HEAD INJURY

Closed head injuries (CHI; nonpenetrating head injury produced by sudden acceleration/deceleration, as in motor vehicle crashes) often cause memory impairments. Both retrograde amnesia (RA) and difficulty in learning and retaining new information (anterograde amnesia) can result from CHI. Post-traumatic amnesia (PTA) refers to the symptom complex of anterograde amnesia, disorientation, and attentional disturbance during the initial stage of recovery, but dissociations can occur in some patients. Even after the abatement of PTA and RA, half of severe CHI victims suffer from residual impairments. (Russell, 1971).

The pathophysiologic contribution to residual memory disturbance is difficult to isolate because of the heterogeneity of many injuries associated with CHI, including primary and secondary causes of brain damage and confounding comorbidities such as alcohol abuse. However, several pathophysiologic features of CHI, including the Glasgow Coma Scale score (GCS) and duration of coma have been linked to memory deficit. Proximity of the sphenoidal ridges and bony protrusions on the base of the skull to the frontal cortex and the anterior temporal lobes makes these areas particularly vulnerable to diffuse CHI, often with superimposed focal lesions (Adams, 1975). Further, magnetic resonance spectroscopy (MRS) studies of persons after CHI reveal that neuroaxonal cellular damage to the frontal lobes may be present even within normal-appearing white matter (Garnett et al., 2000), a finding consistent with the weak correlation between visible structural damage revealed by conventional imaging techniques and performance on neuropsychological tests (Wilson et al., 1988).

Posttraumatic versus Retrograde

In contrast with the duration of PTA, which may exceed a week after severe CHI, memory loss associated with RA typically substantially resolves during the early stages of recovery. RA can initially extend backward several months from the time of injury but eventually shrinks to encompass only the minutes or seconds immediately before the injury. (Russell, 1971). During early recovery, RA frequently manifests backward displacement of temporal orientation far into the past (High, Levin, and Gary, 1990).

Residual Memory Disorders

The possible link between localized traumatic focal lesion and memory disorder is complicated by variation across patients in type and size of lesion. Nonetheless, recent research relating to specific memory deficits after CHI indicates that certain types of memory disorders are a more likely consequence than others, possibly reflecting the greater probability of frontal and temporal lobe damage after CHI.

Verbal and Nonverbal Learning

Adults and children who have had severe CHI and are in the postacute stages of injury are likely to show deficits in immediate and delayed. Many studies have found that individuals with severe CHI suffer from recognition impairment on tests of nonverbal memory that use abstract, nonverbalizable stimuli, drawings of nameable objects, and unfamiliar faces. Although deficient initial learning is common, accelerated forgetting has also occurred in a subgroup of CHI patients. Although most studies of verbal recall report reduction of memory span or other errors of omission after CHI, persons with severe CHI have frequent commission errors, including a high incidence of intrusions and perseverations.

Long-Term Memory, Semantic Knowledge

Although patients with CHI may have normal semantic knowledge, access to it is often slowed or difficult and may be qualitatively different than that of un-injured persons (Haut, 1991). CHI seems to cause impairment of the ability to use semantic information to facilitate recall in children and adults (Levin and Goldstein, 1986). Naming impairments, especially in relation to familiar people, sometimes coexists with accurate and specific semantic knowledge of the people that could not be named (Sunderland, Harris, and Baddeley, 1983). Impaired naming of familiar objects is also frequently present following CHI in adults (Levin, Grossman, and Kelly, 1977). For example, Levin, Grossman, and Kelly (1977) found impaired object naming in 40 percent of the fifty patients they studied in whom PTA had resolved.

Procedural Memory

Most procedural memory studies have focused on the acquisition of the knowledge to perform actions, rather than the systematic testing of loss or preservation of knowledge. Most studies have shown intact procedural learning, even when conjoined with impaired verbal learning (Timmerman and Brouwer, 1999).

Implicit Memory

Although studies directly comparing conscious learning (explicit tests of memory) to learning without conscious awareness (implicit tests of memory) in CHI patients are relatively sparse, findings suggest that implicit memory is more resistant to impairment after CHI than is explicit memory in both adults (Glisky, 1993) and children.

Prospective Memory

There has been little research on prospective memory—the intention to remember in the future—after CHI. Self-reports indicate that adult CHI patients report impaired prospective memory as opposed to uninjured adults. In studies using experimental tasks to investigate prospective memory in adults after CHI, impairments have been reported after short delay (Shum, Valentine, and Cutmore, 1999) but not long delay. Children with severe CHI also suffer impairment on experimental tasks of prospective memory.

Conclusion

Most studies of persons with CHI using verbal and nonverbal learning paradigms have found that learning impairment is a likely consequence of serious head injury. The magnitude of the impairment is related to the severity of the injury as determined by the GCS (Levin, Goldstein, High, and Eisenberg, 1988).

Bibliography

Adams, J. H. (1975). The neuropathology of head injury. In P. J. Binken and G. W. Bruyn, eds., Handbook of clinical neurology, Vol. 23. New York: Elsevier.

Garnett, M. R., Blamire, A. M., Rajagopalan, B., Styles, P., and Cadoux-Hudson, T. A. D. (2000). Evidence for cellular damage in normal-appearing white matter correlates with injury severity in patients following traumatic brain injury. A magnetic resonance spectroscopy study. Brain 123, 1,403-1,409.

Glisky, E. (1993). Computer-assisted instructions for patients with traumatic brain injury: Teaching of domain specific knowledge. Journal of Head Trauma Rehabilitation 7, 1-12.

Haut, M. W., Petros, T. V., Frank, R. G., and Haut, J. S. (1991). Speed of processing within semantic memory following severe closed-head injury. Brain and Cognition 17, 31-41.

High, W. H. J., Levin, H. S., and Gary, H. E. J. (1990). Recovery of orientation and memory following closed-head injury. Journal of Clinical and Experimental Neuropsychology 12, 703-714.

Levin, H. S. (1989). Memory deficit after closed head injury. Journal of Clinical and Experimental Neuropsychology 12, 129-153.

Levin, H. S., and Goldstein, F. C. (1986). Organization of verbal memory after severe closed-head injury. Journal of Clinical and Experimental Neuropsychology 8, 643-656.

Levin, H. S., Goldstein, F. C., High, W. H. J., and Eisenberg, H. M. (1988). Automatic and effortful processing after severe closed-head injury. Brain and Cognition 7, 283-297.

Levin, H. S., Grossman, R. G., and Kelly, P. J. (1977). Aphasic disorder in patients with closed head injury. Journal of Neurology, Neurosurgery and Psychiatry 39, 1,062-1,070.

Russell, W. R. (1971). The traumatic amnesias. New York: Oxford University Press.

Shum, D., Valentine, M., and Cutmore, T. (1999). Performance of individuals with severe long-term traumatic brain injury on time-, event-, and activity-based prospective memory tasks. Journal of Clinical and Experimental Neuropsychology 21, 49-58.

Sunderland, A., Harris, D., and Baddeley, A. D. (1983). Do laboratory tests predict everyday memory? A neuropsychological study. Journal of Verbal Learning and Verbal Behavior 22, 341-357.

Timmerman, M. E., and Brouwer, W. H. (1999). Slow information processing after very severe closed-head injury: Impaired access to declarative knowledge and intact application and acquisition of procedural knowledge. Neuropsychologia 37, 467-478.

Wilson, J. T., Wiedmann, K. D., Hadley, D. M., Condon, B., Teasdale, G., and Brooks, D. N. (1988). Early and late magnetic resonance imaging and neuropsychological outcome after head injury. Journal of Neurology, Neurosurgery and Psychiatry 51, 391-396.

Harvey S.Levin

Revised byGerriHanten

andHarvey S.Levin