Stroke symptoms typically start suddenly, over seconds to minutes, and in most cases do not progress further. The symptoms depend on the area of the brain affected. The more extensive the area of the brain affected, the more functions that are likely to be lost. Some forms of stroke can cause additional symptoms. For example, in intracranial hemorrhage, the affected area may compress other structures. Most forms of stroke are not associated with a headache, apart from subarachnoid hemorrhage and cerebral venous thrombosis and occasionally intracerebral hemorrhage.

Early recognition

Various systems have been proposed to increase recognition of stroke. Different findings are able to predict the presence or absence of stroke to different degrees. Sudden-onset face weakness, arm drift (i.e., if a person, when asked to raise both arms, involuntarily lets one arm drift downward) and abnormal speech are the findings most likely to lead to the correct identification of a case of stroke, increasing the likelihood by 5.5 when at least one of these is present. Similarly, when all three of these are absent, the likelihood of stroke is decreased (– likelihood ratio of 0.39). While these findings are not perfect for diagnosing stroke, the fact that they can be evaluated relatively rapidly and easily make them very valuable in the acute setting.

A Centers for Disease Control and Prevention public service announcement on emergency medical treatment after or during a stroke from 2021.
A mnemonic to remember the warning signs of stroke is FAST (facial droop, arm weakness, speech difficulty, and time to call emergency services), as advocated by the Department of Health (United Kingdom) and the Stroke Association, the American Stroke Association, the National Stroke Association (US), the Los Angeles Prehospital Stroke Screen (LAPSS) and the Cincinnati Prehospital Stroke Scale (CPSS). Use of these scales is recommended by professional guidelines. FAST is less reliable in the recognition of posterior circulation strokes.

For people referred to the emergency room, early recognition of stroke is deemed important as this can expedite diagnostic tests and treatments. A scoring system called ROSIER (recognition of stroke in the emergency room) is recommended for this purpose; it is based on features from the medical history and physical examination.

Subtypes

If the area of the brain affected includes one of the three prominent central nervous system pathways—the spinothalamic tract, corticospinal tract, and the dorsal column–medial lemniscus pathway, symptoms may include:

hemiplegia and muscle weakness of the face
numbness
reduction in sensory or vibratory sensation
initial flaccidity (reduced muscle tone), replaced by spasticity (increased muscle tone), excessive reflexes, and obligatory synergies.
In most cases, the symptoms affect only one side of the body (unilateral). Depending on the part of the brain affected, the defect in the brain is usually on the opposite side of the body. However, since these pathways also travel in the spinal cord and any lesion there can also produce these symptoms, the presence of any one of these symptoms does not necessarily indicate a stroke. In addition to the above CNS pathways, the brainstem gives rise to most of the twelve cranial nerves. A brainstem stroke affecting the brainstem and brain, therefore, can produce symptoms relating to deficits in these cranial nerves.

altered smell, taste, hearing, or vision (total or partial)
drooping of eyelid (ptosis) and weakness of ocular muscles
decreased reflexes: gag, swallow, pupil reactivity to light
decreased sensation and muscle weakness of the face
balance problems and nystagmus
altered breathing and heart rate
weakness in sternocleidomastoid muscle with inability to turn head to one side
weakness in tongue (inability to stick out the tongue or move it from side to side)
If the cerebral cortex is involved, the CNS pathways can again be affected, but also can produce the following symptoms.

aphasia (difficulty with verbal expression, auditory comprehension, reading and writing; Broca's or Wernicke's area typically involved)
dysarthria (motor speech disorder resulting from neurological injury)
apraxia (altered voluntary movements)
visual field defect
memory deficits (involvement of temporal lobe)
hemineglect (involvement of parietal lobe)
disorganized thinking, confusion, hypersexual gestures (with involvement of frontal lobe)
lack of insight of his or her, usually stroke-related, disability
If the cerebellum is involved, ataxia might be present and this includes:

altered walking gait
altered movement coordination
vertigo and or disequilibrium
Associated symptoms
Loss of consciousness, headache, and vomiting usually occur more often in hemorrhagic stroke than in thrombosis because of the increased intracranial pressure from the leaking blood compressing the brain.

If symptoms are maximal at onset, the cause is more likely to be a subarachnoid hemorrhage or an embolic stroke.

Causes

Thrombotic stroke

Illustration of an embolic stroke, showing a blockage lodged in a blood vessel.
In thrombotic stroke, a thrombus (blood clot) usually forms around atherosclerotic plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic strokes is slower than that of a hemorrhagic stroke. A thrombus itself (even if it does not completely block the blood vessel) can lead to an embolic stroke (see below) if the thrombus breaks off and travels in the bloodstream, at which point it is called an embolus. Two types of thrombosis can cause stroke:

Large vessel disease involves the common and internal carotid arteries, the vertebral artery, and the Circle of Willis. Diseases that may form thrombi in the large vessels include (in descending incidence): atherosclerosis, vasoconstriction (tightening of the artery), aortic, carotid or vertebral artery dissection, various inflammatory diseases of the blood vessel wall (Takayasu arteritis, giant cell arteritis, vasculitis), noninflammatory vasculopathy, Moyamoya disease and fibromuscular dysplasia.

Small vessel disease involves the smaller arteries inside the brain: branches of the circle of Willis, middle cerebral artery, stem, and arteries arising from the distal vertebral and basilar artery. Diseases that may form thrombi in the small vessels include (in descending incidence): lipohyalinosis (build-up of fatty hyaline matter in the blood vessel as a result of high blood pressure and aging) and fibrinoid degeneration (a stroke involving these vessels is known as a lacunar stroke) and microatheroma (small atherosclerotic plaques).

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