Clinical
neurologic assessment tool: development and
testing of an instrument to index neurologic
status
Crosby L, Parsons LC
University of Arizona,
USA
The clinical neurologic assessment tool
(CNA) is a 21-item instrument assessing response
to verbal and tactile stimulation, ability to
follow commands, muscle tone, body position,
movement, chewing, and yawning in the patient
with head trauma. The CNA was developed to
detect subtle changes in the patients'
neurologic status that may indicate transitions
in the comatose state. The CNA has been
extensively pilot tested. Reliability determined
by using Cronbach's alpha revealed an internal
consistency of 0.96. Concurrent validity testing
with the Glasgow Coma Scale indicated a strong
positive correlation, r = 0.94. Construct
validity was assessed with factor analysis using
0.50 for a loading criterion. Three factors were
demonstrated: general level of consciousness,
muscle tone and resistance, and chewing or
yawning. Discriminant function analysis revealed
that the CNA scores correctly classified 95.1%
of the patient observations into their
respective Glasgow Coma Scale categories. The
CNA is reliable, valid, convenient, and easily
scored and captures the subtle changes in the
patient with head trauma.
The annual incidence of head injuries, estimated
to be 200 per 100,000 population, demonstrates a
health problem that clinicians frequently
encounter in a variety of settings. The
detection of early warning signs of
complications from head injuries can make a
difference between death or disability and
intact neurologic functioning. Serial assessment
is necessary to detect symptoms of neurologic
deterioration because treatment within 30 to 120
minutes of deterioration can make a difference
in the patient's prognosis .
The Glasgow Coma Scale (GCS), because of its
simplicity, consistency, and degree of
interrater reliability, is a well accepted and
highly utilized instrument for assessing
neurologic status in a patient with head injury.
The GCS has demonstrated predictive validity in
the correlation between a patient's 24-hour
postinjury score and eventual neurologic
outcome? Despite the frequent use of the GCS,
clinicians complain that the scale lacks the
ability to assess subtle changes in the
patient's neurologic status. Such changes may
occur as the patient's level of consciousness
improves or deteriorates. For example, within
the GCS range of 8 to 15, evaluating a person's
leve of cognition and orientation as well as
ability to speak may seem critical, yet the GCS
addresses only speaking ability. In one study,
38% of 451 patients with head trauma could not
be evaluated by one or more components of the
GCS. The use of the GCS is most difficult with
patients who have endotracheal tubes in place,
patients who have periorbital edema, and
patients who have immobilized upper extremities.
The presence of any one of these factors may
encourage the person conducting the assessment
to label the corresponding GCS component as
untestable. The omission of valuable data on an
instrument that has only three testable items
may limit the instrument's clinical
usefulness.
The clinical experiences of the
investigators supported the assumption that a
change in a patient's neurologic status was not
always accompanied by a change in the patient's
GCS score. Colleagues also expressed concern
that several patient behaviors were not included
in the GCS, such as showing signs of recognition
through facial expression, following the
nurse or family members with his or her eyes,
and chewing or
yawning.
The purpose of this article is to discuss
the development of a clinical neurologic
assessment tool (CNA) that may prove to be more
sensitive to subtle changes in level of
consciousness, thus providing earlier detection
of neurologic deterioration or improvement. The
CNA is a valuable tool to use throughout the
hospitalization and is applicable regardless of
the patients GCS score. For example, the CNA is
especially suitable for assessing subtle changes
in the comatose patient as the patient emerges
from coma. At the other extreme, the CNA is able
to more completely evaluate patients with a GCS
score in the 13 to 15 range because degree of a
patient's orientation is evaluated separately
from the patient's ability to communicate.
Overall, the instrument evaluates a patient's
ability to perform verbal, motor, and cognitive
functions. In addition, observations are made of
the patient's body position, muscle tone, and
the occurrence of spontaneous chewing and
yawning (see appendix).
[...]
SUMMARY The CNA is a valid and
reflable instrument consisting of 21 items for
measuring level of consciousness among patients
with severe (GCS 3to 8), moderate (GCS 9 to 12),
and mild (GCS 13 to 15) head injury. Cronbach
alpha reliability coefficients for the CNA with
GCS scores 3 to 8, 9 to 12, and 13 to 15 samples
were 0.85, 0.83, and 0.87, respectively (Table
1). The inclusion of items to evaluate the
patient's ability to communicate separately from
the patient's degree of orientation provides
greater descriptive data of patients who have a
minor neurologic deficit. Statistically, minor
neurologic injuries constitute the vast majority
(49%) of patient with CNS trauma. General
voluntary body movement (item 16) serves as the
best indicator of level of consciousness whereas
spontaneous verbalization (item 20) is the
strongest predictor variable in classifying
subject acuity. Ease of administration, clinical
applicability, and degree of comprehensiveness
arc characteristics supporting the use of the
CNA in assessing patients' level of
consciousness.
Extraits:
VI. Assessment of patient's chewing,
yawning,
verbalization
