The diagnosis of stroke remains a challenge, due to overlapping symptoms with other conditions, limitations in diagnostic tests, and lack of awareness of posterior circulation presentation and workup. Below is a brief overview of the rate and risk factors for missed stroke, common stroke mimics and chamelons, and the challenge of diagnosing stroke in patients presenting with dizziness.

MISSED STROKE: RATE AND RISK FACTORS

From the Canadian Medical Protective Association’s review, “the biggest issue identified in a review of the CMPA’s medical-legal cases involving stroke was diagnosis…While hemorrhagic strokes make up only 10–15% of strokes overall in the clinical arena,¹ close to half of the CMPA cases involved this type of stroke…The common symptoms were headache, dizziness, and nausea and vomiting…Anchoring on a specific diagnosis — most often migraine or psychiatric disorders, but also gastrointestinal, sinus, or musculoskeletal issues — often impeded the final diagnosis of stroke.”

A few recent studies highlighting the rate and risk factors for misdiagnosis

• Missed Ischemic Stroke Diagnosis in the Emergency Department by Emergency Medicine and Neurology Services. Stroke 2016;476:668-673. In this chart review of 465 patients with ischemic stroke presenting to a community and an academic centre, 22% were initially misdiagnosed (a third of whom presented within 3 hours). Symptoms associated with greater risk of missed stroke were nausea/vomiting, dizziness—resulting in a misdiagnosis rate of 37% for posterior circulation stroke (compared with 16% for anterior circulation).
• Acute stroke chameleons in a university hospital: Risk factors, circumstances, and outcomes. Neurology 2015 Aug 11;85(6): 505-11. In this retrospective review of 2,200 acute ischemic strokes, 2% were missed. There was a greater risk with younger age, less CVA risk factors, and presenting at both ends of the spectrum (milder stroke or coma), and with fewer focal signs and greater numbers of cerebellar stroke.
• Potentially Missed Diagnosis of Ischemic Stroke in the Emergency Department in the Greater Cincinnati/Northern Kentucky Stroke Study. Acad Emerg Med 2016 June 17. Of 2027 acute ischemic strokes, 14% were missed in the ED. Risk factors were younger age and altered mental status, and the most common misdiagnosis was altered mental status.
• Pitfalls in the diagnosis of cerebellar infarction: summarized in my previous post here

STROKE MIMICS AND CHAMELONS

Stroke overlaps with other conditions that produce sudden neurological symptoms, so there are both “stroke mimics” (conditions that appear as strokes but that are caused by other conditions) and “stroke chamelons” (symptoms caused by strokes that appear as other conditions). Stroke Chameleons. Journal of Stroke and Cerebrovasc Dis. 2014;23(2):374-378 In this retrospective chart review over 2011 in one hospital there were 94 patients found with stroke chamelons:

• 31% altered mental status (including psychosis, delirium, memory deficits, encephalopathy),
• 16% syncope, eg transient reduced LOC attributed to syncope rather than TIA/CVA
• 13% hypertensive emergency: a hypertensive response to stroke
• 11% systemic infection, eg altered mental status attributed to UTI because of incidental pyuria, or pneumonia because of CXR atelectasis
• 10% suspected ACS, eg left arm paresthesias, ECG changes from neurological event
• 5% seizure, 3% peripheral vertigo, 1% each of cord compression, myasthenia, Bell’s palsy, complex migraine, and hypoglycemia

In a prior study, the authors found nearly 20% of patients initially diagnosed as “stroke” were ultimately diagnosed as stroke mimics:

• seizure
• systemic infection
• brain tumour
• toxic/metabolic.

STROKE AND DIZZINESS: HISTORY/PHYSICAL TRUMPS CT (AND MAYBE EVEN MRI)

Use of CT for dizziness has skyrocketed, bringing not only unnecessary radiation and low yield but also a false sense of reassurance: Missed Strokes Using Computed Tomography Imaging in Patients With Vertigo. Stroke 2015;46:108-113. In this retrospective cohort study of more than 41,000 patients discharged from the ED with a diagnosis of peripheral vertigo, 20% received a CT head that was falsely reassuring: 25 patients were hospitalized for stroke within 30 days (compared with 11 patients who did not receive a CT).

Calling attention to the $1 billion spent on the US for patients presenting with dizziness, and the estimated 20,000 stroke patients in the US that are still missed–because CT miss 80% of posterior circulation stroke–Dr. Newman-Toker (a leader in the field of stroke and dizziness) advocates better history and physical exam: Missed Stroke in Acute Vertigo and Dizziness: It Is Time for Action, not Debate. Annals of Neurology 2015.

“Classifying vertigo or dizziness by timing (episodic or continuous) and trigger (positional or not), rather than type (vertigo vs lightheadedness vs unsteadiness, etc) allows for effective clinical identification of both high-risk-for-stroke and low-risk-for-stroke populations. Those with episodic, positional vestibular symptoms lasting seconds almost always have behing paroxysmal positional vertigo (BPPV). This can be confiemd by careful examination of positional nystagmus and then treated by canalith repositioning. Those with episodic, spontaneous symptoms lasting hours mostly have vestibual migraine, Meniere’s disease, or TIA. Total illness duration and vascular reisk factors can usually differentiate these diseases. Those with acute, continuous vestibual symptosm, nausea/vomiting, intolerance of head motion, and gait unsteadiness lasting days (the “acute vestibular syndrome”) almost always have either vestibular neuritis or a dangerous central mimic, usually ischemic stroke. Assessing three vestibular eye movements (HINTS: Head Impulse test of the vestibule-ocular reflex, Nystagmus in different fields of gaze, and Test for Skew deviation by alterate cover) distinguishes peripheral from central causes of the acute vestibular syndrome with greater accuracy than even MRI.”

For a more detailed look at the history and physical, see Does my dizzy patient have a stroke? A systematic review of bedside diagnosis in acute vestibular syndrome. CMAJ June 2011;183(9): E571-592

In summary, be on guard for stroke mimics and chamelons (especially with altered mental status and dizziness), consider the limitation of CT (especially for posterior circulation stroke), carefully perform and document a full neurological exam (including cranial nerves, HINTS exam, cerebellar tests and gait), and consult neurology if there are any high risk features or concerns.