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Transient ischemic attack (TIA)

Since TIA symptoms can be noted during comparatively short period of time, patients often ignore them and don’t ask for help. That’s why TIA registration is not complete.

Meanwhile, timely recognition of TIAs carries vital importance. This gives a chance to provide a patient with the efficient medical help aimed at the prevention of developing speech, mobility and other disorders, which depend on the location of the damage. Medical aid is also aimed at the prevention of secondary stroke.

Transient ischemic attack (TIA) is a type of transient impairment of cerebral circulation. Traditionally, TIA is defined as an acute disorder of the cerebral circulation accompanied by the short-time disruption of brain functions seen as cerebral or/and focal symptoms. Complete regress of symptoms follows the attack, while signs of cerebral infarction are absent at neuroimaging. It must also be remembered, that transient ischemic attack is a critical condition which is identical to the infarction until the symptoms completely disappear.

It is known, that risk of a stroke increases by 4-10% during first two days after the TIA. The number grows up to 10-20% during following three months. If there is stenosis of the extra cranial section of the carotid artery, which exceeds 70% of its diameter, the risk of a stroke within the first two years after TIA reaches 28%. Based on this data, transient ischemic attack can be considered as one of the stroke predictors. Typically, atherothrombotic stroke develops after TIA in 50% of cases, lacunar stroke developes less often in 20%, cardioembolic in 10% or hemorrhagic in 20%.

Risk factors

The key risk factors of a transient ischemic attack are:

Arterial hypertension;
Diabetes;
Hypercholesterolemia;
Excessive consumption of alcohol;
Smoking;
Sedentary lifestyle;
Overweight.

The most frequent etiologic factors of transient ischemic attackc are:

Cardiogenic embolism;
Atherosclerosis of the vertebral or carotid arteries as well as of their large branches causing arterial embolism;
Symptomatic carotid stenosis of more than 50% of the artery lumen, causing hemodynamic insufficiency;
Coagulopathy;
Developmental abnormalities (doubling, bending, aplasia or hypoplasia) of the vertebral or carotid arteries;
Angiopathy caused by diabetes mellitus, hypertension or other causes;
Dissection of the vertebral or carotid arteries;
Extravasal compression of vertebral arteries, performed by pathologically altered cervical vertebrae;
The use of sympathomimetics.

TIA can be less often preconditioned by the vasculitis (including specific one), antiphospholipid syndrome, blood diseases, migraine, venous thrombosis, oral contraceptive use, or other reasons.

Pathogenesis

Acute, though reversible (no infarction focus) critically lowered blood supply in the certain areas of the artery leads to the TIA development. Key moment of the pathogenesis is exactly the reversibility of the local cerebral ischemia (with cerebral perfusion lowered to 18-22 ml for 100 g/minute).

Transient decrease of the blood flow in the area more distant from the artery occlusion zone and appearance of ischemia in the brain tissue foci that correspond to the damaged arteries cause occurrence of the reversible focal symptoms. If cerebral perfusion has been restored, than clinically, a regress of focal symptoms takes place with the following termination of the TIA episode. If perfusion falls further below the threshold of irreversible changes, cerebral infarction occurs.

TIA’s development mechanisms are basically identical to the ischemic stroke pathogenesis. Cerebral infarction or TIA’s outcome depends on the speed of pathological process development, location of the damage, rheological blood properties, and the state of collateral circulation.

Symptoms

Clinically, transient ischemic attack manifests itself by the symptoms of cerebral ischemia which depend on the location of this disruption. For instance:

Vision loss in both/one eye(s);
Sensibility impairment in the leg and/or in the arm and/or facial muscles;
Disruption in the movement coordination and/or balance;
Epileptic attacks;
Speech disorders;
Memory, behavioral disorders;
Psychomotor agitation;
Loss of consciousness.

Average duration of one TIA episode is 8-14 minutes. The majority of such attacks disappear within an hour or even earlier. According to the statistics, duration of symptomatic TIA’s manifestations up to one hour are noted by 43.5% of patients, 1-3 hours by 45.7% of patients and more than three hours by 10.9% of patients.

Diagnostics

TIAs happen 4 times more often in the carotid arterial system than in the vertebrobasilar system. As a rule, TIA is diagnosed retrospectively as symptoms regress by the time a patient is checked by neurologist. Therefore, clinical manifestations of TIA must be known by the doctors of different disciplines.

Transient ischemic attacks can be single as well as recur often enough. Diagnosis establishment is based on the following:

Identifying etiology of TIA with the help of duplex scanning of cerebral and neck vessels and/or echocardiography. If necessary, an angiographic examination is performed;
Assessment of the clinical picture;
Exclusion of the cerebral infarction with the help of neuro visualization techniques. This stage is required even in case of a complete regress of symptoms.

Key tasks of transient ischemic attacks diagnostics are:

Exclusion of cerebral infarction within three hours after TIA;
Exclusion of other diseases having similar clinical picture;
Identifying etiology of TIA (differentiation between non-embolic and embolic attacks as well as TIA of vertebral and carotid stenosis) is necessary for the timely start of the targeted prevention of the infarction.

MRI or CT of the head is indicated to all patients with possible TIA. In case a patient was hospitalized within 1-6 hours after the attack, then cerebral infarction must be excluded with the help of MRI or CT along with brain tumor or subdural hematoma.

Duplex scanning is applied to evaluate blood flow in the cerebral vessels studying the audiovisual characteristics. Scanning allows detection of various pathological vascular processes on the basis of direct sonographic markers including vasculitides, atherosclerosis, angiopathy, aneurysms, and vascular abnormalities and so on.

Among the technique merits is a possibility to define early pre-clinical signs of the disease presence and evaluate changes of hemodynamic in the real time. Besides, not only organic, but also functional blood flow disruptions can be detected.

CT-angiography or magnetic-resonance angiography is indicated if duplex scanning wouldn’t have given proper results. Carotid angiography is a standard diagnostic procedure carried out before the carotid endarterectomy. This procedure is also indicated for the patients suffered TIA, in case if MRI and duplex scanning give contradictory results or cannot be performed.

Echocardiography is indicated if there is a suspicion of a cardioembolic TIA. Other case, if the history or clinical examination indicates a possible presence of a cardiac pathology or if the patient's age is over 45 years. Also, if the results of the brain, neck vessels examination and blood tests did not reveal the cause of TIA.

Electroencephalography is indicated for the patients, for whom it is necessary to conduct differential diagnosis of epileptic attack and TIA to provide treatment. In addition, the examination plan for a transient ischemic attack usually includes a general blood test, an electrocardiogram, a determination of blood plasma electrolytes, hematocrit, creatinine, prothrombin time, blood viscosity, serum osmolality, international normalized ratio, aggregation of erythrocytes and platelets, blood lipids, glucose and antiphospholipid antibodies.

Hospitalization

Until the end of the episode, the basic principles of managing patients with TIA are similar to the tactics of managing a patient affected by a cerebral infarction. If the symptoms associated with TIA persist for several hours and the patient seeks help, he should be hospitalized in a specialized department for patients with acute cerebrovascular disorders due to emergency indications - for differential diagnosis of TIA with ischemic stroke.

This also applies to patients who experienced TIA for the first time in their life, if no more than 2 days have elapsed since the symptoms regressed. If there is a longer interval from the moment the symptoms have disappeared, the patient is treated and examined on an outpatient basis. The examination includes MRI of the head, echocardiography, duplex scanning and ECG.

Repeated transient ischemic attack, which occurred within 12 hours from the beginning of an outpatient examination, is the reason for changing the tactics of treatment and is an indication for emergency hospitalization. Also, patients with a "crescendo" TIA-transient ischemic attack lasting more than an hour are subject to emergency hospitalization.

In addition, patients with following symptoms should be also hospitalized:

Symptomatic carotid stenosis of more than 50% of the artery lumen, which was detected during the outpatient study;
Heart disease, which can be a source of cardiogenic embolism;
Signs of hypercoagulable arterial thromboembolism in the anamnesis;
Changes in the coagulogram;
Thrombosis of veins.

Main diagnostic tasks to be performed during inpatient stay are identifying TIA’s etiology, exclusion of the cerebral infarction and differential diagnostics.

Further treatment/Rehabilitation

Main efforts of doctors and patient after the termination of TIA should be directed to the prevention of relapses of acute disorders of cerebral circulation. In TIA of a non-cardiovascular nature, antiplatelet agents are considered to be the drug of choice, with anticoagulants and / or antiplatelet agents for cardiogenic embolisms. The main method for the diagnosis of recurrent acute disorders of cerebral circulation in TIA of non-cardioembolic nature is considered long-term daily therapy with the use of antiplatelet agents.

In the presence of symptomatic carotid stenosis more than 50% of the artery lumen for the prevention of stroke, it is necessary to urgently carry out carotid endarterectomy. In a number of cases with carotid stenosis more than 70% of the lumen of the artery, it is possible to perform endovascular operations - stenting of the vertebral or carotid artery and balloon angioplasty.

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