Longitudinal changes in global brain volume between 79 and 409 days after traumatic brain injury: relationship with duration of coma

Neuropathological and experimental animal studies indicate that traumatic brain injury (TBI) results in long-term, neurodegenerative changes. Structural image evaluation using normalization of atrophy (SIENA) offers an automated analysis of the subtle changes in percent brain volume change (%BVC) associated with TBI. In the present study, SIENA was used to evaluate %BVC in individuals who had sustained a mild to severe TBI. We obtained three-dimensional (3D) T1-weighted anatomical magnetic resonance imaging (MRI) scans approximately 79 days and again 409 days post-injury. TBI patients (n = 37) displayed significantly greater decline in %BVC (-1.43%) relative to a normal comparison group (+0.1%, n = 30). Greater %BVC was associated with longer duration of post-injury coma. These results confirm previous findings from cross-sectional studies and argue that the brain undergoes continued structural change for several months post-injury.     

Focal lesions in acute mild traumatic brain injury and neurocognitive outcome: CT versus 3T MRI

Abstract Mild traumatic brain injury (mTBI) is associated with long-term cognitive deficits. This study compared the detection rate of acute post-traumatic focal lesions on computed tomography (CT) and 3T (Tesla) magnetic resonance (MR) imaging with neurocognitive outcomes. Adults (n = 36; age range, 19-52 years) with a single episode of mTBI (Glasgow Coma Scale 13-15, as well as loss of consciousness and post-traumatic amnesia) were prospectively enrolled and had CT within 24 h of injury and 3T MR within 2 weeks of injury. The CT and MR scans were reviewed by two neuroradiologists who were blinded to clinical information. Twenty-eight of these mTBI subjects and 18 matched healthy volunteers also underwent serial neurocognitive testing. Of the 36 mTBI cases, intraparenchymal lesions were detected in 18 CT and 27 acute MR exams, consisting of hemorrhagic traumatic axonal injury (TAI) (eight CT, 17 MR), non-hemorrhagic TAI (zero CT, four MR), and cerebral contusions (13 CT, 21 MR). Mild TBI patients had significantly worse performance on working memory tasks than matched controls at the acute time point (<2 weeks), and at 1 month and at 1 year post-injury; yet there was no significant correlation of imaging findings with working memory impairment. In conclusion, 3T MR detected parenchymal lesions in 75% of this mTBI cohort with loss of consciousness and post-traumatic amnesia, a much higher rate than CT. However, the CT and 3T MR imaging findings did not account for cognitive impairment, suggesting that newer imaging techniques such as diffusion tensor imaging are needed to provide biomarkers for neurocognitive and functional outcome in mTBI.     

Recovery of function following severe traumatic brain injury: A retrospective 10-year follow-up

It has been widely assumed that most of the recovery following severe traumatic brain injury (TBI) occurs within the first 6 months, and that virtually all of the recovery occurs within the first 1-2 years post-injury. In an effort to evaluate the long-term recovery of patients who had sustained severe TBI, we interviewed the relatives and significant others of 20 patients who had sustained TBI at least 5 years earlier, using a modified version of the Portland Adaptability Inventory. Retrospective ratings were collected to evaluate the patients' psychosocial, cognitive, physical, and emotional status prior to their injury, and at 1, 2, 5, and an average of 10-3 years post-injury. The results indicated that TBI patients exhibit significant improvements in their social, cognitive, physical, and emotional functioning after 2 years post-injury regardless of the severity of their initial brain trauma. These data suggest that patients who sustain severe TBI continue to make gradual improvements in their functioning for at least 10 years post-injury. Our findings contradict the widely held assumption that the recovery process ends after 1 or 2 years post-injury.     

The incidence and risk factors for hypotension during emergent decompressive craniotomy in children with traumatic brain injury

We conducted a retrospective cohort study in children <13 yr with traumatic brain injury (TBI) at a Level 1 pediatric trauma center to describe risk factors for intraoperative hypotension (IH) during emergent decompressive craniotomy. Between 1994 and 2004, 108 children underwent emergent decompressive craniotomy for TBI. Overall, 56 (52%) patients had IH. Independent risk factors for IH were each 10 mL estimated blood loss/kg (ARR 1.15 95% CI 1.08-1.22), each mm of computed tomography (CT) midline shift (ARR 1.04 95%CI 1.01-1.07), each 10 mL of CT lesion volume (ARR 1.03 95%CI 1.01-1.05), and emergency department (ED) hypotension (5/5 patients with ED hypotension had IH). CT midline shift > or =4 mm predicted IH (ARR 1.67 95% CI 1.06-2.63), independent of blood loss. IH occurred frequently during emergent decompressive craniotomy in children with TBI. ED hypotension, blood loss, CT lesion volume, and CT midline shift predicted IH. Anesthesiologists can expect children with preoperative CT midline shift > or =4 mm to have IH during this procedure.     

99mTc-HMPAO SPECT of the brain in mild to moderate traumatic brain injury patients: Compared with CT—a prospective study

Single photon emission computed tomography (SPECT) with Technetium-99m hexamethyl propylenamine oxime (Tc-99m-HMPAO) was used in 20 patients with mild to moderate traumatic brain injury (TBI) to evaluate the effects of brain trauma on regional cerebral blood flow (rCBF). SPECT scan was compared with CT scan in 16 patients. SPECT showed intraparenchymal differences in rCBF more often than lesions diagnosed with CT scans (87 -5% vs. 37-5%). In five of six patients with lesions in both modalities, the area of involvement was relatively larger on SPECT scans than on CT scans. Contrecoup changes were seen in five patients on SPECT alone, two patients with CT alone and one patient had contrecoup lesions on CT and SPECT. Of the eight patients (50%) with skull fractures, seven (43-7%) had rCBF findings on SPECT scan and five (31.3%) demonstrated decrease in rCBF in brain underlying the fracture. All these patients with fractures had normal brain on CT scans. Conversely, extra-axial lesions and fractures evident on CT did not visualize on SPECT, but SPECT demonstrated associated changes in rCBF. Although there is still lack of clinical and pathological correlation, SPECT appears to be a promising method for a more sensitive evaluation of axial lesions in patients with mild to moderate TBI.     

Day-of-injury CT as an index to pre-injury brain morphology: Degree of post-injury degenerative changes identified by CT and MR neuroimaging

A detailed case study is presented in which pre-injury CT scan findings are compared and contrasted with post-injury CT and MR results in a case of traumatic brain injury (TBI). The day-of-injury scan represented an adequate estimate of pre-injury morphological status based on cross-sectional area measurements of the ventricular system. By comparing pre-injury CT measurements with those obtained on the day of injury, 2 days post-injury and 16 months post-injury via assessing cross-sectional area of select ventricular regions (e.g. anterior and temporal horns, body and third ventricle) it was demonstrated that the TBI induced over a 50% ventricular expansion. Such ventricular expansions are felt to provide some index into diffuse axonal injury which may provide a means of eventually quantifying the degree of structural damage secondary to TBI. This analysis also demonstrated that there were no significant differences between selected cross-sectional ventricular areas in the 15 day and 16 month post-injury MR scans. This finding suggests that the degenerative effects of TBI have a rapid onset and are becoming readily apparent by 15 days post-injury. Thus, early imaging may provide a good index of long-term morphological outcome in TBI.     

Being restricted in participation after a traumatic brain injury is negatively associated by passive coping style of the caregiver

Purpose: To examine whether the caregivers' coping style is associated with the functional outcome of the traumatic brain injury (TBI) patient 1 year post-injury.

Method: A cross-sectional study among patients with a TBI, including their primary caregivers. The study included 51 patients aged 17-64 years with a moderate-to-severe TBI and 51 caregivers (23 parents and 28 partners) aged 23-67 years. The coping preferences of the caregivers were assessed at minimum 6 and maximum 12 months post-injury, by filling out the Utrecht Coping List (UCL) and were related to limitations in activity, as measured with the Frenchay Activities Index and with restrictions in participation as measured with the Sickness Impact Profile-68 of TBI patients 1 year post-injury. The patients were interviewed at their homes; the caregivers received and returned the UCL by mail.

Results: The patients' age and the caregivers' coping style are independently associated with restrictions in participation 1 year post-injury.

Conclusions: A passive coping style of the primary caregiver is negatively associated with the patient's functional outcome in terms of participation in society.     

Management and outcome in patients following head injury admitted to an Irish Regional Hospital

Primary objective: Each year in Ireland, 11 000 patients are admitted to hospital with a traumatic brain injury (TBI) but there are no data on subsequent disability in such patients. The objective of this study was to assess the management and outcome in patients of working age admitted with TBI to the unit.

Methods: Two hundred and sixteen patients admitted with TBI aged 16-65 were identified. Self-reported incidence of disability and access to appropriate services was assessed using the Glasgow outcome scale and a problem-orientated questionnaire.

Results: Eighty-five per cent of patients eligible for review agreed to participate. The majority of injuries (86%) were mild. An intracranial injury was identified on 35% of CT brain scans performed. Patients with an abnormality on CT scanning were more likely to report difficulties with headache, concentration and memory at time of follow-up. When questioned, 34% of patients still perceived difficulties since their injury. Of this group, 60% didn't receive any input from rehabilitation services. One year post-injury, 11% of patients remained unfit for work.

Conclusion: A significant number of patients, even with mild TBI, continue to suffer sequelae from their injury augmented by difficulty in accessing appropriate rehabilitation services.     

Mechanism-based MRI classification of traumatic brainstem injury and its relationship to outcome

While computed tomography (CT) is the appropriate technique for the urgent detection of hematomas and contusions in the cerebral hemispheres, it is much less effective at documenting diffuse injury and posterior fossa lesions, and is therefore only partially predictive of outcome. More recently, magnetic resonance imaging (MRI) has been used, particularly to examine posterior fossa structures, but the relationship between brainstem injury and outcome is unclear and the types of brainstem injury are poorly understood. The aim of this study was to use acute MRI to examine the types of brainstem injury following severe traumatic brain injury (TBI) and their relationship to supratentorial injury. We also aimed to correlate these findings with outcome at 6 months (Glasgow Outcome Scale [GOS] score). Forty-six patients (mean age, 34 years, range, 16-70 years; 76% male) admitted to a regional neurocritical care unit with TBI requiring ventilation underwent CT and MRI (T2, FLAIR, gradient echo) scanning within 3 days (median, 1 day) of injury. GOS was ascertained by outpatient interview. Brainstem lesions were detected in 13 patients by MRI, only two of which were detected by CT. Eleven out of 13 patients with brainstem injury had an unfavorable outcome (death, vegetative state, or severe disability), of whom five died. Of the 33 patients without brainstem lesions, 18 had an unfavorable outcome, of whom four died. The direct relationship between brainstem lesions and unfavorable outcome was statistically significant (p < 0.05, chi-squared test). With regard to supratentorial injury, all but two brainstem lesions were seen either in the context of severe diffuse axonal injury or a significant mass lesion, and all of these patients had a poor outcome. However, the two patients with brainstem injury and good outcome had relatively few supratentorial abnormalities. From these observations, we have devised a simple classification system that is useful clinically and has potential associations with outcome. Poor prognosis is common following major TBI but is more common in those with brainstem injury. However, brainstem injury is not an absolute indicator of poor outcome. Understanding the anatomy and extent of brainstem injury, as well as its relationship to supratentorial abnormalities, will facilitate a more accurate use of early MRI as a prognostic tool and assist in the counseling of families.     

Variants of the endothelial nitric oxide gene and cerebral blood flow after severe traumatic brain injury

Experimental studies suggest that nitric oxide produced by endothelial nitric oxide synthase (NOS3) plays a role in maintaining cerebral blood flow (CBF) after traumatic brain injury (TBI). The purpose of this study was to determine if common variants of the NOS3 gene contribute to hypoperfusion after severe TBI. Fifty-one patients with severe TBI were studied. Cerebral hemodynamics, including global CBF by the stable xenon computed tomography (CT) technique, internal carotid artery flow volume (ICA-FVol), and flow velocity in intracranial vessels, were measured within 12?h of injury, and at 48?h after injury. A blood sample was collected for DNA analysis, and genotyping of the following variants of the NOS3 gene was performed: -786T>C, 894G>T, and 27bp VNTR. Cerebral hemodynamics were most closely related to the-786T>C genotype. CBF averaged 57.7±3.0?mL/100?g/min with the normal T/T genotype, 47.0±2.5?mL/100?g/min with the T/C, and 37.3±8.8?mL/100?g/min with the C/C genotype (p=0.0146). Cerebrovascular resistance followed an inverse pattern with the highest values occurring with the C/C genotype (p=0.0027). The lowest ICA-FVol of 124±43?mL/min was found at 12?h post-injury in the more injured hemisphere of the patients with the C/C genotype (p=0.0085). The mortality rate was 20% in patients with the T/T genotype and 17% with the T/C genotype. In contrast, both of the patients with the C/C genotype were dead at 6 months post-injury (p=0.022). The findings in this study support the importance of NO produced by NOS3 activity in maintaining CBF after TBI, since lower CBF values were found in patients having the -786C allele. The study suggests that a patient's individual genetic makeup may contribute to the brain's response to injury and determine the patient's chances of surviving the injury. The results here will need to be studied in a larger number of patients, but could explain some of the variability in outcome that occurs following severe TBI.     

Computed tomography findings in young children with minor head injury presenting to the emergency department greater than 24 h post injury

BackgroundLarge studies which developed decision rules for the use of Computed tomography (CT) in children with minor head trauma excluded children with late presentation (more than 24 h).ObjectiveTo assess the prevalence of significant traumatic brain injury (TBI) on CT in infants with head trauma presenting to the emergency department (ED) more than 24 h from the injury.MethodsA retrospective chart review of infants less than 24 months old referred for head CT because of traumatic brain injury from January 2004 to December 2014 in Assaf-Harofeh medical center was conducted. We used the PECARN definitions of TBI on CT to define significant CT findings.Results344 cases were analyzed, 68 with late presentation.There was no significant difference in the age between children with late and early presentation (mean 11.4 (SD 5.6) month vs 10. 5 (SD 7.0) month, P = 0.27). There was no significant difference between the groups in the incidence of significant TBI (22% vs 19%, p = 0.61). Any TBI on CT (e.g. fracture) was found in 43 (63%) patients with late presentation compared with 116 (42%) patients with early presentation (p = 0.002, OR 2.37, 95% CI 1.37–4.1).ConclusionA similar rate of CT-identified traumatic brain injury was detected in both groups.‏ There was no significant difference in the incidence of significant TBI on CT between the groups.‏ Young children presenting to the ED more than 24 hours after the injury may have abnormal findings on CT.     

Low-level laser light therapy improves cognitive deficits and inhibits microglial activation after controlled cortical impact in mice

Low-level laser light therapy (LLLT) exerts beneficial effects on motor and histopathological outcomes after experimental traumatic brain injury (TBI), and coherent near-infrared light has been reported to improve cognitive function in patients with chronic TBI. However, the effects of LLLT on cognitive recovery in experimental TBI are unknown. We hypothesized that LLLT administered after controlled cortical impact (CCI) would improve post-injury Morris water maze (MWM) performance. Low-level laser light (800?nm) was applied directly to the contused parenchyma or transcranially in mice beginning 60-80?min after CCI. Injured mice treated with 60?J/cm2 (500?mW/cm2×2?min) either transcranially or via an open craniotomy had modestly improved latency to the hidden platform (p<0.05 for group), and probe trial performance (p<0.01) compared to non-treated controls. The beneficial effects of LLLT in open craniotomy mice were associated with reduced microgliosis at 48?h (21.8±2.3 versus 39.2±4.2 IbA-1+ cells/200×field, p<0.05). Little or no effect of LLLT on post-injury cognitive function was observed using the other doses, a 4-h administration time point and 7-day administration of 60?J/cm2. No effect of LLLT (60?J/cm2 open craniotomy) was observed on post-injury motor function (days 1-7), brain edema (24?h), nitrosative stress (24?h), or lesion volume (14 days). Although further dose optimization and mechanism studies are needed, the data suggest that LLLT might be a therapeutic option to improve cognitive recovery and limit inflammation after TBI.     

Role of premorbid factors in predicting safe return to driving after severe TBI

Primary objective: The present study explored the possibility of predicting post-injury fitness to safe driving in patients with severe traumatic brain injury (TBI) (n = 66).

Methods and procedure: Sixteen different measures, derived from four domains (demo/biographic, medico-functional, neuropsychological, and psychosocial) were used as predictor variables, whereas driving outcomes were assessed in terms of driving status (post-TBI drivers versus non-drivers) and driving safety (number of post-TBI car accidents and violations).

Main outcomes and results: About 50% of the patients resumed driving after TBI. Compared to post-TBI non-drivers, post-injury drivers had shorter coma duration. With regard to driving safety, the final multiple regression model combined four predictors (years post-injury, accidents and violations before TBI, pre-TBI-risky-personality-index, and pre-TBI-risky-driving-style-index) and explained 72.5% of variance in the outcome measure.

Conclusions: Since the best three predictors of post-injury driving safety addressed patients' premorbid factors, the results suggest that in order to evaluate the actual possibility of safe driving after TBI, it would be advisable to consider carefully patients' pre-TBI histories.     

Prognostic value of magnetic resonance imaging in moderate and severe head injury: a prospective study of early MRI findings and one-year outcome

The clinical benefit of early magnetic resonance imaging (MRI) in severe and moderate head injury is unclear. We sought to explore the prognostic value of the depth of lesions depicted with early MRI, and also to describe the prevalence and impact of traumatic brainstem lesions. In a cohort of 159 consecutive patients with moderate to severe head injury (age 5-65 years and surviving the acute phase) admitted to a regional level 1 trauma center, 106 (67%) were examined with MRI within 4 weeks post-injury. Depth of lesions in MRI was categorized as: hemisphere level, central level, and brainstem injury (BSI). The outcome measure was Glasgow Outcome Scale Extended (GOSE) 12 months post-injury. Forty-six percent of patients with severe injuries and 14% of patients with moderate injuries had BSI. In severe head injury, central or brainstem lesions in MRI, together with higher Rotterdam CT score, pupillary dilation, and secondary adverse events were significantly associated with a worse outcome in age-adjusted analyses. Bilateral BSI was strongly associated with a poor outcome in severe injury, with positive and negative predictive values of 0.86 and 0.88, respectively. In moderate injury, only age was significantly associated with outcome in multivariable analyses. Limitations of the current study include lack of blinded outcome evaluations and insufficient statistical power to assess the added prognostic value of MRI when combined with clinical information. We conclude that in patients with severe head injury surviving the acute phase, depth of lesion on the MRI was associated with outcome, and in particular, bilateral brainstem injury was strongly associated with poor outcomes. In moderate head injury, surprisingly, there was no association between MRI findings and outcome when using the GOSE score as outcome measure.     

The neuropsychology of blunt head injury in the early postacute stage: effects of focal lesions and diffuse axonal injury

This investigation evaluated the neuropsychological symptoms in the early posttraumatic period following blunt head injury and their correlation to routine imaging data in a consecutive series of TBI patients (Magdeburg Neurotrauma Databank). Of 135 consecutive patients, 68 could be assessed neuropsychologically 8-21 days after trauma. In 61 patients, routine clinical CT data were sufficient for neuroradiological analysis focusing on the presence or absence of CT signs of diffuse axonal injury (DAI) or focal traumatic injury. In these patients, the initial GCS score was significantly correlated with the presence of DAI but not with focal pathology. The presence of DAI was correlated with behavioral and cognitive symptoms of frontal lobe dysfunction, especially in interference tasks (Go/NoGO and Stroop reaction times) and semantic fluency. The presence of local frontal or temporal traumatic lesions was associated with deficits in concept formation, fluency tasks and behavioral symptoms, but not with increased interference. Patients with frontal contusions were impaired in a task of visuomotor planning and performance (Block design). Our data indicate that both traumatic DAI and focal lesions result in frontal lobe symptoms. We conclude that, even in clinically "mild" TBI, brain imaging should be used to identify patients with substantial brain damage. These should be assessed neuropsychologically for possible posttraumatic cognitive or behavioral impairment. In consideration of its easy accessibility, the refined use of the CT is considered a promising and valid tool for patient stratification. The application of MRI and biochemical markers may further improve prognostic predictions.     

Paroxysmal sympathetic hyperactivity after traumatic brain injury: clinical and prognostic implications

A proportion of patients surviving severe traumatic brain injury (TBI) have symptoms suggestive of excessive sympathetic discharge, here termed paroxysmal sympathetic hyperactivity (PSH). The goals of this study were: (1) to describe the clinical associations and radiological findings of PSH, its incidence, and features in subjects with severe TBI in the intensive care unit (ICU); (2) to investigate the potential role of increased intracranial pressure in the pathogenesis of PSH; and (3) to determine the prognostic influence of PSH during the ICU stay, on discharge from the ICU, and at 12 months post-injury. A prospective cohort study was undertaken of all ICU admissions with severe TBI older than 14 years over an 18-month period. The PSH symptoms consisted of paroxysmal increases in blood pressure, respiratory rate, and heart rate; worsening level of consciousness; muscle rigidity; and hyperhidrosis. Subjects demonstrating PSH episodes were compared with a group of non-PSH consecutive subjects studied over the first 6 months of the study period. Data were recorded on the clinical variables associated with PSH episodes, early post-injury cerebral CT findings, and neurological status at 1 year. Of 179 severe TBI patients admitted over the study period, 18 (10.1%) experienced PSH. Injury severity-related variables (e.g., initial APACHE II score, admission coma level, and proportion with intracranial hypertension) were similar between the two groups. The PSH group had a longer ICU stay and a greater incidence of infectious complications. At 1 year post-injury, 20% of this group demonstrated ongoing PSH episodes. Over 18 months, 10.1% of admissions following severe TBI demonstrated PSH features in ICU. Subjects with PSH had a longer ICU stay and higher rate of complications, although this did not appear to compromise their long-term neurological recovery.     

Alcohol abuse and traumatic brain injury: quantitative magnetic resonance imaging and neuropsychological outcome

Prior or concurrent alcohol use at the time of traumatic brain injury (TBI) was examined in terms of post-injury atrophic changes measured by quantitative analysis of magnetic resonance imaging (MRI) and neuropsychological outcome. Two groups of TBI subjects were examined: those with a clinically significant blood alcohol level (BAL) present at the time of injury (TBI + BAL) and those without a significant BAL (TBI-only). To explore the potential impact of both acute and chronic alcohol use, subjects in both groups were further clustered into one of four subgroups (NONE, MILD, MODERATE or HEAVY) based upon available information regarding their pre-injury alcohol use. One-way analysis of covariance (ANCOVA) and multiple analysis of covariance (MANCOVA) were used with subject grouping as the main factor. Age, injury severity as measured by Glasgow Coma Scale (GCS) score, years of education, total intracranial volume (TICV), and the number of days post-injury were included as covariates where appropriate. Increased general atrophy was observed in patients with (a) a positive BAL and/or (b) a history of moderate to heavy pre-injury alcohol use. In addition, performance on neuropsychological outcome variables (WAIS-R and WMS-R Index scores) was generally worse in the subgroups of patients with positive BAL and a history of preinjury alcohol use, as compared to the other TBI groups though not statistically significant. Implications of alcohol use, at the time of brain injury, are discussed.     

The role of MR imaging in assessing prognosis after severe and moderate head injury

Purpose  The objective of this work is two-fold: to determine the role of MRI findings in establishing the prognosis of patients with moderate and severe traumatic brain injury (TBI) admitted to our centre, measured with different outcome scales; and to determine in which patients the information given by MR findings adds prognostic information to that from traditional prognostic factors. Methods  One hundred patients suffering moderate or severe head injury in whom MRI had been performed in the first 30 days after trauma were included. The MRI was evaluated by two neuroradiologists who were not aware of the initial CT results or the clinical situation of the patients. Outcome was determined 6 months after head injury by means of the extended version of the Glasgow Outcome Scale. The prognostic capacity of the different factors related to outcome was compared by the analysis of receiver operating characteristic (ROC) curves and the area under the curve (AUC) for each factor. Results  There exists a clear relation between the depth of the traumatic lesions shown on MRI, and their classification by the proposed scale, and the outcome of patients suffering traumatic brain injury determined by different scales 6 months after injury. Conclusions  The anatomical substrate of TBI depicted by MRI could be a useful prognostic tool in patients suffering moderate and severe head injury. Patients with a score of 4 or less on the motor subscale of the GCS scale are those who could benefit most from the prognostic information provided by MRI.     

Frontal hypoactivation on functional magnetic resonance imaging in working memory after severe diffuse traumatic brain injury

Working memory is frequently impaired after traumatic brain injury (TBI). The present study aimed to investigate working memory deficits in patients with diffuse axonal injury and to determine the contribution of cerebral activation dysfunctions to them. Eighteen patients with severe TBI and 14 healthy controls matched for age and gender were included in the study. TBI patients were selected according to signs of diffuse axonal injury on computed tomography (CT) and without any evidence of focal lesions on MRI clinical examination. Functional magnetic resonance (fMRI) was used to assess brain activation during n-back tasks (0-, 2-, and 3-back). Compared to controls, the TBI group showed significant working memory impairment on the Digits Backwards (p=0.022) and Letter-Number Sequencing subtests from the WAIS-III (p<0.001) under the 2-back (p=0.008) and 3-back (p=0.017) conditions. Both groups engaged bilateral fronto-parietal regions known to be involved in working memory, although patients showed less cerebral activation than did controls. Decreased activation in TBI patients compared to controls was observed mainly in the right superior and middle frontal cortex. The correlation patterns differed between patients and controls: while the control group showed a negative correlation between performance and activation in prefrontal cortex (PFC), TBI patients presented a positive correlation in right parietal and left parahippocampus for the low and high working memory load, respectively. In conclusion, severe TBI patients with diffuse brain damage show a pattern of cerebral hypoactivation in the right middle and superior frontal regions during working memory tasks, and also present an impaired pattern of performance correlations.     

Neuroplasticity following non-penetrating traumatic brain injury

The primary objective of this review is to examine the methodology and evidence for neuroplasticity operating in recovery from traumatic brain injury (TBI), as compared with previous findings in patients sustaining perinatal and infantile focal vascular lesions. The evidence to date indicates that the traditional view of enhanced reorganization of function after early focal brain lesions might apply to early focal brain lesions, but does not conform with studies of early severe diffuse brain injury. In contrast to early focal vascular lesions, young age confers no advantage in the outcome of severe diffuse brain injury. Disruption of myelination could potentially alter connectivity, a suggestion which could be confirmed through diffusion tensor imaging (DTI). Initial reports of DTI in TBI patients support the possibility that this technique can demonstrate alterations in white matter connections which are not seen on conventional magnetic resonance imaging (MRI) and might change over time or with interventions. Preliminary functional MRI studies of TBI patients indicate alterations in the pattern of brain activation, suggesting recruitment of more extensive cortical regions to perform tasks which stress computational resources. Functional MRI, coupled with DTI and possibly other imaging modalities holds the promise of elucidating mechanisms of neuroplasticity and repair following TBI.