Evaluating the causes of compressive myelopathy by MRI in PMCH, Patna

Background: Compressive myelopathy is a broad term that refers to spinal cord involvement of multiple etiologies. It is the term used to describe the spinal cord compression either from outside or within the cord itself. In contrast to plain radiograph MRI is considered a better imaging modality to assess soft tissue of spine and spinal cord abnormalities like traumatic myelopathy, spinal tumors and spinal infections. Many of these diseases are potentially reversible if they are recognized on time. Hence the importance of recognizing the signiﬁcance of MRI lies on an early and accurate diagnosis. Keeping this in view, study was aimed to evaluate the causes of compressive myelopathy with their characterization by MRI. Materials and Methods: A descriptive hospital-based study was conducted by purposive sampling. Fifty clinically suspected cases of compressive myelopathy were investigated with MRI. Results: Most common cause for compressive myelopathy in our study was spinal trauma (50%) followed by spinal infection (28%). Extradural compressive lesions (90%) were the most common cause for compressive myelopathy. MRI detected cord changes in 88% of cases with cord compression and also assessed the integrity of spinal cord, intervertebral discs and ligament after acute spinal trauma. Conclusion: Patients with suspected Compressive myelopathies could be beneﬁted with evaluation by MRI, as it is highly accurate and sensitive non-invasive modality for characterizing and identifying the underlying etiology, as well as associated features. Thus, helps in stating the long-term


Introduction
The term myelopathy describes pathologic conditions that cause spinal cord, meningeal or perimeningeal space damage or dysfunction. Thus, myelopathy is a broad term that refers to spinal cord involvement of multiple etiologies and can be divided into compressive and non-compressive. Compressive diseases of the spinal cord are divided into acute and chronic, including degenerative changes, trauma, tumor infiltration, vascular malformations, infections with abscess formation. 1 Spinal cord diseases often have devastating consequences, ranging from quadriplegia and paraplegia to severe sensory deficits. Many of these diseases are potentially reversible if recognized and treated at an early stage. Thus, they are among the most critical neurologic emergencies, where prognosis depends on an early and accurate diagnosis. 1 In comparison with CT, MRI detects more traumatic disc herniations, epidural haematomas and spinal cord abnormality, though it is less sensitive in the detection of posterior element fractures. Now a days MR imaging has replaced CT in noninvasive evaluation of patients with painful myelopathy because of superior soft tissue resolution and multiplanar capability and hence can depicts the spinal cord directly, assesses its contour and internal signal intensity characteristics reliably and early. 2 The present study highlights the various causes of compressive myelopathy and their characteristics evaluated by MRI with their distribution in demographic attributes of suspected cases.

Operational definition
For the purpose of this study Compressive myelopathy is conceptualized as the spinal cord compression either from outside or within the cord itself, excluding degenerative disc herniation.
By prospective sampling total 50 cases who attended / referred to the department with clinical suspicion of compressive myelopathy were selected. were acquired in addition to routine sequences. Thus, obtained data were coded and entered into SPSS version 20.0 (trial) and analyzed further.

Result & Discussion
Among 50 cases, most common cause for compressive myelopathy in our study was spinal trauma (50%) followed by spinal infection (28%) [ Table 1]. This finding is in coherence with the finding of Kulkarni et al (1987). 3 Majority of cases in this present study with posttraumatic myelopathy and primary neoplasms were young adults/ middle age group (31-50 years). While patients with In this study most of the spinal injury (88%) occur in male population while spinal infection/TB (57.1%), primary neoplasms (60%) were more common in female population while secondary neoplasms were seen equally in both the gender [Graph 2]. This is in comparison to the study conducted by Yang R et al. (2014). 5 Graphs 3 and 4 depict trauma & infectious spondylitis were common causes for extradural compression while primary neoplasms were more common in intradural extramedullary compartment in our study. However, one case of primary neoplasm was in intramedullary  It is obvious from Table 2 that in spinal injuries, the common site involved was the cervical followed by thoracic region probably due to more cases of vehicular accident which is in coherence with the study of Granados A et al.
(2011) 1 while in contrast with the findings of the study done by Kulkarni et al. 3 MRI depicts spinal cord changes (high signal intensity on T2WI and STIR sequence) along with the relationship of subluxed / dislocated vertebral bodies to the cord, posterior elements fracture, ligamentous disruption, hematoma & soft tissue injuries (high signal on STIR). All these have prognostic implication and can be used to classify injury into stable / unstable [ Figures 1 and 2 ]. Findings of this current study is in agreement with the study of Kulkarni et al.(1987), Dundamadappa SK (2012), 6 Flanders et al(1997) 7    in which 78% had more the one lesions. In our study most common site of involvement(metastasis) was the thoracic spine (83.3%). This is in comparison to the study done by Livingston et al. 9 where site of epidural tumor in thoracic spine was 68%. We used T1WI, T2WI and STIR sequence to image spinal metastases. T1WI was useful in the detection of bone marrow metastases and STIR helped in picking up more marrow lesions[Graph 7][ Figure 4].
Primary neoplasms (80%) were common in the intradural extramedullary compartment in this study[ Table 3]. In our study, there were 5 cases of primary neoplasm out of which 2 cases were neurofibroma, 2 cases meningioma and rest one case was of ependymoma. Nerve sheath tumors were iso to hypointense on T 1 WI and hyperintense Graph 7: Site of Metastasis Table 3: Primary neoplasms and their compartmental distribution Primary neoplasm (5) No. of patients Meningioma 02 Neurofibroma 02 ependymoma 01 Primary neoplasm (5) No. of patients Intradural -extramedullary 4(80%) Intramedullary 1(20%)   11 and Saweidane et al. 12 In our study ependymoma which was in cervical region, showed T 1 iso to hypointensity & T 2 iso to hyperintensity. A hypointense hemosiderin rim (cap sign) on T 2 weighted images was also observed. Similar finding can be seen in study done by Kahan et al. 13

Conclusion & Recommendation
MR imaging depicts the spinal cord directly, assesses its contour and internal signal intensity characteristics reliably and noninvasively so we can evaluate associated cord oedema or contusion and also the integrity & early changes in intervertebral discs and ligaments which can be crucial in long term prognosis of the patient. So, it makes MRI, an essential modality in assessing soft tissues of the spine and spinal cord abnormalities. Thus, MRI is very sensitive imaging modality to detect, characterize, determine the extent of various Spinal tumours and infections. So, we can conclude that MRI is definitive, accurate, though costly but non-invasive, radiation free modality for evaluation of Compressive myelopathy. Further study could be established to emphasize the role of MRI in determining the severity of cord compression and in evaluating the prognosis. This could be more helpful to determine surgical intervention of needed patients. It can also play a valuable role in triage during disaster, particularly when looking at the patient overload with respect to the patient and infrastructure/resource ratio at our hospitals in India.
Due to lack of quantitative assessment of signal changes in MRI sequences, combination of MRI and 18 F-FDG-PET

Limitations of Study
1. The results cannot be generalized to the whole population of compressive myelopathy. 2. Surgical correlation and histopathological correlation for all cases could not be done.

Source of Funding
Nil.

Conflict of Interests
None.