Short-latency Evoked Potentials Research Articles

Objective parameters of auditory function in premature infants in the first year of life after taking ototoxic antibiotics

To compare the condition of auditory function during the first year of life according to the registration of distortion product otoacoustic emission (DPOAE) and short-latency evoked potentials (SLEP) in premature infants who received ototoxic antibiotics to those ones, who did not. Auditory function was examined in 145 premature infants. Auditory assessment was carried out by registration of DPOAEs, SLEPs and tympanometry. Statistical processing was performed using the program Statgraphics Centurion XV. In this study, according to DPOAE, the average response values of the cochlea in premature infants who had a history of ototoxic therapy, undergo final changes after children reach the age of 6 months. The study of latent periods and threshold values of the V peak of SLEP showed a delay in the maturation process of the perceiving and conducting auditory structures during the first year of life in children who received ototoxic antibiotics in the first month of life. We evaluated the timing of the completion of response changes in children of the control group using the DPOAE and SLEP registration data. In children of the study group, we evaluated the effect of the administered ototoxic antibiotics. Timing of audiological control of the hearing organ condition are demonstrated for premature children after ototoxicosis, required methods of its examination are established.

Screening audiological control in children of different ages after taking ototoxic medications

To compare auditory function during screening of children of different age groups who received ototoxic therapy. Auditory function was studied in various categories of children receiving ototoxic drugs. Hearing was assessed by the registration of distortion product otoacoustic emission (DPOAE), short-latency evoked potentials (SLEP), tympanometry. Statistical processing was performed using the C program Statgraphics Centurion XV. In this study, screening of auditory function in children suffering from cystic fibrosis and receiving ototoxic treatment revealed pathologic conditions of the middle ear according to tympanometry in 15.4% of cases, impaired auditory function in 28.2% of cases according to DPOAE. Early ototoxicosis presented as a decrease in the amplitude of the response at a frequency of 4 kHz, and a change in the structure of the DP-gram in the form of a shift to the low-frequency area. Examination of the auditory function of premature infants receiving potentially ototoxic drugs in the early neonatal period demonstrated that the administration of ototoxic drugs does not affect the maturation of outer hair cells. Audiological control, such as tympanometry and registration of evoked otoacoustic remission should be included in the outpatient observation of children with a history of ototoxic drugs.

The role of middle latency evoked potentials in early prediction of favorable outcomes among patients with severe ischemic brain injuries

ObjectiveTo explore the role of middle latency evoked potentials (EPs) as predictors for favorable outcome in patients with severe ischemic brain injuries by comparing the prognostic ability of short latency somatosensory and auditory evoked potentials (SLSEP and BAEP) with middle latency somatosensory and auditory evoked potentials (MLSEP and MLAEP). MethodsMLSEP, MLAEP, SLSEP and BAEP were recorded in 112 patients with severe ischemic brain injuries (Glasgow Coma Scale≤8). Among them, 83 patients suffered from cerebral ischemic stroke and 29 suffered from anoxic–ischemic encephalopathy after cardiopulmonary resuscitation between 1 and 7days after the onset of stroke. Outcomes were reviewed 6months later using the Glasgow Outcome Scale (GOS). A GOS score of 4–5 was considered as a good outcome while a score of 1–3 was considered as poor. ResultsBy using the prognostic authenticity analysis of predictors for good outcome, at least unilateral N20 of the SLSEP exit and at least unilateral N60 of the MLSEP exit showed the highest sensitivity which was 100% (95% CI: 86.7%–100%). The bilateral normal N60 showed a high specificity of 97.5% (95% CI: 90.4%–99.6%). It also showed the highest positive likelihood ratio of 6.25% (95% CI: 1.28%–30.59%), which was superior to N20 of SLSEP, V of BAEP, and Pa of MLAEP. The analysis demonstrated that the area under the curve for MLSEP grading was the highest (0.838) compared to that of SLSEP grading (0.784), MLAEP grading (0.659) and BAEP grading (0.621). ConclusionsCompared with using N20 of SLSEP analysis alone, adding MLSEP improves the outcome prediction in patients with severe ischemic brain injuries. When an outcome is uncertain after initial evaluation using short-latency EPs, MLSEP is valuable to be used from the first week to further improve prognostication in these patients.

Auditory cortex on the human posterior superior temporal gyrus.

The human superior temporal cortex plays a critical role in hearing, speech, and language, yet its functional organization is poorly understood. Evoked potentials (EPs) to auditory click-train stimulation presented binaurally were recorded chronically from penetrating electrodes implanted in Heschl's gyrus (HG), from pial-surface electrodes placed on the lateral superior temporal gyrus (STG), or from both simultaneously, in awake humans undergoing surgery for medically intractable epilepsy. The distribution of averaged EPs was restricted to a relatively small area on the lateral surface of the posterior STG. In several cases, there were multiple foci of high amplitude EPs lying along this acoustically active portion of STG. EPs recorded simultaneously from HG and STG differed in their sensitivities to general anesthesia and to changes in rate of stimulus presentation. Results indicate that the acoustically active region on the STG is a separate auditory area, functionally distinct from the HG auditory field(s). We refer to this acoustically sensitive area of the STG as the posterior lateral superior temporal area (PLST). Electrical stimulation of HG resulted in short-latency EPs in an area that overlaps PLST, indicating that PLST receives a corticocortical input, either directly or indirectly, from HG. These physiological findings are in accord with anatomic evidence in humans and in nonhuman primates that the superior temporal cortex contains multiple interconnected auditory areas.

Event-related potentials--neurophysiological tools for predicting emergence and early outcome from traumatic coma.

To determine the prognostic value of multimodal evoked potentials (EPs) and event-related (ERPs) potentials in coma (Glasgow Coma Score <8), after severe traumatic brain injury (TBI). Prospective, longitudinal study of neurophysiological responses recorded during traumatic coma. Intensive Care Unit, Frenchay Hospital, Bristol, UK. Fifty-four comatose TBI patients (age range 1-80 years, mean 36.4). Neurophysiological responses were recorded from 11 scalp electrodes with earlobe reference. Conduction times were measured for brainstem auditory, flash visual and somatosensory, short-latency EPs. Peak latencies and amplitudes were determined for long-latency components of visual and auditory ERPs, generated by passive "oddball" paradigms. These neurophysiological and various clinical parameters were correlated with patient outcome using Pearson's coefficient. Three month Glasgow Outcome Scale (GOS). Highly significant (P <0.001) correlations exist between long-latency ERP components and 3-month outcome. Short-latency EPs, brainstem (wave I-V) and somatosensory conduction times also correlate significantly with the GOS (P <0.01). Of the clinical measurements, pupillary response patterns, APACHE II and Glasgow Coma Scores (GCS) correlate significantly with outcome, as do the retrospective measures of duration of coma and post-traumatic amnesia (PTA) in survivors. Unfortunately, due to variance of long-latency responses, even in controls, absolute values cannot be relied upon as prognosticators. The presence of "mismatch negativity" predicted the return of consciousness (89.7% sensitivity and 100% specificity) and preceded changes in GCS. Its latency was the single best indicator of 90-day outcome from coma (r = -0.641).

Brainstem auditory evoked potentials in intensive care patients with encephalitis : G. Litscher ∗, G. Schwarz ∗, G. Pfurtscheller ∗∗, E. Rumpl ∗∗∗. ∗Department of Anesthesiology, University of Graz, Austria; ∗∗ Department of Medical Informatics, Graz University of Technology, Austria; ∗∗∗ Department of Neurology, LKH Klagenfurt, Austria

To explore the role of middle latency evoked potentials (EPs) as predictors for favorable outcome in patients with severe ischemic brain injuries by comparing the prognostic ability of short latency somatosensory and auditory evoked potentials (SLSEP and BAEP) with middle latency somatosensory and auditory evoked potentials (MLSEP and MLAEP).MLSEP, MLAEP, SLSEP and BAEP were recorded in 112 patients with severe ischemic brain injuries (Glasgow Coma Scale ≤ 8). Among them, 83 patients suffered from cerebral ischemic stroke and 29 suffered from anoxic–ischemic encephalopathy after cardiopulmonary resuscitation between 1 and 7 days after the onset of stroke. Outcomes were reviewed 6 months later using the Glasgow Outcome Scale (GOS). A GOS score of 4–5 was considered as a good outcome while a score of 1–3 was considered as poor.By using the prognostic authenticity analysis of predictors for good outcome, at least unilateral N20 of the SLSEP exit and at least unilateral N60 of the MLSEP exit showed the highest sensitivity which was 100% (95% CI: 86.7%–100%). The bilateral normal N60 showed a high specificity of 97.5% (95% CI: 90.4%–99.6%). It also showed the highest positive likelihood ratio of 6.25% (95% CI: 1.28%–30.59%), which was superior to N20 of SLSEP, V of BAEP, and Pa of MLAEP. The analysis demonstrated that the area under the curve for MLSEP grading was the highest (0.838) compared to that of SLSEP grading (0.784), MLAEP grading (0.659) and BAEP grading (0.621).Compared with using N20 of SLSEP analysis alone, adding MLSEP improves the outcome prediction in patients with severe ischemic brain injuries. When an outcome is uncertain after initial evaluation using short-latency EPs, MLSEP is valuable to be used from the first week to further improve prognostication in these patients.

Abnormalities of Cognitive Functions in IDDM Revealed by P300 Event-Related Potential Analysis: Comparison With Short-Latency Evoked Potentials and Psychometric Tests

The possible influence of diabetes on the higher mnestic and cognitive functions has been investigated. The P300 wave latency, an endogenous electrophysiological event, was explored and compared with the multimodal short-latency evoked potential (EP) recordings (visual [VEP], brainstem auditory [BAEP], and median and tibial nerve somatosensory EPs [mSEP and tSEP, respectively]) and psychometric test measures in 16 insulin-dependent diabetic (IDDM) patients, in 16 age- and (IDDM) sex-matched nondiabetic subjects, and in a large normal reference population. The age of subjects, the duration of IDDM, and the metabolic control of patients were taken into account. P300 values were significantly increased in IDDM versus matched control subjects (P less than 0.001), and 3 patients showed values above the reference value range. Abnormal VEP recordings were present in 1 of 16 patients, BAEP in 3 of 16, mSEP in 7 of 16, and tSEP in 6 of 16. Digit-span backward test results were significantly (P less than 0.02) modified in the diabetic cohort. There was no tendency for anomalies of P300, short-latency EPs, and psychometric test values to be contemporarily present, except in 1 patient. Electrophysiological or psychometric abnormalities were not clearly correlated with the duration of IDDM or the degree of short-term metabolic control. These findings give evidence that 1) higher cognitive functions may be affected in diabetes as documented by P300 analysis and short-term memory tests, 2) endogenous electrophysiological analysis highlights neuropsychological changes not detectable by psychometric tests, 3) an alteration of evoked potentials was present in half of the IDDM subjects studied, and 4) anomalies of the CNS are patchily distributed in diabetes.

Central somatosensory conduction time and acoustic brainstem transmission time in post-traumatic coma.

Short-latency evoked potentials (SEPs) of the scalp and neck after median nerve stimulation and acoustic brainstem evoked potentials (BAEPs) were recorded in 85 patients in post-traumatic coma with clinical signs of brainstem impairment between days 2 and 6 after trauma. The central somatosensory conduction time (CCT), the amplitude ratio (AR) N20:N13, the interpeak latencies (IPL) I-III, III-V, I-V, and the ARs between waves I and V (I:V) and between wave I and the wave IV/V complex (I:IV/V) were calculated and related to the outcome of the patients. In cases of coma due to supratentorial lesions, CCT and ARs of SEPs were close to normal in patients with good outcome: CCT increased and ARs decreased with worsening of outcome. In cases of primary brainstem injury, a significant prolongation of CCT was also seen in patients with good recovery, whereas normal CCTs could be found in patients with severe disability and death outcome. In this case, unilateral absent scalp SEPs were frequently found. The IPLs I-III, III-V, I-V, and the ARs of BAEPs increased with worsening of outcome. Significant differences of IPL I-V and III-V (brainstem transmission time) were seen between patients with good recovery or moderate disability outcome and the patients with severe disability or death outcome. There was no difference in BAEPs between patients with primary brainstem lesion and patients with secondary brainstem lesion. Patients with bilateral absent SEPs and bilateral absent BAEPs not related to traumatic or preexisting hearing disorders died or survived severely disabled. Unilateral absence of scalp SEPs and unilateral absence of BAEPs were frequently found in patients who died or who had severe disability. Asymmetries in scalp SEPs appeared to be distributed equally to all outcome categories, but asymmetries in BAEPs increased with worsening of outcome too. In most of the patients who died or survived disabled, both SEPs and BAEPs were abnormal.

Central somatosensory conduction time and short latency somatosensory evoked potentials in post-traumatic coma

Short latency evoked potentials (SEPs) were elicited by stimulation of the median nerve at the wrist and recorded simultaneously from the neck and the contralateral scalp in 44 comatose patients with signs of brain stem impairment due to head injury. Thirty-four patients were studied in acute coma on day 1 or 2 after brain injury. Twenty-three patients were studied in prolonged coma during days 3–12 after trauma. Six patients were examined in brain death. Brain stem involvement was divided clinically and by CT scan into secondary lesions due to supratentorial mass displacement and primary lesions due to direct violence to the brain stem. The central somatosensory conduction time (CCT) was measured by subtracting the peak latency of the major response from the neck (N14) from that of the primary scalp response (N20). The amplitude ratios (ARs) N20/N14 were calculated for each trace. Further asymmetries and absence of SEP over one or both hemispheres were noted. In cases in coma due to supratentorial lesions CCT and AR were close to normal in patients with good outcome. CCT increased and AR decreased with the worsening of outcome both in acute and prolonged coma. Asymmetries of SEPs indicated moderate or severe final disability. Patients with absent SEPs over one or both hemispheres due to supratentorial lesions died or survived severely disabled (1 case). In patients suffering from primary brain stem dysfunction, confirmed by a normal or slightly abnormal CT scan, prolonged CCT, asymmetric but also absent SEPs were also found in patients with good outcome both in acute and prolonged coma. AR was generally low in these cases. Early appearance of SEPs or early recovery of initially distorted SEPs and decrease of CCT in prolonged coma or during recovery was a favourable prognostic sign. Therefore even absent or severely distorted SEPs should be interpreted cautiously in patients who may suffer from primary brain stem involvement. Scalp SEPs were totally absent in patients with brain death.