Added Value of Three-Plane Multiecho Fast Field Echo MRI Sequence in the Evaluation of Acute Spinal Trauma Using Sensitivity: A Prospective Study

Background Multiecho fast field echo (mFFE) MRI sequence provides added value to the conventional MR imaging in evaluation of acute spinal trauma, especially for detecting spinal cord hemorrhage which is a best predictor for patient prognosis. Objective This study aims to evaluate the diagnostic efficacies of three-plane mFFE MRI sequence along with the conventional MRI sequences in acute spinal trauma patients using sensitivity. Materials and methods This prospective study comprised of 48 patients of acute spinal trauma. The neurological deficit of acute spinal trauma patients assessed according to the American Spine Injury Association (ASIA) scale. The correlation between the various MRI findings of acute spinal cord injury and neurological deficits were compared with the Chi-square test. Results Of 48 patients of acute spinal trauma, 36 males and 12 females with a mean age of 38.71±1.42 [SD] years. 22 (45.8%) patients had cord edema with a mean length of was 3.45±5.52 [SD] cm. The mean percentage of spinal canal compromisation was 39.47±25.47 [SD] and spinal cord compression 18.1±24.4 [SD]. There was statistical significance between the ASIA impairment scale and spinal canal compromisation and cord compression with a p-value of 0.0005. Cord hemorrhage observed in 13 (27%), non-hemorrhagic cord contusions in 3 (6.3%), cord transection in 5 (10.4%) and epidural hematoma in 10 (20.8%) patients with an initial high grade of ASIA scale. The visibility score of three-plane mFFE sequence was higher in comparison to the single plane sagittal mFFE and short tau inversion recovery (STIR) sequences. For detection of spinal cord hemorrhage with visibility score of 2, the three-plane mFFE had sensitivity of 77% followed by 38.5% with single plane sagittal mFFE and 7.7% with sagittal STIR images. 26 (54.2%) patients showed neurological improvement in their hospital stay/follow-up period and no improvement observed in 7 (14.6%) patients of acute spinal trauma. Conclusions Application of three-plane mFFE sequences detects more spinal cord hemorrhages and vertebral fractures with a better visibility score as compared to the single sagittal plane mFFE and STIR sequence.


Introduction
Plain radiograph and computed tomography scan are the initial imaging modalities of choice in acute spinal trauma. CT scan plays an important role in the rapid assessment of the acute spinal injury patient. However, MRI is the imaging modality of choice in acute spinal trauma patient which able to accurately detect the various vertebral fractures, ligamentous, disc, spinal cord and muscle injuries [1,2]. MRI precisely detect the various types of spinal cord injuries, which are missed on CT scan [1,2].
MRI plays a pivotal role in prognosticating acute spinal injury patients by detecting various pattern of acute 1 1 1 1 2 The MRI scan was usually subjected to a patient with acute spinal injury, when plain radiographic or CT findings are suspicious for ligamentous injury, to look for spinal cord injuries in patients with profound neurological deficit, to look for extra-medullary hemorrhage, post-traumatic disc herniation and spinal instability [2,4]. The acute spinal cord injuries vary from cord concussion, edema, contusion, hematoma to the transection [5].
MRI remains the mainstay of imaging modality in a suspected patient of acute spinal cord injury as MRI able to identify cord contusion, edema and hemorrhage [6][7][8]. Gradient recalled echo (GRE) sequence has a higher sensitivity to detect hemorrhage compared to a spin-echo sequence [6][7][8]. With the help of single or multiplane GRE sequence like multiecho fast field echo (mFFE) sequence, MRI able to identify the degree and extent of cord hemorrhage and which helps the clinician to predict the patients functional and neurological recovery [6][7][8][9][10]. Previous literature showed poor neurological recovery, especially motor recovery in those patients, who had cord transection, hemorrhage and increased length of cord hemorrhage at initial MRI scan [9,11]. MRI is more sensitive in detecting occult bony injuries in vertebral body than posterior vertebral element because a lesser amount of cancellous bone in posterior vertebral element [12]. GRE sequence able to identify cord hemorrhage as dark signal intensity (blooming), extra-medullary hemorrhage and even vertebral body and posterior elements fractures [13]. The spinal cord hemorrhage appears as low signal intensity on T2WI with surrounding T2WI hyperintense edema. Three-plane mFFE sequence is the best for determining the location, size, extent of spinal cord hemorrhage which may be underestimated on conventional spin-echo MRI sequences [13].
The three-plane mFFE sequence can also detect ligament injury, muscle, paraspinal soft tissue injuries. mFFE can clearly differentiate hemorrhagic from non-hemorrhagic cord contusion [14][15][16]. Three-plane mFFE sequence able to demonstrate the displaced vertebral body or posterior element fractures, detect impingement over thecal sac, spinal cord and nerve root by retropulsed/displaced fractured bony fragment, detect facetal joint subluxation, intra-or extra-medullary hematoma at the level of injury [7,17]. Discontinuity of ligament can also be detected by mFFE sequence along with spin-echo T2W and short tau inversion recovery (STIR) sequences [18].
The prognostic markers of acute spinal injuries are degree of spinal canal compromisation and spinal cord compression, which can be measured by comparison at the site of injured segment, above and below the site of the injured segment [9].
This study aims to evaluate the diagnostic efficacies of three-plane mFFE MRI sequence along with the conventional MRI sequences in acute spinal trauma patients using sensitivity.

Materials And Methods
A prospective study was conducted at our institution on 48 patients of acute spinal trauma over a period of 12 months from August 2019 and July 2020 those underwent an MRI scan of the spine. This prospective study was approved by the Institutional ethics review committee. All acute spinal trauma patients underwent clinical examination during admission or before an MRI scan. The degree of neurological deficit of spinal trauma patients was determined according to the American Spine Injury Association (ASIA) impairment scale. The various MRI images were reviewed by two experienced radiologists blinded to the clinical information. Two radiologists observed for the vertebral body or posterior element fractures, cord edema, cord contusion, cord hemorrhage, cord transection or associated epidural hematoma. The neurological examinations were done by two experienced orthopedician.
Correlation was done between the various MRI findings of spinal injuries and neurological deficit.

Patient selection
Acute spinal trauma patients with a history of injury less than 7 days of duration were included and finally 48 patients, male = 36 (75%) and female = 12(25%) with a mean age of 38.71±1.42 [SD] years were included in the study (Figure 1).

Exclusion criteria
1. Spinal trauma more than seven days of duration.

MRI evaluation
MRI images were evaluated for the site, level, pattern of the vertebral fractures, status of intervening disc, ligaments, ligamentum flavum , para-spinal muscles and various spinal cord injuries (SCI) like cord edema, cord contusion, cord hemorrhage and cord transection.
The maximum spinal canal and cord compromise were calculated in the mid-sagittal T1WI images using these formulae: Spinal canal compromise (%) = (1-Di/(Da+Db)/2) x 100. Di = diameter of spinal canal at the injured site, Da = diameter above the injured segment and Db= diameter below the injured vertebral segment.
Degree of maximum spinal cord compromise measured in vertebral fractures of C2 to L1 vertebral level. In patient with multiple vertebral fractures, the maximum site of spinal canal and cord compromisation was selected for the measurement.

Visibility score of cord hemorrhage
The visibility of the spinal cord hemorrhage was categorised on a 3-point scale from 0 to 2. Score 0 = no cord hemorrhage detected, 1 = probably present cord hemorrhage and 2 = distinctly present cord hemorrhage. To know the diagnostic performance of 3 plane mFFE sequence in the evaluation of spinal cord hemorrhage, the imaging findings were determined on single plane (sagittal) mFFE images and three-plane mFFE images .

Neurological assessment of acute spinal trauma
The degree of neurological deficit of spinal trauma patients were determined according to the American Spine Injury Association (ASIA) impairment scale. Scale A (complete)-No sensory or motor function is preserved in the sacral segments S4-5, Scale B(Sensory incomplete)-Sensory but not motor function is preserved below the neurological level and includes sacral segments S4-5, Scale C (Motor incomplete)-Motor function is preserved below the neurologic level, and more than half of the key muscles below the neurologic level have a muscle grade <3, Scale D(Motor incomplete)-Motor function is preserved below the neurologic level, and at least half of key muscles below the neurologic level have a muscle grade of 3 or more and Scale E(Normal)-Sensory and motor functions are normal.

Statistical analysis
All statistical analysis was performed using Statistical Package for the Social Science (SPSS, version 16) (IBM Corp., Armonk, NY). Chi-square test was used to find out the correlation between the various spinal cord injuries on MRI with the neurological deficits. One-way ANOVA test was used find out the correlation between the maximum spinal canal and cord compromisation with the neurological deficits.

Spinal cord abnormality
Out of 48 patients, spinal cord abnormalities identified in 22 (45.8%) patients. Various spinal cord abnormalities were shown in (Table 3). Spinal cord edema observed in 22 (45.8%) patients with or without cord hemorrhage ( Figure 5). The mean length of cord edema was 3.45±5.52 [SD] cm. There was statistical significance between the ASIA impairment scale and length of cord edema with a p-value of 0.003. Only spinal cord edema observed in 6 (12.5%) patients, where three in the cervical cord, two in the conus medullaris and one in the thoraco-lumbar cord. Cord hemorrhage was observed in 13 (27%) patients, where four in the cervical cord ( Figure 5), four in the dorsal cord, two in conus medullaris, two in cervico-thoracic cord and one in the thoraco-lumbar cord. Non-hemorrhagic cord contusion was observed in 3 (6.3%) patients, where one in cervical cord, one in thoraco-lumbar cord and another one in conus medullaris. Cord transection was observed in 5 (10.4%) patients, where three had partial cord transection ( Figure 4), one had near-total transection ( Figure 6) and another one had complete cord transection.

Sagittal mFFE, STIR and three-plane mFFE visibility score of cord hemorrhage
Thirteen out of 48 patients of acute spinal trauma had spinal cord hemorrhage on mFFE sequence shown in ( Table 4). Out of 13 patients, cord hemorrhage was distinctly visualized (visibility score 2) in 10 (76.9%) patients on three-plane mFFE sequences ( Figure 5) and 5 (38.5%) patients on single plane sagittal mFFE sequence. Detection of spinal cord hemorrhage with visibility score of 2, the three-plane mFFE had a sensitivity of 77% followed by 38.5% with single plane sagittal mFFE and 7.7% with sagittal STIR images.  Out of 13 patients, cord hemorrhage was poorly visualized (visibility score 1) in 3 (23%) patients on threeplane mFFE sequences and 5 (38.5%) patients on single plane sagittal mFFE sequence. Detection of spinal cord hemorrhage with visibility score of 1 or above , the three-plane mFFE had sensitivity of 100% followed by 77% with single plane sagittal mFFE and 61.5% with sagittal STIR images.

MRI sequence
No significant correlation found between the visibility scores of cord hemorrhage and ASIA impairment scale shown in (Table 4).

Ligaments and soft tissue injuries
Various ligaments and soft tissue injuries shown in Table 3

Management
Out of 48 patients of acute spinal trauma, 33 patients treated conservatively and 15 patients treated surgically.

Neurological recovery
The neurological recovery after treatment shown in (

Discussion
Three-plane mFFE sequence was highly accurate in diagnosing spinal cord hemorrhage which helps in prognosticating acute spinal cord injury (SCI) in comparison to single plane mFFE sequence [14,15].
Application of three-plane mFFE sequences can better identify the cord hemorrhage, various vertebral body and posterior element fractures which may in some situations obviate the need for a CT scan [13]. In our study sample of 48 patients, the majority of patients being males (75%). Young-and middle-aged men were the most common age group involved with a mean age of 38.71±1.42 [SD] years. Similar trend reported by Singh et al. [3].
RTA was the comment cause of acute spinal injuries in 29 (60.4%) patients followed by fall from height in 14 (29.2%) and slipped injury in 5 (10.4%) patients. Singh et al. [3] reported that a fall from height was more common.
Parashari et al. [16] and Magu et al. [19] commonly found acute spinal trauma patients of ASIA scale A while in our study sample ASIA scale E was found in 15 (31.2%) patients and least in ASIA scale A in 7(14.6%) patients. This was probably because of more number of patients of thoraco-lumbar injuries in our study sample.
mFFE sequence can also able to detect extra-medullary hemorrhage. Kerslake et al. [18] found epidural hematoma in 41% of patients of acute spinal trauma with a higher incidence in ankylosed spine [20]. In our study sample, 10 (20.8%) patients had an epidural hematoma.
Injuries of cervical spine were commonly observed by Fehlings et al. [21] followed by lower dorsal and upper lumbar spinal injuries. Cervical spine injury is a common site because of excessive mobility during RTA or fall from height and lack of supporting structures observed by Gupta et al. [22]. Looby et al. [23] reported more thoraco-lumbar injuries than cervical spine injuries. In our study sample, most commonly thoracolumbar injuries observed in 25 (52%) patients followed by cervical vertebral injuries in 10 (20.8%) patients.
The degree of spinal canal compromisation and cord compression act as an important factor for spinal cord injury [9] and which also act as a prognostic indicator for neurological deficit [23]. Kulkarni et al. [7] described three patterns of MRI appearances that prognosticate acute spinal cord injury are cord hemorrhage, cord edema, combination of cord hemorrhage and edema. In our study sample, the visibility score of three-plane mFFE sequences was higher in comparison to the single plane sagittal mFFE sequence for detecting cord hemorrhage shown in (Table 4).
Bondurant et al. [24] described four patterns of spinal cord injuries. Normal cord in Pattern 1, cord edema for a single vertebral level in Pattern 2, multiple vertebral level cord edema in Pattern 3 and mixed cord hemorrhage and edema in Pattern 4. Changes in signal abnormalities of cord edema found within the first two weeks following acute spinal cord injury [25].  [8,24,26]. No neurological improvement was observed in patients with cord hemorrhage by Gupta et al. [22] and cord transection by Qiu et al. [27]. In our study, 11 patients with normal cord findings on MRI scan with a neurological deficit of ASIA scale C and scale D showed complete neurological recovery. Patients with initial ASIA scale A have lower chances of recovery (28.6%), whereas maximum chances of recovery were associated with ASIA scale D (100%). Harrop et al. [28] observed 7% neurological improvement in patients with initial ASIA scale A and 94.3% improvement in ASIA scale D.
Out study observed a more detection with higher visibility score of spinal cord hemorrhage, extra-medullary hematoma and vertebral body and posterior element fractures with institution of three-plane mFFE sequences as compared to the single plane sagittal mFFE and STIR sequences. However, no statistically significant difference was observed between these. Therefore, a larger prospective study to confirm these findings is warranted in the future. Another limitation of three-plane mFFE sequence was more timeconsuming in comparison to a single plane mFFE sequence of 2 min 31 sec. MRI is the choice of investigation for the patient with acute spinal injury. MRI with institution of threeplane mFFE sequence can define the spinal cord hemorrhage, vertebral fractures and facetal articulations abnormalities. MRI appearance of length of cord edema, cord hemorrhage, and spinal cord transection are the important considerations in neurological deficit and which helps in planning early patient management.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Tezpur Medical College & Hospital ethics review committee issued approval Applied for. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work.
Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.