Most emergency room visits are, fortunately, for relatively minor concerns. Patients arrive worried that something is seriously wrong, are assessed and reassured, and go home. That is the system working as intended.
For the small number of patients who actually have a life-threatening condition, however, the cost of getting the diagnosis wrong is enormous. Time-sensitive emergencies do not wait for a return visit. By the time the patient comes back, the window in which the outcome could have been changed is often closed.
In medical malpractice cases involving emergency rooms, five diagnoses recur more often than any others. Each of them has the same general shape: it is potentially catastrophic, it can present with non-specific symptoms early in its course, and it requires the treating physician to actively consider it rather than wait for it to become obvious.
1. Subarachnoid hemorrhage from a ruptured brain aneurysm
A brain aneurysm is a weak spot in the wall of a cerebral artery. When it ruptures, blood spills into the space between the brain and the membranes covering it. This is a subarachnoid hemorrhage, and it is one of the most time-sensitive diagnoses in medicine. Without prompt treatment, a significant portion of patients will rebleed, and rebleeding carries a high mortality.
The cardinal symptom is a sudden, severe headache, often described as the worst headache of the patient’s life or as a “thunderclap” headache that reaches maximum intensity within seconds. Other features can include neck stiffness, nausea or vomiting, brief loss of consciousness, sensitivity to light, and seizure.
The misdiagnosis pattern is well documented. The patient is told they have a migraine, a tension headache, sinus pain, or a viral illness, and is sent home. Studies have reported initial misdiagnosis rates as high as fifty percent. The investigation that should have been done, a non-contrast CT of the head followed, where indicated, by a lumbar puncture, was not done or was done too late.
2. Acute myocardial infarction (heart attack)
A heart attack happens when blood flow to part of the heart muscle is suddenly cut off, usually because plaque in a coronary artery has ruptured and a clot has formed. Every minute of delay in restoring blood flow translates into more permanent damage to the heart muscle.
The classic presentation is well known: pressure or squeezing chest pain that may radiate to the arm, jaw, neck, or back, with shortness of breath, nausea, and a cold sweat. The trouble is that not every heart attack presents that way. Older patients, diabetic patients, and women in particular may present with atypical symptoms: shortness of breath alone, fatigue, indigestion, lightheadedness, or back and jaw pain without obvious chest involvement.
The misdiagnosis pattern, especially in women, is for those atypical symptoms to be attributed to anxiety, gastroenteritis, indigestion, or musculoskeletal pain. Published research has consistently identified misinterpretation of the ECG and a failure to order appropriate cardiac investigations as the leading reasons heart attacks are missed in the emergency department.
3. Acute stroke
A stroke occurs when blood flow to part of the brain is interrupted, either by a clot blocking an artery (ischemic stroke, around eighty-seven percent of cases) or by an artery rupturing (hemorrhagic stroke). Brain tissue starts dying within minutes.
The recognition tools used by paramedics, hospitals, and the public are deliberately simple. The BE-FAST mnemonic captures it: Balance (sudden loss of balance), Eyes (sudden vision changes), Face (drooping on one side), Arms (weakness on one side), Speech (slurred or confused), Time (call 911 immediately). Other features include sudden severe headache (especially with hemorrhagic stroke), confusion, and difficulty walking.
The window for the most effective treatments is narrow. Intravenous thrombolytic therapy (“clot-busting” medication) is generally given within 4.5 hours of symptom onset. Endovascular thrombectomy can be effective up to 24 hours in carefully selected patients. Outside those windows, the options narrow significantly. The misdiagnosis pattern is the patient whose stroke is attributed to a migraine, vertigo, an inner ear problem, or “just being tired,” and who is sent home or admitted to a non-stroke service while the window closes.
4. Cauda equina syndrome
The cauda equina is the bundle of nerve roots at the bottom of the spinal cord that supplies the legs, the bladder, the bowel, and the perineum. When those nerves are compressed acutely, usually by a large herniated disc, the result is a true surgical emergency. Without prompt decompression, the deficits can become permanent.
The “red flag” symptoms are well known to anyone who treats back pain: urinary retention or incontinence, bowel incontinence, “saddle anesthesia” (numbness in the area of the body that would touch a saddle), bilateral leg weakness, and severe back or radicular pain. Sexual dysfunction can also feature.
The misdiagnosis pattern is that a patient with severe back pain is treated as a routine mechanical back pain case, with analgesia and discharge. The red flag questions are not asked. The neurological examination, including a check for saddle anesthesia and a post-void bladder scan, is not done. The window for surgical decompression, generally within 24 to 48 hours of acute symptoms, is missed. The deficits become permanent.
5. Compartment syndrome
Compartment syndrome occurs when pressure builds up inside a muscle compartment to the point that blood flow stops. Muscle tissue starts dying within hours. Acute compartment syndrome is most often associated with fractures, crush injuries, and other major trauma to the limbs. It is a surgical emergency. The treatment is fasciotomy, an incision that releases the pressure.
The classic clinical picture is the “five Ps”: pain (especially pain disproportionate to the injury and pain on passive stretch of the muscles in the compartment), pallor, paresthesia, pulselessness, and paralysis. Of these, pain on passive stretch is the most reliable early sign and is part of the standard of care for assessing any high-risk leg injury.
If fasciotomy is performed within six hours, recovery is typically complete. Beyond twelve hours, only about two-thirds of patients regain normal limb function. In delayed cases, amputation may be required.
This was the central issue in Fortune-Ozoike v Wal-Mart Canada Corp., where an Ontario trial judge found that an emergency physician breached the standard of care by failing to assess for compartment syndrome in a patient with a knee dislocation. The patient lost her leg above the knee.
Why these diagnoses get missed
The five diagnoses on this list have something in common. Each is potentially catastrophic, each can present with symptoms that look like much more common (and benign) conditions, and each requires the treating physician to actively consider it and rule it out, rather than wait for it to declare itself.
The recurring patterns in malpractice cases involving these missed diagnoses are familiar. The diagnostic possibility is not raised in the chart. Investigations that would have answered the question (a CT, an ECG and troponin, a neurological exam, a measurement of compartment pressures) are not ordered. A normal-looking initial workup is treated as the end of the inquiry rather than a snapshot in time. The patient is sent home with instructions that fail to identify the specific symptoms that should bring them straight back.
When a missed diagnosis becomes malpractice
A missed or delayed diagnosis is not, by itself, evidence of negligence. Each of these conditions can present subtly. Reasonable physicians, in real time, sometimes get it wrong.
The legal question is whether the care provided fell below the standard a reasonable practitioner would have provided in the circumstances, and whether that failure caused the harm. In emergency department cases, the standard-of-care analysis usually focuses on whether the physician took reasonable steps to consider the dangerous diagnosis, gathered the information needed to confirm or rule it out, and acted on the findings in a clinically appropriate timeframe. The causation analysis usually focuses on whether earlier diagnosis would, on a balance of probabilities, have produced a better outcome.
What patients and families should do
If you suspect a missed or delayed diagnosis in an emergency department contributed to a serious injury or death, the most useful first step is to obtain a complete copy of the medical records from the visit. The triage notes, the physician’s history and physical, the investigations ordered (and not ordered), the imaging reports, the lab results, and the discharge instructions all matter. Reviewed by a malpractice lawyer and the right medical experts, those records will usually answer whether there is a viable claim.
For more on the legal process, see Suing for Medical Malpractice in Ontario: What You Need to Know. The relevant practice areas are Misdiagnosis, Emergency Room Delay, and Stroke.
The first conversation is free and strictly confidential. The earlier we look at the records, the better.
