Objective Signs of Trauma in Very Mild Traumatic Brain Injury

Mild traumatic brain injury (MTBI) is a controversial topic among physicians and attorneys. Many in the medical community are skeptical of MTBI, and consider it to be more psychological than physical.

Part of the problem with brain injury is that it is often difficult to find objective imaging—via CT or MRI—of the actual lesion that may be causing symptoms after a mild head injury. A new study1 has looked at this problem, and found that it is indeed possible to find objective signs of injury, even in cases of very mild traumatic brain injury.

The researchers examined twelve consecutive patients who presented with head injury within 24 hours of the trauma. The patients were included in the study only if they met the following criteria:

No or brief loss of consciousness (<20 minutes).
A maximum score of 15 on the Glasgow Coma Scale.
A normal neurological exam.
Less than one hour of post-traumatic amnesia.
No perceptible disorientation.

These criteria were imposed to limit the cases to those with the mildest forms of traumatic brain injury.

Each patient was tested with a battery of neuropsychological tests. One of these tests was the Galveston Orientation and Amnesia Test (GOAT). They were also given an EEG exam and an MRI scan of the brain. Each of the tests was repeated six weeks later, except that the EEG and MRI scans were done only in patients with initial abnormal findings. These twelve patients' scores were then compared to the results of fifteen healthy control subjects. Two radiologists who were unaware of the patients' condition reviewed and evaluated the MRI scans.

Of the 12 patients, only eight had lost consciousness; four reported being "confused" after the injury. The mean score on the GOAT test was 97.7�with the best possible score being 100�indicating that any brain injury was indeed mild.

The study found that 3 of the 12 patients (25%) showed brain lesions on MRI. One of these patients had no loss of consciousness and another showed no signs of disorientation or amnesia (GOAT score of 100.)

No differences were found between patients and control subjects on the EEG tests.

The authors conclude:

"The most sensitive method for detecting brain damage in this study was the neuropsychological examination: verbal memory is particularly affected, a fact previously reported after MTBI. The significant slowing of reaction time, as well as the results of the arithmetic test, both using more complex pathways in the brain, were additionally related to very MTBI. Verbal fluency, a relevant function of speech with frontal priority, was not significantly impaired, but a trend was noticed. No effect was found in the non-verbal memory tests."

"Improvement, but not full remission, was shown 6 weeks after very MTBI. These findings are in accordance with the literature: Levin et al2 supposed that neuropsychological deficits in minor head injury patients (GCS 13-15) need 3 months for full remission, due to cerebral lesions including diffuse axonal injury, neurotransmitter disturbance, and occult lesions."

The authors suggest that many such cases of very MTBI may be missed completely in the real world:

"Due to lack of medical emergency, some of the patients would not have been medically documented at this extent in clinical routine. Some cases would not have even received CT examination, or were not admitted to hospital."

While this may not be such an important issue in cases of very mild traumatic brain injury, where the patient recovers within a few months, it may be helpful to explain the natural course of such injuries. Some patients may begin to worry that there is something seriously wrong with them, and explaining MTBI may help alleviate their concerns.

Voller B, Benke T, Benedetto K, et al. Neuropsychological, MRI and EEG findings after very mild traumatic brain injury. Brain Injury 1999;13(10):821-827.
Levin HS, Mattis S, Ruff RM, et al. Neurobehavioral outcome following minor head injury: a three-center study. Journal of Neurosurgery 1987;66:234-243.

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