BOSTON
— In emergency department stroke consultations, the National Institute
of Health Stroke Scale (NIHSS) alone does not appear to be a reliable
guide for ordering diagnostic tests for a large vessel occlusion (LVO),
according to large body of data presented at the 2023 annual meeting of
the American Academy of Neurology.
If the goal is not to miss any
LVOs, there is no NIHSS score below which these do not occur, according
to Theresa Sevilis, DO, regional medical director, TeleSpecialists, Fort
Myers, Fla.
For example, her evaluation of a large and nationally
representative dataset shows that more than 10% of the LVOs eventually
identified and accepted for intervention would be missed with a cutoff
of NIHSS score of 6 or higher. Moving the cutoff NIHSS score to 4 or
greater, 6% of LVOs among the 23,166 strokes evaluated would have gone
undetected.
"The current guidelines do not address low NIHSS score
largely due to a paucity of data," according to Dr. Sevilis, who showed
data indicating that there is great variation among institutions in
regard to ordering computed tomography angiography (CTA). She indicated
that CTA is the current imaging standard for detecting LVO.
Large prospective dataset
The
data for this study were derived from the TeleCare database, which
captures acute stroke consultations in the emergency departments in 227
facilities in 27 states. Stroke consultations over a 6-month period from
July through December 2021 were evaluated. The prospectively collected
data were subjected to a multivariate analysis to determine the odds
ratio for a CTA performed and LVO found at each NIHSS score of 0 to 5.
Scores 6 or above served as the reference.
"Only consults performed within 24 hours [of presentation] were included," Dr. Sevilis said.
After
excluding cases in which no NIHSS score was captured, which represented
less than 1% of cases, more than 10,500 cases underwent CTA, providing a
rate of 45.5%. The rate of CTA for the whole dataset was 45.5%. Of the
study population, 24.6% had a NIHSS score of 6 or above.
"When you
are discussing when to perform CTA in patients with a low NIHSS score,
you are discussing the majority of patients," Dr. Sevilis said.
Of
those with a NIHSS stroke of 6 or below, 28.2% had a score of 0. Not
surprisingly, these were the least likely to have a CTA performed on the
basis of an odds ratio of 0.14 and the least likely to have a LVO
detected (OR, 0.1). With the exception of a NIHSS stroke score of 1, the
likelihood of CTA and LVO climbed incrementally with higher stroke
scores. These odds ratios were, respectively, 0.16 and 0.09 for a score
of 1; 0.27 and 0.16 for a score of 2; 0.33 and 0.14 for a score of 3;
0.49 and 0.24 for a score of 4; and 0.71 and 0.27 for a score of 5.
In
the group with NIHSS score of 6 or above, 24.1% were found to have an
LVO. Of these, the proportion accepted for a mechanical thrombectomy was
less than half. The intervention acceptance rate for mechanical
intervention among LVOs in patients with lower NIHSS scores again fell
incrementally by score. The acceptance rate was about 35% among LVO
patients with a NIHSS score of 3 or 4 and 25% for those with a score of
0-2.
The interpretation of these data "depends on goals," Dr. Sevilis
said. "If the goal is to not miss a single LVO, then it is important to
consider the balance between benefits and risks."
No consistent cutoff
In
participating facilities, the protocol for considering CTA to detect
and treat LVOs ranges from neurologist choice to cutoffs of NIHSS scores
of 2, 4, and 6, according to Dr. Sevilis. Where the data suggest that a
cutoff of 4 or above might be reasonable, she said that NIHSS scoring
is not a useful tool for those "who do not want to miss any LVOs."
These
data are based on emergency room stroke consultations and not on
confirmed strokes," Dr. Sevilis emphasized. Indeed, she noted that the
final discharge diagnosis was not available. Recognizing that the
analysis was not performed on a population with confirmed strokes is
particularly important for understanding the limited rate of CTAs
performed even in those with relatively high NIHSS scores. She noted
this could be explained by many different reasons, including suspicion
of hemorrhage or clinical features that took the workup in a different
direction.
Reconsidering protocols
Based
on the large sample size, Dr. Sevilis contended that it is likely that
these data are representative, but she considers this study a first step
toward considering protocols and developing guidelines for addressing
stroke alerts in the emergency department.
A
more important step will be ongoing trials designed specifically to
generate data to answer this question. Pascal Jabbour, MD, chief of the
division of neurovascular and endovascular neurosurgery, Thomas
Jefferson University Hospitals, Philadelphia, is participating in one of
these trials. He agreed with the premise that better evidence-based
criteria are needed when evaluating acute stroke patients with a
potential LVO.
The trial in which he is a coinvestigator, called ENDOLOW,
is testing the hypothesis that outcomes will be better if acute stroke
patients with a LVO and a low baseline NIHSS score (< 5) are treated
with immediate thrombectomy rather than medical management. If this
hypothesis is confirmed in the randomized ENDOLOW, it will provide an
evidence basis for an approach already being practiced at some centers.
"There
should be a very low threshold for CTA," said Dr. Jabbour in an
interview. This imaging "takes less than 2 minutes and it can provide
the basis for a life-saving endovascular thrombectomy if a LVO is
found."
It is already well known that LVO is not restricted only to patients with an elevated NIHSS score, he said.
For
determining whether to order a CTA, "I do not agree with NIHSS score of
6 or above. There is no absolute number below which risk of missing a
LVO is eliminated," Dr. Jabbour said. He also argued against relying on
NIHSS score without considering other clinical features, particularly
cortical signs, which should raise suspicion of a LVO regardless of
NIHSS score.
One problem is that
NIHSS scores are not static. Decompensation can be rapid with the NIHSS
score quickly climbing. When this happens, the delay in treatment might
lead to a preventable adverse outcome.
"There
is a change in the paradigm now that we have more evidence of a benefit
from aggressive treatment in the right candidates," according to Dr.
Jabbour, referring to the recently published SELECT2 trial.
In that trial, on which Dr. Jabbour served as a coauthor, patients with
LVO and large territory infarct were randomized to thrombectomy or
medical care within 24 hours of a stroke. It was stopped early for
efficacy because of the increased functional independence (20% vs. 7%)
in the surgical intervention group.
If
the ongoing trials establish better criteria for ruling in or out the
presence of LVO in patients with acute stroke, Dr. Jabbour predicted
that guidelines will be written to standardize practice.(What useless crapola! GUIDELINES NOT PROTOCOLS!)
Dr.
Sevilis reports no potential conflicts of interest. Dr. Jabbour has
financial relationships with Cerenovus, Medtronic, and Microvention.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.