T LB Pape, Edward Hines Jr. VH; S Lundgren, Minneapolis VAMC; R Sennor, Rehabilitation Institute of Chicago

Objectives: The absence of a measure of cerebral functioning in the unconscious mind has limited medical decision making for veterans surviving severe brain-injury, which results in a altered consciousness and lasts for an unknown duration. Three sub-syndromes describe this state; coma, vegetative (VS) and minimally conscious (MCS). Measures have been inadequate because of insufficient sensitivity to detect subtle indices of and changes in cerebral functioning. Significant progress has been made in the measurement of cerebral functioning with the development of the Disorders of Consciousness Scale (DOCS); a neurobehavioral evaluation tool that when combined with the Glasgow Coma Scale (GCS) verbal item produces a reliable and valid measure of cerebral functioning reflecting neurological functioning one moment in time (static). The objectives of this presentation is to provide information on 1) how to derive the static measure, 2) the most useful time post injury to derive the measure 3) using the measure to differentiate between VS, MCS and consciousness, monitor status, and make medical decisions.

Methods: Severely brain injured participants aged 18 years and older (39 persons) were recruited from the Minneapolis VAMC and the Rehabilitation Institute of Chicago. Serial DOCS and GCS evaluations were conducted yielding 99 response sets. A classification of Coma, VS or MCS was obtained independently. Each participant was observed for indications of consciousness. Scaling analysis was used to examine the reliability and validity of the static measure. Receiver Operating Characteristic curves were used to evaluate the predictive usefulness of the static measure of cerebral functioning.

Results: The DOCS employs a three-point rating scale to describe cerebral functioning (0,1,2). The GCS employs three different scales to describe cerebral functioning (verbal: 1 through 5). Results indicate that the raters used the scales as intended, to reflect progressively improving levels of cerebral functioning.

The separation reliability index of 3.29 for the DOCS and GCS combined items tells us that the items reliably fall within 4 groups (Strata index equals 4).

Concurrent validity was evaluated by computing correlation coefficients between the DOCS and GCS total measures; a moderate association was observed (r = .48).

Evidence of construct validity includes the fit of each item relative to the other items; 7 of the 32 test items had fit statistics outside the acceptable range.

Preliminary results indicate that a measure derived within 45 days of injury compared to within 70 days of injury may be more sensitive to predicting the recovery of consciousness (sensitivity equals 83 % and 77%, respectively).

Conclusions: The conclusions are that the static measure of cerebral functioning 1) reliably discriminates between VS and MCS, 2) is useful for predicting the recovery of consciousness, and 3) can be used to guide medical decision making.

Impact: The static measure of cerebral functioning in the unconscious mind reflects major improvements over past research with this population. Clinical application of the measure improves the quality of care for veterans in altered states of consciousness because it serves as a medical yardstick to guide medical decision making.