FOLLOW-UP-STUDIES OF SOMATOSENSORY-EVOKED POTENTIALS AND AUDITORY BRAIN-STEM EVOKED-POTENTIALS IN PATIENTS WITH POST-COMA UNAWARENESS (PCU)OF TRAUMATIC BRAIN INJURY
O. Keren et al., FOLLOW-UP-STUDIES OF SOMATOSENSORY-EVOKED POTENTIALS AND AUDITORY BRAIN-STEM EVOKED-POTENTIALS IN PATIENTS WITH POST-COMA UNAWARENESS (PCU)OF TRAUMATIC BRAIN INJURY, Brain injury, 8(3), 1994, pp. 239-247
Some patients who suffer severe traumatic brain injury (TBI) fail to r
ecover higher brain functions in spite of giving the appearance of sle
ep-wake cycles. Such a state is called post-coma unawareness (PCU) and
varies in type and degree. Patients may remain in this state for mont
hs or even years. This study focused on the follow-up of upper-limb so
matosensory evoked potential (USEP) measurements and auditory brainste
m responses (ABR), with an emphasis on dynamic changes, in 10 patients
with PCU resulting from TBI. The prognostic value of USEP and ABR was
evaluated. Results showed that the presence of ABR in PCU patients ha
d no prognostic value, because ABRs were found both in patients who re
covered and those who did not, even a year after the trauma. The prese
nce of normal ABR in PCU patients may suggest that the brainstem has b
een spared in the pathoanatomy of the PCU condition, with the signific
ant damage occurring above this level, in cortical and subcortical (th
at is, hemispheral) areas. USEP was graded using the new system of Hou
lden [1] for 'acute' comatose patients. It was found that USEP measure
ments had some prognostic value in PCU patients. Most of the patients
who remained in the PCU state had grade 2 or less initially, whereas m
ost of the patients who later recovered or achieved at least a 'reduce
d life' state were grade 4 or more. On initial testing (when all patie
nts were still in the PCU state), defined cortical potential (mainly i
n the slope of the building NI potential) was seen in only some of the
patients who later recovered. No dynamic changes or signs of improvem
ent were seen in any of the patients who did not recover (that is, who
remained in the PCU state). On the other hand, dynamic changes in evo
ked potential (amplitude, latency and shortened latency) were found in
all patients who got well and, although not homogeneous, the changes
involved all the elements of normal patterns and showed a trend toward
s improvement. Patients who remained comatose showed no change or redu
ction in Houlden's grade, whereas all patients who recovered showed no
change or elevation. (In one of the latter patients, the grade increa
sed from 2 to 5.) In some patients who recovered, morphological change
s in cortical potentials were seen, mainly in NI slopes.