H. Hildebrandt et al., Cardiosomatic coupling as a differential indicator for coma depth and effectivity of sensorial stimulation, AKT NEUROL, 26(4), 1999, pp. 171-179
Coma is understood as a dissociation of endogenous brain stem rhythms or ph
asic activity states of different compartments of the nervous system. Hence
the awakening from coma is connected with a temporal coupling of activity
states and this can be regarded as a presupposition for an integrated behav
iour of the entire organism. Following this theory, we postulate that the a
ctivity coupling between motoric tonus and heart rate (cardiosomatic coupli
ng) increases with growing closeness to consciousness and that if the patie
nt is addressed specifically (sensoric stimulation) a rectified alteration
in coupling can be achieved.
We examined 47 patients with severe brain-head traumata. They were measured
in three different coma depths (Glasgow Coma Scale 3 to 5, 6 to 7, and 8 t
o 10), some of them several times (but due to the clinical conditions not e
ach patient in each of the coma depths). For every patient we recorded the
muscle tonus of the forearm and the frontal muscles (by a surface EMG) as w
ell as the heart rate (HR). Multiple measurements of one patient in one com
a group were averaged, so that we had 82 measurements distributed over the
three coma groups. We analysed the heart rate variability, EMG variability
and the cardiosomatic coupling (crosscorrelation of HR and EMG) for a stand
ardised intervention scheme with a 5-minute baseline and an intervention ph
ase lasting for 6 minutes, which comprised a visual, acoustic, tactile and
vestibular stimulation (each for 1.5 minutes).
The result of this investigation shows that the cardiosomatic coupling incr
eases with closeness to consciousness and under stimulation. Depending on t
he analysed muscle tonus, the increase in cardiosomatic coupling can be con
firmed from the point of reaching a GCS score of 8 to 10 (forearm musculatu
re) or 6 to 7 (frontal musculature). Thus our initial thesis could be confi
rmed. A possible explanation for the differential effect of forearm muscles
and frontal muscles might be the fact that the frontal muscles belongs clo
ser to the axial and proximal motor system and, in addition, mirrors emotio
nal reactions, while the forearm muscles belongs to the distal motor system
. During the re-integration of motor and cardiovascular system the centres
which are controlled by the brain stem would then be reached first, even be
fore cortical centres show a phase coupling.