Missing the obvious – by a long shot

EANS Case of the Month: October 2015
(by Aki Laakso, Department of Neurosurgery, Helsinki University Hospital)

The obvious is that which is never seen until someone expresses it simply”, Kahlil Gibran

A 51-year old, previously healthy male CEO started to suffer from photophobia and nausea, but was otherwise fine. He continued working, despite mild symptoms.

Two days later, he experienced a sudden, sharp, painful headache, and self-medicated the symptom with an over-the-counter dose of ibuprofen. The painkiller dulled the sharpest pain well enough to allow him to join a party in the evening and have a few drinks. The next morning the nausea became more severe. He also felt that the sense of smell had become abnormally sensitive, and many familiar scents seemed very unpleasant. The headache was back as well. Being at work, he went to see the company’s occupational physician (OP), who referred him to local hospital’s emergency room.

Suspecting a common migraine (or a hangover), the ER doctor discharged the patient without performing any imaging studies. The next day, as the symptoms continued, he went to see his OP again. The meeting resulted in a new referral to the local hospital ER, with a plea to perform a CT scan. Still holding on to a hypothesis of migraine, the doctor at the ER refused to image the patient. The patient, already rather frustrated and confused, sought the help of the OP again. This time, the OP sent the patient to a private MRI facility immediately. Right after the scan, the neuroradiologist reviewing the images called our department’s on-call consultant, and we promised to admit the patient via our ER. As if to finalize the absurdity of his own case history, the patient arrived at our ER by driving his own car, carrying the CD with the MRI images in his briefcase…

Figure 1. The first MRI images of the patient, taken at the private facility.

Figure 1A. T2-weighted image, showing the right temporal hemorrhage, with a maximum diameter of 6 cm, and at least two components of slightly different ages. A large aneurysm at right MCA bifurcation can also be seen.

Figure 1B. Time-of-flight (TOF) MR angiography demonstrating the 15 mm large right MCA bifurcation aneurysm more clearly.

Clinical examination did not reveal any obvious deficits, as expected based on the history. We did perform a CT angiography, because microsurgical clipping and ICH evacuation was obviously the treatment of choice, and in our experience CTA gives superior information for surgical planning (better contrast for smaller vessels, relationship to bony structures).

Figure 2. A CT angiography of the patient’s right MCA bifurcation aneurysm, taken for preoperative planning. No other aneurysms were found.

Figure 2A. Axial plane

Figure 2B. Coronal plane

Figure 2C. 3D reconstruction

The surgery was planned for the next morning, and was uneventful. As usual, we controlled the head CT and CTA on first post-operative day.

Figure 3. Post-operative CT and CTA control scans taken on the first post-operative day.

Figure 3A. A native head CT scan demonstrating evacuation of the hematoma.

Figure 3B. Axial plane of the control CTA demonstrating clipping of the aneurysm.

Figure 3C. Coronal plane of the control CTA demonstrating clipping of the aneurysm

The recovery of the patient was uneventful as well, only complicated by a urinary tract infection that was treated succesfully with i.v. cefuroxime. He was discharged home one week after the surgery in good condition. Peroral nimodipine was administered 60 mg x 6 for two weeks after the surgery (based on symptoms, the initial rupture was approximately one week prior to surgery).

For us, neurosurgeons working mostly in tertiary referral centers, it seems obvious that sudden headache accompanied with nausea and sensory disturbances is a subarachnoid hemorrhage (SAH) or other hemorrhagic stroke until proven otherwise. However, even in countries like Finland, with a rather high incidence of SAH and well-equipped and well-funded public emergency medicine, we frequently encounter patients with delayed diagnosis of aneurysm rupture. Although diagnosis in our case was attained with MRI (because of private oupatient clinic setting), a conventional CT scan readily available in any hospital ER would have been brilliantly sufficient, had it crossed the mind of the unfortunate ER physician that this patient really DID have the diagnosis that first comes to mind. But what are the reasons for, and how frequent is, this kind of potentially fatal – and to us, incomprehensible – misjudgement?
Probably the most important reason – and the one perhaps difficult to appreciate from the vantage point of a referral center neurosurgeon – is that SAH is actually not a very common cause of severe headache. Perry et al. (1) have reported that in a Canadian cohort of almost 2000 patients admitted to a hospital ER for a sudden, severe headache, only 6.5% actually had SAH. Althought the cohort only included fully alert, neurologically intact patients, it is noteworthy that 79% of the cohort described their headache as “the worst they’ve ever had”. Even lower figures were seen in a recent UK study (2), where only 2.7% of ER patients with sudden, severe headache had SAH. The authors of this study also questioned the rationale for lumbar puncture to rule out SAH after normal CT scan in headache patients, since the negative predictive value of CT in this population was 99.8%.

So how common in the misdiagnosis in SAH patients? Kowalski et al reported on a US cohort of SAH patients (3), showing that 12% of the patients were initially misdiagnosed by a health care professional. Failure to perform a CT was the most common mistake in 73% of the cases. Of those misdiagnosed, 21% experienced rebleeding before adequate treatment, and this was associated with increased risk of death and severe disability after a long term follow-up. Initial health care professional-related misdiagnosis of 13% was also observed in a Japanese cohort (4), resulting in rebleeding in 26% of the patients with delayed diagnosis.

Although missed SAH diagnoses should definitely be avoided to decrease unnecessary morbidity and mortality from preventable rebleedings, the above-mentioned observations also have interesting connotations for epidemiological studies. Although high, the rebleeding risk of a ruptured aneurysm is clearly less than 100%. If up to 10-15% of SAH patients EVENTUALLY diagnosed are initially misdiagnosed, even in developed countries with adequate health care services, how many mild SAH patients who never experience a rebleeding will go unnoticed? If there are geographic differences in susceptibility to misdiagnose mild SAH, could these explain part of the observed variability of incidence of SAH?

1. Perry JJ, Stiell IG, Sivilotti ML, Bullard MJ, Lee JS, Eisenhauer M, Symington C, Mortensen M, Sutherland J, Lesiuk H, Wells GA. High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study. BMJ, 2010, 341:c5204

2. Cooper JG, Smith B, Hassan TB. A retrospective review of sudden onset severe headache and subarachnoid haemorrhage on the clinical decision unit: looking for a needle in a haystack? Eur J Emerg Med, 2015, Apr 2 [Epub ahead of print]

3. Kowalski RG, Claassen J, Kreiter KT, Bates JE, Ostapkovich ND, Connolly ES, Mayer SA. Initial misdiagnosis and outcome after subarachnoid hemorrhage. JAMA, 2004, 291:866-9

4. Inagawa T. Delayed diagnosis of aneurysmal subarachnoid hemorrhage in patients: a community-based study. J Neurosurg, 2011, 115:707-14