Subtle neuropsychological deficits in patients with good recovery after closed head injury

Attentional deficits following closed-head injury

Aimed to assess, in the light of current attentional theories, the nature of the attentional deficit in a group of severely traumatically head-injured subjects, relative to a group of orthopaedic rehabilitation patients, and to establish which neuropsychological measures best reflected the deficit. Three separate studies were conducted in order to meet these aims. The first study focused on selective attention; the second, on vigilance or sustained attention; the third, on the Supervisory Attentional System. Results provided no evidence for the presence of deficits of focused attention, sustained attention, or supervisory attentional control, but ample evidence for the presence of a deficit in speed of information processing. Those neuropsychological measures shown to be the best measures of this deficit included the Symbol Digit Modalities Test, simple and choice reaction-time tasks, colour naming and word reading scores on the Stroop, and the Paced Auditory Serial Addition Test.

Early and late outcome in head injury patients with radiological evidence of brain damage

This study examined the early and late outcome in head injury patients with focal or multifocal (unilateral or bilateral) brain contusions revealed by computerized tomography (CT) scanning. The outcome was also evaluated in patients hospitalized due to brain concussion. Three months after the injury (the early outcome) 43% of the 86 cases with multifocal contusions on the CT scan were dead. As evaluated by the Glasgow Outcome Scale, all the 57 patients with a focal brain contusion, as well as the 117 cases with brain concussion, made a good recovery or were moderately disabled. The late outcome (1 to 5 years after injury) was evaluated in 78 cases with brain contusion and in 85 cases with brain concussion, and revealed that complaints and impaired adaptive functioning were frequent in both the contusion and concussion group. The occurrence of headache, dizziness and sleep problems did not significantly differ among the various head injury groups. However, focal or multifocal brain contusions on the CT scan increased the frequency of impaired memory, impaired concentration, speech problems, weakness in arms or legs and seizures with loss of consciousness. Cognitive deficits and speech problems were particularly common in patients with a focal contusion in the temporal lobe. The late adaptive and social functioning were most markedly impaired in cases with multifocal bilateral contusions.

Enduring suppression of hippocampal long-term potentiation following traumatic brain injury in rat

This study investigated changes in synaptic responses (population spike and population EPSP) of CA1 pyramidal cells of the rat hippocampus to stimulation of the Schaffer collateral/commissural pathways 2-3 h after traumatic brain injury (TBI). TBI was induced by a fluid percussion pulse delivered to the parietal epidural space resulting in loss of righting responses for 4.90-8.98 min. Prior to tetanic stimulation, changes observed after the injury included: (1) decreases in population spikes threshold but not EPSP thresholds; (2) decreases in maximal amplitude of population spikes as well as EPSPs. TBI also suppressed long-term potentiation (LTP), as evidenced by reductions in post-tetanic increases in population spikes as well as EPSPs. Since LTP may reflect processes involved in memory formation, the observed suppression of LTP may be an electrophysiological correlate of enduring memory deficits previously demonstrated in the same injury model.

Cognitive test performances related to early and late computed tomography findings after closed-head injury

Computed tomography (CT) findings from early (less than 24 hours) and late scan (6 months) after closed-head injury (CHI) were compared to cognitive test scores obtained on an average of 4 months after injury in a consecutive series of 53 patients. The presence of parenchymal lesion was associated with poor test results, indicating cognitive inflexibility and disinhibition of routine response tendencies in novel tasks. These deficits have previously been found to be related in particular to frontal-lobe dysfunction, but the present study did not support the hypothesis that frontal lesion is the principal cause of this impairment in CHI. Parenchymal lesions in the right and left hemisphere were associated with spatial and verbal deficits, respectively. Ventricular enlargement in the late CT was related to cognitive inefficiency, both being strongly associated with age. The results suggest that parenchymal lesion in the early CT is an indicator of diffuse axonal injury, which results in cognitive inflexibility during recovery.

Cognitive deficits after rupture and early repair of anterior communicating artery aneurysms

In a retrospective follow-up study covering a time period of four years 18 patients operated upon early for an aneurysm of the anterior communicating artery (ACoA) and a control group of 21 patients with aneurysmal subarachnoid haemorrhage (SAH) from other sources than ACoA aneurysm and 9 patients with SAH of nonaneurysmal origin were subjected to neuropsychological examination. Both groups were comparable in their neurological condition on admission and in the severity of bleeding seen on CT-scan. Testing included memory functions, concentration, logical and spatial thinking, a Stroop-test, an aphasia screening test and a complex choice reaction task. Patients with SAH of a ruptured ACoA aneurysm did not differ significantly from the control group in any of the tests used. But there was a trend for the ACoA patients to have more memory problems than the patients with SAH of other origins. On the other hand the patients in the control group with aneurysmal SAH of other locations and with non-aneurysmal SAH had not significantly more problems with concentration and aphasia than the patients with ruptured ACoA aneurysm. These results, which differ from the common opinion of frequent occurrence of memory deficits in ACoA aneurysms are interpreted as a consequence of the changes in improved pre-, intra- and postoperative management in modern neurosurgery.

Performance in the Stroop color word test in relationship to the persistence of symptoms following mild head injury

There is much controversy about whether the persistence of postconcussive symptoms (PCS) in mild head injured patients (MHI) is related to the presence of cognitive deficits. Most studies performed so far have relied on normal non-concussed control subjects rather than directly comparing patients with and without PCS following MHI. In addition, subtle cognitive deficits may be present in MHI patients that are demonstrable only with more demanding cognitive tasks. In the present study the Stroop Color Word Interference Test together with a more demanding modified interference subtask was administered to two groups of patients with uncomplicated MHI 10 days, 5 weeks and 3 months after the injury. Ten patients with persistent symptoms at 3 months were selected and individually matched with MHI patients who had initially reported symptoms but who had recovered by 3 months. The scores of the two retrospectively defined groups were compared at the different time points. Between-subjects analysis revealed overall differences for both the original and modified color word interference subtask. Within-subject analysis indicated that only the recovery rate in the modified interference subtask was significantly different between the two groups. The observation that there was a parallel trend between recovery and persistence of PCS and performance on the cognitive interference measures supports the notion that there is a functional relationship between these two phenomena.

Cognitive deficits following traumatic brain injury produced by controlled cortical impact

Traumatic brain injury produces significant cognitive deficits in humans. This experiment used a controlled cortical impact model of experimental brain injury to examine the effects of brain injury on spatial learning and memory using the Morris water maze task. Rats (n = 8) were injured at a moderate level of cortical impact injury (6 m/sec, 1.5-2.0 mm deformation). Eight additional rats served as a sham-injured control group. Morris water maze performance was assessed on days 11-15 and 30-34 following injury. Results revealed that brain-injured rats exhibited significant deficits (p less than 0.05) in maze performance at both testing intervals. Since the Morris water maze task is particularly sensitive to hippocampal dysfunction, the results of the present experiment support the hypothesis that the hippocampus is preferentially vulnerable to damage following traumatic brain injury. These results demonstrate that controlled cortical impact brain injury produces enduring cognitive deficits analogous to those observed after human brain injury.

Long-term neuropsychological outcome after severe head injury with good recovery

The quality of outcome after severe closed head injury has become of increasing concern to neurosurgeons. The assessment of residual deficits in patients who have recovered from closed head injury can be very difficult. Many patients are classified as having a good recovery according to the Glasgow Outcome Scale (GOS), but this may be insufficiently focused or sensitive to demonstrate mental deficits objectively. We investigated 33 patients with severe closed head injury who subsequently were diagnosed as having made a good recovery according to the GOS. The severity of the injury was determined by the Glasgow Coma Scale (GCS) and by the presence of a midline shift in the preoperative CT scans. There was a minimal interval of 15 months (means = 1080.5 days, SD = 491 days) between injury and time of neuropsychological testing. Their performance was compared with that of 15 orthopaedic cases. Residual neuropsychological deficits can be demonstrated on the majority of measures in a group of patients who have achieved good recovery on the GOS. Midline shift in preoperative CT scans is not of prognostic value for long-lasting neuropsychological deficits.

Sustained attention following mild closed-head injury

The sustained-attention performance of patients with mild closed-head injury (CHI) was examined within one month of injury using a high-event rate, digit-discrimination vigilance task with two levels of stimulus degradation (undegraded, highly degraded). Under undegraded stimulus conditions, vigilance performance for mild CHI subjects, uninjured case-matched control subjects, and college students was highly accurate and remained so across the entire task period. When stimuli were presented in degraded fashion, however, all three groups showed a similar decline over time (i.e., vigilance decrement) in hit rates and d' scores. Although mild CHI did not lead to a greater rate of deterioration in vigilance performance in the degraded stimulus condition, it did produce lower overall levels of sensitivity (d') in target detection. These results suggest that, during the first month after mild CHI, vigilance performance is unimpaired under normal task conditions, but may fall short under task conditions that require sustained effortful processing. These findings join a growing body of evidence showing that mild CHI can lead to measurable deficits in cognitive functioning.

Question-asking strategies after severe closed head injury

This investigation examined problem solving behaviors in survivors of severe closed head injury. Fourteen patients and 10 neurologically intact controls were administered the Twenty Questions procedure, requiring them to guess items the examiner was thinking of in a picture array. Relative to controls, survivors required more trials to guess the items and utilized a strategy characterized by attention to the individual pictures rather than to their shared conceptual features. The importance of problem solving impairments to neurobehavioral outcome after head injury is discussed.

The relationship between intelligence and memory following minor or mild closed head injury: greater impairment in memory than intelligence

This study investigated the performance of patients with minor or mild closed head injury and age/education-matched normal controls on the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the Wechsler Memory Scale-Revised (WMS-R). The results demonstrated that the control group had significantly higher scores than the patients with closed head injury on all WAIS-R and WMS-R index scores. Further analysis revealed that the patients with closed head injury showed a greater impairment in delayed memory when directly compared to intellectual performance that was not seen in the control group. These results are discussed in relation to findings in patients with more severe closed head injury, the construction of the WAIS-R and the WMS-R, and the performance patterns of the two groups.

The psychological treatment of memory impairment: a review of empirical studies

Memory impairment is a frequent effect of many different forms of brain dysfunction. Memory impairment is also a frequent focus of treatment interventions, and there have been many different treatment methods suggested. The suggested methods include direct retraining, the use of spared skills in compensating for the impairment (alternate functional systems), and the use of behavioral strategies to circumvent the manifest memory dysfunction (behavioral prosthetics). Unfortunately, there are very few studies comparing the various suggested treatment methods. The present paper evaluates the empirical evidence related to the treatment of memory dysfunction and suggests directions for future investigations. Although the evidence is not conclusive, it appears that some forms of treatment may be helpful in remediating certain types of memory impairment. An approach likely to be productive would include some consideration of the impaired neurological and psychological mechanisms responsible for the manifest memory deficit as well as a consideration of the etiology of the injury thought to be causally related to the memory deficit. As yet, there have been no rigorous empirical evaluations of these considerations.

Prolonged memory impairment in the absence of hippocampal cell death following traumatic brain injury in the rat

Prolonged neurological dysfunction that results from an insult to the brain is often attributed to irreversible structural damage such as loss of neurons or axonal degeneration. For example, following cerebral ischemia even partial hippocampal CA1 neuronal loss has been proposed to be sufficient to result in deficits in hippocampal dependent spatial memory. This study examined if hippocampal CA1 neuronal loss and/or axonal injury was necessary to produce prolonged spatial memory deficits resulting from traumatic brain injury (TBI). Prior to TBI Sprague-Dawley rats were trained on an 8-arm radial maze, a task sensitive to detecting specific lesions of the hippocampus or its extrinsic connections. Following a mild, moderate, or sham injury, rats were tested for working and reference memory for 25 days. After 25 days of maze testing, histological cell counts were made from consistent coronal sections of the mid-dorsal hippocampus. Rats subjected to mild or moderate TBI manifested working memory deficits for 5 and 15 days, respectively, after injury in the absence of overt (all brain regions) or quantitative (CA1 only) evidence of neuronal death. The number of CA1 pyramidal neurons of representative sections of the mid-dorsal hippocampi for injured maze-deficit rats and sham control rats were: 1626 (S.E.M. = +/- 66) and 1693 (S.E.M. = +/- 69) per 10(6) micron2, respectively. Additionally, no overt evidence of axonal injury was observed in any forebrain structure including major intrinsic or extrinsic connecting hippocampal pathways. These data strongly suggest that mild to moderate TBI is capable of producing prolonged spatial memory deficits in the rat without evidence of either neuronal cell death in the intrinsic hippocampus or overt axonal injury in hippocampal pathways.

The recall of prose as a function of importance following closed head injury

Closed head injury (CHI) results in significant memory dysfunction. Although the disabling aspects of memory impairment after CHI have been recognized, little attention has been focused on the theoretical nature of these memory problems. A means of examining semantic sensitivity to the importance of the ideas presented in the Wechsler Memory Scale-Revised Logical Memory subtest was developed. Subjects with CHI were sensitive to the semantic structure of the stories, but lost more important information at a faster rate than controls. Differences in recall, dependent on the passage, suggested that the two stories in the Wechsler Memory Scale-Revised are not equivalent.

Memory deficit after closed head injury

This paper reviews research concerning impairment of memory during the early and late stages of recovery from closed-head injury (CHI). Posttraumatic and retrograde amnesia are discussed, including direct measurement, rate of forgetting and evoked potential correlates. Studies of residual memory deficit in survivors of CHI are reviewed, including the effects of severity and chronicity of injury and features such as utilization of semantic features to guide recall. The evidence for relatively preserved motor and pattern analyzing skills after severe CHI is presented and the implications for rehabilitation are discussed.

Reaction time after head injury: fatigue, divided and focused attention, and consistency of performance

Three groups of patients who had suffered head injury were compared with matched control subjects on reaction time (RT) tasks. Group I consisted of outpatients previously hospitalised for head injury of wide ranging degrees of severity, assessed at varying intervals after injury. Group II was composed of non-hospitalised mildly concussed patients. Group III was made up of head injured patients of varying degrees of severity assessed 7-10 months after initial hospitalisation for their injury. The reaction time tests were graded in difficulty, from a simple RT response to a complex choice RT test. In addition, subjects were compared in their ability to ignore redundant information during one of the choice RT tests. The findings indicate that traumatic brain injury causes slower information processing, deficits in divided attention, an impairment of focused attention, and inconsistency of performance.

Traumatic brain injury, aging and reaction time

The effects of traumatic brain injury (TBI) and aging were compared on tests of simple and complex reaction time (RT). Simple RT was not significantly affected by aging or TBI. TBI patients, however, tended to be slower on Simple RT tasks, and had a larger standard deviation. Individuals over age 60 and patients of any age with TBI demonstrated slower RT with choice RT tests. In addition, both groups (those over 60 and TBI patients) were less able than other groups to inhibit the processing of redundant information. For the TBI patients, this occurred primarily on reassessment. These results suggest that the deficit in both aging and TBI is not only a generalized neuronal slowing but a more specific impairment in attentional control processes, exhibited as a deficit in focused attention.

Memory disorder related to coma duration after head injury

The relationship of memory and intelligence test performances to coma duration was studied in 51 head injured patients who had not been operated on for intracranial haematoma. Memory defect was related to coma duration, and was not secondary to impaired perceptual or conceptual analysis of the material to be remembered.

Disproportionately severe memory deficit in relation to normal intellectual functioning after closed head injury

The presence of disproportionate memory impairment with relatively preserved intellectual functioning was examined in 87 survivors of moderate or severe closed head injury. Approximately one-fourth of the patients tested at 5 to 15 and/or 16 to 42 months after injury manifested defective memory on both auditory and pictorial measures despite obtaining Wechsler Verbal and Performance Intelligence Quotients within the average range. The findings indicate that disproportionately severe memory deficit persists in a subgroup of closed head injured survivors which is reminiscent in some cases of the amnesic disturbance arising from other causes. Evaluation of long term memory in relation to cognitive ability could potentially identify important distinctions for prognosis and rehabilitation in head injured patients.

Influence of injury severity on quality of survival after head injury

The relationship between severity of injury [as determined by the Glasgow Coma Scale (GCS)] and the quality of survival (as determined by neuropsychological measurements and work return) were investigated in 54 conscious survivors within 16 months following head injury. While severely head injured (GCS less than or equal to 8) patients had more neuropsychological impairments in areas of intelligence, attention, memory, visuomotor speed, and motor skills than those with mild injuries (GCS greater than 8), performances after both types of injury were below normative levels in areas of learning, memory, and visuomotor speed. Unemployment increased after both severe and mild injuries, while employment status changed more frequently after severe injuries. Age had a minimal effect on neuropsychological and employment outcomes after minor head injuries (GCS greater than 13). The findings suggest that regardless of acute severity, closed head injury influences long-term quality of survival.

Late post-concussional symptoms in traumatic head injury. An analysis of frequency and risk factors

During follow-up of 485 adult patients with traumatic head injury, 51% of the patients reported new post-concussional symptoms after an observation period of 3-5 years (mean 4.0 years). Most data, including the level of consciousness on admission, length of post-traumatic amnesia and days of hospitalization were poor parameters for predicting which patients would suffer late complications. A few variables were statistically of predictive importance: Sex, repeated head injury and skull fracture. Age was a risk factor for multiple complaints.

Relation of visual field defects to neuropsychological outcome after closed head injury

Neuropsychological outcome within two years after injury was determined in 159 head injured patients who were classified into three groups according to the presence of either unilateral, bilateral, or no visual field defects (VFDs). The VFDs occurred irrespective of injury severity as determined by the Glasgow coma scale, or social outcome as determined by the Glasgow outcome scale. Differences among the three visual field groups were obtained for several neuropsychological functions: intelligence, memory, learning, acquired verbal skills, visuospatial skills, and visuomotor speed. Patients with bilateral VFDs were more severely impaired neuropsychologically than those with unilateral or no VFDs. Occurrences of secondary complications (brain swelling, intracranial hypertension, and hyperemia) were more prevalent among the bilateral VFD cases. The findings suggested that bilateral VFDs may be indicators of increased brain damage from secondary insults.

Programs to produce high quality dichotic tapes for central auditory testing

Dichotic stimulation, the simultaneous presentation of two different acoustic signals to the right and left ears, respectively, is used routinely in the clinical assessment of speech lateralization as well as in other central auditory testing procedures in the clinic and laboratory. At present, most researchers and clinicians depend on a few commercial sources for dichotic tapes, because there are a limited number of facilities which are able to produce such tapes. Moreover, some of the commercial tapes currently offered for sale contain important stimulus errors. In the present paper, we describe a general set of programs for the PDP 11 series of computers, which permits sequences of dichotic stimuli to be generated and output with a high degree of precision. These programs therefore allow researchers to generate any desired sequence of dichotic stimulation, for recording and taping, for use in their research. The programs operate in two stages to generate the required dichotic sequences. In the first stage, the constrained random ordering of the stimuli is generated as specified by the user. In the second stage, after the preliminary stimulus preparation has been completed (for example, using a waveform editing package; cf., D.G. Jamieson and D. A. Naugler, Comput. Biomed. Res., 1985, 18, 480), an audio tape is generated with stimuli presented dichotically, with timing and sequencing precisely as specified.