Post Mild Traumatic Brain Injury Shows Dissociations Between MRI and SPECT
Post Mild Traumatic Brain Injury Shows Dissociations Between MRI and SPECT
Abstract & Commentary
Source: Hofman PA, et al. MR imaging, single-photon emission CT, and neurocognitive performance after mild traumatic brain injury. AJNR Am J Neuroradiol. 2001;22:441-449.
This report describes the presence of moderately severe, abnormal neurological symptoms and their outcomes in 21 persons following mild traumatic brain injury. The literature indicates that symptoms of headache, dizziness, impaired memory, and difficulty in concentration follows 80% of even mild, unexpected head injury. About three-fourths of such reactions disappear within a week or so. This report describes the post-traumatic findings of 21 consecutive, previously healthy persons younger than 50 years of age. Each subject suffered less than 20 minutes of post-traumatic loss of consciousness and/or of amnesia for less than 6 hours. MR images, SPECT quantification, and neurocognitive testing were applied to every subject. "Cognitive tests" included Visual Verbal Learning, Stroop Color Word, Concept Shifting, Letter Digit Substitution, Fluency, and Motor Choice Reaction tests.
Mean age of the 21 subjects amounted to 22.8 years. Mean post-traumatic unconsciousness averaged 4 minutes and the amnesic period lasted 67 minutes. All 21 patients had MRI examinations and 18 had HMPAO-SPECT testing.
Twelve patients had abnormal MRI findings and abnormal SPECT findings. Only 7 patients displayed both abnormalities. As Hofman and associates put it, "the agreement between MR and SPECT studies was . . . poor." FLAIR MR images brought out a larger number and size of abnormalities (mean = 3.61) than did the T2-weighted MR images. Extracerebral hemorrhages affected 2 persons, but 12 suffered a total of 42 lesions in the frontal lobe and/or 16 lesions in the temporal lobe. Neither age, education, nor trauma severity was selectively associated with the MR findings. Brain atrophy appeared at 6 months in the patients who had abnormal post-traumatic MRs.
Neurocognitive evaluations demonstrated a modest abnormality (0-21) 2 months after the accidents but this disappeared (0.45) after 6 months.
Post-traumatic complaints rated on a 28-item questionnaire at 2 months (normal MR = 13.33, abnormal 8.11), changed only slightly at 6 months (12.57 normal MR, abnormal MR 7.30). Long-term complaints included forgetfulness, difficulty in concentration, trouble with word finding, and mental slowness. There was no consistent association between neurocognitive results and SPECT findings. Most of the abnormal SPECT findings indicated regions of hypoperfustion. Explanation of this particular association is presently no more than guess work.
Commentary
As Hofman et al put it, "the most important finding in our series of brain trauma patients was the high prevalence of brain lesions." This may be true, but was there any selection of patients who especially appeared to have surface body injury? Granted that it might be useful to apply brain imaging to all patients who have more than 90 minutes of post-traumatic amnesia, but, with the exception of extra dural hematomas, how does that step improve patient care? Shouldn’t CT scanning provide a much less expensive but equally effective identification for such hematomas?
As for the neuropsychological variations in this cohort of post-traumatic patients, they seem to be dissociated from the severity of the tissue abnormalities. Given the fact that all of the formal psychological deficits disappeared within 6 months, it appears merely that their source reflected temporary psychological disruption rather than tissue damage.
Until some therapy can be found to repair brain structure, your editor doubts the value of applying expensive MRI or SPECT tests for post-traumatic head injury of mild-to-moderate degree. If a research plan on the topic can be funded, follow-up material should last at least 5 years. Otherwise, these data only risk legal invitation for relatively modest injuries. —Fred Plum
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