[Changes in somatosensory evoked potentials in response to the combined use of extra- and intracerebral pressure: an...

The impact of the combined application of extra- and intracerebral pressure on somatosensory evoked potentials (SEP) was investigated on 24 rats. The pressure upon the somatosensory cortex was applied via a 5 x 5 mm glass stamp which included a ceramic-diaphragmal electrode for recording the SEP, EEG and DC-potentials. The intracerebral pressure was evoked by a Fogarty-balloon catheter. The balloon catheter was inserted into the ipsilateral sensorimotor white matter. Slow increase of the balloon volume without additional epicortical pressure caused SEP changes at about 0.08 ml balloon volume. The application of 50 g pressure onto the cortex prior to balloon inflation led to SEP changes at 0.02 ml balloon volume, which showed a steep increase with further expanding balloon volume. In view of possible brain lesions due to brain retraction in intracerebral mass removal procedures the effects of intermittently and continuously applied epicortical pressure in addition to a given intracerebral mass (0.05 ml) were studied. In intermittent as well as in continuous pressure application the effects of both small (P = 25 g) and severe (P = 100 g) pressure were compared with. Even small pressure lasting for 60 minutes continuously caused SEP changes, which recovered only incompletely. In cases of intermittent application of small pressure the SEP pattern recovered completely. Severe epicortical pressure was followed by SEP changes, which did not recover neither in intermittent nor in continuous application. Irreversible disturbance of the microcirculation was assumed to be the reason.(ABSTRACT TRUNCATED AT 250 WORDS)