Serial measurement of Wessex Head Injury Matrix in the diagnosis of patients in vegetative and minimally conscious states: a cohort analysis

Abstract

Objective: To evaluate serial application of the Wessex Head Injury Matrix (WHIM) in diagnosis of prolonged disorders of consciousness (PDOC). Specifically, to determine whether the trajectory of change predicts outcome status, and whether the current hierarchical order of WHIM items is correct for this context.

Design: Analysis of prospectively gathered clinical cohort data.

Setting: Consecutive admissions to a tertiary in-patient neurorehabilitation service for evaluation of PDOC in real-life clinical practice, over a 10-year period (2004-2014).

Participants: Patients (n=65) presenting in sudden-onset vegetative (VS) or minimally conscious states (MCS). Mean age 38.4 (sd14.1) years; male:female ratio 66%:33%. Aetiology of brain injury: 40(62%) traumatic; 12(19%) vascular; 11(17%) hypoxic; 3(3%) other.

Primary outcome measure: WHIM alongside detailed clinical evaluation.

Methods: The WHIM was administered serially by the multidisciplinary team throughout an in-patient evaluation programme (mean length 74 (sd42) days). Patients were divided into four groups, according to PDOC status on discharge (VS, MCS-Minus, MCS-Plus or Emerged).

Results: WHIM hierarchical scores (Most Advanced Behaviour (MAB)) correlated with PDOC status at discharge (Pearson r=0.49, p<0.001). In the original order, the MAB distinguished the 'VS', 'MCS' and 'Emerged' categories (analysis of variance (ANOVA) post hoc p<0.001), but not the subgroups of MCS-Minus and MCS-Plus. In stepwise regression analysis, MAB-Ex (excluding two items) accounted for 68% of the variance in PDOC status at discharge. On multilevel statistical modelling, trajectory of change in MAB separated the four PDOC groups, both at individual and at group level (p<0.001). After reordering of items, the new-order MAB accounted for more (73%) of the variance in PDOC status, and also distinguished significantly between MCS-Minus and MCS-Plus groups at discharge (p<0.002).

Conclusions: The WHIM is a useful diagnostic tool in PDOC, and trajectory of change is an important predictor of outcome. The proposed new hierarchical order requires further evaluation in future multicentre analyses.

Keywords: Brain Injuries; Minimally Conscious State; Patient Outcome Assessment; Prolonged Disorders of consciousness; Vegetative State; Wessex Head Injury Matrix.