AcuteCare Telemedicine Blog

Stroke Mimics in the Emergency Setting

The role of the neurologist in treatment of acute stroke often focuses on the decision to use clot busting medication (tissue plasminogen activator; tPA), recommending care setting (e.g. ICU vs routine admission) based on patient deficits and prognosis, and of course, patient education in the midst of this emotionally charged experience. However, an often overlooked mandate for the neurologist is the proper recognition of stroke itself. Dr. J. Stephen Huff, Associate Professor of Neurology at the University of Virginia, provides a clear and comprehensive review of what are termed stroke “mimics” – disorders which may appear to be a stroke, but are not.

Stroke, broadly defined, is any prolonged disruption of focal neurologic function due to decreased blood flow from blood clotting in a specific region of brain. If that disruption is transient or intermittent it is typically referred to as a transient ischemic attack (TIA). If brain function is disrupted by a cause other than a blood clot, treatment with tPA may not only lack benefit but expose the patient to unnecessary harm. Recognition of “stroke syndromes” that result from specific artery involvement is the bread and butter of neurology. The abrupt onset of aphasia (language deficit) and right sided weakness almost certainly indicates a patient has blocked their left middle cerebral artery. Blocking this same artery on the right results in the classic presentation of left sided weakness and “neglect,” an inability to recognize one’s own physical deficits. In either case, the immediate administration of tPA can be life-saving.

Other disorders may cause brain dysfunction unrelated to a blood clot. This is the case in approximately 13-20% of patients presenting with presumed stroke. If the duration of symptoms is unclear, this number may even be as high as 30%. The most common mimic is seizure. Excessive electrical and chemical brain activity may result in focal weakness (Todd’s paralysis) and other deficits. If the seizure was not witnessed (especially in patients with previous stroke as the cause of seizures), excluding an acute stroke can be difficult. Focal neurologic injury from brain tumor, inflammation (e.g. multiple sclerosis), or even peripheral nerve palsy may be mistaken for stroke.

Stroke can be mimicked without direct injury to the brain. The most common mimic in this category is a complex migraine in which visual disturbance, weakness, numbness and even aphasia can occur. Hypoglycemia or, less often, hyperglycemia (low and high blood sugar) can cause general symptoms of lethargy or coma, but focal brain dysfunction (particularly weakness) often occurs and can outlast normalization of blood glucose. Finally, 30% of patients presenting with psychiatric causes of physical illness (i.e. conversion disorder) exhibit neurologic deficits, typically weakness.

Determining the cause of a patient’s deficits can sometimes be accomplished in an emergency setting through the use of CT imaging and appropriate diagnostic tests. Often the results of serial examinations, detailed history and, increasingly, advances in MR imaging can eventually lead to the correct diagnosis. However, certain diagnoses, notably migraine and conversion, are diagnoses of exclusion, so repeated events and extensive negative testing may be required for confirmation.

Among patients presenting with neurologic deficits, emergency department physicians correctly identify stroke before applying diagnostic studies in about 75% of cases. This means as many as 1 in 4 cases are incorrectly diagnosed. It is the role of stroke experts, like those of AcuteCare Telemedicine, to quickly and accurately determine the likely cause of neurologic deficits, the risks and benefits of multiple treatment options and convey a plan of action simply yet fully to the patient and loved ones. It is a difficult but rewarding task.

The Brain’s Glorious Complexity

The brain is the most complex organ in the human body. In fact, the thinking part of our brains can be thought of as two symmetrical hemi-brains connected by a large bundle of nerves. Unfortunately, this complexity can mean increased susceptibility to diseases.

In the 90% of us that are right handed, the left half of the brain is called dominant and the right half of the brain is called nondominant. Damage to the left brain often leads to language disorders called aphasia and damage to the right brain often leads to loss of awareness called agnosia. A recent patient encounter highlights how knowledge of the brain’s organization can explain abnormal behavior:

A 72 year old man had trouble logging on to his computer to play word games on Saturday. Normally, he has no problem with this, but he had to get his wife to help him three times that day. The next day, he was restless and slept more than usual. On Monday, he was agitated, could not say what was wrong and had to be led to the car. At the hospital, the emergency room doctor could find no evidence of a stroke or intoxication, so depression or psychosis were suspected. The stroke neurologist identified that he was not confused, depressed, or psychotic; he was aphasic and brain imaging confirmed a small recent stroke on the left side of his brain. This man had Wernicke aphasia due to damage to his dominant hemisphere in the area described by Dr. Wernicke in the late 1800s.

Study of patients with brain damage has led to a great deal of understanding about how the normal brain works. For example, the right brain’s abilities lie in its subconscious attention to the details of recognizing faces, objects, sounds, shapes, and smells. These are critical for human survival – imagine the survival disadvantage if you could not rapidly distinguish foe from friend!

For a stunningly lucid overview of current brain knowledge, check out Charlie Rose’s recent Brain Series which explores “the most exciting scientific journey of our time: understanding the brain.”