Resting state networks in patients with acute disorders of consciousness after severe traumatic brain injury.

OBJECTIVES: This study aims to describe resting state networks (RSN) in patients with disorders of consciousness (DOC)s after acute severe traumatic brain injury (TBI). METHODS: Adult patients with TBI with a GCS score <8 who remained in a coma, minimally conscious state (MCS), or unresponsive wakefulness syndrome (UWS), between 2017 and 2020 were included. Blood-oxygen-level dependent imaging was performed to compare their RSN with 10 healthy volunteers. RESULTS: Of a total of 293 patients evaluated, only 13 patients were included according to inclusion criteria: 7 in coma (54%), 2 in MCS (15%), and 4 (31%) had an UWS. RSN analysis showed that the default mode network (DMN) was present and symmetric in 6 patients (46%), absent in 1 (8%), and asymmetric in 6 (46%). The executive control network (ECN) was present in all patients but was asymmetric in 3 (23%). The right ECN was absent in 2 patients (15%) and the left ECN in 1 (7%). The medial visual network was present in 11 (85%) patients. Finally, the cerebellar network was symmetric in 8 patients (62%), asymmetric in 1 (8%), and absent in 4 (30%). CONCLUSIONS: A substantial impairment in activation of RSN is demonstrated in patients with DOC after severe TBI in comparison with healthy subjects. Three patterns of activation were found: normal/complete activation, 2) asymmetric activation or partially absent, and 3) absent activation.

Structural and functional connectivity of the ascending arousal network for prediction of outcome in patients with acute disorders of consciousness.

To determine the role of early acquisition of blood oxygen level-dependent (BOLD) signals and diffusion tensor imaging (DTI) for analysis of the connectivity of the ascending arousal network (AAN) in predicting neurological outcomes after acute traumatic brain injury (TBI), cardiopulmonary arrest (CPA), or stroke. A prospective analysis of 50 comatose patients was performed during their ICU stay. Image processing was conducted to assess structural and functional connectivity of the AAN. Outcomes were evaluated after 3 and 6 months. Nineteen patients (38%) had stroke, 18 (36%) CPA, and 13 (26%) TBI. Twenty-three patients were comatose (44%), 11 were in a minimally conscious state (20%), and 16 had unresponsive wakefulness syndrome (32%). Univariate analysis demonstrated that measurements of diffusivity, functional connectivity, and numbers of fibers in the gray matter, white matter, whole brain, midbrain reticular formation, and pontis oralis nucleus may serve as predictive biomarkers of outcome depending on the diagnosis. Multivariate analysis demonstrated a correlation of the predicted value and the real outcome for each separate diagnosis and for all the etiologies together. Findings suggest that the above imaging biomarkers may have a predictive role for the outcome of comatose patients after acute TBI, CPA, or stroke.

Establishing an acquisition and processing protocol for resting state networks with a 1.5 T scanner: A case series in a middle-income country.

OBJECTIVE: The aim of this study was to characterize the capability of detection of the resting state networks (RSNs) with functional magnetic resonance imaging (fMRI) in healthy subjects using a 1.5T scanner in a middle-income country. MATERIALS AND METHODS: Ten subjects underwent a complete blood-oxygen-level dependent imaging (BOLD) acquisition on a 1.5T scanner. For the imaging analysis, we used the spatial independent component analysis (sICA). We designed a computer tool for 1.5 T (or above) scanners for imaging processing. We used it to separate and delineate the different components of the RSNs of the BOLD signal. The sICA was also used to differentiate the RSNs from noise artifact generated by breathing and cardiac cycles. RESULTS: For each subject, 20 independent components (IC) were computed from the sICA (a total of 200 ICs). From these ICs, a spatial pattern consistent with RSNs was identified in 161 (80.5%). From the 161, 131 (65.5%) were fit for study. The networks that were found in all subjects were: the default mode network, the right executive control network, the medial visual network, and the cerebellar network. In 90% of the subjects, the left executive control network and the sensory/motor network were observed. The occipital visual network was present in 80% of the subjects. In 39 (19.5%) of the images, no any neural network was identified. CONCLUSIONS: Reproduction and differentiation of the most representative RSNs was achieved using a 1.5T scanner acquisitions and sICA processing of BOLD imaging in healthy subjects.

Neuroanatomía funcional de la escala de coma de Glasgow / Functional neuroanatomy of the Glasgow coma scale

Introducción: La escala de coma de Glasgow (ECG) es una escala mundialmente reconocida para la clasificación de pacientes con trauma craneoencefálico de acuerdo a su compromiso neurológico. Esta escala evalúa la apertura ocular, la respuesta verbal y la respuesta motora. La neuroanatomía funcional representa un compromiso secuencial para el descenso en el puntaje de cada uno de estos ítems. El objetivo de esta revisión es describir la anatomía del sistema reticular activador ascendente (SRAA), la anatomía funcional del lenguaje, la anatomía del tallo cerebral y de las vías motoras que representan cada ítem evaluado por la ECG. Materiales y métodos: Se hizo una revisión narrativa bibliográfica de las principales vías para cada ítem de la ECG. Resultados: Las principales vías en relación con la apertura ocular se concentran en las vías del SRAA, las vías de la respuesta verbal incluyen las vías del lenguaje y las vías que provienen del putamen y del cerebelo que regulan la emisión del lenguaje, mientras que las vías que regulan la respuesta motora principalmente se relacionan con la vía piramidal, el sistema rubro-espinal y vestíbulo-espinal. Conclusiones: El descenso del puntaje en los tres ítems que evalúa la ECG se relacionan con vías específicas que predominan en los ganglios basales y en el tallo cerebral.

Introduction: The Glasgow Coma Scale (GCS) is a globally recognized scale for the classification of patients with traumatic brain injury according to their neurological impairment. This scale evaluates the ocular opening, the verbal response and the motor response. Functional neuroanatomy represents a sequential decrease in the score of each of these items. The objective of this review is to describe the anatomy of the ascending reticular activating system (ARAS), the functional anatomy of the language, and the anatomy of the brainstem and the motor pathways that represent each item evaluated by the GCS. Materials and methods: A narrative literature review of the main routes for each item of the scale was performed. Results: The main pathways in relation to the ocular opening are concentrated in the ARAS, the verbal response pathways include the language pathways and the connections that come from the putamen and the cerebellum that regulate the production of the language, while the pathways that regulate the motor response mainly relate to the pyramidal tract, the rubro-spinal and vestibulo-spinal systems. Conclusions: The decline of the score in the three items that evaluates the GCS is related to specific pathways that predominate in the basal ganglia and in the brainstem.

Structural and functional connectivity of ascending reticular activating system in a patient with impaired consciousness after a cardiac arrest: A case report.

RATIONALE: Diffusion tensor imaging (DTI), diffusion tensor tractography (DTT), as well as resting-state-functional magnetic resonance imaging (rsfMRI) are promising methods for assessing patients with disorders of consciousness (DOCs). PATIENT CONCERNS: This work describes the main findings using DTI, DTT, and rsfMRI in a patient with a DOC secondary to an anoxic encephalopathy who had a fatal outcome. She was an 85-year-old woman who presented a cardiac arrest and underwent cardiopulmonary resuscitation for 20 minutes then returning to spontaneous circulation. After sedation withdrawal, 2 days after the event, she remained with a Glasgow Coma Scale score of 3/15 and with an absence of brainstem reflexes. DIAGNOSES: DOC secondary to an anoxic encephalopathy after cardiovascular resuscitation. INTERVENTIONS: A complete brain MRI scan was performed 72 hours after the initial event, including DTI, DTT, and rsfMRI. DTT demonstrated disruption of both ventral and dorsal tegmental tracts bilaterally. DTI showed a reduction of fractional anisotropic level in the mesencephalic nuclei. Moreover, changes in the number of fiber tracts were not evidenced in any portions of the ascending reticular activating system (ARAS). Finally, an increase in the anticorrelated and correlated association among the nuclei in the ARAS and the cortex was evidenced. OUTCOMES: Patient deceased. LESSONS: Neuroimaging demonstrated low FA values in the ARAS, destruction of dorsal and ventral tegmental tracts, as well as hyper-connective (highly correlated or anti-correlated) association among ARAS and cortical nuclei compared with 3 healthy control subjects.

Recovery of consciousness after a brainstem cavernous malformation hemorrhage: A descriptive study of preserved reticular activating system with tractography.

The aim of this study is to describe the imaging features, the relevant anatomy, and the fractional anisotropy (FA) values in diffusion tensor tractography (DTT) of the ascending reticular activating system (ARAS) fiber tracts in 2 patients who recovered from initial altered consciousness after presenting with a brainstem cavernous malformation (BSCM) hemorrhage. A DTT was performed in 2 patients with impaired consciousness after a brainstem cavernous malformation hemorrhage. A 1.5 T scanner was used to obtain the axial tensors. Post-processing was performed and the mean FA values were recorded. The FA maps were used to seed the following regions of interest: the ventromedial midbrain, the anterior thalamus bilaterally, and the hypothalamus bilaterally. The first case presented with posterior displacement of the dorsal raphè fiber tracts, with preservation of all the ascending reticular activating fiber tracts and spontaneous recovery of consciousness after 20 days. The second case presented with no destruction but also had posterior displacement of the inferior dorsal raphè fiber tracts, with recovery of consciousness 1 month after resection surgery. Described in this study are affected fibers of the ARAS, as well as the FA value abnormalities in 2 patients, with recovery of a transient disorder of consciousness after a BSCM hemorrhage.

Reconstruction of the Ascending Reticular Activating System with Diffusion Tensor Tractography in Patients with a Disorder of Consciousness after Traumatic Brain Injury.

This work describes the reconstruction of the ascending reticular activating system (ARAS) with diffusion tensor tractography in three patients with altered consciousness after traumatic brain injury. A diffusion tensor tractography was performed in three patients with impaired consciousness after a severe traumatic brain injury. A 1.5 T scanner was used to obtain the tensor sequences; axial tensors were acquired. Post-processing was performed, and the mean fractional anisotropy (FA) values were recorded. The FA maps were used to do a manual tracing of the following regions of interest (ROIs): the ventromedial midbrain, the anterior thalamus, and the hypothalamus. Case 1 presented destruction of the right dorsal and ventral tegmental tracts as well as destruction of the right middle forebrain bundle, case 2 had destruction of the right dorsal tegmental tract, and case 3 had destruction of the bilateral ventral and dorsal tegmental tracts, as well as destruction of the right middle forebrain bundle. The affected fibers of the ascending reticular activating system with diffuse axonal injury and the FA values abnormalities in the ascending reticular activating system in three patients with a disorder of consciousness (DOC) after traumatic brain injury are described.