Phosphorus-31 magnetic resonance spectra revealprolonged intracellular acidosis in the brain following subarachnoidhemorrhage.

Subarachnoid hemorrhage may be complicated bycerebral ischemia which, though reversible initially, can progress to anirreversible neurological deficit. 31P magnetic resonance spectroscopy, whichcan determine intracellular pH and thus detect areas of ischemia noninvasively,was applied to 10 patients on 30 occasions, at various times after subarachnoidhemorrhage. In 5 of them, there were focal areas of the brain in which theintracellular pH was reduced to < 6.8 compared with the normal range of 7.05+/- 0.05. Consciousness was impaired in 4 of these patients. Repeat studies inthese 4 patients showed that intracellular pH remained abnormally low forseveral days but eventually returned toward normal. The return of intracellularpH to normal paralleled an improvement in clinical condition in each case. Inthe fifth patient with lowered regions of intracellular pH, there had been animpaired level of consciousness and a transient focal deficit prior to thesingle study. In the other 5 patients there were no areas of reduced pHi eventhough in 3 of them there was intraventricular or cisternal blood shown on braincomputerized tomography. In 2 of these 3 patients there were no abnormalneurological signs at the time of the magnetic resonance study. The thirdpatient had a dense and persistent hemiparesis. The remaining two patients hadno abnormal neurological signs at any stage. We suggest that the areas ofacidosis may reflect ischemia which is potentially reversible. Since thetechnique is noninvasive, sequential 31P magnetic resonance spectroscopy of thebrain offers a method of detecting cerebral ischemia and, more importantly, ofassessing methods of treatment.