Magnetic resonance imaging in acute head injury

Deficits in comprehension of speech acts after TBI: The role of theory of mind and executive function

Theory of mind (ToM) is critical to effective communication following traumatic brain injury (TBI) however, whether impairments are specific to social cognition, or reflective of executive demands is unclear. This study examined whether ToM impairments are predicted by executive function difficulties using everyday conversation tasks. Twenty-five individuals with severe-TBI were compared to 25 healthy controls on low- and high-ToM tasks across four conditions: (1) low cognitive load, (2) high flexibility, (3) high working memory (WM) and (4) high inhibition. TBI individuals were impaired on high-ToM tasks in the WM condition. When the WM demands of the task were controlled, the impairments were no longer apparent. TBI individuals were not impaired on high-ToM tasks in the inhibition and flexibility conditions, suggesting these tasks may not have been sufficiently demanding of ToM abilities. The results suggest that ToM impairments in everyday communication may arise due to WM demands, in individuals with TBI.

Visuospatial Learning in Traumatic Brain Injury: An Examination of Impairments using the Computerised Austin Maze Task

An important aspect of cognitive functioning that is often impaired following traumatic brain injury (TBI) is visuospatial learning and memory. The Austin Maze task is a measure of visuospatial learning that has a long history in both clinical neuropsychological practice and research, particularly in individuals with TBI. The aim of this study was to evaluate visuospatial learning deficits following TBI using a new computerised version of the Austin Maze task. Twenty-eight individuals with moderate-to-severe TBI were compared to 28 healthy controls on this task, together with alternative neuropsychological measures, including the WAIS-III Digit Symbol and Digit Span subtests, the Trail Making Test, WMS-III Logical Memory, and Rey Osterrieth Complex Figure Test. The results demonstrated that TBI individuals performed significantly more poorly on the Austin Maze task than control participants. The Austin Maze task also demonstrated good convergent and divergent validity with the alternative neuropsychological measures. Thus, the computerised version of the Austin Maze appears to be a sensitive measure that can detect visuospatial learning impairments in individuals with moderate-to-severe TBI. The new computerised version of the task offers much promise in that it is more accessible and easier to administer than the conventional form of the test.

Impairments in social cognition following severe traumatic brain injury

Severe traumatic brain injury (TBI) leads to physical, neuropsychological, and emotional deficits that interfere with the individual’s capacity to return to his or her former lifestyle. This review focuses on social cognition, that is, the capacity to attend to, recognize and interpret interpersonal cues that guide social behavior. Social cognition entails ‘‘hot’’ processes, that is, emotion perception and emotional empathy and ‘‘cold’’ processes, that is, the ability to infer the beliefs, feelings, and intentions of others (theory of mind: ToM) to see their point of view (cognitive empathy) and what they mean when communicating (pragmatic inference). This review critically examines research attesting to deficits in each of these domains and also examines evidence for theorized mechanisms including specific neural networks, the role of simulation, and non-social cognition. Current research is hampered by small, heterogeneous samples and the inherent complexity of TBI pathology. Nevertheless, there is evidence that facets of social cognition are impaired in this population. New assessment tools to measure social cognition following TBI are required that predict everyday social functioning. In addition, research into remediation needs to be guided by the growing empirical base for understanding social cognition that may yet reveal how deficits dissociate following TBI.

Emotion Perception and Alexithymia in People With Severe Traumatic Brain Injury: One Disorder or Two? A Preliminary Investigation

Primary objective:Recent research studies attest to the presence of deficits in emotion perception following severe traumatic brain injury (TBI). Additionally, a growing number of studies report significant levels of alexithymia (disorder of emotional cognition) following TBI. This research aimed to examine the relation between the two, while assessing the influence of posttraumatic stress disorder (PTSD).Design:Cross-sectional study examining levels of alexithymia, emotion perception disorders and PTSD and their association, in 20 people with severe, chronic TBI and 20 adults without brain injuries.Methods:Participants were assessed on the Toronto Alexithymia — 20 Scale, the Posttraumatic Diagnostic Scale and on two emotion perception tasks: matching and labelling of photos depicting the 6 basic emotions.Results:The group with TBI were impaired relative to controls when matching facial expressions. Their performance on ‘fear’ was especially poor. Performance on labelling was similar in pattern, although failed to reach significance. There was no association between poor performance on fear, or other negative expressions, and either PTSD or alexithymia symptoms in the TBI group.Conclusions:Alexithymia, as assessed by the TAS-20, taps a constellation of difficulties that do not appear to include difficulties with emotion perception in people with traumatic brain injuries.

Loss of emotional experience after traumatic brain injury: Findings with the startle probe procedure

The authors used affective modulation of the eyeblink startle response to examine the impact of traumatic brain injury (TBI) on emotional reactions to pictures. Participants were 13 individuals with severe TBI and 24 controls. Participants were presented with pictures that differed in affective valence (e.g., mutilated bodies, erotic couples, and household objects) while the eyeblink startle response to an acoustic probe was measured. Startle amplitude was used to assess valence of emotional response, and startle latency was used to index interest in the pictures. Subjective ratings of the affect and arousal elicited by the various pictures were also obtained. TBI impaired startle potentiation to unpleasant pictures but not startle attenuation to pleasant pictures. Further, subjective ratings indicated that TBI participants found unpleasant pictures less arousing than did controls. The results are consistent with recent evidence of differential impairment in negative versus positive emotions after TBI and are discussed in relation to 2 competing explanations of startle modulation.

Abnormalities on magnetic resonance imaging seen acutely following mild traumatic brain injury: correlation with neuropsychological tests and delayed recovery

Mild traumatic brain injury (MTBI) is a common reason for hospital attendance and is associated with significant delayed morbidity. We studied a series of 80 persons with MTBI. Magnetic resonance imaging (MRI) and neuropsychological testing were used in the acute phase and a questionnaire for post-concussion syndrome (PCS) and return to work status at 6 months. In 26 subjects abnormalities were seen on MRI, of which 5 were definitely traumatic. There was weak correlation with abnormal neuropsychological tests for attention in the acute period. There was no significant correlation with a questionnaire for PCS and return to work status. Although non-specific abnormalities are frequently seen, standard MRI techniques are not helpful in identifying patients with MTBI who are likely to have delayed recovery.

[Multimodal monitoring of head injuries in children]

As in the case of adults, there are three main goals in the monitoring of severe head trauma in children: to prevent or minimize the apparition of secondary lesions, to optimize treatment, to help make precise prognosis. The basic monitoring is composed of repeated clinical examinations, brain radiological imaging and control of vital parameters (blood pressure, temperature, PaO2 (SpO2), PaCO2 (FETCO2), haemoglobin, haematocrit. On the other hand, during specific brain monitoring, the brain perfusion (TCD, intracranial pressure), the electrical activity of the brain and sometimes the brain oxygenation (SvjO2) are controlled. The data obtained from the brain monitoring must always be interpreted carefully. A child with a severe head trauma, in ICU, always requires constant and competent medical attention.

Diffusion-weighted imaging demonstrates transient cytotoxic edema involving the corpus callosum in a patient with diffuse brain injury

Reversible T2 hyperintense signal abnormality in the corpus callosum, although frequently seen after diffuse brain injury, has not been well clarified. With some accumulated evidence, we report a case of diffuse brain injury in a 24-year-old man. Magnetic resonance imaging (MRI) demonstrated T2 hyperintense signals in the trunk and the splenium of the corpus callosum 12 days postinjury. Echo-planar diffusion-weighted imaging was also performed on the same day, which revealed decreased diffusion (hyperintense signals) in the same site and almost the same size as T2 hyperintense signals. T1-weighted images were normal. Neuropsychological examination of the patient did not show callosal syndrome, namely hemialexia, unilateral agraphia and unilateral apraxia. Repeat MRI on day 20 demonstrated a signal decrease of both T2-weighted images and diffusion-weighted images (DWI) in the lesion. Follow-up MRI at 6 months showed complete resolution of the T2 signal abnormalities and of the corresponding decreased diffusion. Considering that diffusion-weighted imaging showed transient decreased diffusion, the lesion in the corpus callosum indicated the existence of cytotoxic edema. Also, transient DWI hyperintensity, namely cytotoxic edema, in the trunk and the splenium of the corpus callosum does not necessarily reveal callosal deficits.

Technical report: minor head injury in children

Minor head trauma affecting children is a common reason for medical consultation and evaluation. In order to provide evidence on which to base a clinical practice guideline for the American Academy of Pediatrics, we undertook a systematic review of the literature on minor head trauma in children.

METHODS

Medline and Health databases were searched for articles published between 1966 and 1993 on head trauma or head injury, limited to infants, children, and adolescents. Abstracts were reviewed for relevance to mild head trauma consistent with the index case defined by the AAP subcommittee. Relevant articles were identified, reviewed, and abstracted. Additional citations were identified by review of references and expert suggestions. Unpublished data were also identified through contact with authors highlighting child-specific information. Abstracted data were summarized in evidence tables. The process was repeated in 1998, updating the review for articles published between 1993 and 1997.

RESULTS

A total of 108 articles were abstracted from 1033 abstracts and articles identified through the various search strategies. Variation in definitions precluded any pooling of data from different studies. Prevalence of intracranial injury in children with mild head trauma varied from 0% to 7%. Children with no clinical risk characteristics are at lower risk than are children with such characteristics; the magnitude of increased risk was inconsistent across studies. Computed tomography scan is most sensitive and specific for detection of intracranial abnormalities; sensitivity and specificity of skull radiographs ranged from 21% to 100% and 53% to 97%, respectively. No high quality studies tested alternative strategies for management of such children. Outcome studies are inconclusive as to the impact of minor head trauma on long-term cognitive function.

CONCLUSIONS

The literature on mild head trauma does not provide a sufficient scientific basis for evidence-based recommendations about most of the key issues in clinical management. More consistent definitions and multisite assessments are needed to clarify this field.

Comparative use of magnetic resonance imaging and electrophysiologic investigation for the prognosis of head injury

BACKGROUND

To compare magnetic resonance imaging (MRI) and electrophysiologic investigation as prognostic methods in acute head injury.

METHODS

Fifty-seven patients suffering moderate to mild (Glasgow Coma Scale score > 8) or severe (Glasgow Coma Scale score < 8) head injury were included. Both groups were analyzed as a total and separately for outcome as assessed by Glasgow Outcome Score. Two outcome groups were separated (Glasgow Outcome Score 1-3: unfavorable vs. Glasgow Outcome Score 4-5: favorable). MRI scans (T1-, T2-, T2*-sequences; transverse, coronal, and sagittal slices) were obtained 1 to 39 days after trauma (mean, 14 days). Electrophysiologic investigations consisted of median nerve-evoked somatosensory responses to assess corticosubcortical function and brain stem auditory-evoked potentials and brain stem reflexes for brain stem function. Recordings were performed 24 to 72 hours after trauma and repeated every 3 to 5 days.

RESULTS

Evaluation of all patients revealed a prognostic significance of MRI lesions within the corpus callosum, the basal ganglia, the hippocampus, the midbrain, and the pons. In the severe head injury subgroup, significance was limited to lesions within the corpus callosum, the basal ganglia, and the midbrain. Among the electrophysiologic findings, dysfunction of the corticosubcortical region as well as of the midbrain were linked to an unfavorable outcome. In severe head injury, prognostic significance was restricted to bilateral corticosubcortical dysfunction. A statistical test for diagnostic convergence of both methods indicated a distinct convergence only for lesions of the midbrain and the pons.

CONCLUSION

MRI scans performed early after head injury provide several indicators for unfavorable outcome. Electrophysiologic investigations add to this prognostic evidence. Both methods have comparably high specificity. However, because of the higher density of prognostic information obtained, MRI seems superior to electrophysiologic testing.

Neuropsychological consequences of two patterns of brain damage shown by MRI in survivors of severe head injury

Two subgroups of patients were identified from 48 patients with traumatic head injury who had MRI during the acute stage: (a) those with severe diffuse injury--six patients with lesions in both the corpus callosum and the brain stem; (b) those with severe focal injury--16 patients with extensive frontotemporal lesions. Most patients with diffuse injury were in a coma on admission to hospital, whereas most patients with focal injury were out of coma. Duration of post-traumatic amnesia was prolonged in both groups. Patients were followed up at six months after injury, when a battery of neuropsychological tests was given. Patients with both diffuse and focal patterns of injury were impaired by comparison with controls on a range of measures, including tests of memory and attention. The findings contrast with the view that diffuse injury is of much greater importance than focal injury in determining outcome after head injury.

Post-traumatic amnesia: still a valuable yardstick

Records of coma and post-traumatic amnesia (PTA) were collected for a group of 38 patients with closed head injury. The results confirmed earlier studies indicating that patients may have short or negligible coma but report prolonged PTA. Comparison of eight patients with prolonged PTA (> 7 days) and short coma (< 6 hours) with the rest of the group on MRI in the acute stage showed that these patients had significantly more extensive hemispheric damage. In the group as a whole both coma and PTA were related to the number of areas in central brain structures in which lesions were detected, but only PTA was significantly related to the number of hemispheric areas in which lesions were found. It is concluded that although both coma and PTA are related to brain damage they reflect disparate patterns of lesions. Assessment of PTA can thus provide additional information concerning severity of injury.

Late MRI after head injury in children: relationship to clinical features and outcome

To characterize the brain pathology in relation to long-term outcome after pediatric head injury, 55 children were studied by magnetic resonance imaging (MRI) at least 3 months after sustaining moderate to severe closed head injury (CHI). Thirty-nine of the patients had abnormal signal intensity consistent with residual brain lesions, including 28 children with lesions involving the frontal lobes. The clinical features of children with frontal lesions, extrafrontal lesions, and diffuse injury were compared. The analysis disclosed that children with frontal lobe lesions were more frequently disabled than children who sustained diffuse injury. Our MRI findings indicate that residual brain lesions are more common after moderate to severe CHI in children than previously thought and that the frontal lobes are most frequently involved. Further investigation is indicated to elucidate whether distinctive cognitive and behavioral sequelae are associated with frontal lobe lesions in children.

Intercorrelation of lesions detected by magnetic resonance imaging after closed head injury

Forty-three patients with closed head injuries were followed up 5 to 12 months post-injury. Patients had magnetic resonance imaging (MRI) and performed a variety of neuropsychological tests. There were systematic relationships between lesions in different sites: depth of lesions in orbito-frontal regions, frontal regions, and temporal poles were particularly strongly intercorrelated. Depth of lesions in specific sites also correlated with an overall measure of brain damage: the number of areas with lesions present. After correcting for premorbid differences there were significant correlations between lesions in specific sites and scores on three out of five WAIS subtests. Scores on these three subtests also correlated significantly with overall brain damage. In general, hemispheric sites which were significantly related to neuropsychological measures also showed significant intercorrelations among themselves. The findings stress the importance of patterns of lesions in head injury, and emphasize the difficulty of showing differential localization of cerebral function in this population.

Gadolinium DTPA enhanced magnetic resonance imaging in acute head injury

We studied the effect of contrast enhancement on magnetic resonance imaging (Gadolinium DTPA Magnetic Resonance) in 10 patients with a recent head injury. The use of contrast did not increase the number of traumatic lesions identified and we did not detect evidence of altered blood brain barrier permeability in any of the 7 patients, who had a total of 27 lesions, imaged between one and 4 days after injury. Enhancement was found in each of 3 patients imaged 6 or more days after injury. These findings suggest that traumatic cortical and intraparenchymal lesions are not associated with increased cerebrovascular permeability within the first 96 hours of a head injury.

Diagnostic capabilities of magnetic resonance imaging and computed tomography in acute cervical spinal column injury

The present study was conducted to evaluate the imaging capabilities of magnetic resonance imaging (MRI) in evaluating acute cervical spinal column injury and compare these results to that of computed tomographic (CT) imaging. Forty-nine patients undergoing MRI at a Level I and regional spinal cord trauma center to evaluate cervical spinal column injury were studied. Seventy-one injuries were identified by MRI. These injuries were classified as osseous (fracture/dislocation) (n = 21), disc herniation (n = 29), and spinal cord injury (edema/contusion/transection) (n = 21). Diagnostic imaging results in 33 of the 49 patients undergoing both MRI and CT were compared. CT demonstrated 22 fracture/dislocations compared to 10 on MRI. MRI demonstrated 19 disc protrusions compared to 7 on CT. Additionally, MR imaged 13 cord injuries as compared to 0 by CT. MR imaging proved superior in demonstrating spinal cord pathology and intervertebral disc herniation. CT was superior to MRI in demonstrating osseous injury. CT and MRI may be useful together in determining presence and extent of spinal column injury.

Magnetic resonance imaging in clinical psychiatry

Although psychiatric researchers have been quick to adopt magnetic resonance imaging (MRI) of the brain in their investigations, its clinical application has been slow to develop and most psychiatrists remain unaware of its potential advantages and disadvantages compared with CT scanning. In this article the procedures are compared and the potential advantages of MRI highlighted with the help of neuropsychiatric case histories. Clinical situations are then discussed in which a psychiatrist should consider ordering a MRI scan subsequent to or instead of a CT scan.

Magnetic resonance imaging of the brain and spine

The efficacy of magnetic resonance imaging (MRI) in the diagnosis of diseases of the central nervous system is reviewed. MRI, computed tomography (CT) and certain radionuclide studies are compared in the evaluation of intracranial tumours, cerebral vascular disease, multiple sclerosis and other white matter diseases, dementia, head injury, infection, epilepsy, spinal lesions and in paediatric central nervous system disorders. The measurement of cerebrospinal fluid volumes and dynamics by MRI is discussed. MRI most clearly has advantages where CT is degraded by bone hardening and streak artefacts (spine, skull base, posterior and temporal fossa, sella and parasellar regions) and in diseases in which the X-ray attenuation of the suspected lesion differs little from normal parenchyma (paediatric brain disorders, demyelination and dysmyelination, early oedema associated with infarction, infection or low-grade infiltrating neoplasm, subacute and chronic haemorrhage and lesions in the spinal subarachnoid space and cord). Elsewhere MRI and CT should be seen as complementary rather than competitive methods of imaging. In spite of an absence of information about the contribution of MRI to management decisions and a lack of rigorous, prospective controlled trials, MRI will play an increasing role in the diagnosis of diseases of the central nervous system.