric hearing aid transducer that is suitable for implantation in patients with sensorineural hearing loss. The transducer does not transmit sound but conducts micromechanical vibrations to the cochlea. In ten cat ears we investigated the efficiency of the implantable transducer with respect to the direct transfer of vibrations within the audible frequency range via the ossicles to the cochlea or directly into the vestibule. The acoustically evoked brainstem potential (ABR) threshold was determined prior to implantation, and the middle ear was then opened and the piezoelectric transducer coupled to the ossicles or to the perilymph. Acoustically evoked brainstem potentials were recorded following stimulation at the umbo, long process of the incus, stapes head, stapes foot plate, and in the vestibulum. Comparisons of the acoustically and mechanically evoked thresholds revealed a good correlation of the two stimulation levels. An electrical transducer voltage of 1 V(RMS) produced equivalent sound pressure levels (SPL) of 100-128 dB at the tympanic membrane. To assess the hearing we compared stimulus-dependent latencies of the early potentials (peaks P1-P5) and thresholds. This evaluation was based on four ears with normal hearing in which the piezoelectric transducer was coupled to the long process of the incus. The mean values of the latencies and their scattering range correlated extremely well in the two stimulation modes. They were nearly identical when the equivalent SPL of 100 dB was assigned to the maximally applied electrical level of 0 dB. These in vitro and in vivo findings demonstrate that the characteristics of the transducer warrant its development further from the prototype stage to become a component of an implantable hearing device for patients with sensorineural hearing loss.

Brainstem-evoked muscle potentials: their prognostic value in experimental spinal cord injury in the rat

Recording myoelectric motor-evoked potentials is frequently used as an in vivo evaluation technique in experimental studies of spinal cord injury (SCI). The aim of the present study was to determine whether specific neuronal pathways conduct these potentials. Stainless steel screws were permanently implanted into the cranium of 18 rats for stimulation of brainstemevoked muscle potentials (B-MPs). Twelve rats were subjected to spinal cord lesions that restricted the continuity of the spinal cord to different discrete sections of the lateral and/or ventral white matter (WM) of the left hemicord. Sham rats ( n = 6) were subjected to laminectomy only. Left hind limb B-MPs and motor function (open field walking test) were recorded before surgery and weekly thereafter for six consecutive weeks. Motor function was severely affected by SCI in all rats but recovered significantly during the first 14 postoperative days. The degree of functional recovery depended not only on the amount of spared WM but also on the particular section of WM that had been spared. In contrast, B-MP amplitudes also were severely reduced by SCI, but did not recover during the survival period. Moreover, B-MP amplitudes correlated only weakly with the amount of spared WM and were not influenced by which section of WM had been spared. While functional recovery correlated significantly with the amount of spared WM, no correlation was found between B-MP amplitudes and functional recovery. B-MP conduction velocities were not affected by SCI. It is therefore believed that B-MPs have little prognostic value for experimental studies of SCI in the rat.

An optimal electrode position for recording auditory evoked brain stem potentials within the scope of pediatric audiology

Estimation of hearing threshold in children is based on reliable identification of a response to a stimulus in the near-threshold range. It is well known that only wave V can be detected in brainstem potentials evoked by near-threshold stimuli. So the question arises as to whether or not a noncephalic reference electrode compared to the common lateral postition of the reference electrode on the ipsilateral mastoid produces a more stable wave V of increased amplitude. Thirty-three normal hearing children in three age groups (< 6 years, 6-10 years, > 10 years) were investigated. For a near-threshold stimulation with 100-microsecond-clicks (10, 20, 30 dB nHL), bioactivity was simultaneously recorded with the reference electrode in four different locations (ipsilateral mastoid, contralateral mastoid, ipsilateral earlobe, and noncephalic electrode). The noncephalic reference produced the highest absolute and scaled amplitudes. This finding was statistically significant. For all investigated intensities, recording with the noncephalic reference electrode yielded the highest number of reliable detectable potentials. Evaluation of the residual noise in the four recording locations revealed a significantly increased noise level for the noncephalic electrode at the nape of the neck. Even if the residual noise is increased, the use of noncephalic reference results in a more reliable detection of wave V compared to the conventional locations of the reference electrode.

Influence of electrode position on near-threshold recording of auditory evoked brainstem potentials.

Use of brainstem potentials in audiology is based on identifying a response in the near-threshold range. Wave V has turned out to be the component of the brainstem potentials that can be detected with a great deal of reliability when assessment of the threshold for the particular stimulus is desirable. As the detection of Wave I can be dispensed within audiologic diagnosis, the question arises as to whether or not a non-cephalic reference electrode compared to the common lateral position of the reference electrode on the ipsilateral mastoid produces a more stable Wave V of increased amplitude. In a group of 20 normal-hearing adults, near-threshold stimulation with clicks was conducted and the brainstem potentials recorded simultaneously with the reference electrode placed in four different locations (ipsilateral mastoid, contralateral mastoid, non-cephalic electrode, and ipsilateral earlobe). At all of the three intensities studied (10 dB nHL, 20 dB nHL and 30 dB nHL), recording with the non-cephalic reference yielded the highest amplitudes, the finding being statistically significant.

Chronic tinnitus in children and adolescents

The problem of tinnitus in adults is reviewed systematically in nearly all standard otolaryngology reference works, whereas textbooks and monographs that focus on pediatric otorhinolaryngology or audiology and hearing in children and adolescents provide only little information concerning the epidemiology, etiology and therapy of tinnitus. The purpose of this study was to evaluate the psychosomatic aspects of chronic tinnitus in this younger age group. A rational diagnostic approach is discussed as to which diagnostic measures are necessary in the pediatric group for deciding which therapeutic option to chose. The therapeutic outcome of tinnitus counselling in non-severe cases and of parenteral lidocaine infusions in cases of a troublesome tinnitus is presented. From January 1992 to December 1995, 31 children and adolescents in the age range from 6 to 17 years were treated for a chronic tinnitus without a measurable hearing loss. In 20 cases the tinnitus was bilateral; in 11 cases it was unilateral, without side preference. In 24 patients the case history gave no hint of a major annoyance by the tinnitus or significant psychological components. In these cases tinnitus counselling was carried out. In 7 cases-3 girls and 4 boys in the age range from 10 to 17 years-the kind and grade of symptom satisfied the ICD-10 criteria of a depressive episode. These patients were hospitalized for 10 days and a lidocaine infusion therapy (2 mg/kg Xylocain Cor in 500 ml HAES 6%) was performed as treatment for the somatic component of the disorder. Data were analyzed catamnestically using the patients' files. In all cases normal hearing threshold and speech intelligibility were ascertained by pure-tone and speech audiometry. Auditory evoked brainstem potentials gave no further information. The measurement of transient evoked otoacoustic emissions gave no consistent results in either of the two groups. Tinnitus measurement and audiometric masking could only be carried out in patients older than 10 years and showed non-reproducible results. In all cases with no major symptoms tinnitus disappeared. During a follow-up of 12-44 months, 4 cases treated with lidocaine achieved complete remission; in 3 cases the tinnitus eased off to such an extent that it was no longer regarded as annoying. In one girl of the lidocaine group a somatisation disorder developed independently of the tinnitus and was treated by psychotherapy. No side-effects of the lidocaine occurred. All aspects of chronic tinnitus in children and adolescents can be covered best when regarding this symptom as a psychosomatic disorder. The diagnostic approach in this age group has to include a detailed case history embracing both organic and psychological and social aspects. It should also include pure-tone and speech audiometry. Only in cases with an uncertain hearing threshold auditory evoked brainstem potentials have to be measured. Otoacoustic emissions give no further information about the development and therapeutic outcome of the tinnitus. In this age group tinnitus measurement and masking is of no diagnostic value. In patients with no signs of a hearing loss and no other organic symptoms there is no need for further diagnostic measures such as imaging or serological investigations. In cases with severe annoyance, tinnitus counselling is sufficient therapy. In cases with severe symptoms, lidocaine infusion therapy may be a therapeutic option for the somatic component of the disorder. In adolescents with chronic tinnitus psychotherapy will be necessary only in rare cases. The overall prognosis of this disorder is good.

Language disorders in children with autism

Language development is delayed in most children on the autistic spectrum. The children are dysphasic as well as autistic. Comprehension and pragmatics are invariably affected. Lower level mixed receptive/expressive disorders involve phonological and syntactical processing, whereas higher level processing disorders involve semantics and formulation of discourse. In some children, lower level disorders may be so severe as to preclude speech, whereas in others phonology may be deficient in spontaneous production but not in repetition. Abnormal features of autistic language include aberrant prosody, immediate and delayed echolalia (scripts), and perseveration. Electrophysiological studies indicate that brainstem-evoked potentials are normal. Even in fully verbal individuals with autism, early and late cortical components of auditory, but not visual, event-related potentials are abnormal. Appropriate intervention must address language and behavioral issues. In children with severely defective auditory language, provision of visual language to supplement speech is essential.

A Brief Overview of the Use of Evoked Potentials in Pediatrics

.Evoked potential (EP) testing of all modalities has specific uses and particular challenges in the pediatric population. Methods and techniques for encouraging cooperation for the test vary with the modality. For example, auditory and somatosensory evoked potentials are recorded best from sleeping children; visual evoked potentials are more accurate when recorded from awake children. A major use of the brainstem evoked potentials (BAEPs) is the evaluation of hearing in children at risk for hearing difficulties whether that risk is congenital or postnatal. BAEPs help in the diagnosis and follow-up of children with inherited demyelinating conditions. Visual evoked potentials (VEPs) can be used to evaluate conditions that affect the optic nerve, i.e., compression, tumor, or demyelination. VEPs are less reliable in determining cortical blindness. Normative data for both age and size are especially important in somatosensory evoked potentials (SEPs) to take into account both the length of the pathway and the changes in transmission time with maturation and myelination. SEPs serve as a very good prognostic tool in children in coma, especially coma following head injury. They are also widely used to monitor surgical procedures on the spine.

Brainstem evoked potentials in three groups of prisoners after release from detention camp.

Brainstem evoked potentials (BAEPs) were determined in three groups of male prisoners of war (POWs) released from detention camps and a control group. The first group comprised 21 POWs in whom BAEPs were determined 10-60 days after release (group I). The second group comprised 24 POWs in whom BAEPs were determined 6-9 months after release (group II), and the third group comprised 22 POWs in whom BAEPs were determined 12-18 months after release (group III). The control group comprised 32 subjects. The following changes were found in relation to the control group: in group I significantly longer interpeak latencies (IPLs) P1-P3; in group II significantly longer IPLs P1-P3 and P3-P5; and in group III significantly longer IPLs P1-P3. The subjective symptomatology of the POWs and the results of a routine examination indicate subclinical functional changes of the central nervous system, reflecting the dynamics of these changes. It is suggested that the basis of these changes may be a demyelinization intrathecal process, which occurred as a result of immunological changes during prolonged and intensive post-traumatic stress syndrome.

Development of vestibular and auditory function: Effects of hypothyroidism and thyroxine replacement therapy on nystagmus and auditory evoked potentials in the pigmented rat

The functional development of semicircular canals and some brainstem structures of the auditory system was followed in parallel with time in control and propylthiouracyl-induced hypothyroid pigmented rats by respective recording of postrotatory nystagmus response and auditory evoked brainstem potentials, with the aim of discovering the timing of permanent alterations of these responses in congenital hypothyroidism. A group of hypothyroid rats which underwent thyroxine-replacement therapy from postnatal day 12 onward was also included in our studies to corroborate the involvement of thyroid hormones in these effects. Postrotatory nystagmus and auditory evoked responses were absent in congenital hypothyroid rats. In the thyroxine-replaced group postrotatory nystagmus values showed no differences from the control group from postnatal day 28 onward. Auditory evoked potentials in thyroxine-replaced animals could not be elicited at 30 dB, but by increasing the intensity of stimulus to 70 dB, values of latencies of the four waves composing the response were indistinguishable from controls from postnatal day 39 and thereafter. These results show that hypothyroidism affects both semicircular canal and auditory function, the latter more severely than the former, but that these effects can be prevented when thyroxine replacement treatment is started in early stages of postnatal development.

The Post-Concussional State: Neurophysiological Aspects

Twenty-six young men admitted to an Accident and Emergency Department for observation following a minor closed head injury (post-traumatic amnesia (PTA) less than 12 hours) were investigated within 24 hours of admission (day 0) and followed up at 10 days, 6 weeks and 1 year after the trauma. Investigations at day 0 included physical examination, completion of post-concussional symptom and stress-arousal checklists, computerised EEG (CEEG) and auditory brainstem evoked potential (BAEP) recordings. These were repeated at ten days and six weeks. At 12 months follow-up, the Present State Examination (PSE) was carried out and a further post-concussional symptom checklist completed. Post-concussional symptomatology declined progressively from day 0 but half had residual symptoms at 1 year. Seventy-two per cent ran an acute course with recovery by 6 weeks, 8% chronic unremitting course and 20% initially improved but had an exacerbation of symptoms between 6 weeks and 12 months. The CEEG alpha-theta ratios decreased significantly between days 0 and 10, reaching a baseline thereafter. Measures of CEEG recovery from all channels correlated with symptom counts at six weeks; the slower the recovery the greater the symptoms. A relative delay in left temporal recovery was associated with residual psychiatric morbidity (PSE ID scores) at 12 months. Prolonged central brainstem conduction times occurred in 27% of patients at day 0. These correlated positively with PTA and degree of psychiatric morbidity (PSE ID scores) at 12 months. Symptom chronicity was accompanied by continuing brainstem dysfunction, while the degree of transient cortical dysfunction appeared to have a direct influence in the intensity of early organic symptom reaction to the trauma. Levels of perceived stress at the time of the injury, or afterwards, were not related to symptom formation.

Acoustic brain-stem evoked potential (BAEP) investigation in Bell's palsy

Acoustic brain-stem evoked potential (BAEP) investigation in Bell's palsy

Effects of myelin or cell body brainstem lesions on 3-channel Lissajous' trajectories of fast and slow components of feline auditory brainstem evoked potentials.

Auditory brainstem evoked potentials (ABEP) were recorded from 16 awake cats using three orthogonal differential electrode pairs before and during a week after inducing neuronal lesions localized to the cochlear nucleus (CN) or the superior olivary complex (SOC), or myelin lesions localized to the fibers of the trapezoid body. ABEPs were digitally filtered to include only the slow ('pedestal') component, or only the faster first to fifth components, and three-channel Lissajous' trajectories (3CLTs) of these fast and slow components of ABEP were obtained. Cell body lesions and myelin lesions induced effects on 3CLT measures of both fast and slow components of ABEP. The results suggest a primary contribution of cell body activity to the slow component, and a primary fiber tract contribution to the fast components. However, the results do not support exclusive generation of the pedestal by cell body and dendritic post-synaptic potentials and of the faster components by action potentials along fibers. The results are consistent with a set of generators for each of the slow and fast components of ABEP, consisting of both cell bodies and their output fibers, that are spatially distributed in the brainstem.

The effect of broad-band noise on the binaural interaction components of human auditory brainstem-evoked potentials.

Three-channel Lissajous trajectories (3-CLTs) of binaural interaction components (BI) of auditory brainstem potentials (ABEPs) were derived from 13 normally hearing adults by subtracting the response to binaural clicks from the algebraic sum of monaurally evoked responses to clicks. ABEPs were recorded in response to 65 dB nHL, alternating-polarity clicks, presented at a rate of 11/s. The procedure was repeated with clicks alone as well as with clicks with broad-band masking noise. Noise was presented at 25 and 45 dB nHL, producing a signal-to-noise ratio of +40 and +20 dB, respectively. All BI 3-CLTs included 6 planar segments (labeled BdI, BdII, BdIII, BeI, BeII and Bf) whose apex latencies, except Bf, increased with increasing noise level above 25 dB nHL, and whose durations, sizes, shapes and orientations did not change across noise levels. There were also significant increases in peak latencies of the BI from single channels vertex-mastoid and vertex-neck with increasing noise level. No significant change was found in the trajectory amplitude of apices, with the exception of apices BdIII and Bf whose amplitudes increased with increasing noise level. We suggest that the paradoxical increase in BI amplitude with masking noise may reflect a binaural enhancement of the effect of noise. The effects observed indicate that, whereas the response to clicks displays occlusion, the response to noise displays spatial facilitation at the brainstem level.

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.

Experiences in Kiel with the cochlear implant

Since 1988 22 deaf patients were provided with a 22-channel cochlear implant at the Kiel University Hospital. No surgical or postoperative complications were seen in any of the patients. Side effects like facial stimulation and pain sensation during electrode activation do not reduce the utility. Tinnitus may initially be severe but usually subsides to preop levels after a few days. A tinnitus masking effect is pronounced during stimulation but hardly lasts long after switch off. Besides an individually arranged hearing training the accurate speech processor fitting to the needs of the patient remains the cornerstone of successful rehabilitation. Objective intraoperative measurements such as the electrically evoked brain stem potentials and the middle ear reflexes yield estimates of the threshold values relevant for initial processor programming. Further information needed for the following extensive fine adjustment is obtained by subjective evaluation of loudness growth during electrical stimulation with variable parameters, by loudness scaling of narrow band noises with different middle frequencies and intensities presented under free field conditions and by speech audiometric procedures. The latter include a monosyllabic rhyme test and a logatom test developed at this institution. More speech testing is applied to document the degree of auditive rehabilitation. The results of speech tracking and the Freiburg tests as well as a new sentence test in silence and noise are discussed. In the multisyllable Freiburg test all but two of the adults understand the complete presented material, in the open set monosyllable test an average of 55% correct is achieved. Speech discrimination-oriented ranking showed 95% of all postlingually deaf patients in the highest performance category.

Evoked potentials in inherited ataxias: a multimodal electrophysiological study.

A multimodal electrophysiological study, including median nerve somatosensory evoked potentials (SSEPs), motor cortical stimulation (CS) and brainstem evoked potentials (BAEPs), was performed on 34 patients with hereditary ataxias (HAs): 15 with Friedreich's disease (FD), 10 with early onset cerebellar ataxia (EOCA), and 9 with autosomal dominant cerebellar ataxia (ADCA). A higher incidence of abnormal central motor conduction was observed in FD than in EOCA patients, but was never observed in ADCA. A relationship between central motor conduction abnormalities and disease duration and clinical impairment was found only in FD patients. All FD patients showed severe impairment of the SSEPs that was not related to disease duration. In EOCA patients, less frequent and more variable SSEP abnormalities were observed. The lowest incidence of central SSEP abnormalities was observed in ADCA. The BAEP findings in all 3 groups of patients (but particularly those with EOCA) suggest prevalent brainstem damage.

Evoked potentials from the auditory nerve following sinusoidal electrical stimulation of the cochlea: new possibilities for preoperative testing in cochlear-implant candidates?

To predict the possible benefit of a cochlear implant to a patient, the clinician requires a reliable objective method to monitor the presence of surviving fibres in the 8th nerve. The subjective promontory test and the evaluation of electrically evoked brainstem potentials are not adequate. An electrical stimulus artefact interferes badly with the potential recorded, but with electrical sinusoidal stimulation this stimulus artefact can be suppressed. The highly synchronous excitation of the auditory nerve fibres results in compound action potentials that can be recorded from the round window. The present animal experiments show that the method proposed is effective. Clinical tests are suggested.

P 039 Brainstem reflexes — Brainstem auditory evoked potentials and MRI in Behçet's syndrome

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.

P 047 Magnetic resonance imaging and brainstem auditory evoked potential in neuro-Behçet's disease

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.