How MRI of the lumbar spine can help General Practitioners to manage sciatica: The role of GP open-access MRI scanning

Summary

• MRI is the investigation of choice of patients with persistent sciatica or symptoms of spinal stenosis unresponsive to conservative treatment.

• The diagnostic yield of lumbar spine MRI scans is the same if requested by GPs as it is for scans requested by hospital clinicians.

• Waiting lists for hospital out-patient review of patients with persisting sciatica are often undesirably long.

• Many patients with clear-cut symptoms of sciatica would benefit from MRI before clinical review.

• Open-access GP lumbar MRI is an effective means for accelerating appropriate management of patients with sciatica.

Plain film of lumbar spine in patient with severe sciatica: Minor degenerative changes are seen.	Same patient on same day: MRI showing large central L3/4 disc prolapse causing severe spinal stenosis

1. Imaging of the Lumbar Spine
It is widely recognised amongst radiologists and specialists who treat back pain that Magnetic Resonance Imaging (MRI) is the first-line investigation of choice for imaging of patients with symptoms referable to the spine. MRI routinely provides high-resolution cross-sectional imaging of the body with exquisite depiction of normal and pathological anatomy. MRI is of particular value in patients with sciatica unresponsive to conservative treatment, where disc prolapses are shown far more clearly than with any other imaging modality.

Plain X-rays have been shown to be of minimal, if any, diagnostic value in disc prolapse¹, and have the added disadvantage of using X-rays, a form of ionising radiation. Computed Tomography (CT) is more accurate than plain films but less accurate than MRI, and also results in a relatively high radiation dose to the patient. The National Radiation Protection Board has targeted the use of x-rays in medical imaging as a specific area where the population dose should be reduced. MRI is associated with no ionising radiation dose, and is one of the safest imaging techniques available. There are very few contraindications to MRI. With modern short-bore scanners, over 98% of patients referred for MRI can be scanned.

2. MRI scanning and Primary Care
There is increasing evidence in the published literature that General Practitioners (GPs) are equally as good as hospital doctors in utilising non-invasive diagnostic tests^{2 3}. This applies across the board, from conventional projectional radiographs to cross-sectional imaging with ultrasound, CT and MRI ^{4 5 6}. Several studies have assessed the value of a GP direct-access service for MRI of the spine^{7 8 9 10}. Their findings are as follows:

• The diagnostic yield of MRI requested by GPs is the same as that of hospital clinicians (40- 50%)
  
  
• The service can allow redirection of some patients to non-surgical treatment options, freeing up out-patient appointments, and helping to reduce out-patient waiting times.
  
  
• For patients with sciatica, a pre-appointment lumbar MRI may avoid the need for up to 38% of review out-patient appointments (as management can be initiated at the first hospital consultation without the need to return to discuss the scan results).
  
  
• The service can help to expedite surgical treatment of patients with large disk prolapses threatening neurological integrity.
  
  
• Open-access MRI is strongly supported by those GPs, hospital clinicians, and patients who benefit from such a service.

3. Hospital waiting lists: Effective use of hospital resources
There are widespread chronic problems with long waiting lists for hospital appointments for new out-patient referrals with back problems. This is a particular problem for patients with persisting sciatica unresponsive to conservative management referred for neurosurgical or orthopaedic review.

In a significant number of patients with sciatica, a diagnosis of prolapsed intervertebral disc is accurately predicted by the referring GP. Often the GP is well aware that the patient requires an MRI scan to confirm or exclude a lesion suitable for surgical treatment. However, without direct access to MRI, they are forced to send the patient via conventional out-patient referral routes, resulting in an inevitable delay in diagnosis. In addition to the out-patient appointment delay, there is a further delay from hospital appointment to MRI scanning, due to the high demand on hospital MRI services.

Thus, a significant proportion of patients wait a very long time for confirmation of a diagnosis of which the GP was confident at the time of referral. Patients not only suffer prolonged pain due to these long waiting times, but some lose their job due to lengthy sick leave. Neuroscience and other hospital clinicians are recognising increasingly that for certain clearcut indications (such as patients with severe sciatica or symptoms of spinal stenosis), having an MRI available at the time of hospital consultation expedites diagnosis and helps the clinician to select appropriate management.

4. Cost-effective MRI
There is a misconception that MRI scanning is considerably more expensive than other imaging. Improvement in scan times, the use of batched scans, digital image review and ergonomic throughput of patients over an extended working day has reduced the cost of MRI to an affordable price. In addition, MRI can avoid the need for multiple other investigations (such as plain films, CT and bone scans).

Mobile MRI scanners can provide imaging facilities near to the patient’s home or medical practice, avoiding problematic journeys for patients disabled by pain. Teleradiology, which is the transmission of digital images via telephone lines or over the internet, means that scan can be reported the same day by specialist radiologists remote from the scanning site, with reports available within 24 hours.

5. Conclusion
MRI remains the primary investigation of choice for patients with persistent sciatica or symptoms of spinal stenosis, and an ‘open-access’ GP MRI service is an effective means of expediting the management of patients with back problems.

Expert Eye has over seven years experience of providing a dedicated GP open-access MRI service. Contact us now to find out more.

References:

1. Ferriman A. 2000. Early X-ray for low back pain confers little benefit. BMJ, 321, 1489
2. The Royal College of Radiologists and the Royal College of General Practitioners. 1993. Radiology and the patients of GPs. London.
3. Royal College of Radiologists. Diagnostic imaging and the Primary Care Sector. London; Royal College of Radiologists. 1996
4. Collie DA, Paul AB, Wild SR. 1994. The diagnostic yield of intravenous urography: a demographic study. BR J Urol, 73, 603-606
5. Chan TYK, Said S, Ellis D.1992. Diagnostic yield of barium enema in a district general hospital. BJR, 65(S): S2
6. Kearney SE, Loughran CF. 1996. Direct access to CT screening. Br J Gen Pract. 46, 320.
7. Chawda SJ, Watura R, Lloyd DCF. 1997. Magnetic resonance imaging of the lumbar spine: direct access for general practitioners. Br J Gen Pract, 47, 575-576
8. Apthorp LA, Daly CA, Morrison ID, Field S. 1998. Direct access MRI for general practitioners – the influence on patient management. Clin Rad, 53, 58-60
9. Collie DA, Sellar RJ, Steyn JP, Cull RE. 1999. The diagnostic yield of MRI of the brain and spine requested by general practitioners: comparison with hospital clinicians. Br J Gen Pract, 49, 559-561
10. White PM, Halliday-Pegg JC, Collie DA. 2001. Open-access neuroimaging for general practitioners – diagnostic yield and influence on patient management. Br J Gen Pract, In press.