Diagnosis of discogenic low back pain in patients with probable symptoms but negative discography.

OBJECTIVE: The purpose of the current study was to determine, whenever the patients complained of probable symptoms of discogenic low back pain and had obvious disc pathological changes on magnetic resonance imaging (MRI) but showed negative in discography, whether we could absolutely exclude the diagnosis of discogenic pain or not.

METHODS: The patients we selected in our study had only one segmental disc pathology on MRI for the purpose of minimizing the interference and all patients complained of probable discogenic pain symptoms. Some special lumbar diseases were excluded by physical examination and CT or MRI scan. Finally, 45 isolated patients with negative discography were enrolled in our study from January 2006 to June 2008. Twenty-three patients were randomly distributed in experimental group, who underwent provocative discography plus intradiscal injection of dexamethasone (5 mg in each patient), while the other 22 patients in the control group received intradiscal injection of saline as a placebo. Visual analog scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the changes of pain and function after discography.

RESULTS: The mean age of the 16 male and 29 female patients was 44.9 years, whose main clinical manifestations included axial back pain (100%), pain in the region of Groin (33.3%), pain in the anterior or posterior region of thigh (42.2%), buttock pain (24.4%) and lower extremity pain (11.1%), and among them L3-L4 pathological disc was found in three patient, L4-L5 pathological disc in 28 patients and L5-S1 pathological disc in 14 patients. Discography and CT scans of the 45 patients revealed that there were grade 5 in 38 discs and grade 4 in seven discs by means of Modified Dallas classification. After about 6-month follow-up, the results showed that VAS scores and ODI scores were greatly improved during the first 3-month follow-up in the experimental group compared with pre-discography and between groups (p < 0.05), but no statistically significant difference after 24-week follow-up (p > 0.05). The probable symptoms of discogenic low back pain were significantly improved in the experimental group in the short term.

CONCLUSION: The study indicated that negative discography in patients with probable symptoms of discogenic low back pain cannot absolutely exclude the diagnosis of discogenic pain. Patients of this kind may suffer from other diseases, but we cannot ignore the existence of discogenic pain.