Umberto Leon-Dominguez

The Infrascanner, a handheld device for screening in situ for the presence of brain haematomas

Purpose: Early identification and treatment of intracranial haematomas in patients sustaining traumatic brain injury is fundamental to successful treatment. This pilot study evaluates the Infrascanner as a handheld medical screening tool for detection, in situ, of brain haematomas in patients with head injury. Methods: This study included 35 TBI patients aged 17–76 (M = 47.6), admitted to the neurosurgical intensive care unit and observation unit of a University Hospital in a Level 1 trauma centre. The Infrascanner™ NIRS device uses near infrared light measurements to calculate optical density in brain regions. Results: Results show Infrascanner sensitivity at 89.5% and specificity at 81.2%. PPV was 85% and NPV 86.7%. The device detected 90% of extra-axial, 88.9% of intra-axial and 93.3% of non-surgical haematomas (less than 25 mL). PPV for this classification was 82.3%; 87.5% sensitivity was found when the Infrascanner exam was performed within 12 hours post-trauma, whereas after 12 hours post-trauma, exams had 90.1% sensitivity. Conclusions: This study demonstrates that the Infrascanner is useful in initial examinations and screenings of patients with head injury as an adjunct to a CT scan or when it is not available and may allow earlier treatment and reduce secondary injury caused by present and delayed haematomas.

Synchronization between the anterior and posterior cortex determines consciousness level in patients with traumatic brain injury (TBI)

Survivors of traumatic brain injury (TBI) often suffer disorders of consciousness as a result of a breakdown in cortical connectivity. However, little is known about the neural discharges and cortical areas working in synchrony to generate consciousness in these patients. In this study, we analyzed cortical connectivity in patients with severe neurocognitive disorder (SND) and in the minimally conscious state (MCS). We found two synchronized networks subserving consciousness; one retrolandic (cognitive network) and the other frontal (executive control network). The synchrony between these networks is severely disrupted in patients in the MCS as compared to those with better levels of consciousness and a preserved state of alertness (SND). The executive control network could facilitate the synchronization and coherence of large populations of distant cortical neurons using high frequency oscillations on a precise temporal scale. Consciousness is altered or disappears after losing synchrony and coherence. We suggest that the synchrony between anterior and retrolandic regions is essential to awareness, and that a functioning frontal lobe is a surrogate marker for preserved consciousness. This article is part of a Special Issue entitled: Brain Integration.

Functional Near-Infrared Spectroscopy (fNIRS): Principles and Neuroscientific Applications

fNIRS is a device designed to detect changes in the concentration of oxygenated (oxyHb) and deoxygenated (deoxyHb) haemoglobin molecules in the blood, a method commonly used to assess cerebral activity. Over the last decade, functional near-infrared spectroscopy (fNIRS) has widely extended its applications due to its capacity to quantify oxygenation in blood and organic tissue in a continuous and non invasive manner (Chance & Leigh, 1977; Villringer & Chance, 1997). This technique is an effective, albeit ‘indirect’, optical neuroimaging method that monitors hemodynamic response to brain activation, on the basis that neural activation and vascular response are tightly coupled, so termed ‘neurovascular coupling’. Different studies show that neural activity and hemodynamic response maintain a lineal relationship (Arthurs & Boniface, 2003; Logothetis et al., 2001), suggesting that these changes in hemodynamic response could provide a good marker for assessing neural activity. In neuroscience, functional near-infrared spectroscopy (fNIRS) is used to measure cerebral functions through different chromophore mobilization (oxygenated haemoglobin, deoxygenated haemoglobin and cytochrome c-oxidase) and their timing with concrete events. Due to methodological and theoretical problems associated with cytochrome c-oxidase functioning (Cyt-Ox) (see section 3.2.), current neuroscience studies on cerebral functions only assesses and analyzes oxyHb and deoxyHb mobilizations. These chromophore mobilizations are directly related to the cerebral blood flow (CBF) associated with an event and the physiological reactions provoked by the brain’s functional state (fNIRS measures these reaction in the cerebral cortex). The assessment of these taskrelated mobilizations performed in light of a base line established by the researcher him/herself. The difference in oxyHb and deoxyHb concentrations at baseline and at task performance determines the location in the cortex of an increase or decrease in CBF. An increase in CBF is associated with cerebral activity, making the temporal and spatial correlation between CBF and task a determinant of cerebral function. This capacity to study cerebral functions, both spatial and temporal, is what gives name to the technique described in this chapter: functional near-infrared spectroscopy (fNIRS). fNIRS has become a valuable neuroimaging technique, novel in its easy application and characterized by its small size, portability, and reliability. Although relatively new to the

Recovery of cognitive function during comprehensive rehabilitation after severe traumatic brain injury.

OBJECTIVE To explore the course and timing of functional recovery in patients who have emerged from coma after undergoing severe traumatic brain injury. METHODS An observational study involving 19 patients with traumatic brain injury recovered from coma who underwent holistic, intensive and multidisciplinary neurorehabilitation. Daily performance in each cognitive function (long-term memory, short-term memory, orientation, calculation, attention, mental control, automation, and planning) was clinically scored and compared at admission and discharge. RESULTS The course of cognitive recovery after post-traumatic coma is not uniform, offering a curve with many ups, downs and plateaus. To achieve a good response and outcome nearing normalcy, a patient needs over 300 h of intensive rehabilitation. CONCLUSION The consolidation of functional recovery in patients with traumatic brain injury requires time and adequate training, and discharge is not recommended until cognitive improvement is established.

A chronometric functional sub-network in the thalamo-cortical system regulates the flow of neural information necessary for conscious cognitive processes

The thalamo-cortical system has been defined as a neural network associated with consciousness. While there seems to be wide agreement that the thalamo-cortical system directly intervenes in vigilance and arousal, a divergence of opinion persists regarding its intervention in the control of other cognitive processes necessary for consciousness. In the present manuscript, we provide a review of recent scientific findings on the thalamo-cortical system and its role in the control and regulation of the flow of neural information necessary for conscious cognitive processes. We suggest that the axis formed by the medial prefrontal cortex and different thalamic nuclei (reticular nucleus, intralaminar nucleus, and midline nucleus), represents a core component for consciousness. This axis regulates different cerebral structures which allow basic cognitive processes like attention, arousal and memory to emerge. In order to produce a synchronized coherent response, neural communication between cerebral structures must have exact timing (chronometry). Thus, a chronometric functional sub-network within the thalamo-cortical system keeps us in an optimal and continuous functional state, allowing high-order cognitive processes, essential to awareness and qualia, to take place.

The sooner patients begin neurorehabilitation, the better their functional outcome.

Abstract Primary objective: To determine whether early neurorehabilitation improves a patient’s functional recovery. Research design: A retrospective study was carried out on patients with severe traumatic brain injury (TBI) who underwent a minimum of 4 months of integral and multidisciplinary neurorehabilitation. Methods and procedures: Fifty-eight patients with severe TBI were assessed at admission and at discharge using the FIM + FAM scale. Two groups were formed based on time elapsed from brain injury to onset of rehabilitation. The early treatment group (ET) included patients who began rehabilitation within the first 9 months post-trauma; the late treatment group (LT) began after the 9-month cut-off date. Intra- and between-group analysis of FIM + FAM scores were carried out at admission and discharge. Multiple linear regression was used to determine the best predictors for functional rehabilitation. Main outcomes and results: After neurorehabilitation, all subjects showed significant improvement in cognitive, motor, communication and psychosocial functioning. Moreover, the ET group showed better global functional outcome at discharge than patients who began later treatment. The best predictors for functional neurorehabilitation were months since injury, age, GCS score and months of treatment. Conclusions: It is concluded that the sooner patients begin neurorehabilitation, the better their functional outcome.

Molecular concentration of deoxyHb in human prefrontal cortex predicts the emergence and suppression of consciousness.

This is the first study to use fNIRS to explore anaesthetic depth and awakening during surgery with general anaesthesia. A 16 channel continuous wave (CW) functional near-infrared system (fNIRS) was used to monitor PFC activity. These outcomes were compared to BIS measures. The results indicate that deoxyHb concentration in the PFC varies during the suppression and emergence of consciousness. During suppression, deoxyHb levels increase, signalling the deactivation of the PFC, while during emergence, deoxyHb concentration drops, initiating PFC activation and the recovery of consciousness. Furthermore, BIS and deoxyHb concentrations in the PFC display a high negative correlation throughout the different anaesthetic phases. These findings suggest that deoxyHb could be a reliable marker for monitoring anaesthetic depth, and that the PFC intervenes in the suppression and emergence of consciousness.

Safe Driving and Executive Functions in Healthy Middle-Aged Drivers.

ABSTRACT The introduction of the point system driver’s license in several European countries could offer a valid framework for evaluating driving skills. This is the first study to use this framework to assess the functional integrity of executive functions in middle-aged drivers with full points, partial points or no points on their driver’s license (N = 270). The purpose of this study is to find differences in executive functions that could be determinants in safe driving. Cognitive tests were used to assess attention processes, processing speed, planning, cognitive flexibility, and inhibitory control. Analyses for covariance (ANCOVAS) were used for group comparisons while adjusting for education level. The Bonferroni method was used for correcting for multiple comparisons. Overall, drivers with the full points on their license showed better scores than the other two groups. In particular, significant differences were found in reaction times on Simple and Conditioned Attention tasks (both p-values < 0.001) and in number of type-III errors on the Tower of Hanoi task (p = 0.026). Differences in reaction time on attention tasks could serve as neuropsychological markers for safe driving. Further analysis should be conducted in order to determine the behavioral impact of impaired executive functioning on driving ability.

Restoring Cortical Connectivity Directionality and Synchronization is Essential to Treating Disorder of Consciousness

The design of neurorehabilitation therapy to treat subjects with altered consciousness provides opportunities and challenges to professionals involved with the care for these severely ill patients. While there is an increased interest in determining methods to restore consciousness in these patients, the process is complex and challenging, due in part to the diverse aetiology of these states of consciousness, and also to the intricate cerebral connectivity involved in their treatment. The present case study examines a patient who showed signs of emergence from the vegetative state after neurorehabilitation using The Combined Method Therapy (CMT). In this case, neurorehabilitation therapy was applied simultaneously with pharmacological treatment, stimulation, and neuroimaging techniques to help adjust drug dosage. The results of this study suggest that this combined approach to treatment promoted connectivity among posterior and anterior cortical regions aiding emergence from the vegetative state.