SAN FRANCISCO — The largest series of head injury patients to undergo magnetic resonance imaging found brain stem injuries in 60% of 200 patients, a much higher rate than the 10% usually quoted in the literature, Dr. Raimund P. Firsching reported at the annual meeting of the American Association of Neurological Surgeons.
Fewer than 1 in 10 brain stem lesions were visible on CT scans, he said.
Investigators performed CT and MRI scans on patients within a week of head injury; all patients were in a coma for at least 1 day.
Functional and mortality outcomes 3 months after injury were associated with the location of brain injury on MRI, with much worse prognoses in patients who had brain stem lesions, said Dr. Firsching, of the department of neurosurgery at Otto-von-Guericke University, Magdeburg, Germany, who conducted the study with Dr. Dieter Woischneck, also of the university.
The results challenge the commonly held notion that when CT shows no lesions after brain trauma, a patient's failure to improve must be a result of diffuse brain injury, Dr. Firsching said.
Among patients who emerged from coma after 1 day, 63% had brain stem lesions seen on MRI.
The longer the coma lasted, the greater the likelihood of brain stem lesion: Of patients who were in a coma for 1 week, 96% had brain stem lesions. “This is really in sharp contrast to the literature,” he noted.
The imaging could not differentiate between primary and secondary lesions, he acknowledged.
Commenting on the study at the meeting, Dr. M. Ross Bullock said that it was limited by not identifying postherniation changes in the brain, by not reporting how many patients had lesions removed, and by not discussing the implications of high intracranial pressure with the MRI findings.
“If these data represent simply a very high, unusual incidence of herniation, that's not a major contribution to our knowledge base,” said Dr. Bullock, the Reynolds Professor of neurosurgery at Virginia Commonwealth University, Richmond, Va.
At his institution, MRIs on 13 patients with trauma found brain stem lesions in 10%, he noted.
Among all patients in Dr. Firsching's study, 37% had supratentorial lesions confined to the hemispheres or the corpus callosum; two-thirds of this group had a good outcome, and 10% died, Dr. Firsching reported. A lesion in a unilateral region of the brain stem, seen in 20% of patients, was associated with a slight or moderate functional handicap after 3 months, and 21% of these patients died. Severe disability was likely in the 22% of patients with bilateral mesencephalic lesions, and 21% died. Among the 21% of patients with a bilateral pontine lesion, 92% died.
Lesions on the corpus callosum did not predict the likelihood of death or the length of coma, he added. Pontine and midbrain lesions, which CT failed to detect, are most important for prognosis, he emphasized.
In nearly 10 years of doing MRIs on brain trauma patients, “we have yet to see a patient who was in a vegetative state who did not exhibit a bilateral pontine lesion,” Dr. Firsching said.
The investigators began the series of MRIs on head trauma patients after a man in a bus accident failed to emerge from his coma. The patient's brother, a neuroradiologist, insisted on getting an MRI, which showed lesions that were invisible on CT. MRI is indicated in the evaluation of some head trauma patients who don't improve over time, according to Dr. Bullock.
CT shows large extradural hematoma (left). MRI of midline shows traumatic lesion; tissue extends into brain stem (right). Courtersy Dr. Raimund P. Firsching
