Brainstem Auditory Evoked Potentials Waves Research Articles

Neuroprotective Effects of Artificial Cerebrospinal Fluid: Analysis of Brainstem Auditory-Evoked Potential Monitoring During Microvascular Decompression in 117 Consecutive Patients.

To study the efficacy of irrigation with artificial cerebrospinal fluid (aCSF) for protection of cranial nerves during surgery; the time required for recovery of brainstem auditory-evoked potentials (BAEPs) that would reflect cochlear function was analyzed in comparison with that for saline irrigation. This retrospective study included 117 consecutive patients (95 women, mean age 51.5 ± 11.4 year) who underwent microvascular decompression for hemifacial spasm. During surgery, BAEPs were monitored to avoid damage to the auditory pathways. When a delayed latency of >1 ms or a decrease in amplitude of >50% was detected in BAEP wave V, surgical maneuvers were halted, and the operative field was irrigated with saline or aCSF. Saline was used for irrigation in 58 patients and aCSF in the other 59. The time required for BAEP recovery at the first halt in each patient was analyzed, and the results were compared between the groups. Surgical procedures were interrupted because of BAEP latency delays or decreases in amplitude in 51 of the patients in the saline group and 54 in the aCSF group. In both groups, the latencies and amplitudes recovered significantly with time and both recovered earlier after aCSF irrigation than after saline irrigation. Hearing outcome was not significantly different between 2 groups. aCSF is effective for protection of cochlear nerve and promotes recovery from transient dysfunction during surgery. The protective effect may be attributed to multiple factors including conditioned pH, electrolyte composition, glucose, and microelements, such as magnesium and phosphate.

Study of Short Latency Somatosensory and Brain Stem Auditory Evoked Potentials Patients with Acute Ischemic Stroke Involving Middle Cerebral Artery Territory.

Background The precise timings of evoked potentials in evaluating the functional outcome of stroke have remained indistinct. Few studies in the Indian context have studied the outcome of early prognosis of stroke utilizing evoked potentials. Objective The aim of this study was to determine somatosensory evoked potentials (SSEPs) and brain stem auditory evoked potentials (BAEPs), their timing and abnormalities in acute ischemic stroke involving the middle cerebral artery (MCA) territory and to correlate SSEP and BAEP with the functional outcome (National Institutes of Health Stroke Scale (NIHSS), modified Rankin scale (mRS) and Barthel’s index) at 3 months. Methods MCA territory involved acute ischemic stroke patients ( n = 30) presenting consecutively to the hospital within 3 days of symptoms onset were included. Details about clinical symptoms, neurological examination, treatment, NIHSS score, mRS scores were collected at the time of admission. All patients underwent imaging of the brain and were subjected to SSEP and BAEP on two occasions, first at 1 to 3 days and second at 4 to 7 days from the onset of stroke. At 3 months of follow-up, NIHSS, mRS, and Barthel’s index were recorded. Results P37 and N20 amplitude had a strong negative correlation (at 1–3 and 4–7 days) with NIHSS at admission, NIHSS at 3 months, mRS at admission, and mRS at 3 months and a significant positive correlation with Barthel’s index ( p < 0.0001). BAEP wave V had a negative correlation (at 1–3 and 4–7 days) with NIHSS at admission, NIHSS at 3 months, mRS at admission, and mRS at 3 months and a positive correlation with Barthel’s index ( p < 0.0001). Conclusion SSEP abnormalities recorded on days 4 to 7 from onset of stroke are more significant than those recorded within 1 to 3 days of onset of stroke; hence, the timing of 4 to 7 days after stroke onset can be considered as better for predicting functional outcome.

Association between the inter-aural latency difference of brainstem auditory evoked potential wave V and neonatal hyperbilirubinemia

OBJECTIVE To study brainstem auditory evoked potential (BAEP) in neonates with hyperbilirubinemia using short auditory stimuli (60 dBnHL), and to investigate the differences in the inter-aural latency difference (ILD) of wave V between neonates with different total serum bilirubin (TSB) levels. METHODS A prospective study was conducted in neonates with hyperbilirubinemia who were admitted to the Department of Neonatology, Yuhuan People's Hospital of Zhejiang Province, from May 2019 to October 2020. The neonates were divided into a severe group (n=50) and a mild group (n=50) according to their TSB levels. The mild group was divided into two subgroups: 7-10 days (n=20) and 11-14 days (n=20) according to their age. ILD was compared between the neonates with different TSB levels, and its diagnostic value was analyzed. RESULTS Compared with the mild group, the severe group had significantly higher proportions of neonates with abnormal hearing threshold and abnormal ILD (P 0.05). The receiver operating characteristic (ROC) analysis showed that ILD had predictive value for hearing impairment caused by neonatal hyperbilirubinemia (P < 0.05), with an area under the ROC curve of 0.727 as well as a sensitivity of 52.4% and a specificity of 90.9% at the optimal cut-off value of 0.365 ms. CONCLUSIONS Serum bilirubin in neonates affects the ILD of BAEP wave V, especially in those with severe hyperbilirubinemia. ILD at the optimal cut-off value of ≥0.4 ms shows potential value in the diagnosis of hearing impairment caused by neonatal hyperbilirubinemia.

Comparative assessment of brainstem auditory evoked potentials in apparently healthy medical students with a family history of diabetes mellitus type 2

Background: Neuronal studies on diabetes mellitus (DM) were previously based on peripheral and autonomic nerves. With the advent of Brainstem Auditory Evoked Potential (BAEPs), studies on sensory pathways in the central nervous system become easier and more productive. BAEPs is a non-invasive electrophysiological tool to detect retro-cochlear lesion. Hence, it is helpful to detect early Impairment of the auditory nerve and brainstem function. Aim and Objective: DM Type 2 (T2DM) is a known cause of neuropathy and in earlier course, it involves sensory nerves. T2DM runs in families and it has a genetic predisposition. BAEP is one of the methods to find out problems related to hearing by analyzing latencies of waveforms and inter-peak latencies. Hence, BAEPs in apparently healthy subjects with and without family history of T2DM is assessed. Materials and methods: This is a cross-sectional, casecontrol study. We have taken 110 volunteers from MBBS students of IMS, BHU of 17–23 years of age. Those with co-morbid conditions (eg. diabetes and hypertension), neurodegenerative diseases, neuropathy, schizophrenia, and those on ototoxic and neurotoxic drugs are excluded from the study. After taking consent and conducting a preliminary physical examination, BAEPs are recorded using a proper BAEP recording device. Statistical analysis is done using SPSS 2016 software trial version with Chi-square test. Results: The subjects with positive family history of T2DM in paternal grandfather showed deviation in latencies of BAEPs wave I (P < 0.001), wave III (P = 0.019), wave V (P = 0.033), and inter-peak latency between wave I and wave V (P = 0.019) from the normal values in the left ear. The subjects with positive family history of T2DM in paternal grandmother showed deviation from the normal in case of V/I % in the right ear (P = 0.016). Conclusion: The presence of T2DM in families can affect the wave latencies and inter-peak latencies of BAEPs.

Phonophobia and brainstem excitability in migraine.

Phonophobia in migraineurs may be due to lower hearing threshold (HT) and higher brainstem neuronal excitability. We report the correlation of phonophobia in migraineurs with HT, brain stem auditory evoked potential (BAEP) findings, and auditory triggers. Sixty-one migraineurs and 101 controls were included for HT, of whom 59 migraineurs and 31 controls had BAEP studies. Clinical details, migraine triggers, and headache frequency were noted. Hearing threshold was measured, and amplitudes of waves I to V of BAEP studies were measured. Migraineurs had lower HT compared with controls (41.61±5.25 versus 45.39±6.26dB; p<0.001) especially in chronic migraine (40.24±4.81; p<0.001). Hearing threshold correlated with headache frequency (p<0.05) and auditory, visual, and tactile (p<0.05) triggers. Hearing threshold was lower during headache (p<0.001). Wave II, III, and IV amplitudes of BAEP were higher in migraineurs than the controls. Wave II (p<0.05) and III (p<0.05) amplitudes correlated with HT. Migraineurs have lower HT, especially in those having chronic migraine, ictal HT recording, and multiple sensory triggers. Higher amplitudes of BAEP waves in migraineurs and their relationship with the frequency of headache and HT suggest the sensitization of brainstem auditory neurons.

The Difference of Brainstem Auditory Evoked Potential Latency in Diabetic Patient with Good and Poor Glycemic Control

BACKGROUND: Diabetes mellitus (DM) is a metabolic disorder which may complicate other organs, including the nervous system. Literatures which discuss about DM complications in the peripheral nervous system are easy to find but not so many of the central nervous system. Central diabetic neuropathy is a new concept which could be detected by a simple and non-invasive method, called brainstem auditory evoked potential (BAEP).&#x0D; AIM: The aim of the study was to find differences in BAEP latencies of a diabetic patient with good and poor glycemic control.&#x0D; METHODS: This was a cross-sectional study of 80 patients who came for follow-up in diabetic center and neurology polyclinic at Sanglah Hospital, from April to July 2016. The subjects were divided into two groups, depending on their glycemic control, then having BAEP examination.&#x0D; RESULTS: The unpaired t-test found prolonged BAEP latencies (either peak latency of wave III, V, IPL I-III, III-V, and I-V) in both ears at the poor glycemic control group, but the results were not differed significantly (p &gt; 0.05).&#x0D; CONCLUSION: BAEP wave latencies were found prolonged in DM patient with poor glycemic control but not statistically significant. Further evaluation of BAEP latencies in DM patients is needed with prolonged duration and their relation with other comorbid factors, especially smoking habit.

The potential role of auditory evoked potentials to assess prognosis in comatose survivors from cardiac arrest

AimFew data are available on the use of brainstem auditory evoked potentials (BAEPs) in combination with other electrophysiological tools to assess prognosis of comatose survivors from cardiac arrest (CA). MethodsRetrospective analysis of data from all adult patients (>18years of age) admitted to our Dept of Intensive Care after CA over a 6-year period who were comatose (Glasgow Coma Scale <9) on admission, had been treated with targeted temperature management and had BAEP testing. We collected variables related to CA, as well as electroencephalography (EEG) findings, N20 somatosensory evoked potentials, and the presence of I, III and/or V waves on BAEP testing. Outcome was assessed at 3 months using the Cerebral Performance Categories (3–5=poor outcome). ResultsWe studied 65 patients; 48 (74%) had a poor neurological outcome. BAEP assessment was performed day 3 [3,4] after the CA. At least one of the three waves was absent bilaterally in 34 patients (52%); of these patients, 29 (85%) had a poor neurological outcome (sensitivity 60%, specificity 71%, positive predictive value [PPV] 85% and negative predictive value [NPV] 39%). Three patients (5%) had bilateral absence of all three waves, all of whom had a poor neurological outcome. ConclusionsIn this series of patients after CA, at least one of the BAEP waves was absent bilaterally in half the survivors; however, their use for prediction of poor neurological outcome remains limited.

Auditory- and Vestibular-Evoked Potentials Correlate with Motor and Non-Motor Features of Parkinson's Disease.

Degeneration of several brainstem nuclei has been long related to motor and non-motor symptoms (NMSs) of Parkinson’s disease (PD). Nevertheless, due to technical issues, there are only a few studies that correlate that association. Brainstem auditory-evoked potential (BAEP) and vestibular-evoked myogenic potential (VEMP) responses represent a valuable tool for brainstem assessment. Here, we investigated the abnormalities of BAEPs, ocular VEMPs (oVEMPs), and cervical VEMPs (cVEMPs) in patients with PD and its correlation to the motor and NMSs. Fifteen patients diagnosed as idiopathic PD were evaluated by Unified Parkinson’s Disease Rating Scale and its subscores, Hoehn and Yahr scale, Schwab and England scale, and Non-Motor Symptoms Scale. PD patients underwent pure-tone, speech audiometry, tympanometry, BAEP, oVEMPs, and cVEMPs, and compared to 15 age-matched control subjects. PD subjects showed abnormal BAEP wave morphology, prolonged absolute latencies of wave V and I–V interpeak latencies. Absent responses were the marked abnormality seen in oVEMP. Prolonged latencies with reduced amplitudes were seen in cVEMP responses. Rigidity and bradykinesia were correlated to the BAEP and cVEMP responses contralateral to the clinically more affected side. Contralateral and ipsilateral cVEMPs were significantly correlated to sleep (p = 0.03 and 0.001), perception (p = 0.03), memory/cognition (p = 0.025), and urinary scores (p = 0.03). The oVEMP responses showed significant correlations to cardiovascular (p = 0.01) and sexual dysfunctions (p = 0.013). PD is associated with BAEP and VEMP abnormalities that are correlated to the motor and some non-motor clinical characteristics. These abnormalities could be considered as potential electrophysiological biomarkers for brainstem dysfunction and its associated motor and non-motor features.

Effect of granulocyte colony-stimulating factor on the cochlear nuclei after creation of a partial nerve lesion: an experimental study in rats.

OBJECTIVE The risk of injury of the cochlear nerve during angle (CPA) surgery is high. Granulocyte colony-stimulating factor (G-CSF) has been found in various experimental models of peripheral and CNS injury to have a neuroprotective effect by inhibiting apoptosis and inflammation. However, to the authors' knowledge, the influence of G-CSF on cochlear nerve regeneration has not been reported. This study investigated the neuroprotective effect of G-CSF after a partial cochlear nerve lesion in rats. METHODS A lesion of the right cochlear nerve in adult male Sprague-Dawley rats was created using a water-jet dissector with a pressure of 8 bar. In the first group (G-CSF-post), G-CSF was administrated on Days 1, 3, and 5 after the surgery. The second group (G-CSF-pre/post) was treated with G-CSF 1 day before and 1, 3, and 5 days after applying the nerve injury. The control group received sodium chloride after nerve injury at the various time points. Brainstem auditory evoked potentials (BAEPs) were measured directly before and after nerve injury and on Days 1 and 7 to evaluate the acoustic function of the cochlear nerve. The animals were sacrificed 1 week after the operation, and their brains were fixed in formalin. Nissl staining of the cochlear nuclei was performed, and histological sections were analyzed with a light microscope and an image-processing program. The numbers of neurons in the cochlear nuclei were assessed. RESULTS The values for Waves 2 and 4 of the BAEPs decreased abruptly in all 3 groups in the direct postoperative measurement. Although the amplitude in the control group did not recover, it increased in both treatment groups. According to 2-way ANOVA, groups treated with G-CSF had a significant increase in BAEP Wave II amplitudes on the right side (p = 0.0401) after the applied cochlear nerve injury. With respect to Wave IV, a trend toward better recovery in the G-CSF groups was found, but this difference did not reach statistical significance. In the histological analysis, higher numbers of neurons were found in the G-CSF groups. In the statistical analysis, the difference in the numbers of neurons between the control and G-CSF-post groups reached significance (p = 0.0086). The difference in the numbers of neurons between the control and G-CSF-pre/post groups and between the G-CSF-post and G-CSF-pre/post groups did not reach statistical significance. CONCLUSIONS The use of G-CSF improved the function of the eighth cranial nerve and protected cochlear nucleus cells from destruction after a controlled partial injury of the nerve. These findings might be relevant for surgery that involves CPA tumors. The use of G-CSF in patients with a lesion in the CPA might improve postoperative outcomes.

English

Background & Objectives: The central nervous system (CNS) is frequently affected by primary hypertension leading to features of motor, sensory and cognitive deficits. Brainstem auditory evoked potentials (BAEPs) may provide an early evidence of sensory dysfunction. Correlation of BAEPs with severity of blood pressure has not been studied much. In the present study, BAEPs were recorded in primary hypertensive patients and its correlation with mean arterial blood pressure (MAP) was carried out. Materials and Methods: BAEPs were recorded from Cz-A1 & Cz-A2 scalp regions in 30 hypertensive subjects and in 30 normotensive controls. Absolute peak latencies and interpeak latencies of different waves were compared in both the groups by using unpaired student’s T test. Systolic, diastolic and mean arterial blood pressures were also compared between the groups. Bivariate correlation analysis was done to find out any correlation between mean blood pressure and different waves of BAEPs. Results: Significant increase in peak latencies of wave I, IV & V was seen in hypertensive subjects as compared to controls. Significant correlation between mean arterial pressure and absolute peak latencies of BAEP waves I, IV, V and interpeak latencies I-V, III-V was found in hypertensive patients. The amplitude of wave I was found to be negatively correlated with MAP. Conclusion: This study indicates that auditory brainstem conduction pathways get delayed in hypertensive subjects and latencies are positively correlated with mean arterial blood pressure (MABP). Blood pressure regulatory mechanisms in the brainstem may influence the generators of different waves of BAEPs.

Peripheral and Central Nervous System Involvement in Recently Diagnosed Cases of Hypothyroidism: An Electrophysiological Study.

Background:Hypothyroidism, one of the most common endocrine disorders, may induce neurological abnormalities at an early stage of the disease.Aim:The study was designed to assess the electrophysiological alterations of some selected variables of nerve conduction, brainstem auditory evoked potentials (BAEPs), and visual evoked potentials (VEPs) in hypothyroid patients.Subjects and Methods:Sixty patients of newly diagnosed hypothyroidism and an equal number of age-matched controls were selected for the study. Nerve conduction studies that included parameters as latencies, conduction velocities, and amplitude of motor nerves, i.e., median, ulnar, common peroneal, tibial nerve, and sensory nerves, i.e., median and sural nerves was performed in both hypothyroid patients and controls. Further, BAEPs and VEPs of all the patients were done. The data were compiled and statistically analyzed using Student's unpaired t-test to observe any electrophysiological alterations in hypothyroid patients as compared to healthy controls.Results:On comparative evaluation, statistically significant increase in latency of median, ulnar, tibial, and sural nerves; decrease in conduction velocities of all the tested nerves and decrease in amplitude of median, tibial, and sural nerves was observed in hypothyroid patients. Statistically significant increase in latencies, interpeak latencies, and decrease in amplitudes of BAEP waves and statistically significant increase in P100 latency of VEP was seen in hypothyroid patients.Conclusion:The results of our study suggest that peripheral and central neuropathy develops in patients of hypothyroidism at an early stage of disease and the electrophysiological investigations of such patients can help in timely detection and treatment of neurological disorders that occur due to thyroid hormone deficiency.

Visual and brainstem auditory evoked potentials in children with obesity

AimsThe aim of our study is to investigate alterations in visual evoked potentials (VEP) and brainstem auditory evoked potentials (BAEP) in children with obesity. MethodsA total of 96 children, with a mean age of 12.1±2.0years (range 9–17years, 63 obese and 33 age and sex-matched control subjects) were included in the study. Laboratory tests were performed to detect insulin resistance (IR) and dyslipidemia. The latencies and amplitudes of VEP and BAEP were measured in healthy and obese subjects. ResultsThe VEP P100, BAEP interpeak latency (IPL) I–III and IPL I–V averages of obese children were significantly longer than the control subjects. When the obese group was divided into two subgroups, those with IR and without IR, BAEP wave I, wave III and P100 wave latencies were found to be longer in the group with IR. A statistically significant correlation was observed between BAEP wave I latency, IPL I–V, IPL I–III and the homeostatic model assessment insulin resistance (HOMA IR) index and fasting insulin level. ConclusionsOur findings suggest that VEP and BAEP can be used to determine early subclinical on auditory and visual functions of obese children with insulin resistance.

Intraoperative neurophysiological monitoring of microvascular decompression for glossopharyngeal neuralgia.

To evaluate if adding cranial nerves (CNs) V and VI to standard intraoperative neurophysiological monitoring (IONM) of microvascular decompressions for glossopharyngeal neuralgia improve its efficacy. We reviewed all patients who received a microvascular decompression for glossopharyngeal neuralgia at our institution between January 2008 and August 2012. All received upper extremity somatosensory evoked potentials, brainstem auditory evoked potentials, and free-running electromyography of muscles innervated by ipsilateral CNs VII, IX, and X. The sample was divided into 12 patients who received additional monitoring of CNs V and VI and 15 who did not. No difference on neurotonic activity presence was found on CN V (standard IONM: 0% versus additional CNs IONM: 8.33%; p = 0.423), CN VI (never present on the additional CN patients), CN VII (standard IONM: 73.33% versus additional CNs IONM: 66.64%; p = 0.973), CN IX (standard IONM: 40.0% versus additional CNs IONM: 25.0%; p = 0.683), or CN X (standard IONM: 46.67% versus additional CNs IONM: 33.33%; p = 0.701) between groups. Additionally, no differences of brainstem auditory evoked potentials wave V's delay, and amplitude at the end of the decompression, or closing of the case were found between groups. Monitoring free-running electromyography of additional CNs V and VI does not improve the efficacy of IONM of microvascular decompressions for glossopharyngeal neuralgia.

Significance of brain stem auditory evoked potential and somatosensory evoked potential on prognosis evaluation in patients with acute cerebral infarction

Objective To investigate changes of brainstem auditory evoked potential (BAEP)and somatosensory evoked potential (SEP) in patients with acute cerebral infarction,and discuss their relation with prognosis of the patients.Methods The study involved 60 patients with acute cerebral infarction.Changes of BAEP and SEP in each patient were detected and recorded continuously.Prognosis evaluation was performed by using GCS.Another 60 age-matched and gender-matched healthy human beings were enrolled as controls.Results Incubation period of BAEP wave Ⅰ had no significant difference between the cerebral infarction and control groups (P ＞ 0.05).However,interspike intervals of other BAEP waves in cerebral infarction group were different from those in control group (P ＜ 0.05).A series of waves of SEP (P14-N60) were all significantly prolonged in cerebral infarction group (P ＜0.05).Conclusion BAEP and SEP can effectively reflect function of brain stem in patients with acute cerebral infarction and have some values in determining their prognosis. Key words: Brain injuries; Evoked potential,auditory; Evoked potential,somatosensory; Acute cerebral infarction

Brain-stem auditory evoked responses in COPD patients

BackgroundCOPD is a multi-system disorder. It appears to be associated with the presence of systemic inflammatory markers as C reactive protein. Aim of the workThe present study aimed to evaluate the brain-stem auditory evoked potentials (BAEP) abnormalities in stable COPD patient and its correlation with high sensitivity C reactive protein (hs-CRP) as a part of multi-system disorder. Subjects and methodsThis case control study was carried out at Mansoura University Hospital Egypt from October 2009 to February 2010. The study comprised 40 stable COPD patients and 15 healthy controls with no risk that may lead to neuropathy. All the patients and controls were subjected to the following: I-Thorough history taking and clinical examination. II-Pulmonary function tests including: 1-Spirometry 2-Body plethsymography 3-Arterial blood gases analysis. III- Record of brain-stem auditory evoked potentials (BAEP) including: latencies of waves I, II, III, IV and V together with interpeak latencies (IPLs) of I–III, I–V and III–V and amplitudes of waves I–Ia and V–Va. IV–Measurement of serum high sensitivity C reactive protein (hs-CRP) by ELISA technique. V–Statistical analysis. ResultsThe level of hs-CRP reactive protein in COPD was significantly elevated and correlated with spirometric, blood gases parameters and GOLD stage. The BAEP latencies of waves I, II, III, IV and V, together with interpeak latencies and amplitudes of waves I–Ia and V–Va measured on both ears were significantly different in COPD patients than controls. The prevalence of brain-stem auditory evoked potentials abnormalities was higher among very severe group of COPD. Most of BAEP wave latencies together with interpeak latencies and wave amplitudes on both ears were significantly correlated with the spirometric and blood gases parameters. The level of hs-CRP was correlated significantly with abnormalities of BAEP variables. ConclusionThis study showed significant subclinical BAEP abnormalities in studied stable COPD male patients. This indicates conductive defect of auditory nerve, cochlea and even hearing pathway in the brain as a part of systemic inflammation.Theses BAEP abnormalities were significantly correlated with GOLD classification, hs-CRP and PaO2.

Beyond herniation

Few data are available on the use of brainstem auditory evoked potentials (BAEPs) in combination with other electrophysiological tools to assess prognosis of comatose survivors from cardiac arrest (CA).Retrospective analysis of data from all adult patients (>18 years of age) admitted to our Dept of Intensive Care after CA over a 6-year period who were comatose (Glasgow Coma Scale <9) on admission, had been treated with targeted temperature management and had BAEP testing. We collected variables related to CA, as well as electroencephalography (EEG) findings, N20 somatosensory evoked potentials, and the presence of I, III and/or V waves on BAEP testing. Outcome was assessed at 3 months using the Cerebral Performance Categories (3–5 = poor outcome).We studied 65 patients; 48 (74%) had a poor neurological outcome. BAEP assessment was performed day 3 [3,4] after the CA. At least one of the three waves was absent bilaterally in 34 patients (52%); of these patients, 29 (85%) had a poor neurological outcome (sensitivity 60%, specificity 71%, positive predictive value [PPV] 85% and negative predictive value [NPV] 39%). Three patients (5%) had bilateral absence of all three waves, all of whom had a poor neurological outcome.In this series of patients after CA, at least one of the BAEP waves was absent bilaterally in half the survivors; however, their use for prediction of poor neurological outcome remains limited.

Brainstem Auditory Evoked Responses in Different Phases of Menstrual Cycle

Brainstem Auditory Evoked Potentials (BAEP) show variations with age, sex and other physiological factors. The gonadal steroids may also alter the neuronal functioning, but an electrophysiological evidence is sparse. This study was undertaken to analyze the auditory evoked response in females of the reproductive age group during four different hormonal states of the menstrual cycle. This was a prospective, single centered, longitudinal study. The waves of BAEP were recorded in 50 young females (of the ages of 19-36 years, who used no hormonal therapy) during four different phases of the same menstrual cycle. The peak latencies of the waves, I, II, III, IV and V, IPL I-III, I-V and III-V and the amplitude ratio, V/I were recorded and statistically analyzed. A significant increase in the peak latencies of the waves, I-V in the oestrogen peak mid cycle was observed, while a significant decrease in the progesterone peak mid-luteal phase was observed. However, IPL did not show any statistically significant change in the above two phases. All the parameters did not show significant changes in the menstrual and the pre-menstrual phases. The results indicated the BAEP changes in the mid follicular and the mid luteal phases of the menstrual cycle, thus suggesting the changes which were attributable to oestrogen and progesterone.

Glasgow Coma Scale, Brain Computerized Tomography and Neurophysiological Methods as Prognostic Factors of Pediatric Coma

Background and objectives: Coma is characterized by the total absence of both arousal and awareness. The outcome of coma depends on the etiology, depth and duration of impaired consciousness. It is likely that brain electrical function monitoring will play an increasingly important role in evaluating prognosis of coma in children. Aim: To compare the predictive values of clinical examinations combined with the recordings of Electroencephalography (EEG) and Brainstem Auditory-Evoked Potentials (BAEP) and computed tomography (CT) of the brain in the evaluation of coma outcome in children. Methods: Twenty children with coma aged 3-14 years were included in the study and subjected to: full history, clinical, neurological and otological examination. Medical investigations for coma, EEG, CT brain and auditory brainstem evoked potential (BAEP) measurements were performed for all patients. They were subdivided into 2 groups: group 1 included 8 patients with surgical causes of coma, group 2 include 12 patients with medical causes of coma. Results: There was younger age, lower Glasgow Coma Scale (GCS) and more significant incidence of unfavourable outcome (death, disability) in patients of surgical coma (group 1). A significant difference between both groups was observed regarding the presence of brain edema and intracranial hemorrhage (100% in group 1) while normally visualized basal cisterns were significantly more in group (2) (p=0.02). Favourable outcome was strongly related to normally visualize basal cisterns in CT brain (p=0.002), normal/ borderline EEG activity (p=0.03) and normal BAEP waves (p=0.009). Disability was significantly related to slow activity waves (p=0.015) and diffuse high voltage EEG discharges (0.009). While mortality was significantly related to the presence of intracranial bleeding in CT brain (p=0.02), silence EEG waves (p=0.005) and absent BAEP waves (0.012). Conclusion: EEG and Auditory brainstem response are valuable as prognostic predictors of pediatric coma either due to medical or surgical causes. The Glasgow Coma Scale (GCS) has several important limitations as a predictor of survival in the general critically ill population while CT brain is mostly important for diagnostic rather than prognostic factor in comatosed children.

Malnutrition during central nervous system growth and development impairs permanently the subcortical auditory pathway

The brain that grows and develops under the continued influence of malnutrition presents permanent impairment on functioning and neurotransmitter release. The aim of this study was to investigate the chronic effects of neonatal food restriction on neurochemical and neurodynamical aspects within the primary auditory sensory pathway. Our working hypothesis is that neonatal malnutrition may affect the flow of primary sensory information both at a neurochemical and neurodynamical level. To test this hypothesis, three groups of rats were assigned, from birth to 370 days of life, to the following dietary scheme: a well-nourished (WN) group fed ad libitum lab chow diet; an undernourished (UN) group fed 60% of diet consumed by WN group; and a rehabilitated group, undergoing same dietary restriction as undernourished until 42 days of age and thereafter fed ad libitum until the end of the experiment. At 370 days of age, the animals were submitted to brainstem auditory-evoked potentials (BAEPs) recordings and sacrificed for neurochemical evaluation of glutamate release. Undernutrition decreased glutamate release in the cortex, hippocampus, midbrain and brainstem, and significantly increased the latency of BAEP wave V. In addition; the re-establishment of the dietary conditions was not sufficient to reverse the neurochemical and electrophysiological alterations observed in the UN group. Taken altogether, our results suggest that malnutrition imposed at a critical development period caused an irreversible effect within the auditory primary sensory pathway.

Application of Electrophysiologic Techniques in Poor Outcome Prediction Among Patients With Severe Focal and Diffuse Ischemic Brain Injury

To explore various electrophysiologic examinations as predictors for poor outcome in patients with severe ischemic brain injury, by comparing the prognostic ability of EEG, short-latency somatosensory evoked potentials (SLSEP), and brain stem auditory evoked potentials (BAEP). EEG, SLSEP, and BAEP were recorded in 161 patients with severe ischemic brain injuries (Glasgow Coma Scale ≤ 8), 77 with anoxic-ischemic encephalopathy after cardiopulmonary resuscitation, while 84 experienced massive hemispheric infarction at between 1 and 7 days after the onset. Outcomes were reviewed after 6 months using the Glasgow Outcome Scale. Six months after the onset, poor outcomes (Glasgow Outcome Scale, 1-2) were identified in 66 and 54 patients among the anoxic-ischemic encephalopathy and the massive hemispheric infarction group, respectively. By using the prognostic authenticity analysis of predictors, unfavorable EEG patterns, lack of EEG reactivity, pathologic N20 of SLSEP, and pathologic wave V of BAEP showed the high sensitivity (92.4%-97.0%, 95% confidence interval [CI]: 82.5%-99.5%), while bilateral absence of SLSEP N20 showed the highest specificity (100%, 95% CI: 67.9%-100%) and positive predictive value (100%, 95% CI: 90.4%-100%) in the anoxic-ischemic encephalopathy group. In the massive hemispheric infarction group, unfavorable EEG patterns showed the highest sensitivity (96.3%, 95% CI: 86.2%-99.4%) while bilateral absence of SLSEP N20 and BAEP wave V showed the highest specificity (100%, 95% CI: 85.9%-100%) and positive predictive value (100%, 95% CI: 80.8%-100%). The predictive power of electrophysiologic examinations is different according to the etiology of ischemic brain injury. Short-latency somatosensory evoked potentials (N20) can be considered the most powerful method to predict poor outcome in anoxic-ischemic encephalopathy. Combination of EEG (unfavorable EEG patterns) and SLSEP (N20)/BAEP (wave V) is best suited in massive hemispheric infarction to predict poor outcome.