Out-of-Hospital Stroke Screen Accuracy in a State With an Emergency Medical Services Protocol for Routing Patients to Acute Stroke Centers
From: Annals of Emergency Medicine 2014 April 16
Andrew W Asimos, Shana Ward, Jane H Brice, Wayne D Rosamond, Larry B Goldstein, Jonathan Studnek
Emergency medical services (EMS) protocols, which route patients with suspected stroke to stroke centers, rely on the use of accurate stroke screening criteria. Our goal is to conduct a statewide EMS agency evaluation of the accuracies of the Cincinnati Prehospital Stroke Scale (CPSS) and the Los Angeles Prehospital Stroke Screen (LAPSS) for identifying acute stroke patients.
We conducted a retrospective study in North Carolina by linking a statewide EMS database to a hospital database, using validated deterministic matching. We compared EMS CPSS or LAPSS results (positive or negative) to the emergency department diagnosis International Classification of Diseases, Ninth Revision codes. We calculated sensitivity, specificity, and positive and negative likelihood ratios for the EMS diagnosis of stroke, using each screening tool.
We included 1,217 CPSS patients and 1,225 LAPSS patients evaluated by 117 EMS agencies from 94 North Carolina counties. Most EMS agencies contributing data had high annual patient volumes and were governmental agencies with nonvolunteer, emergency medical technician-paramedic service level providers. The CPSS had a sensitivity of 80% (95% confidence interval [CI] 77% to 83%) versus 74% (95% CI 71% to 77%) for the LAPSS. Each had a specificity of 48% (CPSS 95% CI 44% to 52%; LAPSS 95% CI 43% to 53%).
The CPSS and LAPSS had similar test characteristics, with each having only limited specificity. Development of stroke screening scales that optimize both sensitivity and specificity is required if these are to be used to determine transport diversion to acute stroke centers.
Diagnosis of stroke emergency
The FAST test is an easy way to recognise and remember the most common signs of stroke. Using the FAST test involves asking three simple questions. If the person has a problem with any of these functions, dial triple zero (000) for an ambulance immediately.
FAST stands for:
Facial weakness – check their face. Has their mouth drooped?
Arm weakness – can they lift both arms?
Speech difficulty – is their speech slurred? Do they understand you?
Time – is critical. If you see any of these signs, call 000 straight away.
If you suddenly experience any of these symptoms, get to a hospital immediately. Remember, a stroke is a life-threatening emergency.
Symptoms of a stroke
A stroke is not a heart attack. A stroke happens when the supply of blood to the brain is suddenly interrupted. Some strokes are fatal, while others cause permanent or temporary disability. The longer a stroke remains untreated, the greater the chance of stroke-related brain damage. Emergency medical treatment soon after symptoms begin improves the chance of survival and successful rehabilitation. Facial weakness, arm weakness and difficulty with speech are the most common symptoms or signs of stroke, but they are not the only signs. Other signs of stroke may include one, or a combination of:
- weakness or numbness or paralysis of the face, arm or leg on either or both sides of the body
- difficulty speaking or understanding
- dizziness, loss of balance or an unexplained fall
- loss of vision, sudden blurring or decreased vision in one or both eyes
- headache, usually severe and abrupt onset or unexplained change in the pattern of headaches
- difficulty swallowing.
The signs of stroke may occur alone or in combination, and they can last a few seconds or up to 24 hours and then disappear. When symptoms disappear within 24 hours, this episode may be a mini stroke or transient ischaemic attack (TIA).
How stroke affects the brain
The brain can be considered as a four-part organ, which includes the right and left hemispheres, the cerebellum and the brain stem. A stroke has different effects, depending on which part of the brain is targeted during the attack.
Some of the major functions of the right hemisphere include perception and control of the left side of the body. A stroke which affects the right hemisphere can cause many changes, including:
- the inability to judge distances, which can lead to falls or loss of hand-to-eye coordination
- short-term memory loss
- neglecting or ignoring anything situated on the left of the body
- impulsive behaviour
- paralysis of the left side of the body (‘left hemiplegia’).
Some of the major functions of the left hemisphere include speech and control of the right side of the body. A stroke affecting the left hemisphere can cause many changes, including:
- paralysis of the right side of the body (‘right hemiplegia’)
- various problems with speech and communication
- short-term memory loss.
- Some of the major functions of the cerebellum include coordination and balance.
A stroke affecting the cerebellum can cause many changes, including:
- nausea and vomiting
- loss of coordination
- a tendency to unbalance and fall
- slurred speech.
Some of the major functions of the brain stem include breathing, heart rate and blood pressure. A stroke that affects the brain stem can cause many changes, including:
- complete paralysis
- double vision
- swallowing difficulties
- Effects of a stroke
There are several factors that impact on recovery and the effects of stroke. These factors include:
- type of stroke
- location of the blocked or burst artery
- which area of the brain is damaged
- how much brain tissue is permanently damaged
- your general health before the stroke
- your level of activity before the stroke.
The brain is divided into several areas that control different functions. These include how you move your body, receive sensory messages (such as touch, sight or smell), use language and think. Because different arteries supply different areas of the brain, where the brain is damaged will determine which functions are affected. Every stroke is different. Each person affected by stroke will have different problems and different needs. The way in which you might be affected depends on where in the brain the stroke happens and how big the stroke is. A stroke on the right side of the brain generally causes problems on the left side of the body. A stroke on the left side of the brain causes problems on the right side of the body. Some strokes happen at the base of the brain and can cause problems with eating, breathing and moving.
Living with the effects of stroke
In some cases, the effects of a small stroke can be overcome and the person can live an almost completely normal life. In other cases, the disabilities are severe and permanent. Support and understanding from family and friends, plus intensive rehabilitation from healthcare professionals, can always improve a stroke survivor’s quality of life.
Some of the healthcare professionals who can help include:
speech therapists – to maintain or improve speech and communication and assess swallowing difficulties
occupational therapists – to teach coping strategies and new skills, and help adapt the family home to the needs of the stroke survivor
physical therapists – to maintain or improve the movement and functioning of the body.
Cerebral haemorrhage is a type of stroke
A cerebral haemorrhage is a type of stroke caused by bleeding from a ruptured blood vessel in the brain. It is sometimes called a haemorrhagic stroke. Without prompt medical treatment, this can result in death. A person who survives is often left with permanent disabilities. Causes include weakened blood vessel walls, head trauma or congenital conditions (conditions that are present at birth). A cerebral haemorrhage is a life-threatening emergency. Approximately one in 10 strokes is caused by cerebral haemorrhage. This type of stroke (haemorrhagic stroke) is usually much more severe than ischaemic stroke, although symptoms are similar. The major risk factor for cerebral haemorrhage is long-standing high blood pressure (hypertension) that weakens the walls of blood vessels, which then may split under the pressure.
Treatment of cerebral haemorrhage
After admission to hospital, treatment depends on the location and severity of the haemorrhage, but may include:
medications to lower blood pressure after onset of haemorrhage
treatment for underlying causes, such as long-term use of antihypertensive medications
certain surgical procedures.
Any suspected signs and symptoms of cerebral haemorrhage require urgent medical attention. Dial triple zero (000) to call an ambulance to take the person to the nearest hospital emergency department.
Confusion of stroke with migraine
A migraine is a type of headache, caused by spasms of the arteries leading into the head. Stroke, TIAs and migraine can share certain symptoms (visual disturbances, numbness, tingling, speech difficulties and muscle weakness on one side of the body), which may lead someone with a migraine to fear they are having a stroke.
Problems can occur if a TIA is mistaken for a migraine, because a TIA is usually a warning of a possible stroke. Since the symptoms of TIAs go away within hours, the person may mistakenly believe they suffered nothing more than a migraine. It is extremely dangerous for people to diagnose themselves and they should always seek medical advice.
The broad differences between a migraine and a TIA include:
- visual disturbances – in TIA, the only disturbance is vision loss, whereas visual disturbance in migraine includes flashing lights and zigzagging lines as well
- speed of attack – in TIA, the symptoms occur suddenly. In migraine, symptoms spread slowly over a few minutes
- age of onset – migraine tends to first occur when a person is young, whereas stroke is more common in older people.