The pattern of magnetic resonance imaging findings of pyogenic, tuberculous and brucellar spinal infections at Kenyatta National Hospital

Abstract

INTRODUCTION AND BACKGROUND Spinal infections account for 2 – 4% of all skeletal infections. The biggest challenge is making an early diagnosis before serious morbidity occurs, this is particularly true in the early stages of infection. Confirmation and localization of a spinal infection usually depends on imaging findings. The imaging modality of choice for spinal infection is MRI. The aim of this study is to understand the pattern of occurrence and to analyze the various pathological features of spinal infections by using MRI at KNH, the largest referral hospital in Kenya.Spinal infections can be classified anatomically as involving the vertebral column, intervertebral disc space, the spinal canal and adjacent soft tissues. Vertebral osteomyelitis is the commonest form. Intervertebral disc space infections involve the space between adjacent vertebrae. Spinal canal infections include spinal epidural abscess, subdural abcess and intramedullary abscess. They can also be classified aetiologically as pyogenic and non-pyogenic. OBJECTIVE The main objective of this study was to determine the patterns of MRI findings in patients presenting with pyogenic, tuberculous and brucellar spinal infections at Kenyatta National Hospital. METHODS This was a one year cross-sectional descriptive study with retrospective and prospective data collection carried out over the period between February 2013 and February 2014 for 45 patients. Retrospective data collection period was of eight months duration and includedpatients with a previousMRI diagnosis of suspected spinal infection. The prospective data collection period was four months and included patients referredfor spinal MRI with clinically suspected spinal infection.All patients had suspected MRI diagnosis of infection. The gold standard used in this study was MRI findings. Patients in the prospective study were recruited into the study after signing an informed consent. A 1.5 Tesla MRI scanner performed the imaging studies. The images were reviewed by the primary investigator and a consultant radiologist. Data analysis was done using a statistical package for social science research (SPSS 20.0). The results were presented in the form of tables, graphs and charts followed by a discussion of the results. During the one year study period a total of 45 patients were recruited into the study. The age distribution ranged between 11 and 81 years with spinal infections being most prevalent in the 30-39 age group (31.1%) with a mean age of 36.9 years. There were more males(53.3%) affected by spinal infections.Back pain (36 cases,80%) was the commonest presenting complaint followed by neurological deficits (29 cases, 64.4%) and fever (22 cases, 48.9%). Overall spinal infections affected mainly the thoracic region (17 cases, 37.8%) or lumbar regions (15 cases, 33.3%). Spondylodiscitis present in 77.8% of the cases was the commonest anatomical lesion seen, the rest were isolated epidural abscess (11.1%), spondylitis (8.9%) and discitis (2.2%). The commonest infection was tuberculous, accounting for 38 (84.4%) cases. Pyogenic and brucellar infections were seen 6 (13.3%) cases and 1 (2.2%) case respectively based on suggestive MRI findings. Neurological deficits and spinal deformities were used to correlate MRI findings with the clinical presentation; Neurological problems were found to correlate poorly with MRI findings but spinal deformities correlated very well with MRI findings. Plain radiographs performed on 34(75.6%)cases were the only imaging studies done prior to MRI examination. These were done using the standard anteroposterior and lateral views on the vertebral regions affected. Radiographic findings correlated highly with vertebral and disc changes seen on MRI but showed very poor correlation with soft tissue changes seen on MRI. The main risk factor for spinal infections was HIV infection (37.5% ) though previous TB infection was the commonest risk factor in TB cases (31.6%). 11.1% of the cases had no identifiable risk factors. Vertebral body changes (39cases, 86.7%), disc changes (37 cases, 82.2%) and soft tissue changes (43 cases, 95.6%) were the main MRI findings in spinal infections.Atypical changes were seen in 36.8% of cases and almost all were seen in TB cases.