In this post, I link to and excerpt from Stroke risk stratification in acute dizziness presentations: A prospective imaging-based study [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Neurology. 2015 Nov 24;85(21):1869-78.
All that follows is from the above resource.
Objective: To estimate the ability of bedside information to risk stratify stroke in acute dizziness presentations.
Methods: Surveillance methods were used to identify patients with acute dizziness and nystagmus or imbalance, excluding those with benign paroxysmal positional vertigo, medical causes, or moderate to severe neurologic deficits. Stroke was defined as acute infarction or intracerebral hemorrhage on a clinical or research MRI performed within 14 days of dizziness onset. Bedside information comprised history of stroke, the ABCD(2) score (age, blood pressure, clinical features, duration, and diabetes), an ocular motor (OM)-based assessment (head impulse test, nystagmus pattern [central vs other], test of skew), and a general neurologic examination for other CNS features. Multivariable logistic regression was used to determine the association of the bedside information with stroke. Model calibration was assessed using low (<5%), intermediate (5% to <10%), and high (≥10%) predicted probability risk categories.
Results: Acute stroke was identified in 29 of 272 patients (10.7%). Associations with stroke were as follows: ABCD(2) score (continuous) (odds ratio [OR] 1.74; 95% confidence interval [CI] 1.20-2.51), any other CNS features (OR 2.54; 95% CI 1.06-6.08), OM assessment (OR 2.82; 95% CI 0.96-8.30), and prior stroke (OR 0.48; 95% CI 0.05-4.57). No stroke cases were in the model’s low-risk probability category (0/86, 0%), whereas 9 were in the moderate-risk category (9/94, 9.6%) and 20 were in the high-risk category (20/92, 21.7%).
Conclusion: In acute dizziness presentations, the combination of ABCD(2) score, general neurologic examination, and a specialized OM examination has the capacity to risk-stratify acute stroke on MRI.
© 2015 American Academy of Neurology.
Patients with dizziness from stroke are challenging to identify because they often lack typical stroke warning signs or symptoms.1,–6
Prior studies have been performed to assess bedside decision support tools that could help to discriminate stroke from other causes of acute dizziness.3,4,7 The ABCD2 score (age, blood pressure, clinical features, duration, and diabetes) may also be useful in discriminating vascular from nonvascular events.8,–10 When assessed in a retrospective study of emergency department dizziness presentations, the visits with a low-risk ABCD2 score (ABCD2 < 4) had a stroke frequency of 1% (5/512 patients) compared with 8.1% (32/395) in the high-risk group (ABCD2 ≥ 4).3 Another tool that has been developed to identify cases of dizziness-stroke is the HINTS assessment (head impulse, nystagmus pattern, test of skew), which is based on a specialty bedside ocular motor (OM) examination.4 HINTS has shown promising results, superior to the ABCD2 score (sensitivity/specificity: ABCD2, 61%/62%; HINTS, 96.5%/84.4%) in a prospective study of acute dizziness.4
In this study, we expand on this prior work by evaluating the ability of the combination of bedside predictors of stroke—including both the ABCD2 score and the specialized OM examination—to stratify stroke risk using an MRI-based gold standard.
The target population was patients presenting for acute dizziness without an obvious cause who also had examination findings (i.e., nystagmus [spontaneous or gaze-evoked] or imbalance when walking) that could be attributable to neurologic dysfunction (table 1). To identify potentially eligible cases, we used active and passive surveillance methods (appendix e-1 on the Neurology® Web site at Neurology.org).
Baseline clinical measurements.
History of present illness information was obtained in a structured fashion by either a research assistant or investigator. The physical examination was performed in a structured fashion by a study investigator, either a neurologist fellowship trained in neuro-otology (K.A.K.) or vascular neurology (E.E.A.), or an emergency medicine physician fellowship trained in vascular neurology (W.J.M.). Study examinations were performed before the MRI whenever possible or blinded to the results of the MRI. The general neurologic examination included assessment of visual fields, cranial nerves, strength, sensation, coordination, and balance. Patients were given up to 2 attempts to walk 10 consecutive steps in tandem, and the maximum number of steps taken before a side step was recorded or a 0 was recorded if the patient declined the test. Hearing impairment was assessed using finger rub.
The OM examination was performed including a nystagmus assessment, assessment of skew deviation, and the head impulse test (HIT) (appendix e-1). Patients were classified as having a central pattern of nystagmus if any of the following were observed: bidirectional gaze-evoked nystagmus, vertical nystagmus in any position, or isolated torsional nystagmus (i.e., nystagmus that was only in the torsional vector). Frenzel lenses were used as a complementary part of the nystagmus assessment in a convenience sample of 106 patients. Within individual patients, the categorization of nystagmus applied in this study (see categories below) did not change from the examination without Frenzel lenses to an examination with them, so further details are not presented. Skew deviation was classified as present when alternating vertical refixations were observed. The HIT vestibulo-ocular reflex to each side was scored by examiners as normal (0), inconsistent/slight corrective saccade (1), small-amplitude corrective saccade (2), medium-amplitude corrective saccade (3), or large-amplitude corrective saccade (4). The HIT vestibulo-ocular reflex was considered normal (finding absent) if the examiner scored 0 or 1 and abnormal (finding present) if the examiner scored 2, 3, or 4. A second examiner, when available, also performed an OM examination so that interobserver agreement could be estimated. So that examination reliability could be measured including all patients, the OM examination was also video-recorded.
From the medical record, we collected arrival date/time, first recorded blood pressure, demographic information, and administered medications. From the physician’s note, we abstracted medical history and current medications.
The ABCD2 score was calculated for each patient by assigning points as follows: age 60 years or older = 1; systolic blood pressure ≥140 or diastolic blood pressure ≥90 = 1; clinical features (new symptoms or examination findings of unilateral weakness = 2, speech disturbance without weakness = 1); duration of symptoms (<10 minutes = 0, 10–59 minutes = 1, ≥60 minutes = 2); and diabetes (either medical history or current use of an oral hypoglycemic medicine or insulin documented in the emergency department physician’s note) = 1.8
The results of the OM examination were categorized into one of the following 3 categories for each patient: no nystagmus or skew, HINTS negative, or HINTS positive. Patients were assigned to the no-nystagmus or skew category when there was no nystagmus or skew deviation on examination. The HIT was not considered in this category because the value of the HIT in an acute presentation without nystagmus is uncertain as exemplified by the inclusion of patients without nystagmus in the first HINTS development study but not the second.4,11 Patients were assigned to the HINTS-negative category for the following findings: noncentral classification of nystagmus (i.e., direction-fixed horizontal nystagmus), plus an abnormal HIT (i.e., HIT score of ≥2, suggesting a peripheral lesion) to the side opposite the fast phase of the horizontal nystagmus, plus the absence of skew deviation. Patients were assigned to the HINTS-positive category for any of the following findings: a central pattern of nystagmus, or a normal HIT (i.e., HIT score of 0 or 1, suggesting a central lesion) to the side opposite the fast phase of direction-fixed horizontal nystagmus, or the presence of skew deviation.11 Using this scheme, a patient with nystagmus and bilaterally abnormal HITs would be included in the HINTS-negative category as long as central nystagmus and skew were not present.
A variable called “other CNS features” was used to indicate the presence of new CNS signs or symptoms not included in the ABCD2 or HINTS scales. This variable was dichotomized (0/1) with a score of 1 indicating the presence of any possible or mild bilateral weakness (note, the ABCD2 score specifies unilateral weakness) or sensory signs or symptoms, visual field deficit, or dysmetria on the finger-nose-finger test. As previously stated, patients with moderate to severe other CNS features were excluded from enrollment. The variable “prior stroke” (0/1) was scored as a 1 when the treating physician’s note indicated that the patient had a medical history of stroke.