Today or tomorrow? A retrospective analysis of the clinical indications used to request urgent magnetic resonance imaging of the spine

INTRODUCTION The finite resources available to National Health Service institutions require clinicians to order investigations that are not readily available appropriately. This is particularly true for the radiological assessment of patients presenting with features pertaining to acute spinal cord dysfunction. Such cases conventionally require urgent magnetic resonance imaging (MRI) which is sometimes performed 'out-of-hours'. There is evidence to suggest, however, that a high proportion of patients do not have a structural abnormality on MRI to account for their clinical findings, and consequently the majority of scans that are requested urgently are normal. The primary aim of this study was to determine whether any clinical feature(s) could accurately predict the presence of a structural abnormality on MRI. As a secondary objective, the ability of such features to predict the need for spinal surgery was assessed. PATIENTS AND METHODS A retrospective analysis of consecutive patients who warranted urgent MRI was conducted. Eighty-one patients were eligible for study. The Fisher's test was used for statistical analysis of all data. A P-value of less than 0.05 was considered to be significant. RESULTS MRI was performed within 24 h of admission in 16 patients, and of these, seven had surgery within 24-48 h. Only two patients were found to have significant neurological compromise. Despite both a history and examination suggesting otherwise, MRI was normal in 10 patients (12%). CONCLUSIONS We were unable to elucidate any clinical features that were able to predict the presence of an abnormal MRI. We did find, however, that patients with a combination of both subjective neurological findings and positive neurological signs (P = 0.02), saddle anaesthesia and/or decreased anal tone (P = 0.03) or sciatica (P = 0.02) had pathology on MRI that warranted surgical intervention. The authors recommend that the aforementioned features formulate the basis of guidelines used to request and/or perform MRI urgently since they are highly suggestive of surgical intervention. Conversely, patients who do not exhibit the above examination findings might not require either an urgent or 'out-of-hours' scan, but could potentially be investigated less expediently and/or wait until 'normal working hours'.