Tag Archives: MRI

CNS

Using MRI To Predict Outcome From Diffuse Axonal Injury (DAI)

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Has this happened to you? A patient with a serious head injury is not waking up as expected. There were a few punctate hemorrhages seen on the initial CT scan. Your neurosurgery colleague orders an MRI to “provide a prognosis on the patient’s injury.”

Is this a legitimate request? Sure, MRI is very sensitive at detecting very small hemorrhages that may signal the presence of diffuse axonal injury (DAI). But do more abnormalities on MRI equal a poorer prognosis or longer recovery time?

A group from Vanderbilt presented their data from a retrospective cohort study at EAST earlier this year.  They reviewed 7 years of data from 2006 to 2012, including all patients with a head CT positive for intracranial injury and an MRI within 2 weeks. They excluded penetrating injuries and patients with psychiatric or neurologic disorders. They analyzed information on three year mortality, functional outcome, and quality of life.

Here are the factoids:

  • A total of 311 patients met all inclusion/exclusion criteria, with a median age of 40 and serious injury (average ISS 29, average ICU length of stay 6 days)
  • Functional status at discharge could be assessed in 240 patients, and only 118 could be contacted for long-term followup questions
  • Only 56% of patients with severe TBI had an MRI positive for DAI
  • Functional status was lower on discharge for patients positive for DAI on MRI
  • There was no difference in Glasgow Outcome Score, quality of life, or 3 year survival in patients with MRI evidence of DAI compared to those without

Bottom line: This is a relatively large study, but there are still several weaknesses that could skew the numbers a bit. However, it appears that MRI for prognostication of outcomes in patients with clinical DAI is not very helpful. First, only about half with a clinical picture of DAI showed it on MRI. And sure, MRI may tell us a little bit about their status when they are discharged from the hospital to rehab or transitional care. But is that information very useful? It certainly does not help predict their outcome in the longer term. So why order an expensive and difficult study (think restraints, sedation, lots of pumps and monitors) to tell us what we already know based on our experience with severe TBI?

Reference: Prognosis of diffuse axonal injury with traumatic brain injury. J Trauma 85(1):155-159, 2018

Imaging

Do We Need Cervical MRI Scans If The CT Is Negative?

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The debate on how to clear the cervical spine just never ends. We have finally come to some degree of agreement that certain patients (awake, alert, not impaired or head injured, without distracting injury) can undergo clinical clearance alone.

But if those criteria are not met, what next? Universally, adults receive a CT scan of the cervical spine. In the majority of centers, this is coupled with a good clinical examination. And if both are negative, the collar can be removed.

But recent literature suggest that a good, high-quality cervical CT read by a skilled neuroradiologist may be good enough. This has been demonstrated in several papers involving patients who are comatose or other-wise unable to participate with a clinical exam.

Many centers and trauma professionals are still reluctant to remove the cervical collar without that clinical examination. A new study asked the question: would an MRI provide additional, significant information over and above the CT scan in those patients who could not be examined or had persistent neck pain?

A consortium of 8 Level I and II trauma centers in New England participated in this study coordinated by Yale. Blunt trauma patients who underwent MRI after negative cervical CT were considered for the study. On further review, if they received the scan because they could not be clinically evaluated, or if they had complaints of persistent neck pain, they were enrolled. CT scanners with at least 64-slice capabilities were required. There was no mention of the qualifications or special experience of the radiologists reading the images at each center.

Here are the factoids:

  • 767 patients were enrolled in this 30-month study. A total of 43% were for persistent neck pain, 44% for inability to examine, and 9% for both.
  • Nearly a quarter had an abnormal MRI scan:
    • 17% ligamentous injury
    • 4% soft tissue swelling
    • 1% disk injury
    • 1% dural hematoma
  • The collar was removed in most (88%) patients with a normal MRI, but in only 13% with ab-normal MRI
  • 11 patients underwent a surgical procedure and half had neurologic signs or symptoms. 10 of them had ligamentous injury, 1 had dural hematoma, and 1 had both

Bottom line: Looks almost compelling, right? One would think that we had better get an MRI on all of these patients! But read more closely, please. Yes, injuries were found. But did they really “require” an intervention? For some injuries, it’s a chip shot. A three column ligamentous injury equals stabilization in any textbook. But management of lesser injuries is less clear. And could some of these injuries have been recognized by a skilled neuroradiologist reading the CT image?

So what to do? There is not enough data for a universal protocol yet. Unfortunately, you will need to develop your own institutional policy based on the experience and opinions of your spine and neurosurgeons. They are the ones who will have to deal with the decision making during and after these studies. Until the definitive study comes along.

Reference: Cervical spine MRI in patients with negative CT: A prospective, multicenter study of the Research Consortium of New England Centers for Trauma (ReCONECT). J Trauma 82(2):263-269, 2017.

Imaging

Cervical Spine MRI After Negative CT

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dislocation-atlanto-axial-0005

There are multiple ways to clear a cervical spine! Most centers use a combination of clinical decision tools and CT scan in adults. The gold standard tie breaker, warranted or not, seems to be MRI. This tool is only used in select cases where conventional imaging is in doubt, or the clinical exam is puzzling.

Some centers clear based on CT only as long as imaging is indicated. Some use MRI in cases where patients continue to complain of midline neck pain or tenderness after negative CT. A multi-center trial encompassing 8 Level I and II centers prospectively performed MRI on patients who could not be clinically evaluated, or had persistent midline cervical pain after normal CT.

A total of 767 patients were seen over a 30 month period. Besides looking at the usual data points, the authors were interested in new diagnoses and changes in management based on the MRI results.

Here are the factoids:

  • Neck pain and inability to evaluate occurred with equal frequency, about 45%; the remaining 10% had both
  • 23% of MRIs were abnormal, with 17% ligament injury, 4% swelling, 1% disk injury, and 1% dural hematomas.
  • Patients with normal and abnormal MRI had neurologic anomalies about equally (15-19%). [Why are these patients included? Were they initially not evaluable?]
  • The cervical collar was removed in 88% of patients with normal MRI (??), and in 13% with abnormal MRI
  • After (presumably) positive MRI, 14 (2%) underwent spine surgery; 8 of these had neurologic signs or symptoms

Bottom line: I’m a bit confused. If the authors were really trying to figure out the rate of abnormal MRI after negative CT, they should have excluded the patients with known neurologic findings. These patients should nearly always have an abnormal MRI. And why did they not take the collar off of the 12% of patients with both normal CT and MRI??

Hopefully, details in the presentation next week will help explain all this. I suspect that the study will show that there are cases where CT is normal but MRI is not. The abstract does not clearly describe how many of these are clinically significant.

I admit, I’m not very comfortable clearing the cervical spine in a patient with negative CT (even if read by a neuroradiologist) and obvious midline neck pain/tenderness. I hope this study helps clarify this issue. We shall see…

Reference: Cervical spine MRI in patients with negative CT: a prospective, multicenter study of the research consortium of New England centers for trauma (ReCONECT). AAST 2016, Paper 61.

General
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Clearing The Cervical Spine With MRI

If you follow the trauma literature, clearance of the cervical spine in obtunded patients is confusing at best. Although there is some literature out there that suggests that a good cervical CT alone is adequate, I’m not a believer. I’ve seen a case where the radiologist called the scan normal and a good spine surgeon called an injury and was right. So I’m reluctant to use CT alone because the skills of radiologists vary widely. I might be able to believe a dedicated neuroradiologist, but you can’t guarantee one will be reading your patient’s images.

So I fall back on the routine of clearing the bones with a CT scan, and the ligaments with something else. That something else could be a clinical exam (not available in the obtunded patient), flexion-extension images under fluoroscopy (makes a lot of people nervous), keeping the patient in a collar for weeks (skin breakdown), or an MRI. The problem is that there is little guidance in the literature regarding how good MRI is or the best way to use it.

A recent paper in the Journal of Trauma retrospectively looked at 512 out of 17,000 patients (!) seen over 5 years at one trauma center who had both CT and MRI of the c-spine. They wanted to determine if MRI was of any value in cervical spine clearance. Only 150 met the inclusion criteria (GCS<13, no obvious neuro deficit, normal CT). Half of the MRIs were normal. Of the abnormal ones, 81% showed a ligamentous or soft tissue injury. None were deemed unstable and no specific management was needed for any of the abnormal scans.

The authors interpreted their data as showing that MRI provided no additional useful information. However, numbers were (very) small, so the likelihood of them seeing someone with an unstable ligamentous injury was low. Could it be that they showed that MRI detected stable injuries well, and that they could essentially remove the collar based on that?

Bottom line: We still don’t know how to use MRI for clearance. My bias (no good data I can find) is that it is good in suggesting ligamentous injury via nearby edema. If this injury involves only one set of ligaments, it is very likely a stable one and the collar can be removed. If it involves several groups of ligaments, that is probably not the case. And how soon do we have to get the MRI after injury? Some have suggested that 72 hours is the ideal window because edema decreases afterwards. Sounds reasonable, but I can’t find a shred of evidence in the literature. For now, I’ll get an MRI within 72 hours and if it is abnormal, pass the buck to my neurosurgical colleagues so they can gnash their teeth, too.

I would be very happy if someone can help me out and point me towards some good literature on this topic!

Reference: The value of cervical magnetic resonance imaging in the evaluation of the obtunded or comatose patient with cervical trauma, no other abnormal neurological findings, and a normal cervical computed tomography. J Trauma 72(3):699-702, 2012.