Neuropsychological deficits in symptomatic minor head injury patients after concussion and mild concussion. Leininger BE, et al.

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Prior studies indicated that most minor head injury (MHI) patients one month postinjury do not have neuropsychological deficits. However, minor head injury experts point to evidence that a subgroup of patients who experience minor head injury (MHI) exhibit postconcussive symptoms and persistent neuropsychologic dysfunction. Nonetheless, crucial issues such as the relative effect of loss of consciousness on the development of neuropsychologic deficits had not previously been studied by minor head injury experts. This study was designed to determine whether minor head injuries (MHIs) accompanied by a loss of consciousness produce similar neuropsychologic deficits to injuries that result in dazing but no loss of consciousness.

In this study, “concussion” was defined as a brief loss of consciousness, and dazing, which is more formally known as “mild concussion,” was defined as acute disorientation or confusion with or without perceptible amnesia and no loss of consciousness. This investigation included only individuals who complained of continuing postconcussive symptoms at one or more months postinjury. Individuals who had a history of significant head trauma, substance abuse, or low academic achievement were excluded from the study. In addition, practice effects were avoided by testing patients and control subjects only once.
This investigation included 53 patients with minor head injury (MHI) and 23 control subjects. Of the 53 patients with minor head injury (MHI), 31 of them sustained a brief loss of consciousness, or “concussion.” The other 22 patients with minor head injury (MHI) experienced dazing injuries in which no loss of consciousness occurred. The two subgroups of minor head injury (MHI) patients compared favorably to each other with respect to age, race, years of education, mode of injury, for example, motor vehicle accident (MVA), time elapsed between injury and testing, and pursuit of claims for compensation. The control subjects were chosen for their similarity to the head injury patients on demographic and comparison variables.

Head injury patients and control subjects were tested with the vocabulary subtest from the Wechsler Adult Intelligence Scale-Revised (WAIS-R), which is relatively insensitive to acquired brain dysfunction. These groups obtained similar WAIS-R vocabulary scores. This and the aforementioned demographic variables suggested that the groups had a similar ability to perform the neuropsychologic battery barring the possibility of acquired brain dysfunction in the patient sample. Thus, the groups were then administered eight neuropsychologic tests that were selected for their sensitivity to brain dysfunction. These tests were: (1) WAIS-R Vocabulary and WAIS-R Digit Span, (2) Category Test, (3) the Trail Making Test: Part B, (4) Auditory Verbal Learning Test, (5) Complex Figure Test: Copy Trial, (6) Complex Figure Test: Memory Trial, (7) Controlled Oral Word Association (COWA), and (8) Paced Auditory Serial Addition Task-Revised (PASAT-R).
Results indicated that minor head injury (MHI) patients performed significantly poorer (P < 0.05) than control subjects on five of the eight neuropsychologic tests that included the Category Test, PASAT-R, Auditory Verbal Learning Test, and both copy and memory trials of the Complex Figure Test. The differences remained significant on four of the five aforementioned tests (all but the memory trial of the Complex Figure Test) when the multistage Bonferroni procedure to control for multiple comparisons was employed. Therefore, the authors concluded there was unequivocal evidence of neuropsychologic impairment in the minor head injury (MHI) patients. However, no significant differences between the concussion and mild concussion groups were obtained on any of the eight neuropsychologic tests. In addition, two series of analyses did not find a significant difference in neuropsychologic performance between patients tested within 3 months of injury and patients tested thereafter, nor between patients pursuing litigation versus those patients not pursuing litigation.
The authors conclude that minor head injury (MHI) patients who experience postconcussive symptoms 1 month postinjury and beyond demonstrate measurable neuropsychologic deficits, and the severity of these deficits are independent of whether the head injury was accompanied by a brief loss of consciousness or by dazing without a loss of consciousness. In addition, the authors note that there are four factors that are felt to have contributed to the magnitude of performance discrepancy between head injury patients and control subjects in this study compared to prior investigations. First, in this investigation, all patients suffered postconcussive symptoms at 1 month or more postinjury and, therefore, they were at greater risk for neuropsychologic deficits. Second, the percentage of MVA victims in this investigation is substantially higher than that reported in most previous studies of minor head injury (MHI). MVAs may possess greater opportunity for acceleration-deceleration injury than falls, sports injuries, and assaults. Third, this sample of patients may have exhibited higher levels of impairment than found in most prior studies, because these patients were injured during the third decade of life or later, and increasing age appears to be associated with poorer outcomes. Last, this investigation used tests that were sensitive to the variety of cognitive deficits associated with minor head injury (MHI) and eliminated practice effects that could be of unequal magnitude for patients and control subjects. Having said all of the above, attention should be focused on the early identification of neuropsychologic deficits in minor head injury (MHI) patients and the rehabilitation of these patients.

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