Evaluation of brain dysfunction in hypertensive putaminal hemorrhage with multimodality evoked potentials

Changes in multimodality evoked potentials (MEP's), consisting of somatosensory evoked potentials (SEP's), visual evoked potentials (VEP's), and auditory evoked brainstem responses (AEBR's), were studied in 36 patients with hypertensive putaminal hemorrhage to ascertain the relation among areas and distribution of brain dysfunction, the size of hemorrhage on computerized tomographic scan, and the clinical outcome. Among MEP's, SEP's were most significantly involved in all patients. Abnormalities in VEP's and AEBR's remained mild or moderate when the hemorrhage did not extend to the diencephalon. If SEP's were normal or mildly abnormal, they improved early the ictus. These patients did well clinically. If SEP's were absent, the patients had poor outcome even when the hemorrhage was small and located outside the internal capsule. In contrast, deterioration or persistence of MEP's indicated secondary insult to the brain and poor patient outcome. Early and serial MEP studies are useful in evaluating primary and secondary brain dysfunction and in predicting patient outcome in hypertensive putaminal hemorrhage.     

脑干及其附近手术诱发电位术中监护的研究

目的 探讨脑干及其周围手术损伤与脑干听觉诱发电位（ＢＡＥＰ）和体感诱发电位（ＳＥＰ）不同指标之间的关系,找出神经功能损伤第三的电生理指标。方法 对２３例脑干肿瘤病人进行手术中ＢＡＥＰ和ＳＥＰ连续监测。结果 脑干及其周围手术操作均可以引起ＢＡＥＰ、ＳＥＰ的改变。ＳＥＰ的Ｎ１３－Ｎ２０中枢传导时间（ＣＣＴ）和Ｎ２０潜伏期及波幅的变化和ＢＡＥＰＶ波潜伏期（ＰＬ）、Ⅲ－Ｖ、Ｉ－Ｖ峰间潜伏期（ＩＰＬ）的变化     

Midbrain deafness with normal brainstem auditory evoked potentials

The authors report two cases of patients with word deafness. The word deafness occurred after a head injury for the first patient and after an arterio venous malformation embolization for the second patient. MRI demonstrated bilateral lesions of the inferior colliculi but brainstem auditory-evoked potentials (BAEP) were within normal limits. These cases demonstrated that lesions involving the two inferior colliculi induced pure word deafness but do not affect BAEP.     

Utility of multimodality evoked potentials in cerebral injury

With technical rigor and a few modifications, reliable recordings of multimodality evoked potentials can be obtained in patients suffering head injury. The integrity or complexity of the EP waveform appears to be the best indicator of the reversibility of injury to the CNS. A multimodality approach is recommended in head trauma to enhance the sample of brain tissue evaluated, as a single pathway courses a very limited region of brain. In head injury, the EP and clinical findings do not correlate perfectly, although they are generally in agreement. In most cases, the EPs are accurate prognostic indicators and the rate of error of prediction is actually slightly lower than that of the clinical examination in head trauma. Serial evaluations are often necessary as a patient's course and prognosis may change. These changes may not be readily apparent on clinical examination. The information provided by MEP studies is quite helpful when the clinical examination is incomplete or inconsistent. Even when clinical data are available, the EP results, when combined with other indicators of neurologic integrity, afford a firmer basis for diagnostic and prognostic decisions.     

Abnormalities of multimodality evoked potentials in amyotrophic lateral sclerosis

Thirty-two patients with amyotrophic lateral sclerosis were studied with somatosensory evoked potentials (SEPs), visual evoked potentials, and brain-stem auditory evoked potentials. H-reflexes were used to screen for abnormalities of peripheral nerve conduction. Nineteen patients (59%) showed an abnormality of lower extremity SEPs. In 13 patients (40%) the delay was of central origin, while in six patients (19%) peripheral conduction delay was possible. Abnormality of upper limb SEPs was seen in 11 patients (34%), all but two of whom had abnormal lower limb SEPs as well. Four patients (12%) had abnormal brain-stem auditory evoked potentials, all of whom had abnormal SEPs from upper and lower limbs. Four patients had abnormal visual evoked potentials, which in three patients were of minor degree. These results give physiologic evidence to suggest that abnormalities in amyotrophic lateral sclerosis occur outside the motor system.     

Auditory brainstem evoked potentials during sleep apnea

Auditory brainstem evoked potentials (ABEPs) were recorded from seven subjects with predominantly central sleep apnea. ABEPs were recorded during: (1) waking, (2) non-REM sleep between apneic episodes, (3) first half of apneas, and (4) second half of apneas. Latencies of vertex positive peaks III, V, and VI as well as the V-III interpeak latency difference were determined, and the effect of apnea phase on these measures were evaluated. The measures studied did not reveal chronic or acute functional abnormality of auditory brainstem, which may result from or cause apneic episodes during non-REM sleep. The normality and stability of ABEPs during apneic sleep indicate effective compensatory mechanisms in auditory brainstem. Brainstem functional changes associated with central apneas may not be reflected in the ABEP measures studied, unless they are part of a more extensive dysfunction.     

Evaluation of various brain structures in multiple sclerosis with multimodality evoked potentials,blink reflex and nystagmography

Summary Pattern reversal visual evoked potentials (VEP), blink reflexes, auditory brainstem evoked potentials (ABEP), spinal and scalp recorded somatosensory evoked potentials (SSEP), and nystagmographic records were investigated in 55 patients with multiple sclerosis (MS), who were separated in different categories of probability according to the clinical history, symptoms, and signs. The combined use of different electrophysiological methods forms a sensitive battery for investigating clinically uncertain cases of MS. It was stressed that care should be taken in the interpretation of the electrophysiological findings, since a single lesion in the central nervous system, particularly in the brainstem, may affect different functional systems simultaneously and therefore mimic a disseminated disease.

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Zusammenfassung Visuelle musterevozierte Potentiale, der elektrisch ausgelöste Blinkreflex, auditorisch evozierte Hirnstammpotentiale, somatosensorisch evozierte Potentiale mit Ableitung über dem unteren Cervicalmark und dem jeweiligen kontralateralen Handfeld sowie nystagmographische Ableitungen wurden bei 55 Patienten mit einer Multiplen Sklerose untersucht. Die Patienten wurden entsprechend der anamnestischen Daten und der klinischen Symptomatologie in vier Gruppen unterschiedlicher diagnostischer Wahrscheinlichkeit getrennt. Die Resultate zeigten, daß die Kombination verschiedener evozierter Potentiale einen hohen Aussagewert in solchen Fällen haben kann, in denen die Diagnose einer MS klinisch nicht eindeutig ist. Es wird jedoch hervorgehoben, daß die Interpretation der elektrophysiologischen Befunde mit großer Sorgfalt vorgenommen werden soll, da eine einzige Läsion im Zentralnervensystem, besonders im Bereich des Hirnstammes, gleichzeitig verschiedene funktionelle Systeme befallen und dadurch eine disseminierte Erkrankung vortäuschen kann.

     

Electrocutaneous reflexes and multimodality evoked potentials in multiple sclerosis

Electrical stimulation of the digital nerves of the index finger produces changes in the EMG signal during steady voluntary contraction of the first dorsal interosseous muscle. This electrocutaneous reflex (ECR) was studied in 90 patients classified into different categories according to diagnostic criteria for multiple sclerosis. In addition, pattern reversal visual evoked responses (VER), brainstem auditory evoked responses (BAER) as well as spinal and scalp recorded somatosensory evoked potentials (SSEP) were investigated by stimulating both the index finger and the posterior tibial nerve. The reflex response was altered uni- or bilaterally in 56 per cent of the patients and the abnormalities of the ECR were related to the categories of diagnostic probability. Pathological results were found in 28 per cent of the hands without clinical evidence of sensorimotor deficit. Although ECR abnormalities were often associated with clinical signs, significant correlation was found only with hyperreflexia and/or increased muscle tone in the corresponding upper limb. Pathological ECR were more common than pathological SSEPs with finger stimulation recorded under identical stimulus conditions. Fewer abnormalities were found by ECR testing than with VER, but the proportion of abnormal ECR was higher than that of BAER. ECR provides a valuable supplement to existing electrophysiological procedures for detecting lesions in the central nervous system.     

Evaluation of ipsilateral and contralateral brainstem auditory evoked potentials in multiple sclerosis patients

Brainstem auditory evoked potentials (BAEP) were recorded simultaneously between the vertex and the mastoid ipsilateral and contralateral to the ear stimulated in 30 patients with multiple sclerosis (MS) and compared with the responses in a control group of 30 normal hearing adults. The control group showed that significant latency differences exist between ipsilateral and contralateral recording. Definitions of abnormalities were based on interwave separation and the wave V amplitude ratio. No case was found among the MS patients with an abnormal contralateral but normal ipsilateral response.     

Quantitative assessment of brainstem development in Joubert syndrome and Dandy-Walker syndrome.

Key features of Joubert syndrome include developmental delay, hypotonia, hyperpnea and apnea, oculomotor apraxia, and the presence of the molar tooth sign on axial imaging through the brainstem isthmus--the junction of the pons and mesencephalon. Interestingly, 1 in 10 patients with Joubert syndrome has abnormal cerebrospinal fluid collections misdiagnosed as Dandy-Walker variants. Because of important differences in patient management, genetic counseling, and prognosis between these conditions, we undertook a study to determine if the brainstem isthmus is normal in Dandy-Walker syndrome. Using standard landmarks, we evaluated development of the isthmus in normal subjects and in subjects with Joubert syndrome and Dandy-Walker syndrome. Four of five brainstem measures increased with age in normal subjects. In subjects with Joubert syndrome, the depth and length of the interpeduncular fossa were increased, and the width of the isthmus was decreased. In subjects with Dandy-Walker syndrome, the width of the brainstem isthmus was normal, and the molar tooth sign was absent. Although the pons can be hypoplastic in Dandy-Walker syndrome, we conclude that the pontomesencephalic junction is normal. Thus, the molar tooth sign can effectively distinguish between Joubert and Dandy-Walker syndromes. Genetic heterogeneity or epigenetic factors may account for abnormal cerebrospinal fluid collections in some cases of Joubert syndrome.     

脑白质疏松症脑干听觉诱发电位研究

在２４例经颅脑ＣＴ确诊的脑白质疏松症和２０例健康老年人中进行脑干听觉诱发电位（ＢＡＥＰ）研究。结果，病例组ＢＡＥＰ总异常１９例，异常率８３．３％，Ⅲ、Ⅴ波波峰潜伏期及各峰间潜伏期异常率较高；病例组Ⅲ、Ⅴ峰潜伏期及Ⅰ～Ⅲ、Ⅲ～Ⅴ、Ⅰ～Ⅴ峰间潜伏期均数比对照组大，ｔ－检验；Ｐ＜０．０１。结论：在脑白质疏松症早期临床未提示脑干功能受累时，脑干电生理功能已出现异常ＢＡＥＰ可作为脑白质疏松症脑干功能受累的客观指标在临床上推广应用。     

Auditory brainstem evoked potentials in early-treated congenital hypothyroidism

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

Exploring brainstem function in multiple sclerosis by combining brainstem reflexes,evoked potentials,clinical and MRI investigations

ObjectiveTo investigate vestibulo-masseteric (VMR), acoustic-masseteric (AMR), vestibulo-collic (VCR) and trigemino-collic (TCR) reflexes in patients with multiple sclerosis (MS); to relate abnormalities of brainstem reflexes (BSRs) to multimodal evoked potentials (EPs), clinical and Magnetic Resonance Imaging (MRI) findings.MethodsClick-evoked VMR, AMR and VCR were recorded from active masseter and sternocleidomastoid muscles, respectively; TCR was recorded from active sternocleidomastoid muscles, following electrical stimulation of the infraorbital nerve. EPs and MRI were performed with standard techniques.ResultsFrequencies of abnormal BSRs were: VMR 62.1%, AMR 55.1%, VCR 25.9%, TCR 58.6%. Brainstem dysfunction was identified by these tests, combined into a four-reflex battery, in 86.9% of cases, by EPs in 82.7%, MRI in 71.7% and clinical examination in 37.7% of cases. The sensitivity of paired BSRs/EPs (93.3%) was significantly higher than combined MRI/clinical testing (70%) in patients with disease duration ⩽6.4 years. BSR alterations significantly correlated with clinical, EP and MRI findings.ConclusionsThe four-BSR battery effectively increases the performance of standard EPs in early detection of brainstem impairment, otherwise undetected by clinical examination and neuroimaging.SignificanceMultiple BSR assessment usefully supplements conventional testing and monitoring of brainstem function in MS, especially in newly diagnosed patients.     

Air pollution is associated with brainstem auditory nuclei pathology and delayed brainstem auditory evoked potentials

We assessed brainstem inflammation in children exposed to air pollutants by comparing brainstem auditory evoked potentials (BAEPs) and blood inflammatory markers in children age 96.3 ± 8.5 months from highly polluted (n = 34) versus a low polluted city (n = 17). The brainstems of nine children with accidental deaths were also examined. Children from the highly polluted environment had significant delays in wave III (t(50) = 17.038; p < 0.0001) and wave V (t(50) = 19.730; p < 0.0001) but no delay in wave I (p = 0.548). They also had significantly longer latencies than controls for interwave intervals I-III, III-V, and I-V (all t(50) > 7.501; p < 0.0001), consisting with delayed central conduction time of brainstem neural transmission. Highly exposed children showed significant evidence of inflammatory markers and their auditory and vestibular nuclei accumulated α synuclein and/or β amyloid_1-42. Medial superior olive neurons, critically involved in BAEPs, displayed significant pathology. Children's exposure to urban air pollution increases their risk for auditory and vestibular impairment.     

Magnetic evoked potentials in neurocritical care patients with acute brainstem lesions

OBJECTIVES: Motor evoked potentials (MEPs) are widely used in various neurological diseases, but have not been systematically employed in neurocritical care patients. We evaluated the clinical and predictive value of MEPs by magnetic transcranial stimulation in intensive care patients with acute brainstem lesions of predominantly vascular origin. METHODS: In a prospective trial, a total of 30 patients with acute brainstem lesions were studied. Diagnoses were brainstem infarction (n=15), brainstem hemorrhage (n=3), encephalitis (n=1), basilar artery aneurysm (n=1), and space-occupying cerebellar infarct (n=5), cerebellar hemorrhage (n=3), and brainstem contusion (n=2). We performed MEP tests by transcranial stimulation to the abductor pollicis brevis bilaterally, bilateral somatosensory (SEPs) and auditory evoked (BAEPs) potentials. We determined motor function at the time of electrophysiological testing and after 3 months, the presence of radiologically confirmed lesions, and clinical outcome after 3 months. At the time of MEP recordings, ten patients were comatose, twelve stuporous, seven somnolent and one awake. RESULTS: MEPs were present bilaterally in seventeen, absent unilaterally in eight and bilateral absent in five patients. Absent MEP highly correlated with the presence of persisting motor deficit 3 months later (P<0.0001). Absent MEPs predicted motor deficit after 3 months with a high specificity and more precisely than the clinical examination at the time of MEP testing. MEP findings correlated with the presence of radiologically confirmed lesions within the brainstem (P<0.0001). Combined with SEP and BAEP data, MEPs predicted the presence of unilateral brainstem lesions with high accuracy. CONCLUSIONS: MEP recordings can be safely performed in neurointensive care patients and yield utilizable results. In patients with brainstem lesions, MEPs correlate with radiological findings and predict final motor function more accurately than clinical findings. MEPs are a reliable diagnostic tool for assessing motor function in otherwise unresponsive patients.     

Monitoring of multimodality evoked potentials during open heart surgery under hypothermia

Multimodality evoked responses (ERs) were monitored in 16 adults who had cardiac surgery under cardiopulmonary bypass and moderate hypothermia (19-25 degrees C). Cooling affected all sensory ERs by progressively increasing the latencies of the major components. The effect was more profound on the later than on the earlier ER components. Visual evoked responses (VERs) were most inconsistent and always disappeared at temperatures below 25 degrees C. The later components of the long latency somatosensory evoked responses (SERs) also attenuated or disappeared rather early during hypothermia. On the other hand, short latency SERs were more resistant to the effects of hypothermia. They were always recordable at temperatures of 25 degrees C or above; and usually persisted even at temperatures between 20 and 25 degrees C. Brain-stem auditory evoked responses (BAERs) were consistently present at temperatures above 25 degrees C, wave V was recordable in majority between 20 and 25 degrees C. All sensory ERs disappeared with severe hypothermia (20 degrees C or less) except the components generated more peripherally such as N10 of the short latency SERs. We feel that BAERs and short latency SERs may serve as useful intraoperative monitors of brain function during hypothermia.