Patients with a severe prolonged Disorder of Consciousness can show classical EEG responses to their own name compared with others' names.

Agnieszka M Kempny,E Diane Playford,Simon F Farmer,Sophie Duport,Kudret Yelden,Alexander P Leff,Leon James

doi:10.1016/j.nicl.2018.04.027

Abstract

Patients in Vegetative State (VS), also known as Unresponsive Wakefulness State (UWS) are deemed to be unaware of themselves or their environment. This is different from patients diagnosed with Minimally Conscious state (MCS), who can have intermittent awareness. In both states, there is a severe impairment of consciousness; these disorders are referred to as disorders of consciousness (DOC) and if the state is prolonged, pDOC. There is growing evidence that some patients who are behaviourally in VS/UWS can show neural activation to environmental stimuli and that this response can be detected using functional brain imaging (fMRI/PET) and electroencephalography (EEG). Recently, it has also been suggested that a more reliable detection of brain responsiveness and hence a more reliable differentiation between VS/UWS and MCS requires person-centred and person-specific stimuli, such as the subject's own name stimulus.In this study we obtained event related potential data (ERP) from 12 healthy subjects and 16 patients in pDOC, five of whom were in the VS/UWS and 11 in the Minimally Conscious State (MCS). We used as the ERP stimuli the subjects' own name, others' names and reversed other names. We performed a sensor level analysis using Statistical Parametric Mapping (SPM) software. Using this paradigm in 4 DOC patients (3 in MCS, and 1 in VS/UWS) we detected a statistically significant difference in EEG response to their own name versus other peoples' names with ERP latencies (~300 ms and ~700 ms post stimuli). Some of these differences were similar to those found in a control group of healthy subjects.This study shows the feasibility of using self-relevant stimuli such as a subject's own name for assessment of brain function in pDOC patients. This neurophysiological test is suitable for bed-side/hospital based assessment of pDOC patients. As it does not require sophisticated scanning equipment it can feasibly be used within a hospital or care setting to help professionals tailor medical and psycho-social management for patients.

Highlights

Patients who emerged from coma following a severe brain injury, into a state of wakefulness but unresponsiveness were diagnosed as being in a Vegetative State (VS) (Jennett and Plum, 1972), called the Unresponsive Wakefulness Syndrome (UWS) (Laureys et al, 2010)
Note that the response to others' names was greater than own name centrally at ~300 ms, while the later, left-lateralized response at ~700 ms was of a negative polarity for own name
The patients had been in prolonged Disorder of Consciousness (pDOC) for 17.31 months on average (Table 2)

Summary

Introduction

Patients who emerged from coma following a severe brain injury, into a state of wakefulness but unresponsiveness were diagnosed as being in a Vegetative State (VS) (Jennett and Plum, 1972), called the Unresponsive Wakefulness Syndrome (UWS) (Laureys et al, 2010). A new diagnostic term of Minimally Conscious State (MCS) was introduced by Giacino et al (Giacino et al, 2002) in order to distinguish this patient group form those in the VS/UWS state. Both types of patients (UWS and MCS) are said to suffer from a Disorder of Consciousness (DOC) or prolonged Disorder of Consciousness (pDOC), which recognizes that the two sub-types exist on a continuum (TurnerStokes, 2014). It has been estimated that approximately 10% of the patients with a diagnosis of VS/UWS, have some preserved higher brain function (Turner-Stokes et al, 2012)

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