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July 16, 2007

Imaging Recovery? — Using MRI to Predict Outcomes for Patients With Spinal Cord Injuries
By Dan Harvey
Radiology Today
Vol. 8 No. 14 P. 15

Radiologists and physicians frequently employ MRI for an initial diagnosis in patients suffering from severe spinal cord injuries (SCI). Now, researchers are reporting that MRI can help clinicians more accurately predict recovery outcomes in those patients.

The investigators drew their conclusions from their study involving SCI patients admitted between March 2000 and March 2005 to the Toronto Western Hospital and the University of Maryland Medical System. The study, titled “Acute Cervical Traumatic Spinal Cord Injury: MR Imaging Findings Correlated with Neurologic Outcome—Prospective Study with 100 Consecutive Patients,” was published in the June issue of Radiology. Coauthor Michael G. Fehlings, MD, PhD, FRCSC, FACS, says the study demonstrates that a more thorough assessment of MR images enables clinicians to determine the chances for full or partial recovery within 48 hours following injury.

The study also shows that MRI not only provides considerable added value for prognosticating outcomes, but it can be useful in determining treatment strategies as well, adds Fehlings, who is a professor of neurosurgery at the University of Toronto and medical director at the Krembil Neuroscience Centre at Toronto Western Hospital. “A more systematic assessment of MR images could result in a more aggressive clinical treatment for patients who may appear to have a severe SCI but may indeed have the capacity for substantial neurological recovery,” he says.

MRI exams are commonly but not universally performed on SCI patients, Fehlings says. Typically in spinal injury cases, an initial MRI reveals the extent of neurological damage and helps determine the prognosis. “Some surgeons still question whether it provides value over x-rays or CT scans, but we strongly believe MRI adds tremendous value,” he says.

Qualitative and Quantitative Parameters
Fehlings believes that added value can be realized through what he describes as a rigorous assessment of the MR images. This systematic evaluation, he explains, involves both the qualitative and quantitative measurements of spinal cord compression. “An association exists between the amount of pressure on the spinal cord and the outcome,” he says.

The six qualitative parameters that radiologists typically examine include cord hemorrhage, cord swelling, edema, soft tissue and ligamentous injury, canal stenosis, and disc herniation. In most of the similar studies previously conducted, researchers have focused on these qualitative measures in examining the association between imaging parameters and patient outcomes. But, as the researchers indicate in their paper, few studies have focused on quantitative measures. Fehlings and colleagues developed a radiologic method to assess spinal canal compromise and cord compression involving the qualitative and quantitative measures. The three quantitative measures they employed include maximum spinal cord compression (MSCC), maximum canal compromise (MCC), and length of lesion.

Uncovering Key Prognostic Indicators
For their study, the researchers examined 100 patients (79 men and 21 women between the ages of 17 and 96) with traumatic cervical SCI. Most patients suffered their spinal injuries in motor vehicle accidents. Twenty-six patients experienced complete motor and sensory SCI, while 51 experienced incomplete SCI, and 23 were neurologically intact upon admission.

MRI exams were obtained within 24 to 48 hours of injury. The six qualitative imaging parameters were studied along with the three quantitative measures. Exams were performed with a 1.5-Tesla magnet (Signa, GE Medical Systems).

Researchers employed standardized MRI protocols for the severely injured spine. They performed T1- and T2-weighted examinations in the anteroposterior frequency direction by using an 8CTL12 coil, a section thickness of 3 millimeters, an intersection gap of 0.5 mm, and a 24-centimeter field of view. No contrast material was administered.

For sagittal T1-weighted imaging, they performed a 2-D spin-echo sequence by using a conventional imaging option with no phase wrap; 450 per minimum (repetition time per millisecond/echo time per millisecond), a receiver bandwidth of 15.63 kilohertz, a matrix of 512 X 192 (frequency encoding X phase encoding), three acquired signals; and no phase correction. For sagittal T2-weighted imaging, they performed a 2-D fast-recovery, fast-spin echo sequence by using imaging options that included no phase wrap, an extended dynamic range, tailored radiofrequency, and fast recovery; an echo train length of 33; a receiver bandwidth of 41.67 kilohertz; a matrix of 512 X 224; four acquired signals; and phase correction.

Images were analyzed by an observer blinded to the patients’ clinical and neurologic data. The observer collected data on the qualitative and quantitative parameters.

Results reveal that the severity of MSCC direct spinal cord compression and cord bleeding and swelling were key indicators of a poor prognosis following traumatic cervical SCI. Specifically, patients with complete motor and sensory SCI had more substantial MCC, MSCC, and lesion length than patients with incomplete or no SCI. Also, patients with complete SCI exhibited higher frequencies of intramedullary hemorrhage, cord edema, cord swelling, stenosis, and soft-tissue injury. The researchers described a poor prognosis as a more critical injury with reduced possibility for recovery. Alternately, a good prognosis was indicated for patients without the aforementioned symptoms, even if their injury appeared severe.

In addition, the researchers report that their results suggest MSCC is a more reliable predictor of neurologic outcome than the presence of canal stenosis. Also, as compression severity is a key predictor of outcomes following SCI, Fehlings indicates that the MRI examinations could help physicians determine which patients should undergo spinal cord decompression surgery.

Increased Usage Encouraged
The researchers report that, as far as they know, theirs was the first study that combined qualitative and quantitative MRI parameters to predict patient neurologic outcomes. Fehlings believes that, because of the study results, MRI for SCIs should become the standard of care as long as significant medical circumstances don’t prohibit an examination. But he’s also aware of reservations people have about MRI. “Sometimes, physicians are concerned about a patient’s health, and they want to minimize the number of tests performed to get on with treatment as soon as possible,” he says. “But we’ve tried to point out that radiologists performing an MR evaluation of the spine can be very focused at a particular point. This makes the examination less time-consuming.”

Further, the protocol described in the paper enables radiologists to perform MRI in a very efficient and effective manner. “The measurement techniques add a great deal of practical information that can help determine the most appropriate management algorithm for the patient,” says Fehlings.

Also, as it provides accurate and practical information, MRI is cost-effective. “Therefore, I not only feel that it should be done frequently, I also feel it should be done in all cases,” Fehlings recommends.

STASCIS Connection
Fehlings says the study arose from the work of a research team he cochairs called the Spine Trauma Study Group, an international coalition of specialists who treat spinal cord trauma. The group is currently involved in the Surgical Treatment for Acute Spinal Cord Injury Study (STASCIS), an observational and prospective randomized study aimed at determining if patients with SCI will benefit from earlier treatment to reduce pressure on the spinal cord.

“The hypothesis is that it is best to take pressure off of the spinal cord by going in earlier after an injury,” explains Fehlings. “The Radiology paper emanated from that work because we had to develop a technique that would assess the extent of spinal cord compression. We were also interested in looking at other factors that predict outcome.”

Fehlings says investigators are taking the next steps in this direction of research. First, the researchers are collecting data to validate the idea that earlier surgical intervention relieves pressure on the spinal cord. “This points to practical therapeutic application that can potentially make a difference for patients,” he says.

Second, as researchers move forward, they will continue to improve the imaging algorithm. “I feel we’re going to see huge advances in MRI techniques and technology, and it would be helpful in the future to have evidence of reparative strategies,” he adds.

Meanwhile, the researchers have clearly indicated that MRI can be a valuable tool in predicting a patient’s chances for full or partial neurologic recovery. Further, it can direct clinicians toward optimal treatment strategies. As such, Fehlings recommends that MRI be performed on all patients with severe SCI whenever possible. “I am coming at this as a surgeon speaking to two audiences: radiologists and my colleagues in neurosurgery and spinal surgery,” he says. “My hope is that radiologists will adopt the methods described in the paper and that more surgeons will adopt MRI usage.”

— Dan Harvey is a freelance writer based in Wilmington, Del. He is a frequent contributor to Radiology Today.