Use of functional magnetic resonance imaging to assess cognition and consciousness in severe Guillain-Barré syndrome

Objective: Functional neuroimaging may provide a viable means of assessment and communication in patients with Guillain-Barré Syndrome (GBS) mimicking the complete locked-in state. Functional neuroimaging has been used to assess residual cognitive function and has allowed for binary communication with other behaviourally non-responsive patients, such as those diagnosed with unresponsive wakefulness syndrome. We evaluated the potential application of functional neuroimaging using a clinical-grade scanner to determine if individuals with severe GBS retained auditory function, command following, and communication. Methods: Fourteen healthy participants and two GBS patients were asked to perform motor imagery and spatial navigation imagery tasks while being scanned using functional magnetic resonance imaging. The GBS patients were also asked to perform additional functional neuroimaging scans to attempt communication. Results: The motor imagery and spatial navigation task elicited significant activation in appropriate regions of interest for both GBS patients, indicating intact command following. Both patients were able to use the imagery technique to communicate in some instances. Patient 1 was able to use one of four communication tasks to answer a question correctly. Patient 2 was able to use three of seven communication tasks. However, two questions were incorrectly answered while a third was non-verifiable. Conclusions: GBS patients can respond using mental imagery and these responses can be detected using functional neuroimaging. Furthermore, these patients may also be able to use mental imagery to provide answers to ‘yes’ or ‘no’ questions in some instances. We argue that the most appropriate use of neuroimaging-based communication in these patients is to allow them to communicate wishes or preferences and assent to previously expressed decisions, rather than to facilitate decision-making. (AU)

Avances en la evaluación del estado de conciencia: Papel de la evaluación a pie de cama y las técnicas de neuroimagen en el proceso diagnóstico / Advances in the assessment of disorders of consciousness: The role of bedside assessment and neuroimaging techniques in the diagnostic process

El estado vegetativo se define clínicamente por la falta de conciencia de uno mismo y el entorno, junto con el mantenimiento de funciones básicas como la respiratoria, cardiaca, o los ciclos de sueño y vigilia. Se trata de pacientes incapaces de reaccionar de un modo intencional a la estimulación externa y que no manifiestan ninguna capacidad comunicativa. Estudios recientes han demostrado que en torno al 40% de estos pacientes han sido incorrectamente diagnosticados y se encuentran, en realidad, conscientes. Sin embargo, en los últimos años se ha producido una revolución en las herramientas disponibles para evaluar a estos pacientes. El presente artículo tiene como objetivo discutir el papel de las escalas de evaluación clínica estandarizadas, así como técnicas avanzadas de neuroimagen, en la reducción del alarmante error diagnóstico. Se revisarán el alcance y las limitaciones de cada aproximación para identificar signos de conciencia externos o encubiertos, y se presentará evidencia a favor de una evaluación multimodal, combinando la información clínica, estructural y funcional para garantizar el diagnóstico correcto en cada caso individual

Patients in a vegetative state are considered to lack awareness of themselves or the environment, but preserve respiratory and cardiac functions, as well as sleep/wake cycles. These patients are incapable of producing intentional responses to external stimulation and do not demonstrate any communication skills. Recent studies have shown that around 40% of vegetative state patients have been misdiagnosed. However, in recent years there has been a revolution in the tools that are available for the assessment of these patients. The objective of this article is to discuss the diagnostic role of behavioural scales, as well as advanced neuroimaging techniques in reducing the misdiagnosis rate. We review the scope and limitations of these approaches for the identification of overt and covert signs of awareness, and we present evidence to support a multimodal assessment that combines information from behavioural, structural, and functional imaging tools to ensure an accurate diagnosis for each individual patient