© copyright annals of internal medicine, 2011 ann int med. 154 (1): itc1-1. terms of use the in...

© Copyright Annals of Internal Medicine, 2011Ann Int Med. 154 (1): ITC1-1.

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in the clinic

Transient Ischemic Attack


What is a transient ischemic attack?

Classical definition: Episode of focal cerebral, retinal, or spinal cord ischemia causing transient neurologic dysfunction lasting <24 h (most TIAs resolve in <1 h)

But : despite complete symptom resolution… 20%-50% w/TIA have evidence of acute tissue infarction on MRI

AHA revised definition: TIA should only refer to transient episode of neurologic dysfunction due to ischemia w/o evidence acute infarction, regardless symptom duration

Intent: Better align terminology w/actual disease process

Encourage neurodiagnostic testing to ID brain injury


What is a transient ischemic attack?

TIA and ischemic stroke fundamentally identical disease processes

Differ in:

Duration & degree of cerebral ischemia

Whether permanent detectable brain injury ensues (radiographic/clinical)

Shared pathophysiology supports data extrapolation from selected clinical trials of stroke Rxs to pts w/TIA

Most TIA studies to date use “classical definition”

this review uses “classical definition”


What causes TIA and what are the risk factors?

Mechanism of TIA is…

Large artery atherosclerosis (~20%-25%)

Cardioembolism (10%-15%)

Small vessel disease (10%-15%)

Unusual diverse rare causes (~5%)

Undetermined cause (~50%)


Common Risk Factors for TIA and Stroke

Age >50 y

Hypertension

Diabetes mellitus

Elevated cholesterol levels

Smoking

Carotid stenosis

Hx TIA or stroke

Hx paroxysmal or persistent AF

Hx CAD or PAD

Family Hx CAD, CVD, or PAD before age 60 y


What is the spectrum of presentations for patients with TIA? Symptoms of TIA

Impaired speech and/or language

Visual loss in one or both eyes

Double vision

Facial drooping

Swallowing dysfunction

Unilateral weakness

Unilateral sensory loss

Impaired limb coordination

Vertigo

Gait dysfunction


What is the spectrum of presentations for patients with TIA?

Sxs depend on area of ischemia (brain, retina, or spinal cord)

Lethargy or loss of consciousness atypical ? alternative Dx

Vertigo possible, particularly w/other typical symptoms

isolated vertigo only very rarely due to TIA

Most TIAs quite brief:

60% <1 h, 71% <2 h

Only 14% >6 h

Deficits often resolved by time of medical attention


How should clinicians use history and physical examination to evaluate patients with suspected TIA? Neurologic exam

May be normal (most resolve by time seen); if persistent deficits at evaluation more likely stroke

“Localize the lesion” often challenging (patient recall & description of symptoms may not reliably reflect deficit)

Unilateral weakness often perceived as heaviness; unilateral sensory loss often perceived as tingling, pain

Nonspecific gait dysfunction common; lateropulsion suggests focal deficit

Abnormal speech common challenge to differentiate if aphasia or dysarthria

Blurred vision may be cortical visual field deficit, monocular visual loss, or diplopia


How should clinicians use history and physical examination to evaluate patients with suspected TIA?

Check for any of the following:

Carotid artery bruit

Cardiac arrhythmia or murmur

Impaired distal pulses

Fundi: chronic hypertensive vascular changes

May aid assessment of vascular risk factors

Identify cause of current event


What other disorders should clinicians consider in patients with suspected TIA?

TIA/stroke Abrupt onset; fixed focal findings refer to arterial distribution DW-MRI abnormal in 20%-50% w/transient symptoms

Seizure Abrupt onset and termination; often includes responsiveness, involuntary movements, and/or incontinence during; usually lethargy or confusion after Focal findings occur + resolve over hrs to days May accompany stroke (~2%-3%)

Hypo-/hyperglycemia Usually occurs in pts w/diabetes (diagnose by measuring blood glucose); may be accompanied by seizure


Complicated migraine Severe headache usually precedes/follows; sensory & visual disturbances often prominent; sensory symptoms spread over affected area slowly Younger pts, those w/history severe headache; MRI usually normal; stroke may accompany

Mass lesion e.g., tumor, abscess, herpes encephalitis, subdural hematoma, demyelination Focal symptoms over h to d; may not follow cerebrovascular territory; 1° cancer, fever, trauma, or immunosuppr’n often present Brain imaging distinguishes from stroke

Cervical or lumbar spine disease Focal symptoms isolated to peripheral nerve root distribution in single limb, associated w/depressed reflexes in that region Symptom recurrence may be demonstrated w/maneuvers (e.g., cervical stretch test)


Benign paroxysmal positional vertigo Very brief (seconds) spells of vertigo precipitated by head movement Reproducible w/Dix-Hallpike maneuver Associated w/specific characteristics (torsional nystagmus w/latency, fatigability)

Psychogenic (functional) May look like stroke Often not in vascular territory; findings often nonanatomical/ inconsistent MRI usually normal More likely conversion disorder than malingering


What diagnostic tests are helpful in diagnosis? Brain CT: To exclude brain hemorrhage, large mass lesions, and

identify old areas of infarction

Brain MRI: Evidence acute infarction in 20%-50% with TIA

Carotid US: Sensitivity & specificity 80%-90% for carotid bifurcation stenosis >70%; not helpful for TIA in vertebrobasilar system

Transcranial doppler US: Sensitivity ~70%; specificity 30%-50% for intracranial stenosis >50%

MRA, CTA: Sensitivity & specificity 80%-90% for stenosis >50%; Gd-enhanced cervical MRA ups accuracy; CTA requires IV contrast

Catheter angiography: Reference standard; invasive procedure; use when revascularization considered; requires contrast

ECHO: To detect intracardiac thrombus, tumors, valve disorders

EKG: To identify AF

Serum glucose & hemoglobin A1C: To detect latent diabetes mellitus


Serum lipids: To detect hyperlipidemia

Clotting studies: Obtain baseline prothrombin/partial thromboplastin time to prep for possible anticoagulation

Toxicology screen: To detect sympathomimetic drug use

Blood cultures: If patient febrile, especially if endocarditis, embolic stroke, or TIA suspected

ESR: Patient >50 y: unexplained TIA or headache + possible giant cell arteritis

Rheumatologic serologies: If systemic vasculitis or autoimmune-mediated hypercoagulable state or valvular disease suspected

VDRL/RPR testing: Unexplained TIA + possible meningovascular syphilis

Hb electrophoresis: For anemia and atypical cerebral vasculopathy

Genetic testing: For rare inherited diseases associated with stroke


When should clinicians consult a neurologist for the diagnosis of TIA?

When patient has suspected TIA

Patients evaluated urgently by stroke specialists have lower rates of subsequent stroke

Compared with patients in nonspecialty settings

Early evaluation & therapy associated w/80% reduction in risk early recurrent stroke


CLINICAL BOTTOM LINE: Diagnosis… Transient neurologic symptoms characterize TIA

Evaluate: Are the symptoms due to cerebral ischemia?

If so, what is the mechanism by which it occurred?

Perform tests to identify and treat the causes of TIA

Vascular imaging, electrocardiography, echocardiography

Lab testing, basic blood work

Brain MRI-DWI: Sensitive to acute infarction (seen in ~33% of TIA patients despite symptom resolution)


What is the role of risk assessment in the acute care of patients with TIA? Essential component of management

Overall: 5.2% stroke risk w/in 7 days most w/in first 48 h

Up to 20% stroke risk w/in 90 days in patients with high-risk features of TIA

Risk of early stroke varies by health care setting:

Lowest risk in patients receiving emergency Rx from specialist stroke services (0.9% at 7 days)

Highest risk in general population-based studies w/o urgent Rx (11.0% at day 7)

Observed risk also depends on study methodology higher risks in studies w/active outcome ascertainment


How should clinicians assess the risk for subsequent stroke in patients after TIA?

Score Risk Stroke Risk

2 Days 7 Days 90 Days

0-3 Low 1.0 1.2 3.1

4-5 Moderate 4.1 5.9 9.8

6-7 High 8.1 11.7 17.8

Clinical risk scores: ABCD2 Score Age: ≥60 y = 1 point

Systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg = 1 point

Unilateral weakness = 2 points

Diabetes: yes = 1 point

Symptom duration: ≥60 min = 2 points; 10-59 min = 1 point


Brain imaging studies: CT or MRI

Cerebral infarction = significantly increased short-term stroke risk

On CT: indicates background presence of CVD

On MRI-DWI: provides information about acute clinical event

Vascular imaging studies

Estimate risk

Identifies candidates for revascularization

If large-vessel stenosis causes TIA: high short-term stroke risk


Are there any patients with suspected TIA that are at very low risk for stroke?

Isolated sensory symptoms lasting <10 min

Isolated visual symptoms lasting <30 min

Transient isolated vertigo

Symptoms may be due to nonvascular process


CLINICAL BOTTOM LINE: Risk stratification… Tools help predict who is at highest risk for stroke after TIA

~5%-10% of patients will have a stroke within 1 week

Clinical risk scores

ABCD2 score: incorporates age, blood pressure, weakness or speech impairment, duration of event, and Hx of diabetes: Low score = low short-term risk (~1% at 7 days)

Brain imaging with CT or MRI-DWI and vascular imaging

Acute infarction on MRI-DWI, old or new infarction on CT, or large-vessel stenosis on vascular imaging = higher risk in short-term

Normal MRI-DWI = low risk


When should clinicians hospitalize patients with suspected TIA?

All patients w/acute TIA

Observe for 24 hours while determining mechanism of TIA and treatment strategy

Patients at high risk for subsequent TIA or stroke

For intensive treatment and close monitoring

AHA 2009 guidelines: Hospitalize patients with TIA who present ≤72 hours of symptom onset if:

ABCD2 score ≥3 or

ABCD2 score 0-2 in either: the setting of inability to complete diagnostic evaluation within 48 h or evidence of focal ischemia


What drug therapy should clinicians consider for patients having acute TIA?

Clopidogrel Antiplatelet: for acute TIA in patients with aspirin allergy

Heparin Anticoagulant: consider if documented cardioembolic

source, severe large vessel stenosis, history of multiple TIAs

Warfarin Anticoagulant: for TIA due to AF; reduces stroke, recurrent TIA

Dabigatran Anticoagulant: for TIA due to AF; direct thrombin inhibitor;

more effective than antiplatelet Rx in this setting

Aspirin Antiplatelet: for acute TIA; to prevent stroke

Combined aspirin + dipyridamole Antiplatelet: benefit over aspirin alone; similar to clopidogrel


How should clinicians manage antihypertensive medications in the setting of acute TIA?

In the first 24 h, optimize cerebral blood flow

Avoid BP-lowering agents (i.e., permissive HTN)

Use IV normal saline to ensure euvolemia

Position patient with head of bed flat

If patient stable for 24 h

Restart antihypertensive medications

Do so more cautiously in patients with TIA due to severe large-vessel stenosis


When should clinicians use anticoagulant and antiplatelet therapy to prevent recurrent TIA or stroke?

Warfarin anticoagulation

If TIA or stroke due to AF: Reduces risk of future stroke

Oral anticoagulation

If TIA due to other high-risk cardioembolic sources

Aspirin + clopidogrel combination

For patients unable to take warfarin for reasons other than bleeding risk

Antiplatelet therapy If no cardioembolic TIA source; clopidogrel or ASA-ER DP better than

aspirin to prevent recurrent vascular events after stroke


What other drug therapy has a role in preventing recurrent TIA or stroke?

Statins

Reduce risk for recurrent vascular events after stroke or TIA

Recommended target LDL <70 mg/dL with atherosclerotic stroke or TIA

Multiple mechanisms ameliorate stroke risk

Antihypertensive Agents

Use outside acute period

Long-term aggressive BP lowering significantly reduces future vascular event risk

Beneficial even in normotensive pts w/stroke or TIA


What surgical or other nondrug therapies can be used to prevent recurrent TIA or stroke? CEA

If carotid stenosis ≥50%: reduces future stroke risk (especially when stenosis >70%)

Best if performed within 2 weeks of TIA, especially when carotid stenosis 50%-69%

Carotid angioplasty and stenting

Alternative to CEA

Use if surgery contraindicated (high carotid bifurcation, previous neck radiation, extremely high cardiac risk)


How should clinicians follow patients with TIA?

Focus on controlling vascular risk factors

Emphasize

Healthy diet and regular exercise

Medication compliance

Smoking cessation

Pay close attention to new neurologic symptoms that suggest recurrent TIA or stroke

In absence of new symptoms, no routine follow-up studies needed


CLINICAL BOTTOM LINE: Treatment… Immediate evaluation important to determine cause of TIA and

strategies to reduce the risk for recurrent TIA or stroke

Hospitalization appropriate for most patients with acute TIA

Administer antiplatelet therapy promptly

Administer long-term anticoagulation to patients with a cardioembolic source, such as AF

Consider carotid revascularization for patients with carotid stenosis >50%, preferably by CEA and within 2 weeks of TIA

Provide long-term antithrombotic therapy and control of vascular risk factors to all patients

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