SAN FRANCISCO - In the fevered race to diagnose patients with vague neurological symptoms, emergency doctors must keep an eye out for unusual stroke types that can require different imaging exams or treatment approaches, according to Dr. E. Bradshaw Bunney.
Yesterday at the American College of Emergency Physicians (ACEP) annual meeting, Bunney looked at three cases in which the routine stroke workup should be anything but -- and when a noncontrast head CT alone might not lead to adequate diagnosis and care.
Knowing what to look for and what to exclude can help the radiologist know what to look for too, of course, particularly when dealing with the odd posterior circulation stroke, carotid or vertebral arterial dissection, or cavernous sinus thrombosis. How many cases might be seen retrospectively when enlightened suspicions are on target?
At the least, knowing when to administer contrast to the head CT, or skip it entirely in favor of MRI or MR angiography can save valuable time, said Bunney, who is an associate professor of emergency medicine at the University of Illinois in Chicago.
To be sure, choosing an imaging modality is anything but a coin toss. At the university where he teaches, Bunney noted that a new 9.4-tesla MR scanner had just been installed. On the other hand, the community hospital where he practices regularly is limited to CT or nothing.
Bunney's audience on Tuesday, comprising perhaps 200 emergency physicians, mostly, appeared even less fortunate than Bunney from a statistical point of view. Virtually all hands when up when the group was asked how many had access to fast head CT for stroke evaluation 24/7. Fewer than 10 attendees indicated similar access to MRI.
For some indications, it's worth moving the patient to another institution to get the MR if necessary, Bunney said, though he did not specifically address the newest CT techniques such as perfusion imaging. He did offer compelling detail in the case of three real patients.
Case 1: Posterior circulation stroke
A 41-year-old man was out with some friends at a bar. And although he was apparently not intoxicated, the man found himself suddenly unable to stay on his feet.
"All of the sudden he's dizzy, he's vomiting, he can't stand up, and he's complaining about right-sided weakness," Bunney said. "He also has a bit of slurred speech; his friends brought him in (to the ER) and said, 'You know what, he's just not making sense.'"
At presentation the man's vital signs were stable, neurologically he was alert and oriented, and his motor skills were mostly intact, though he was somewhat dysarthric. The head CT was normal.
"One of most important things to remember is that posterior circulation stroke comprises almost one-fifth of all strokes," Bunney said. "The reason we want to catch these is that they have some rather unfavorable outcomes, with 50% or more ending up with significant disability," he added. The most serious of these, basilar artery occlusions, have mortality rates as high as 90%. These patients often suffer from "locked-in syndrome," and are able to move only their eyes.
The good news is that mortality has declined in recent years with aggressive treatment, coinciding with the compilation of a registry of posterior circulation strokes (Annals of Neurology, September 2004, Vol. 56:3, pp. 389-398).
It's important to know that vertebral arteries are prone to atherosclerosis, which may be presumed to be the leading cause of posterior circulation strokes and consequent ischemia, he said. Patients frequently present with a vague history that can make diagnosis difficult.
But a hallmark of posterior stroke is the development of cross-findings at presentation -- for example weakness or numbness on the right side of the face, an arm, or a leg, that crosses over to the contralateral side. Other common signs at presentation are dizziness, diplopia, dysarthria, ataxia, and dysphagia, along with nausea or vomiting.
Syndromes include vertebrobasilar insufficiency (VBI), which can progress to stroke within a few days or weeks. Wallenberg syndrome patients typically have pain or temperature sensation on the side of the face that will have the lesion, with a crossover loss of sensation on the contralateral side of the body. Horner's syndrome is also common.
Anton syndrome patients "present in a way that we see a lot of other patients present," he said. "They're sleepy, they're having hallucinations, and they're confused." The first choices of many physicians might be toxicity, including drug use, or psychiatric problems, he said, but it's essential to weigh Anton syndrome as a differential diagnosis. Complete paralysis, except for vertical eye movement, often accompanies complete basilar occlusion.
The first imaging test should be noncontrast head CT to determine if the stroke is hemorrhagic or ischemic, he said. CT can pick up even a small bleed with 90% to 95% sensitivity, he said.
"The problem is that CT is not necessarily the best way of imaging the structures in the posterior fossa," he said. "It is now widely believed that MRI is superior to CT in the posterior fossa." However, MRI may be less adept at detecting early bleeding, he said, so if it is available, MR angiography is probably the best imaging test when posterior circulation stroke is suspected. These days, duplex sonography can also serve as a backup.
There are no randomized controlled trials to prove the efficacy of therapy for posterior stroke patients, but the poor outcomes seen in untreated patients have led to the routine use of heparin and anticoagulation therapy in many cases. Good recanalization rates are now occurring with tPA up to 12 hours after symptom onset, he added.
Bunney counsels ischemic stroke patients and their families that there is a tenfold increase in the risk of bleeding (from 0.6% to 6%) with thrombolytic therapy, but no increased risk of mortality after three months. Second, treatment provides a 30% chance that the patient will emerge after three months with little or no neurological deficit. At that point, he said, he allows the patient or family to make an informed decision.
Angioplasty, stenting, and the "corkscrew" or Merci Retriever (Concentric Medical, Mountain View, CA) are new therapeutic solutions in trials, he said, though he cautioned that "the brain and neurons do pretty well with the actual ischemic event; it's the reperfusion that causes a number of problems." New therapies are addressing this issue as well.
The 41-year-old patient had a negative noncontrast CT, Bunney said; the posterior stroke was diagnosed with diffusion-weighted MRI. He deteriorated initially in the hospital, but was given tPA, regained consciousness, and was discharged three days later, eventually recovering with follow-up physical therapy.
Case 2: Vertebral artery dissection
A 31-year-old woman who had been driving and talking on her cell phone got out of her car when she arrived home, and fell to the ground. Staggering to the house, she lay down on the floor immediately. She was unable to focus, the dog was licking her face, and the room was spinning around her. After about five minutes, the symptoms disappeared completely, and she was left with only a severe right-sided headache.
At presentation her vital signs were normal, her neck was supple with a full range of motion, and her neurological exam was normal. The head CT was completely normal as well.
It wasn't a migraine or subarachnoid hemorrhage. It was a vertebral artery dissection, Bunney said. Carotid and vertebral artery dissections comprise 2.5% of all strokes, and can occur in any age group. They typically occur in association with trauma -- even cocking the head to hold a cell phone could conceivably do it. Patients typically present with signs of either a stroke syndrome or ischemic attack.
To detect such dissections, look for a history of arteriopathy such as Marfan syndrome, or small traumas ranging from turning the head to coughing, to air-bag deployment, or even chiropractic manipulation, he said. Most important, look for associated head or neck pain.
They can occur both intracranially and extracranially, but mostly around the C1 or C2 vertebrae, where operating is difficult and therefore of little interest to neurosurgeons, he said.
"Vertebral artery dissection is one of the hardest things to diagnose, and you won't be able to diagnose it if you don't think about it," Bunney said. "So that's one of the main take-home points -- the fact that you're going to pick these up, you're going to have to have thought about it, and at least included it in your differential diagnosis."
"Anybody who has neural deficits that are either transient or have continued since you examined them -- accompanied by headache or neck pain -- that combination should trigger in your head that this disease needs to be investigated," he said. As many as 70% of patients present with concomitant pain.
Here again, head CT is the first imaging exam, but barring a complete opening of the vessel leading to subarachnoid hemorrhage, these are generally negative. The study of choice is MR angiography, he said. However, he said, if no one is available in the middle of the night to do an MRA, duplex ultrasound has improved to the point where in experienced hands, at least, it can find intimal tears in the vertebral arteries and arrive at a reliable diagnosis, he said.
Once again, there are no randomized controlled trials for such dissections, but anticoagulation is the mainstay of therapy, Bunney said. Certainly thrombolysis might seem to be a counterintuitive and even risky choice, but the good news is that case reports and anecdotal reports indicate that the patients actually do quite well, he said. And recurrence rates are about 3% for the carotids and 5% for vertebral arteries. But why is tPA routine in the first place?
"You have no idea that this is a vertebral artery dissection at the time you're giving thrombolysis," he said. "If you can get an MR angiogram within the three-hour window (after symptom onset), I'd like to know about it."
As for the young patient with the cell phone, her left vertebral artery dissection was detected on MRA. She was heparinized, discharged from the hospital, treated with Coumadin for six months, and lived happily ever after.
Case 3: Venous thrombosis
A 25-year-old woman had a headache lasting two weeks, especially in the frontal right facial region, increasing in severity over the last three days. She was normal neurologically; had no photophobia or neck pain, and her vital signs were normal.
The patient's head CT was normal, she began to feel better, and was discharged after given antinausea medication.
Venous thrombosis is generally divided into infected and noninfected categories. It is relatively rare, Bunney said, citing a Massachusetts General Hospital study in Boston that reported only 150 cases over 44 years. Roughly two-thirds of these were cavernous sinus thrombosis, and the mortality rate among all patients was more than 30%. Sadly, he said, up to a quarter of these occur as a result of patients squeezing acne pimples around the eyes and nose.
Transverse and sigmoid sinus thrombosis has been decreasing in incidence over the past 10 years -- due generally to increased immunization, since the main source of this kind of thrombosis has been chronic otitis or mastoiditis, he said. The most devastating type is superior sagittal sinus thrombosis. Patients generally present with headaches, nausea, and vomiting, and they deteriorate rapidly. They often have concomitant meningitis.
Patients initially present with fever, headache, and malaise, but they also tend to end up with some type of pain in the retro-orbital area. Broad-spectrum antibiotics and sometimes thrombolysis can be used as last-ditch effort, he said. Thrombosis should be considered in any patient that appears to have a facial infection, especially when accompanied by headache, he said. The imaging exam of choice is contrast CT.
"The reason we want to do (CT) with contrast is not so much to be able to delineate the cavernous sinuses from the other sinuses, but you can end up with enhanced contrast uptake in the meninges when they're inflamed," Bunney said. MR venography provides a good confirmatory study; the radiologist is generally looking for an absence of flow with the development of thrombosis, he said.
In the 25-year-old patient, the radiologist found only opacification of the right ethmoid and right sphenoid sinuses on CT. The patient was telephoned at home, and given the option of going to the emergency department or to her primary care physician.
But the woman progressed to worsening symptoms of confusion, hallucination, and was finally admitted to the hospital, undergoing two MR exams that depicted the superior sagittal sinus thrombosis and infection. Leukocytosis in the cerebrospinal fluid led to additional antibiotic administration. But the patient developed severe orbital pain, apoptosis, increased inflammation of the orbital area, and died on the 19th day.
It is critical that the emergency physician look at the CT images along with the radiologist, hypotheses in mind, Bunney said. Also, just as doctors document why they decided to administer thrombolytic therapy, they should routinely document the decision process in cases in which thrombolytic therapy was considered but rejected.
"Always consider these strokes in your differential diagnosis, and be able to include those differential diagnoses on the chart," he said.
By Eric Barnes
AuntMinnie.com staff writer
October 20, 2004
Related Reading
MRI as good as CT in detecting acute intracerebral hemorrhage, October 20, 2004
GE installs 9.4-tesla MRI unit, September 17, 2004
MR vs. CT? Stroke imaging hinges on more than modality, August 25, 2004
Cerebral microbleeds not linked to cardiovascular risk factors, July 27, 2004
DWI proves best of seven in subacute stroke imaging, May 17, 2004
Short MRI exam extends stroke tPA window, with good results, April 30, 2004
Perfusion CT predicts, measures, thrombolysis benefit after acute stroke, December 24, 2003
Perfusion CT offers speedy access, but MRI gives the "big" picture, February 19, 2003
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