Observer variation in MRI evaluation of patients with suspected lumbar disc herniation and nerve root compression: comparison of neuroradiologist and neurosurgeon's interpretations.

OBJECTIVE To analyse inter-observer variation between a neuroradiologist and neurosurgeon in the MRI diagnosis of lumbar nerve root compression. Although lumbar MFI is primarily analyzed and reported by a radiologist, neurosurgeons often analyse it independently as they have sufficient clinical background as well as radiological expertise to diagnose most spinal pathologies on Magnetic Resonance Imaging (MRI). METHODS Retrospective analysis was carried out for images of 54 patients who underwent MRI between March and July 2010 of lumbar spine with suspected lumbar disc herniation and nerve root compression, at Aga Khan Hospital, Karachi, Pakistan. One fellowship trained neuroradiologist and one neurosurgeon evaluated the images on PACS system separately. Both observers were unaware of the patient's clinical history and each other's findings. Lumbar discs at L3-L4, L4-L5 and L5-S1 levels were evaluated by both observers for disc disease and nerve compression. Findings were recorded on a proforma and analysed with SPPS Version 16. RESULTS Total 162 lumbar discs were studied by both readers in 54 patients. Excellent inter-observer agreement was seen for the presence or absence of nerve root compression (Percentage agreement = 88.89%; k = 0.774; p = 0.737). For disc bulge, inter-observer agreement was fair but statistically insignificant (Percentage agreement = 72.84%; k = 0.414; p = 0.132). In case of disc herniation, although inter-observer agreement was fair, but the difference was statistically significant (Percentage agreement = 84.57%; k = 0.511; p = 0.002). CONCLUSION Inter-observer agreement between neuroradiologist and neurosurgeon in diagnosing nerve root compression due to lumbar disc disease was excellent. Agreement regarding disc bulge and herniation was fair.