Non­-Traumatic Emergencies of Spinal Column A Bird's Eye View

Disclosures – None

 To have an understanding of the common and uncommon, non-traumatic but potentially life- threatening conditions of the spinal column.  To discuss the important Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) findings of these conditions. Purpose

 Elaborate search was made for all cases of non-traumatic emergency conditions of the spine from the case database available on PACS from 2005 to  Patients charts were reviewed for clinical history, imaging findings, complications and surgical details. Approach / Methods

Discussion Infection ­ Discitis/Osteomyelitis, Septic Facet Joint, Epidural Abscess. Inflammatory ­ Transverse Myelitis, Multiple Sclerosis, Neurosarcoidosis/Guillain-Barré Syndrome, CPPD, Rheumatoid Arthritis. Neoplastic ­ Lymphoma, Meningioma, Paraganglioma, Myxopapillary Ependymoma, Metastasis with epidural extension. Nonneoplastic Epidural Hematoma, Chiari 1 Malformation, Dural Venous Fistula, Epidural Lipomatosis, Hardware Failure, Herniated Disk, Hematoma.

INFECTION – Discitis / Osteomyelitis Discitis results from direct inoculation from trauma or surgery, extension of an adjacent infection, or hematogenous spread of infection. MRI MR is the imaging modality of choice. High signal intensity on T2 inversion recovery images and low signal intensity on T1-weighted images. Enhancement of the involved disk space and adjacent bone marrow. MR also allows accurate assessment of complications of discitis, including direct assessment of effect on neural structures.

Sagittal T1 & T2 weighted images showing a retro-pharyngeal abscess leading to C5/C6 spondylo-discitis with small enhancing epidural collection.

Septic Arthritis Septic facet arthritis is an uncommon cause. It typically involves a single vertebral level and results from hematogenous spread of infection, most commonly S. aureus infection. MRI MR imaging is more sensitive than CT for the detection of associated osteomyelitis, myositis, and epidural extension. Effusion appears hypointense on T1 and hyperintense on T2 weighted images Shows homogenous enhancement in the joint space. Adjacent soft tissues show increased signal on T2 and enhancement suggestive of phlegmonous changes.

Sagittal Contrast enhanced sequences showing left L3/L4 facet joint arthritis in a patient with streptococcal bacteremia.

Axial sequences showing associated phlegmonous changes of the left paraspinal muscles

MRI Gadolinium-enhanced MRI is the imaging modality of choice for diagnosis of spinal epidural abscess. There are two basic patterns: Phlegmonous stage of infection results in homogeneous enhancement of the abnormal area, which corresponds to granulomatous, thickened tissue and embedded micro- abscesses, without a significant pus collection. Liquid abscess surrounded by inflammatory tissue which shows varying degree of peripheral enhancement after i.v. gadolinium. Epidural Abscess

Axial sequences showing epidural and paravertebral contrast enhancement indicative of phlegmonous stage. Associated vertebral body edema/enhancement - vertebral osteomyelitis.

Sagittal pre-contrast T1 and post-contrast T1 fat sat images showing epidural abscess and vertebral osteomyelitis at L3/L4.

INFLAMMATORY – Transverse Myelitis May occur anywhere within the spinal cord, however, the thoracic cord is the most frequently involved site. MRI Up to 40% of cases have no findings at MRI. In the remainder, the appearance is variable and non-specific. There is a large variation in lesion size, which most commonly extend for 3-4 spinal segments. Lesions typically occupy greater than two thirds of the cross- sectional area of the cord. Typical signal characteristics include: T1: isointense or hypointense T2: poorly delineated hyperintense signal T1 C+ (Gd): variable enhancement patterns (none, diffuse, patchy, peripheral)

Sagittal T1 and T2 sequences in a patient with abnormal sensations and limb weakness, showing altered signal in the cord over a few segments.

The cervical spine is frequently involved in RA (approximately 50% of patients), whereas a thoracic and lumbar involvement are rare. Findings include: - Erosion of the dens - Atlanto-axial subluxation - Atlanto-axial impaction (cranial settling): cephalad migration of C2 - Erosion and fusion of uncovertebral and facet joints - Osteoporosis and osteoporotic fractures - Erosion of spinous processes MRI Features of RA are best demonstrated with MRI and include: - Synovial hyperemia: indicates acute inflammation - Synovial hyperplasia - Pannus formation - Decreased thickness of cartilage - Subchondral cysts and erosions Rheumatoid Arthritis

Plain radiograph and CT show lucency/erosion of the posterior odontoid process with a soft tissue mass lined by calcific rim.

Soft tissue pannus (low signal in all sequences) showing spinal canal compromise and compression of the cord.

Contrast enhanced & STIR sequences showing no signal change or enhancement of the pannus. Transverse high signal line through the odontoid is likely a chronic fracture.

Rare Solitary or multiple lesions Rapidly progressive symptoms It may originate in para-vertebral lymph nodes and extend to the vertebral column/epidural space through the neural foramina Extranodal (epidural, spinal) origin is rare. Can encase the cord and potentially cause compression. NEOPLASTIC – Lymphoma Cont.

MRI Reported signal characteristics include: T1: typically hypointense to white matter T1 C+ (Gd) –typical high grade tumours show intense homogeneous enhancement, while low-grade tumours have absent to moderate enhancement –peripheral ring enhancement may be seen in immuno- compromised patients (HIV/AIDS) T2: variable –majority are iso to hypointense isointense: 33% hypointense: 20% –hyperintense: 15-47%, more common in tumours with necrosis Lymphoma (cont’d)

Coronal & sagittal images showing epidural extension and cord encasement with likely cord compression.

Axial image showing a paravertebral mass extending into the epidural canal through the neural foramina on the left side.

Plexiform Neurofibroma MRI Reported signal characteristics include: T1: hypointense T2: hyperintense +/- hypointense central focus (Target Sign) T1 C+: mild enhancement

Axial & sagittal sequences showing lobulated neurofibromas invading the spinal canal and causing compression of the cord with myelopathic changes. Cont..

NON-NEOPLASTIC – Epidural Hematoma Signal characteristics of acute spinal EDH T1: isointense or hypo-intense to spinal cord T2: heterogeneously hyperintense to spinal cord with hypointense foci T2*: blooming artifact

A large epidural hematoma evidenced by intermediate signal on T1 and high signal on T2 in the posterior upper thoracic epidural space on these axial & sagittal sequences. Cont..

Spinal Dural Venous Malformations MRI There is typically cord enlargement in the lower thoracic region and conus, with signal change involving multiple spinal segments. Signal characteristics T1 Intramedullary hypointensity and flow voids on the cord surface may be seen. T2 Diffuse multilevel intramedullary hyperintensity (oedema). Regardless of the location of the fistula, the T2 hyperintensity involves the conus in up to 90% of cases because of orthostasis. Usually, but not always, prominent serpiginous intradural extramedullary flow voids along the dorsal aspect of the spinal cord.

Extensive flow voids with cord oedema / hyperintensity.

Intra-dural / extra-medullary flow voids on axial & sagittal sequences.

Acute Spinal Cord Ischemia Syndrome Acute spinal cord ischaemia syndrome represents only 5-8% of acute myelopathies and less than 1% of all strokes. The majority of patients develop symptoms quickly, with maximal symptomatology reached within 12 hours for >50% of patients and within 72 hours for the vast majority of patients. MRI is the gold standard imaging modality for the spinal cord. The hallmark of spinal cord infarction is the presence of abnormal T2 signal within the cord, the pattern of which will depend on the territory.

Anterior spinal artery Involvement represents the majority of cases, and the anterior and central portion of the cord are involved, most frequently bilaterally. In many instances the anterior horn cells are appear primarily involved and demonstrate prominent high T2 signal resulting in pencil-like hyperintensities extending over a number of levels. On axial imaging this appears as two bright dots, the so called owl eye appearance. Posterior spinal artery Involvement is unilateral (as posterior spinal arteries are paired) and usually confined to the dorsal columns

Sagittal and axial sequences showing enlarged cord with hyperintense T2 signal, suggesting myelopathy. The pattern will depend on the territory involved.

MRI spine There is an often generalised excess of fat seen in the extradural space. As a result, the dural sac can appear narrowed or even have a "Y" shaped configuration. Signal characteristics follow fat on all sequences: T1: high signal T1 (FS): shows fat suppression T2: high signal Epidural Lipomatosis

Sagittal and axial sequences showing clumping of cauda equina roots in the spinal canal by surrounding epidural fat tissue.

Summary  With the advent and easy accessibility of MRI, these non- traumatic emergencies have become more noticeable and easier to detect.  The understanding of clinical context and imaging findings is of paramount importance to determine suitable management for these patients.  Therefore, increased awareness of these conditions is of utmost significance for radiologists.