Delta wave

As we relax in preparation for and pass into sleep, the active desynchronised awake EEG characterised by the low-amplitude (5-10 pV) high-frequency (10-30 Hz) beta waves becomes progressively more synchronised giving larger (20-30 pV) and slower (8-12 Hz) alpha waves, and then even slower (1-4 Hz) and bigger (30-150 pV) delta waves. This so-called slow-wave sleep is interrupted at intervals of some 1-2h by the break-up and desynchronisation of the EEG into an awake-like pattern. Since this is accompanied by rapid eye movements, even though sleep persists and can be deeper, the phase is known as rapid eye movement, REM or paradoxical, sleep. It is a time when dreaming occurs and when memory may be secured. 

Amzica, F. Steriade, M. (1998). Electrophysiological correlates of sleep delta waves. Electroencephalogr. Clin. Neurophysiol 107, 69-83. 

Shipley JE, Kupfer DJ, Griffith R, et al Computer analysis of EEG sleep delta waves and rapid eye movements a comparison of two techniques. Sleep Res 17 353, 1988... 

A 61-year-old man with epilepsy had altered consciousness after his dose of valproate was increased because of poor seizure control. Electroencephalography showed triphasic waves and high-amplitude delta-wave activity with frontal predominance. Although serum aspartate transaminase and alanine transaminase were normal, the serum ammonium concentration was high at 960 ng/ml (reference range 30-470). Serum amino acid analysis showed multiple minor abnormalities. Valproate was withdrawn. He improved within 4 days... 

Stage 3 and 4 are stages of deep sleep and differ only in amount of very slow brain (or delta) waves cycling at 0.5 1 Hz. The amount of deep sleep varies amongst genders and different age groups, and it decreases dramatically from a young age, where it comprises a quarter of one s sleep, to almost nil in males in their seventies. 

Abnormal ground pattern. More or less continuous high voltage delta waves followed by short periods of suppression ... 

Multifocal theta, bilateral frontotemporal, followed by asymmetrisch waves with a mitigated epileptiform aspect Left temporal slow theta and delta waves of middle high to high... 

Each P wave is followed rapidly by a QRS. A delta wave leads into the QRS. Rate can exceed 300 beats/minute. 

The normal EEG consists of waves in the alpha range of 8 - 13 Hz (a waves) and beta range of 13 - 25 Hz (P waves). Waves in the theta range of 4 - 8 Hz (9 waves) constimte a very minor component of the normal EEG and delta wave activity in the range of 1-4 Hz (8 waves) is absent. 

Valproate may contribute to hyperammonemia by inhibiting carbamoylphosphate synthetase-I, the enzyme that begins the urea cycle. Phenobarbital may potentiate the toxic effect of valproate. The electroencephalogram in severe hyperammonemic encephalopathy exhibits continuous generalized slowing, a predominance of theta and delta waves, bursts of frontal intermittent rhythmic delta activity, and triphasic waves (Segura-Bruna et al., 2006). 

From wakefulness to deep sleep, there is a progression of EEG activity, slowing from beta wave activity (about 18 Hz) to theta-delta wave activity (3.5 to 8 Hz). Figure 17.43 shows the appearances of the major brain wave frequencies. The delta waves occur in deep sleep or coma. Theta waves are... 

Figure 11.3 Typical samples of human EEG brainwaves (a) Delta wave, (b) Theta wave, (c) Alpha wave and (d) Beta wave, (e) Blocking of the Alpha wave by eye opening, (f) 1 s time marker [34],...

Alpha, Beta and Gamma waves. Each of them has a specific frequency and amplitude. Typical samples of human EEG signals are shown in Fig. 11.3. The Delta wave is the largest wave with amplitude between 20 and 200 pV, but has the lowest occurring fi-e-quency at less than 4 Hz. The amplitude of the Theta wave is between 20 and 1(X) pV and its frequency between 4 and 7 Hz. The Alpha wave is the most commonly recorded wave, at a frequency between 8 and 13 Hz and amplitude at about 20—60 pV. The Beta wave is relatively faster, occurring at 14—30 Hz frequency with amplitude at around 2—20 pV. Finally, the Gamma wave is the smallest and fastest wave, which occurs over 30 Hz, and its amplitude is between 5 and 10 pV. 

Significant differences of Delta wave power were observed in five electrode channels as shown in Fig. 11.33. They are the Fpl and Fp2 channels in the prefirontal lobe, the C4 channel at the right of the central sulcus, and the 01 and 02 channels over the occipital lobe. The mean of the difference in these channels is less than zero at 80% and 85% confidence levels, which shows that Pattern 4.1 evoked less Delta power than Pattern 4.2 in these locations of the brain. 

Among patients >65 years of age, the ECj, for delta-wave formation on EEG is 50% lower thus, the initial dose should be reduced accordingly, with careful titration to effect. 

A delta wave occurs at the beginning of the QRS complex, usually clausing a distinctive slurring or hump in its initial slope. 

On a 12-lead ECG, the delta wave will be most pronounced in the leads lcx>king at the part of the heart where the accessory pathway is loc ated. 

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