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Three Part Question

In [pregnant women] [does lumbar spine MRI] [pose any significant risks]?

Clinical Scenario

20 year old student radiographer is brought to emergency department by ambulance after being involved in a RTC a few hours earlier. It’s a busy Friday afternoon and she’s been sat in waiting room. You call her through to be seen and you notice she obviously has difficulty walking; her concerned looking mother helps her in to a nearby wheelchair and brings her through. She is complaining of lumbar back pain. On examination you are concerned by your neurological findings in her lower limbs: clonus, 4/5 power throughout and some subtle paraesthesia. You explain you would initially like to perform an x-ray and that she may require a CT. She asks her mum to go and get her a drink of water and quietly reveals to you she’s 8 weeks pregnant. You think that MRI is likely to be safer but are not sure if there any significant risks?

Search Strategy

Cochrane Database
Medline 1966 - October 2014 using Pubmed interface. Google scholar

Cochrane database using the search terms [“Magnetic Resonance Imaging” AND “pregnancy”]

Medline 1966 - October 2014 using Pubmed interface. The first search was as follows:
((("Magnetic Resonance Imaging"[Mesh]) AND "Pregnancy"[Mesh]) AND "Spine"[Mesh]) AND "Safety"[Mesh]
This yielded one paper which considered MR scanning for fetal spine not the mother. A second search was conducted as above without the term “spine”. This yielded 139 papers. Further searches were performed using a combination of the above and related terms. The “related citations in PubMed” tool was used. Searches on Google scholar were also performed.

Search Outcome

Search outcome
No papers were found directly relevant to the three part question. 14 papers looking at safety in pregnancy were reviewed.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses

Comment(s)

No study was found that specifically looked at the safety of spinal MR during pregnancy. The majority of the literature found related to MR scans focused on finding fetal rather than maternal pathology. Bulas et al (2013) described ultrasound as the method of choice for fetal imaging but state that fast sequences on MR pose low risk. Bahado-Singh R et al (2012) advised MR should be used when the clinical situation dictates but caution use in early pregnancy which they defined as before 24 weeks. The most thorough systemic review by Patenaude et al(2014) concluded that there was no evidence of risk during 2nd and 3rd trimesters when MR was used without contrast agents. The authors recommend that this should only be used for maternal indications when considered “clinically imperative” during the first trimester. Most authors supported this notion of weighing up potential risk vs benefit. However, in terms of risk there is no clear cut evidence either way. No papers were identified demonstrating good evidence that spinal MR in pregnancy could cause harm. There are two main theoretical risks of MR in pregnancy that have been demonstrated in animal models; acoustic damage and teratogenicity. The review by Bulas et al summarised these and concluded no direct extrapolations could be made from these studies due to small sample size and study methods. Several small animal studies such as that by Tyndall D (1993) demonstrated mice exposed to MR in utero had reduced crown-rump length and craniofacial perimeter (preceding eye development). Concerns mainly exist around radio-frequency induced tissue heating. However the review by Lubarsky M et al (2013) and Chen et al (2008) highlighted that no clear risks have been identified in over 20 years of use and this method of imaging (if imaging is required) is clearly preferable over any form of ionising radiation.

Clinical Bottom Line

The risk vs benefit of MR scanning pregnant patients should be made on a case by case basis. There are currently no proven risks of MR scanning during pregnancy and it is used as a method for fetal imaging. However, the theoretical risk of teratogenicity and acoustic damage warrants reasonable caution and for this reason most authors advise avoiding when possible before 1st trimester. However if imaging is required for emergency management MR scanning appears to be relatively safe and is preferable over imaging involving ionising radiation.

Level of Evidence

Level 3 - Small numbers of small studies or great heterogeneity or very different population.

References

1. Bulas D, Egloff, A Benefits and Risks of MRI in Pregnancy Seminars in Perinatology 2013: 37(5): 301-4
2. Bahado-Singh R, Goncalves L Techniques, terminology, and indications for MRI in pregnancy Seminars in Perinatology 2013; 37(5): 334-9
3. Patenaude Y, Pugash D, et al. The use of magnetic resonance imaging in the obstetric patient Journal of Obstetrics and Gynaecology 2014; 36(4):349-63
4. Tyndall D MRI effects on craniofacial size and crown-rump length in C57BL/6J mice in 1.5T fields Oral Surgery, Oral Medicine, and Oral pathology 1993; 76(5): 655-60
5. Lubarsky M, Kalb B, Sharma P, Keim S, Martin D MR Imaging for Acute Nontraumatic Abdominopelvic Pain: Rationale and Practical Considerations Radiographics 2013; 33(2):313-37
6. Chen MM, Coakley FV, Kaimal A, Laros RK Guidelines for computed tomography and magnetic resonance imaging use during pregnancy and lactation Obstetrics and Gynaecology 2008; 112(2 Pt 1):333-40