De la genese et de la signification des rythmes recueillis à distance dans les cas de tumeurs cérébrales: Conclusions d'une discussion entre

Abstract

The authors, on the basis of empirical observation, suggest a number of parameters to describe the varieties of electrical activity recorded at a distance from cerebral tumors (C.T.), the different types of electrical activity in such cases, the genesis and significance of these electrical patterns. 1. A. Parameters: 2. (1) Amplitude; (2) frequency; (3) phase relations (morphology); (4) secondary components and relations with the fundamental rhythm; (5), (6), (7) geometrical distribution; (8) temporal distribution during recording; (9) correlations with local signs of C.T.; (10) evolution in time from one examination to the other; (11) reactivity to physical, chemical, psychological, physiological stimuli; (12) correlations with neuropsychiatral findings; (13) correlations with site and nature of lesion. It is emphasized that the value of each of these parameters may be variable. 1. B. Types of activity: 2. (1) Monorhythmic delta rhythm: large amplitude; frequency from 1 to 4 c/sec.; simple, sinusoidal, always regular in form; strong predominance of fundamental element; possible existence of second harmonic and mixture with fundamental rhythm; anterior bilateral, synchronous, more marked in longitudinal run and long interelectrode distances, can be unilateral; appears in bursts as spindles; synchrony between this rhythm and one of the local delta rhythms; variable evolution in time; increased by torpor, drowsiness, light sleep, decreased by eyes opening; would be in relation to the effect of lesions in the basal structures of the brain in the posterior or middle fossa. 3. (2) Slow theta rhythm: moderate amplitude; frequency from 4 to 7 c/sec.; regular sinusoidal in form often with but one fundamental element; mostly in temporal regions and recorded in coronal run; probably of deep origin; variable bilaterality, symmetry and synchrony, semi-permanent with no reinforcement; tendency to react to stimuli, possible relation with lesions in the lateral thalamus. 4. (3) Six per second theta rhythm: fairly high amplitude; frequency 6 c/sec.; regular sinusoidal in form; with one predominant fundamental element; localized to fronto-temporal regions; symmetrical, bilateral synchronous, semi-permanent, with paroxysmal reinforcement; reactive possibly in relations with a median or para-median mesodiencephalic lesions. 5. (4) Eight per second activity: fairly high amplitude; frequency from 7.5 to 9 c/sec.; wave regular, sinusoidal, monorhythmic; generalized, recorded both in coronal and longitudinal runs, but maximum posteriorly; permanent, without reinforcement; reactive; found in lesion in meso-diencephalic regions. 6. (5) Rapid activity: low amplitude, frequency from 16 to 25 c/sec.; variable and complex phase relationship; generalized; permanent; non-reactive; found in posterior fossa and inferior brain stem lesions. 7. (6) Posterior delta activity: waves of high amplitude; frequency from 1 to 4 c/sec.; less regular than anterior monorhythmic delta waves; always superimposed upon an alpha or theta rhythm basic; found posteriorly either bilateral though asymmetrical or unilateral; appear as sporadic elements; react to eyes opening; found mostly in posterior fossa tumors and predominantly in homolateral side in cerebellar tumors. 8. (7) Generalized slow delta activity: moderate or high amplitude frequency of 0.5 to 1.5 c/sec.; irregular, non harmonic waves; activity generalized, synchronous, symmetrical, permanent, non reactive; found in intracranial hypertension and sub-thalamic lesions. 9. (8) Wave and spike or slow spike paroxysmal activity: not discussed in this classification. The mechanisms underlying these rhythms can be: 1. (1) An electrical transmission of abnormal potentials caused by the presence of the tumor. 2. (2) A physiological transmission either over axonal pathways or by neuronal contiguity. 3. (3) An active or passive influence in a normal area by abnormal signals, or absence of normal afferent supply. The only hypothesis suggested for the genesis of some of these rhythms is that they may be a result of an activation of or an interference with the reticular system studied by Morruzi and Magoun. Grey Walter suggests that these slow waves may act as a protective mechanism of cerebral function.