Feature

MRI for Emergency Clinicians

Emergency Medicine. 2018 December;50(12):1-6

References

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Common MRI indications in the ED

Central nervous system MRI

Spinal cord compression may occur due to a neoplastic process, either primary or metastatic, infection (epidural abscess is a particular concern), or hematoma. CT myelography is another diagnostic option, but MRI offers ease of performance, superior resolution, multiplanar imaging, lack of ionizing radiation, and the ability to detect multiple lesions with a single scan. For non-traumatic myelopathy evaluation (most commonly due to cancer), perform a non-contrast MRI of the entire spinal canal since multiple lesions may be present. Repeat the MRI with contrast if the cause of the myelopathy is not clear after the non-contrast study.¹⁰ Gadolinium does help detect and define inflammatory, infectious, and neoplastic lesions, but spinal cord compression can be diagnosed without it if the patient cannot receive gadolinium (see Cautions and Limitations section).¹¹ Only a non-enhanced MRI, limited to the traumatized area, is required in the evaluation of trauma-induced myelopathy.¹⁰

Dural venous sinus thrombosis (DVST) is best assessed with a combination of MRI and MR venography.¹⁰ DVST is clot formation within any of five major dural venous sinuses. DVST risk factors include: dehydration; infections, both systemic and local; pregnancy and the puerperium; neoplastic incursion; trauma; and coagulopathies.^10,12 MR venography is an essential part of DVST evaluation since it assesses patency of the involved dural venous sinus.¹⁰

Carotid artery dissection is a leading cause of stroke in those younger than 45 years of age.¹³ Carotid and vertebral artery dissection, due to trauma, hypertension, vascular disease, or local infections, can be diagnosed with endovascular angiography.^10,14 However, MRI in combination with MRA can be diagnostic as well.^10,13,14 MRI delineates the intramural clots while MRA shows the degree and extent of endovascular compromise.^10,13

Meningoencephalitis and vasculitis are usually diagnosed with a combination of clinical findings, laboratory data, CT, and lumbar puncture results. However, MRI is highly sensitive for the CNS lesions associated with infection or vasculitis. Consider MRI as an alternative to the usual work up in selected patients if aggressive early therapy for viral infection (eg, herpes) or vasculitis is being contemplated.¹⁰

Acute subarachnoid hemorrhage (SAH) is usually best demonstrated on CT. However, MRI may have a role, especially in posterior fossa SAH.¹⁰