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)

Functional Neuroimaging as an Assessment Tool in Critically Ill Patients.

OBJECTIVE: Little is known about residual cognitive function in the earliest stages of serious brain injury. Functional neuroimaging has yielded valuable diagnostic and prognostic information in chronic disorders of consciousness, such as the vegetative state (also termed unresponsive wakefulness syndrome). The objective of the current study was to determine if functional neuroimaging could be efficacious in the assessment of cognitive function in acute disorders of consciousness, such as coma, where decisions about the withdrawal of life-sustaining therapies are often made. METHODS: A hierarchical functional magnetic resonance imaging (fMRI) approach assessed sound perception, speech perception, language comprehension, and covert command following in 17 critically ill patients admitted to the intensive care unit (ICU). RESULTS: Preserved auditory function was observed in 15 patients (88%), whereas 5 (29%) also had preserved higher-order language comprehension. Notably, one patient could willfully modulate his brain activity when instructed to do so, suggesting a level of covert conscious awareness that was entirely inconsistent with his clinical diagnosis at the time of the scan. Across patients, a positive relationship was also observed between fMRI responsivity and the level of functional recovery, such that patients with the greatest functional recovery had neural responses most similar to those observed in healthy control participants. INTERPRETATION: These results suggest that fMRI may provide important diagnostic and prognostic information beyond standard clinical assessment in acutely unresponsive patients, which may aid discussions surrounding the continuation or removal of life-sustaining therapies during the early post-injury period. ANN NEUROL 2023;93:131-141.

Seizure detection with a commercially available bedside EEG monitor and the subhairline montage.

INTRODUCTION: Availability of standard, continuous electroencephalography (cEEG) monitoring in ICU is very limited, although commercially available 4-channel modules are present in many ICUs. We investigated the sensitivity of such modules compared with the more complete monitoring with a standard EEG system. METHODS: Seventy patients at high risk of seizures in the medical-surgical intensive care unit and Epilepsy Monitoring Unit were recorded simultaneously for at least 24 h with a 4-channel commercial ICU bedside monitoring system (Datex-Ohmeda) with a subhairline montage and a standard EEG machine (XLTEK) using the international 10-20 system of electrode placement. Recordings were interpreted independently from each other. RESULTS: The 4-channel recordings demonstrated a sensitivity of 68 and 98% specificity for seizure detection, and a sensitivity of 39% and a specificity of 92% for detection of spikes and PLEDs. CONCLUSIONS: The 4-channel EEG module has limited but practical usefulness for seizure detection when standard cEEG monitoring is not available.

Continuous EEG monitoring in severe Guillain-Barré syndrome patients.

When patients Guillain-Barré syndrome have complete paralysis clinical measures of sedation cannot be applied. In this situation continuous EEG offers a convenient, effective method of monitoring the depth of sedation, using spectral edge frequency (SEF) to quantify EEG activity. The authors report 3 patients with severe Guillain-Barré syndrome managed with sedation aimed at a SEF95 below 4.0 Hz (delta coma), using a subhairline montage with the DATEX bedside EEG module. Two of the patients were easily managed using this system for an average of 16 days, and both were completely amnestic of this period of time with no serious complication. The third one had still some residual muscle activity and SEF was unreliable in this case, so its use was abandoned. Continuous EEG monitoring using SEF is a useful tool to manage sedation in the most severely paralyzed Guillain-Barré syndrome patients. Incorporation of a low-pass filter would be of benefit to remove any residual muscle activity, which confounds the target level of sedation with this method; SEF has theoretical advantages over the bispectral index in this population. Comparative studies of various continuous EEG monitoring methods in such patients should better define their relative effectiveness.