Recovery of movement-related potentials in the temporal course after prefrontal traumatic brain injury: a follow-up study

OBJECTIVE: The movement-related potential (MRP) is an EEG measure related to self-initiated movements, consisting of the Bereitschaftspotential (BP), the negative slope, and the motor potential. Since in a former study the BP was reduced in acute prefrontal traumatic brain injury (TBI) patients, the present study examined the MRPs' course in follow-up examinations. METHODS: Right index finger MRPs of 22 patients with contusions of the prefrontal cortex were recorded 12, 26, and 52 weeks after TBI and compared to controls. RESULTS: Within the patient group, a significant increase of the BP in the temporal course after TBI was observed. MRPs 12 and 26 weeks after TBI did not differ significantly from the control group. One year after TBI, significantly enhanced BPs were found. CONCLUSIONS: In the temporal course after prefrontal TBI, a recovery of the initially reduced BP was observed. The enhanced BP areas 1 year after TBI might represent the need for increased cognitive resources during movement preparation, supporting a recovered, but less effective neuronal network. SIGNIFICANCE: The present study represents the first longitudinal follow-up study of MRPs after prefrontal brain lesion. The observed changes reflect the plastic capacity of the brain, reorganizing the neuronal network function.     

Impaired capillary-to-arteriolar electrical signaling after traumatic brain injury

Traumatic brain injury (TBI) acutely impairs dynamic regulation of local cerebral blood flow, but long-term (>72 h) effects on functional hyperemia are unknown. Functional hyperemia depends on capillary endothelial cell inward rectifier potassium channels (Kir2.1) responding to potassium (K⁺) released during neuronal activity to produce a regenerative, hyperpolarizing electrical signal that propagates from capillaries to dilate upstream penetrating arterioles. We hypothesized that TBI causes widespread disruption of electrical signaling from capillaries-to-arterioles through impairment of Kir2.1 channel function. We randomized mice to TBI or control groups and allowed them to recover for 4 to 7 days post-injury. We measured in vivo cerebral hemodynamics and arteriolar responses to local stimulation of capillaries with 10 mM K⁺ using multiphoton laser scanning microscopy through a cranial window under urethane and α-chloralose anesthesia. Capillary angio-architecture was not significantly affected following injury. However, K⁺-induced hyperemia was significantly impaired. Electrophysiology recordings in freshly isolated capillary endothelial cells revealed diminished Ba²⁺-sensitive Kir2.1 currents, consistent with a reduction in channel function. In pressurized cerebral arteries isolated from TBI mice, K⁺ failed to elicit the vasodilation seen in controls. We conclude that disruption of endothelial Kir2.1 channel function impairs capillary-to-arteriole electrical signaling, contributing to altered cerebral hemodynamics after TBI.     

Depression in patients with acute traumatic brain injury.

OBJECTIVE: This study was undertaken to examine patients with closed head injuries for the presence of depressive disorders. METHOD: A consecutive series of 66 patients with closed head injuries but no significant spinal cord or other organ system injury were examined by means of a semistructured psychiatric interview. The Hamilton Rating Scale for Depression as well as scales measuring impairment in activities of daily living, intellectual functioning, and social functioning were administered. The patients' CT scans were also examined. RESULTS: Seventeen patients had major depression and two had minor depression. The presence of left dorsolateral frontal lesions and/or left basal ganglia lesions and, to a lesser extent, parietal-occipital and right hemisphere lesions was associated with an increased probability of developing major depression. Compared to the nondepressed group, the group with major depression had a higher frequency of previous psychiatric disorder and showed evidence of poorer social functioning. CONCLUSIONS: Major depression occurs in about one-quarter of patients after traumatic brain injury. This is the same frequency as in other major disorders such as stroke. Major depression appears to be provoked by one or more factors that include poor premorbid social functioning and previous psychiatric disorder or injury to certain critical brain locations.     

Vestibular dysfunction in acute traumatic brain injury

Journal of Neurology - Traumatic brain injury (TBI) is the commonest cause of disability in under-40-year-olds. Vestibular features of dizziness (illusory self-motion) or imbalance which affects...     

Overlap of attention and movement-related activity in lateralized event-related brain potentials.

OBJECTIVE: In tasks that involve lateralized visuospatial attention and a lateralized motor response, the associated brain electrical potentials, i.e. the attention-related N2pc and the lateralized readiness potential, typically overlap at central scalp sites. The manifestation of the N2pc at central electrode sites is commonly attributed to electric volume conduction effects, assuming the N2pc to be generated in occipito-temporal brain areas. We evaluated this explanation in a simulation study. METHODS: Using a forward modeling approach with a realistically shaped volume conduction model, we calculated the range of amplitude ratios between occipital and central electrode sites when a single source is assumed in area V4 or in area TO, at the temporo-occipital convexity. RESULTS: A comparison of the simulated amplitude ratios with reported data indicates that volume conduction effects from the investigated source origins in the occipito-temporal region are insufficient to explain the experimental data. CONCLUSIONS: We conclude that the anterior spread of the N2pc from its occipito-temporal maximum to central electrode sites is probably due to simultaneous attention-related activity in posterior and central brain areas.     

Ventral frontal cortex functions and quantified MRI in traumatic brain injury

Ventral frontal cortex is commonly involved in traumatic brain injury (TBI). The smell identification test (SIT), object alternation (OA), and the Iowa gambling task (IGT) are associated with this brain region in experimental and neuropsychological research. We examined the relationship of performance on these tests to residual structural brain integrity quantified from MRI in 58 TBI patients, including 18 patients with focal cortical contusions and 40 patients with diffuse injury only. Image analysis yielded regional volumetric measures of gray matter, white matter and cerebrospinal fluid. Multivariate analyses identified distributed patterns of regional volume loss associated with test performance across all three behavioral measures. The tasks were sensitive to effects of TBI. In multivariate analyses, performance in all three tasks was related to gray matter loss including ventral frontal cortex, but the SIT was most sensitive to ventral frontal cortex damage, even in patients without focal lesions. The SIT was further related to temporal lobe and posterior cingulate/retrosplenial volumes. OA and the IGT were associated with superior medial frontal volumes. Complex tasks, such as OA and the IGT, do not consistently localize to a single cortical region. The SIT is associated with the integrity of ventral frontal regions, but it is also affected by distributed damage, although the contribution of undetected olfactory tract or bulb damage could not be ruled out. This study illustrates the scope and limitations of functional localization in human ventral frontal cortex.     

Preparation to respond as manifested by movement-related brain potentials

Ten subjects were instructed to squeeze a dynamometer in a prescribed manner in order to assess the effects of motor preparation on event-preceding brain potentials. Right and left hand responses were required in 5 different experimental conditions allowing different degrees of advance preparation. Six channels of EEG (F3, F4, C3′, C4′, P3, P4) and two channels of EMG were digitized over a 3000 msec epoch, and response-locked averages were computed. Event-preceding negative potentials were evident well in advance of movement if the subject was informed of the timing of the response. These premovement potentials were asymmetrical on the scalp (contralaterally dominant at the central sites) if the subject knew which hand would be required to respond. Thus, we conclude that the appearance and asymmetry of these potentials reflect preparation to execute specific motor acts.     

Impaired auditory gating and P50 nonsuppression following traumatic brain injury

Traumatic brain injury (TBI) can produce persistent attention and memory impairment that may in part be produced by impaired auditory sensory gating. The P50 evoked waveform response to paired auditory stimuli appears to be a useful measure of auditory gating. The first controlled measurement of the P50 ratio in TBI patients is described: when 20 patients with persistently symptomatic TBI were compared with 20 control subjects, the P50 ratio was significantly greater in the TBI group. The potential neurophysiologic and therapeutic implications of this finding in TBI patients who report symptoms consistent with impaired auditory gating are discussed.     

重型颅脑损伤术中急性脑膨出应对措施

目的探讨重型颅脑损伤手术中急性脑膨出的机理与处理措施。方法回顾性分析58例在颅脑手术过程中发生脑膨出的重型颅脑损伤患者临床资料,影像学资料及应对措施,采用标准大骨瓣减压、过度通气、咬除颅底骨质、阶梯性减压、及时复查颅脑CT等综合措施。结果术后随访三月按GOS评定预后恢复良好19例、轻残11例、重残11例、植物生存5例、死亡12例。迟发性血肿(63.8%),弥漫性脑肿胀(27.6%)及脑梗死(8.6%)是重型颅脑损伤手术中急性脑膨出的主要原因。结论对重型颅脑损伤手术中急性脑膨出的患者要正确判断,区别原因采取相应的措施。     

Prospective memory assessment in acute mild traumatic brain injury

Abstract

Objective: Prospective memory (PM) is the ability to remember to perform an intention at the appropriate time in the future. It is of primary importance for daily living, and its disruption may impact functional autonomy. To date, few studies have examined PM during the acute phase of mild traumatic brain injury (mTBI), despite the high prevalence of this neurological condition and its potential impact on cognition.

Method: Twenty mTBI patients (time since injury ranged from 45 to 73?days) and 15 healthy control participants performed the Ecological Test of Prospective Memory (TEMP), a simulated errand task in which participants were required to execute 10 event-based (EB) and five time-based (TB) tasks. The TEMP separately evaluates PM phases as well as prospective and retrospective components in event- and time-based conditions. Participants also completed a neuropsychological test battery. Correlations were performed between cognitive composite scores and the TEMP.

Results: mTBI patients experienced difficulty in learning the content of intentions, retrieving these intentions in the time-based condition (prospective component) and recalling the associated actions in the event- and time-based conditions (retrospective component). Retrospective memory composite score was correlated with the learning and retention phases of the TEMP, whereas attention/working memory and executive composite scores were correlated with the time-based condition and performance on the ongoing task.

Conclusion: These results suggest the presence of global PM impairment during the acute phase of mTBI, as well as impairment of retrospective memory, attention/working memory, and executive functions, which are key components for PM performance.     

Short and long latency auditory evoked potentials in traumatic brain injury patients

Short latency auditory nerve and brainstem evoked responses (BAERs) and long latency cortical auditory evoked responses (CAERs) in 75 long-term traumatic brain injury (TBI) cases were compared. CAERs were found to be significantly correlated with clinical disability as measured by the Disability Rating Scale, while BAERs were not. Also, BAER patterns were consistently and significantly less abnormal and less sensitive to overall dysfunction than CAER patterns. Findings support previous observations that BAERs have relatively little utility for evaluating in surviving TBI patients the degree of overall brain impairment. In general, long latency AEP patterns are better able to reflect the extent and severity of brain dysfunction and overall clinical condition than are short latency AEP patterns in long-term severe TBI patients, and these patterns should be obtained routinely in the evaluation of such patients.     

Impaired National Adult Reading Test (NART) performance in traumatic brain injury

Some research suggests the National Adult Reading Test (NART) may be impaired by traumatic brain injury (TBI). To investigate this, a prospective, longitudinal study included 214 Australian TBI participants given the NART within 1 month post-injury, and at 6 and 12 months. TBI severity, age, education, sex, and mood (HADS) were examined, and significant improvement in NART- estimated full-scale IQ (FSIQ) was noted over time (p?<?.001). A three-way interaction of time, severity, and age showed younger and middle-aged mild TBI sub-groups improved significantly between 1 and 6 months post-injury, and the older sub-group between 6 and 12 months. In severe TBI, significant NART-estimated FSIQ improvement was noted only for the middle-aged and only between 6 and 12 months post-TBI. NART administration soon after TBI underestimated premorbid IQ, with a complex relationship between time post-injury, severity, and age. Participants with a longer education had higher NART FSIQs, although those with less education gained more IQ points between initial and 6 months assessments suggesting higher initial NART impairment. Regression equations predicted NART FSIQ at 6 (R?=?0.813) and 12 months post-trauma (R?=?0.792–0.845), their effectiveness being confirmed via cross-validation. No significant relationships were noted between NART-estimated FSIQ and mood variables, or evidence of significant gains in estimated FSIQ between 12 and 24 months post-injury.     

Cognitive estimation in traumatic brain injury.

The present study explores the construct and ecological validity of the Biber Cognitive Estimation Test (BCET) in a traumatic brain injury (TBI) sample. Participants completed the BCET in the course of a neuropsychological evaluation at 1-15 years after injury. BCET scores correlated moderately with other standard measures of executive functioning, and contrary to our hypotheses, at least as high with neuropsychological tests with minimal demands on executive functioning. Moreover, partialing out the portion of BCET variance not attributable to executive functioning markedly attenuated the former correlations. With respect to ecological validity, BCET scores did not predict concurrent functional status, as measured by the Disability Rating Scale. By comparison, standard measures of executive functioning strongly correlated with each other, correlated less strongly with nonexecutive functioning measures, and predicted functional status. In conclusion, unlike standard measures of executive functioning, the BCET demonstrated poor construct and ecological validity in TBI patients.     

Clinical application of magnetic resonance in acute traumatic brain injury

PURPOSE: To evaluate the clinical applications of magnetic resonance imaging (MRI) in patients with acute traumatic brain injury (TBI): to identify the type, quantity, severity; and improvement clinical-radiological correlation. METHOD: Assessment of 55 patients who were imaged using CT and MRI, 34 (61.8%) males and 21 (38.2%) females, with acute (0 to 5 days) and closed TBI. RESULTS: Statistical significant differences (McNemar test): ocurred fractures were detected by CT in 29.1% and by MRI in 3.6% of the patients; subdural hematoma by CT in 10.9% and MRI in 36.4 %; diffuse axonal injury (DAI) by CT in 1.8% and MRI in 50.9%; cortical contusions by CT in 9.1% and MRI in 41.8%; subarachnoid hemorrhage by CT in 18.2% and MRI in 41.8%. CONCLUSION: MRI was superior to the CT in the identification of DAI, subarachnoid hemorrhage, cortical contusions, and acute subdural hematoma; however it was inferior in diagnosing fractures. The detection of DAI was associated with the severity of acute TBI.     

Treating acute stress disorder following mild traumatic brain injury

OBJECTIVE: Acute stress disorder permits early identification of trauma survivors who are at risk of developing chronic posttraumatic stress disorder (PTSD). This study aimed to prevent PTSD in people who developed acute stress disorder after a mild brain injury by early provision of cognitive behavior therapy. METHOD: Twenty-four civilian trauma survivors with acute stress disorder were given five individually administered sessions of either cognitive behavior therapy or supportive counseling within 2 weeks of their trauma. RESULTS: Fewer patients receiving cognitive behavior therapy than supportive counseling met criteria for PTSD at a posttreatment evaluation (8% versus 58%, respectively). There were also fewer cases of PTSD at a 6-month follow-up evaluation among those receiving cognitive behavior therapy (17%) than among those receiving supportive counseling (58%). Patients in the cognitive behavior therapy condition displayed less reexperiencing and avoidance symptoms at the follow-up evaluation than patients receiving supportive counseling. CONCLUSIONS: These findings suggest that PTSD following mild brain injury can be effectively prevented with early provision of cognitive behavior therapy.     

重型颅脑损伤术中急性脑膨出治疗体会

目的探讨影响重型颅脑损伤开颅术中急性脑膨出的原因及有效防止措施。方法回顾分析我院2009-01—2010-12收治的12例重型颅脑损伤术中急性脑膨出采取新处理方法的病例资料作为研究组,同时选择2007-01—2008-12收治的9例重型颅脑损伤术中急性脑膨出病例资料作为对照组,分析2组的疗效。结果研究组恢复较好5例,重残5例,死亡2例;对照组恢复较好1例,重残3例,死亡5例。2组比较差异有统计学意义(P<0.05)。结论重型颅脑损伤术中发生急性脑膨出,要排除迟发颅内血肿后采取控制降压、过度换气、脑室引流、切除颞叶脑组织等综合措施,能够明显提高治疗效果,降低致残率和病死率。