PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Brain waves”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed2004

Left-hemispheric abnormal EEG activity in relation to impairment and recovery in aphasic patients.

Focal electromagnetic slow-wave activity is generated in the vicinity of brain lesions. The present study confirmed this for the EEG delta band (1-4 Hz): Activity in the waking state was pronounced over the hemisphere of the lesion in 11 stroke patients suffering from aphasia, but not in 10 healthy controls. Changes of abnormal slow waves patterns were tracked from 1-3 months to 2 years poststroke by recording the EEG five times at 4-month intervals. Across the first year poststroke, mean left-hemispheric delta amplitude and equivalent current dipole strength decreased in parallel with the spontaneous recovery of language function, whereas the regional distribution of delta activity sources was stabile across time. No changes were observed during the second year poststroke. Results suggest that abnormal slow waves in the vicinity of brain lesions may be related to impairment in brain function, and that their measurement may assist in depicting the course of functional recovery.

Adult↗
PubMed2001

A history and review of quantitative electroencephalography in traumatic brain injury.

The electroencephalogram (EEG) is a physiologic measure of cerebral function that has been used by some to assess coma and prognosticate survival and global outcome after traumatic brain injury (TBI). Surface recordings of the brain's electrical activity reveal distinct patterns that indicate injury severity, depth of unconsciousness, and patient survival. The data produced with traditional qualitative studies, however, does not allow resolution and quantification of the wave frequency spectrum present in the brain. As a result, conventional EEG typically has only been used for gross and qualitative analyses and is not practical for use in long-term patient monitoring or as a sophisticated prognostic tool. One area of investigation that is working to address the limitations of conventional EEG has been the development and implementation of Fourier Transform (FT) EEG which resolves and quantifies frequency bands present in the brain. When FT analysis is applied to EEG, it provides concurrent and continuous monitoring, resolution, and quantification of all frequencies emitted. This review discusses the history and significance of conventional EEG and provides a review of how FT-EEG, commonly referred to as Quantitative EEG (QEEG), is being used in the clinical setting. The specific applications and significance of QEEG methods regarding treatment of patients with TBI are discussed in detail. The advantages, disadvantages, and future directions of QEEG in TBI are also discussed.

Brain Injuries↗
PubMed1983

Disturbances of the sleep-waking cycle in patients with vascular brain stem lesions.

Continuous polygraphic recordings of six patients with vascular brain stem lesions were evaluated to investigate the relationship between 1) the localization or extent of the lesions and the alteration of the sleep-waking cycle, and 2) the evolution of the clinical condition and the sleep-waking cycle. Absent REM sleep and severely disorganized NREM sleep were associated with extensive pontine lesions involving the pontine tegmentum. In "locked-in" syndrome, the neural mechanisms responsible for both REM and NREM sleep continued to function, but the sleep-waking cycle was disturbed and marked by sleep-onset REM periods. Lesions in the lower brain stem resulted in absent slow-wave sleep and sleep-onset REM, suggesting that vascular lesions may involve the neural mechanisms responsible for slow-wave sleep. In general, the acute stage of illness was marked by increased awakenings and time spent awake, absent REM sleep, and little or no slow-wave sleep. These results indicate that continuous polygraphic recordings can reveal severe abnormalities due to vascular lesions of the brain stem whereas the waking EEG can only detect mild abnormalities. Improvement in the organization of the sleep-waking cycle in successive polygraphic examinations is likely to be followed by an improvement of the clinical condition. Continuous polygraphic recording is thus a valuable prognostic indicator for vascular brain stem lesions.

Aged↗
PubMed2001

Band-specific electroencephalogram and brain cooling abnormalities during NREM sleep in patients with winter depression.

BACKGROUND: We previously reported that delta wave activity and facial skin temperatures, an index of brain cooling activity, were both abnormal during sleep in patients with winter depression (SAD). Because other electroencephalographic (EEG) frequencies may also convey relevant thermal, homeostatic, and circadian information, we sought to spectrally analyze delta, theta, alpha, and sigma frequencies during sleep from 23 patients with SAD and 23 healthy control subjects. METHODS: We computed means for delta, theta, alpha, and sigma power during both NREM and REM sleep. We also generated 22 cross-correlation functions for each group by crossing facial and rectal temperature with each other, as well as with delta, theta, alpha, and sigma frequencies. RESULTS: We found that delta, theta, and alpha frequency activities were all increased during NREM, but not REM sleep, in patients with SAD. In addition, there were significant and abnormal cross-correlations between facial temperatures and delta and theta frequencies during NREM sleep in patients with SAD. CONCLUSIONS: Patients with winter depression exhibit correlated abnormalities of sleep homeostasis and brain cooling during NREM sleep. Their EEG profiles during NREM sleep resemble the EEG profiles of subjects who have been sleep deprived. Further studies of NREM sleep homeostasis in patients with SAD seem warranted.

Adult↗
PubMed2000

Neural and humoral pathways of communication from the immune system to the brain: parallel or convergent?

The first studies carried out on the mechanisms by which peripheral immune stimuli signal the brain to induce fever, activation of the hypothalamic-pituitary-adrenal axis and sickness behavior emphasized the importance of fenestrated parts of the blood-brain barrier known as circumventricular organs for allowing blood-borne proinflammatory cytokines to act on brain functions. The discovery in the mid-1990s that subdiaphragmatic section of the vagus nerves attenuates the brain effects of systemic cytokines, together with the demonstration of an inducible brain cytokine compartment shifted the attention from circumventricular organs to neural pathways in the transmission of the immune message to the brain. Since then, neuroanatomical studies have confirmed the existence of a fast route of communication from the immune system to the brain via the vagus nerves. This neural pathway is complemented by a humoral pathway that involves cytokines produced at the level of the circumventricular organs and the choroid plexus and at the origin of a second wave of cytokines produced in the brain parenchyma. Depending on their source, these locally produced cytokines can either activate neurons that project to specific brain areas or diffuse by volume transmission into the brain parenchyma to reach their targets. Activation of neurons by cytokines can be direct or indirect, via prostaglandins. The way the neural pathway of transmission interacts with the humoral pathway remains to be elucidated.

Animals↗
PubMed1991

Triphasic waves in coma from brainstem infarction.

There have been reports on patients in stupor or coma from a variety of disorders that affect the brain diffusely, notably hepatic failure, whose EEGs showed triphasic waves. We describe a patient in coma with neurologic signs localizing to the brainstem who had triphasic waves on EEG. This case further confirms the nonspecific nature of triphasic waves.

Aged↗
PubMed2005

The use of indomethacin in the treatment of plateau waves: effects on cerebral perfusion and oxygenation.

OBJECT: Plateau waves are sudden and steep increases in intracranial pressure (ICP) that can develop in patients with cerebral injuries, reduced pressure-volume compensatory reserve, and preserved autoregulation. They are caused by cerebral vasodilation in response to a reduction in cerebral perfusion and are associated with increased cerebral blood volume and reduced cerebral blood flow. The authors evaluated the hypothesis that administration of indomethacin, a potent cerebral arteriolar vasoconstrictor, could interrupt the vicious cycle that occurs during plateau waves, extinguishing these waves and, ultimately, restoring cerebral perfusion and oxygenation. METHODS: Plateau waves developed in nine patients, seven with severe traumatic brain injury and two with intraparenchymal hemorrhage. One to four episodes of plateau waves per patient were treated with indomethacin (15-20 mg), which was delivered by an intravenous bolus injection. Each patient's mean arterial blood flow (MABP), ICP, cerebral perfusion pressure (CPP), and cerebral tissue PO2 were continuously monitored and the data obtained were stored in a personal computer. Each patient's jugular venous O2 saturation (SjvO2) and venoarterial difference in PCO2 were evaluated by intermittent blood sampling. During five episodes of plateau waves, middle cerebral artery flow velocities were evaluated by transcranial Doppler ultrasonography. Indomethacin extinguished all plateau waves. On average, the ICP decreased from an initial value of 58.9 +/- 11.6 mm Hg to 21.2 +/- 8.6 and 25.8 +/- 13.7 mm Hg after 5 and 10 minutes, respectively (p < 0.01). The MABP did not change significantly. As a consequence the CPP increased by 98 and 81% after 5 and 10 minutes, respectively (p < 0.01). Five and 10 minutes after indomethacin was administered, SjvO2 increased from an initial value of 50 +/- 10.5% to 62 +/- 7.6 and 59.9 +/- 9.3%, respectively (p < 0.01); the cerebral tissue PO2 increased from an initial value of 13.4 +/- 10.6 mm Hg to 23.6 +/- 9.58 and 21.9 +/- 9.2 mm Hg, respectively (p < 0.05); and the venous-arterial PCO2 decreased significantly. The mean and diastolic flow velocities increased significantly, whereas the pulsatility index decreased from 1.39 +/- 0.56 to 1.09 +/- 0.4 at 5 minutes and 1.06 +/- 0.36 at 10 minutes (p < 0.05). CONCLUSIONS: The findings confirm that plateau waves are caused by vasodilation and show that indomethacin, by constricting the cerebral arteries, is effective in extinguishing plateau waves, ultimately restoring cerebral perfusion and oxygenation.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

SPECT findings in an unusual case of visual hallucinosis.

A 64-year-old right-handed man acutely developed elementary visual hallucinations (monochromatic, moving geometrical figures), visual illusions (distortion of the right side of faces) with achromatopsia and blurred vision restricted to the left visual hemi-field. CT of the brain before and after administration of contrast medium and a repeat examination 2 months later showed no abnormalities, while brain mapping (power analysis of EEG) demonstrated theta wave slowing of the curve over the posterior part of the right hemisphere. 99mTC HMPAO SPECT of the brain, however, demonstrated an area of definite focal hypoperfusion in the right occipito-temporal region. Echo-Doppler-duplex and continuous wave examination of the cervical arterial blood vessels disclosed bilateral discrete atheromatous plaques that did not affect the blood flow. Transoesophageal echocardiography demonstrated slight mitral valve insufficiency. Cerebral angiography showed an occlusion of the right posterior cerebral artery. After the visual hallucinations had subsided, SPECT showed partial normalization of the right occipito-temporal perfusion. In the absence of CT evidence for a structural lesion in the clinically suspected areas, only functional imaging revealed an obviously significant lesion. This case furthermore demonstrates that SPECT can contribute to the identification of the pathophysiology underlying visual hallucinosis.

Brain↗
PubMedDate not supplied

Absence of later auditory brain stem response components, congenital horizontal nystagmus, and hypotonia in male infants.

Five male infants, all of whom showed findings of wave I or waves I and II only of the auditory brain stem response (ABR), congenital horizontal pendular nystagmus, and hypotonia of head and limbs in the early infantile period with later paresis, are discussed. Their ages ranged from 3 to 13 months at the first examination, at which time neither head control, sitting, nor walking had been attained. Follow-up studies of ABRs revealed persistent abnormalities with neither remission nor progression. In spite of these abnormalities, these infants responded well to voices and other sounds. The congenital nystagmus in each case was demonstrated by electronystagmography to have a frequency of 2 to 3 Hz. The correlation between clinical signs and ABR is uncertain as yet. However, our findings are strongly indicative of nonprogressive inborn abnormalities in the lower brain stem.

Brain Stem↗
PubMed1990

[The brain stem function in patients with brain bladder--clinical evaluation using dynamic CT scan and auditory brainstem response].

A syndrome of detrusor-sphincter dyssynergia (DSD) is occasionally found in patients with brain bladder. To evaluate the brain stem function in cases of brain bladder, urodynamic study, dynamic CT scan of the brain stem (DCT) and auditory brainstem response (ABR) were performed. The region of interest of DCT aimed at the posterolateral portion of the pons. The results were analysed in contrast with the presence of DSD in urodynamic study. DCT studies were performed in 13 cases with various brain disease and 5 control cases without neurological diseases. Abnormal patterns of the time-density curve consisted of low peak value, prolongation of filling time and low rapid washout ratio (low clearance ratio) of the contrast medium. Four of 6 cases with DSD showed at least one of the abnormal patterns of the time-density curve bilaterally. In 7 cases without DSD none showed bilateral abnormality of the curve and in 2 of 7 cases only unilateral abnormality was found. ABR was performed in 8 patients with brain diseases. The interpeak latency of the wave I-V (I-V IPL) was considered to be prolonged in 2 cases with DSD compared to that of 4 without DSD. In 2 cases with DSD who had normal DCT findings, measurement of the I-V IPL was impossible due to abnormal pattern of the ABR wave. Above mentioned results suggests the presence of functional disturbance at the posterolateral portion of the pons in cases of brain bladder with DSD.

Adult↗
PubMed1997

[A case of primary acute pulmonary cavitation in sarcoidosis complicated by multiple nodular lesions in the central nervous system].

A 20-year-old man visited our hospital complaining of headache and a dry cough. Chest X-ray and chest CT showed bilateral hilar and mediastinal lymphadenopathy, multiple cavitations with thin, smooth walls, and diffuse granular shadows. A transbronchial biopsy specimen revealed sarcoid granuloma. Primary acute pulmonary cavitation of sarcoidosis was diagnosed, since there was no evidence of infection, emphysematous change, fibrotic or cystic bronchiectatic change on chest X-ray. EEG, contrast enhancement of brain CT scans and MRI were performed because the patient complained of headache. EEG showed a high voltage paroxysmal slow wave and giant build-up, whereas brain CT showed no abnormalities. T1-weighted MRI with gadolinium enhancement showed multiple high intensity nodules in the convexity, brain stem, and spinal cord. Corticosteroid therapy (60 mg/day) was started. After 1 week of treatment, the headache ceased. After 2 weeks of treatment, both the cavities in the lung field's and the nodules in the central nervous system disappeared. Therefore, the dose of corticosteroids was gradually reduced to a maintenance dose of 5 mg/day, and no relapse was noted. We report a very rare case of primary acute pulmonary cavitation in sarcoidosis complicated by multiple nodular lesions in the central nervous system.

Adult↗
PubMedDate not supplied

Auditory evoked potentials from the primary auditory cortex of the cat: topographic and pharmacological studies.

Wave VI (8.4 msec) of the brain-stem auditory evoked potential (BAEP) was maximal in a discrete region of primary auditory cortex (AI) of the anesthetized cat. Wave VI underwent rapid amplitude decrease over millimeter distances in the AI region and followed high stimulation rates. Wave VI did not show intracortical polarity inversion nor was it abolished by epicortical or intracortical GABA administration. The data are compatible with a wave VI source in the terminal axons of the thalamo-cortical radiations. Middle latency auditory responses (MAEPs) generated 10-40 msec after auditory stimulation were also recorded in a circumscribed area of AI. In contrast to wave VI, these primary auditory cortex potentials (Pa 18.3 msec; Nb 31.9 msec) underwent transcortical polarity inversion, correlated with intracortical multi-unit activity in the AI region and were reversibly altered or abolished by epicortical or intracortical GABA administration to the AI region. The data suggest that the Pa and Nb components of the cat MAEP are intracortically generated by neuronal elements in the AI region.

Acoustic Stimulation↗
PubMed1995

Spreading waves of a reduced diffusion coefficient of water in normal and ischemic rat brain.

Using echo planar diffusion-weighted magnetic resonance imaging, we measured three-dimensional changes in the apparent diffusion coefficient (ADC) of water in eight contiguous coronal slices, encompassing the entire rat brain, before and after local cortical stimulation. We applied chemical (potassium chloride application; n = 6) and mechanical (needle stab; n = 4) stimulations to the right posterior parietal rat cortex. In all animals in which potassium chloride or the needle stab was applied, a region of decreased ADC values to a mean of 0.45 +/- 0.03 x 10(-5)cm2/s occurred. These reduced ADC levels appeared in the posterior parietal cortex within 1 min after cortical stimulation and the change recovered within 1 min. Then a ripple-like movement of similar changes developed across the unilateral cortex. This change was localized to the cortex and no significant ADC changes occurred in subcortical structures. The propagating speed of this movement was 3.4 +/- 0.5 mm/min. These findings are compatible with spreading depression as observed electrophysiologically. Similar ADC changes occurred in areas distinct from the ischemic lesion in 3 of 12 animals subjected to focal cerebral ischemia. This magnetic resonance method could detect spreading ADC decline if it occurred in human diseases including brain ischemia.

Animals↗
PubMed1994

The brain stem evoked response and medial nucleus of the trapezoid body.

Single-unit responses of cat superior olivary complex neurons to acoustic stimuli were examined to determine whether the units' action potentials were sufficiently synchronized to contribute to the brain stem evoked response. The medial nucleus of the trapezoid body and lateral superior olive are two major nuclei within the cat superior olivary complex. The first-spike discharge latencies of medial nucleus of the trapezoid body and lateral superior olivary neurons to monaural presentations of tone burst stimuli were measured as a function of stimulus level. Evidence is provided to support the hypotheses that in cat the medial nucleus of the trapezoid body may contribute directly to the monaural brain stem evoked response by producing action potentials synchronized to stimulus onset and may also contribute indirectly to the brain stem evoked response binaural difference wave bc by inhibiting the lateral superior olive unit excitatory responses synchronized to stimulus onset.

Acoustic Stimulation↗