The Art of Differential Diagnosis

A Case Study

(Names/Dates have been excluded to protect patient privacy. Photos are representations only.)


One of the most important tasks required of pre-hospital emergency workers is obtaining the information and evidence on scene that can help develop pertinent differential diagnoses. This job can be made especially difficult by poor historians, unusual patient presentation and the potential urgency to transport to definitive care. The purpose of differential diagnoses is to come up with several ideas that may be causing a patient’s signs and symptoms, and then attempt to rule them out systematically. The process helps determine the most appropriate pre-hospital treatment, the facility and department the patient should be transported to, and to approximate the time necessary to see a physician according to CTAS. This paper will demonstrate the challenge and importance of skilled paramedical differentiation while exploring a step by step case in the field. This particular patient presented with borderline excited delirium and the EMS differentials ranged from a diabetic emergency, a cerebrovascular accident (CVA), acute onset psychosis, infection, and drug overdose/withdrawal.


Dispatch relayed the call, code four, as a forty six year old female demonstrating odd behavior. An attendant, a driver, and a paramedic student would compose the response team. The location was a trailer park approximately thirty five minutes from the ambulance bay at 23:00. The scene assessment began on arrival; the property was unkempt, poorly lit, and cluttered with garbage. Two dogs were barking viciously in the door way and EMS personnel had to wait for a middle aged man to remove them from the entrance. The man did not appear in obvious distress and did not verbally acknowledge the paramedics. He led them up a set of rotten wooden steps and into the trailer home. The air inside was thick with cigarette smoke, and the path that led towards the back of the home was narrowed by mismatch furniture and stacks of magazines. The evident hoarding added mental health issues to the differential before patient contact was even made. Besides the dogs there was nothing that appeared dangerous or illegal.


The man’s wife, the apparent patient as he gestured towards her, was sitting in an old recliner, next to an unmade pullout couch. She appeared disheveled, her eyes darting wildly around the room, muttering incoherently. Her hands were fidgeting in her lap, her thin body rocking back and forth. She was wearing small cotton nightgown that barely covered her, and she was obviously perspiring. As the paramedic student began an introduction the patient’s response was something that everyone in the room interpreted as, “going to kill you.” This was followed by a squeal of laughter and more babbling. The attendant immediately took over patient care. The threat could not be taken lightly regardless of her minute stature, and it was barely the student’s third shift.

The attendant began a primary assessment and to obtain a set of baseline vitals, complete with blood glucose sampling which was indicated by the agitated change in behavior. The patient’s appearance exhibited many signs and symptoms related to hypoglycemia such as; confusion, nervousness, sweating, shakiness, anxiety, and difficulty speaking.1 If her blood glucose was below 4mmoL, her symptoms could be corrected with glucagon and glucose paste. However, the BGL sample read 4.6mmoL and a diabetic emergency was ruled out.


The attendant struggled to obtain a reliable history from his patient. Her confusion and agitation had created a communication road block. However, he was also simultaneously beginning an analysis based on her presentation and vital signs. Expressive (Broca’s) aphasia is a sign exhibited by 34-38% of CVA patients. 2 Broca’s aphasia is characterized by disjointed words, lack of sentence structure, labored, and halting speech. In the most extreme cases, patients may be able to produce only a single word. The most famous case of this was Paul Broca’s patient Leborgne, nicknamed “Tan”, after the only syllable he could say.3 This female patient had so far retained a cocktail of words, but was obviously focused on the words “sticky” and “no”. For example, when asked if she was experiencing any pain she quickly replied “No, my stocks are sticky, no, the air’s sticky.” The patient very well could have been experiencing receptive aphasia as well, characterized as being unable to understand what others are saying.4 The patient’s speech was so random, unorganized, and slurred that without the proper tests it could only be broadly classified as aphasia. Aphasia has also been known to be caused by brain injury, cancer, and dementia.Despite the lack of facial droop and presence of symmetrical grip strength, the EMS team added stroke/TIA to the top of the differential checklist. Unlike the other causes of aphasia, an embolic/thrombotic stroke required TPA (tissue plasminogen activator) treatment within 3.5 hours of symptom onset.6

DBAphasia1aaaphasia comic part two

Meanwhile, the student had begun gathering a history from the patient’s husband and son who had appeared from another room. So far she had learned that the patient had not suffered any physical trauma, spent most of her time sitting in her recliner, and could usually carry on a conversation. The son was asked to put out his cigarette as he was blowing smoke into the paramedics face. This irritated the son and he lashed out at the student yelling, “You are supposed to be a professional, can’t you see that my mother is sick?” After explaining that the information they were gathering was very important to his mother’s treatment the situation was diffused. The husband stated that his wife had begun acting strangely a couple of hours ago, although he could not pinpoint a time. He stated that her behavior had gotten progressively worse which is when he chose to call the ambulance. The inability to establish a definitive time that the patient had been last seen normal ruled the patient out of the Acute Stroke Protocol, but not the possibility of having a stroke.

According to the husband the patient had not slept in three days because she had ran out of her sleeping pills. He did not know what they were called and had not kept the package with the information. Beyond having trouble sleeping, he did not know of any medical reason she had been taking them. The husband’s eyes were glassy, and he seemed confused about most of the questions. According to him she was not on any other medications, had not taken any drugs or alcohol to the best of his knowledge, did not have any allergies, and had eaten a sandwich around lunch time- but she may have given it to the dog. The son interjected that she had had a similar episode when her daughter died fifteen years ago. He informed them that today she had also been talking to her daughter and mother as if they were in the room, and they were both deceased. However, the family stated that nothing out of the ordinary had happened today and she had been sitting in her recliner watching t.v. at the onset of the symptoms. An acute psychotic episode was possible and was added to the list.

The patient’s blood pressure was obtained at 146/92, with a heart rate of 156bpm, 02SATs of 96. Her breathing was full and regular around 22. Her pupils were slightly dilated and sluggish at about 6mm. The EMS team had begun to rule in a possible crack/cocaine overdose due to patient presentation and the unreliable history they had gathered. Crack, like cocaine, increases the user’s heart rate, blood pressure, and temperature.7 It can also cause rapid speech, skewed sleeping patterns, loss of appetite, dilate pupils, paranoia, and delusions.8 Besides the woman’s malnourished appearance, there were no obvious physical signs of crack use such as track marks, septal malformations, or scabbing. However, as the paramedics prepared to transport the patient to the ambulance the son warned them to be careful because earlier his mother had slapped him in the face repeatedly. She had never done that before today and according to him, it had hurt.


In the back of the ambulance the patient’s agitation seemed to increase. Her heart rate rose to 166bmp and she began to hum to herself while continuing to look around nervously and rocking. The tachycardic heart rate could also have been indicative of a stroke. A study in Germany had found that 15% of stroke patients had an increase in heart rate >120bpm.9 Considering the patient’s diaphoresis and warm skin despite the cool evening air, the student took the patient’s tympanic temperature. It registered at 39.6 C, marked hyperthermia (defined as a temperature greater than 37.5–38.3 °C (100–101 °F)10). So far the patient’s presentation, vital signs, and history gathered from her family, all suggested borderline excited delirium. The crew decided to transport return priority 4, CTAS 2.

Link to video of similar presentation of excited delerium>>>

Similarly, a related syndrome called neuroleptic malignant syndrome (NMS) was described in the 1960s as a potentially fatal complication of antipsychotic drugs. This highly lethal disorder is seen in patients taking dopamine (DA) antagonists or following abrupt withdrawal.12 DA drugs are often used in schizophrenics and patients with bipolar disorder. It is possible that the “sleeping pills” the husband had referred to were in fact antipsychotics. If so, sudden withdrawal coupled with a psychiatric disorder could be also be the cause.

Furthermore, the elevated temperature combined with the patient’s other symptoms could also be indicative of a systemic infection. A core body temperature reading is impossible in the pre-hospital field but considering the tympanic was 39.6C, it was likely the patient was actually experiencing hyperpyrexia internally. The paramedics kept the ambulance slightly below room temperature to try to bring down the patient’s elevated temperature without sending her into shock.


The patient’s temperature and other vital signs remained constant throughout transport. She never exhibited any outward aggression towards the paramedics, although they had been careful in ensuring she was properly packaged and secured on the stretcher. The paramedics were vigilant in their ongoing assessment, assessing her vitals q5, prepared for potential caradiac/respiratory arrest, nausea/vomiting, seizure activity, and a demonstration of super-human strength. The patient continued to alternate between humming exuberantly and muttering incoherently, often mentioning her mother.

On arrival at the hospital the assigned RN, based on his experience, agreed that it appeared the patient had likely ingested crack in some form. Upon inquest the following day the RN stated that over a twelve hour period the patient had developed from appearing overly joyful, to sobbing inconsolably. Accordingly, when a crack high wears off, the user can hit a low that matched the high in intensity. Mood swings, depression, and fatigue are typical signs of someone coming down from the drug.13 A final in-hospital diagnosis was unfortunately not possible to obtain due to shift changes.

As a final note, it would be beneficial to have the hospital collaborate with EMS to prepare an automated patient report log available to paramedics regarding in-hospital treatment. It would help with future differentials, verifying or discrediting particular patterns of professional consideration. It would also prepare the paramedic for what they may have been exposed to on the job. Between the distractions, the challenges of gathering a good history, and balancing patient management, differential diagnoses in the field of paramedicine is truly a skill. It would be beneficial to have a built in system geared at enhancing that skill, so EMS had the opportunity to improve on every call.







1 National Institute of Diabetes and Digestive and Kidney Diseases (06/11/2012) Retrieved from

2 Bakheit, AMO; Shaw, S; Carrington, S; Griffiths, S (2007). “The rate and extent of improvement with therapy from the different types of aphasia in the first year of stroke”. Integumentary Rehabilitation 21 (10): 941–949. 

3-4 Wikipedia (30/11/2012) “Expressive Aphasia” Retrieved from

5 Wikipedia (26/12/2012) “Aphasia”

6 Ministry of Health and Long Term Care (23/02/2011) “Acute Stroke Protocol” Retrieved from

7 (2000-2012) “Crack” Retrieved from

8 Delray Recovery Center (2012) “Signs of Crack Use” Retrieved from

9 Martin A Ritter1*Anne Rohde1Peter U Heuschmann2Rainer Dziewas1Jörg Stypmann3Darius G Nabavi4 and Bernd E Ringelstein1BMC Neurology (2011, 11:47) “Heart rate monitoring on the stroke unit. What does heart beat tell about prognosis? An observational study” Retrieved from

10 Axelrod YK, Diringer MN (May 2008). “Temperature management in acute neurologic disorders”. Neurol. Clin. 26 (2): 585–603, xi.

11-12 Caroff et al., 2007; Friedman et al., 1985; Kosten and Kleber, 1988; Levenson, 1985; Strawn et al., (2007) “Excited Delerium” Retrieved from

13 Delray Recovery Center (2012) “Signs of Crack Use” Retrieved from


5 thoughts on “The Art of Differential Diagnosis

  1. Hey Vanessa, love the blog so far! I think you make a great point about knowing in-hospital treatment to improve differentials. In the service I did placement we weren’t even allowed to ask nurses about previous patients we brought in. It is quite the dilemma because the focus is on patient confidentiality of course, but sometimes getting that confirmation that your differential was bang on sure is great for your EMS confidence and future endeavours with similar patients.

    Keep up the good work!

    • Thanks for reading Chris! I’m glad you agree. I just worry it may be easy to get pigeon holed when there is no real authentication process in place post-pre-hospital treatment, besides the obvious- did the guy live or not?

    • I agree as well. Not getting any feedback about your performance is unacceptable. What types of performance evaluations are paramedics given? What happens if you begin to recognize a pattern of S&S’s in patients and you assess/manage them the same way every time, but you realize a year later that you were actually somewhat wrong in differential diagnosis? There’s nobody to tell you that you were wrong?

      • Hey Zak,
        So I got some information on performance reviews in Sudbury. According to my preceptor you are evaluated every 2080 hours or once a year if you are full time. They ask what are some of your strengths and weaknesses are, two year and five year improvement goals and any suggestions for divisional changes and that is pretty much it.

  2. Pingback: Zebras, hoof-beats and Dr. House: Differential Diagnosis | ADD . . . and-so-much-more

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