A 58-year lady presented with backache for 3 months, radiating to left leg, and weakness of left foot. She had severe pain 3 months back. A magnetic resonance imaging ( MRI) scan of lumbosacral spine was taken at that time. It showed L3-4 disc extrusion and canal stenosis and grade 1listhesis at L5-S1(Fig. 1). Surgery was advised at that time. But the patient opted conservative treatment. She had significant improvement in symptoms.
But she had recurrence of symptoms 10 days back. Straight leg raising test was positive at 40 degree on left side. Dorsiflexion was grade 4 on left side. Sensations of touch and vibration were reduced in L4 dermatomal region.
A repeat MRI scan was done to plan surgery.The disc extrusion at L3-4 had shrunk, with the residual listhesis at L5-S1(Fig. 2). She was given another trial of conservative treatment with gabapentin, methylcobolamine, and physiotherapy. She improved over 1 week in pain, power, and sensation.
A large number of the extruded lumbar disc herniations have been found to regress over time. Kesikburun et al. have reported that about three-fourths of the patients with extruded lumbar disc herniation can have complete resolution in the repeat Magnetic resonance imaging(MRI) after an average follow-up period of 17 months1. Turk et al. found that the average time for disappearance of extruded discs in MRI was 26 weeks2. But they noted that the patients continued to be symptomatic and even with deficits in spite of radiological improvement. Spontaneous regression was more common in sequestrated fragments than subligamentous disc herniations. Chiu et al. found that the rate of complete resolution of disc herniation was 43% for sequestrated discs and 15% for extruded discs3. The mechanisms behind the regression are dehydration, shrinkage, retraction, and resorption by inflammation4. Phagocytosis by macrophages has been observed.
But the reports of spontaneous regression within a short term are few. Kim SG et al. described two male patients with clinical and radiological regression of lumbar discs in 3 months5. Albayraket al. published a report of regression of L5-S1 discsequestrationof a 32-year-old man in 14 days6. Kim ES et al. reported about a 58-year-old woman with a large L2-3 disc extrusion7. She underwent microdiscectomy after 2 months. But the expected disc fragment was not found. Immediate MRI showed the absence of the fragment. But in our case, it was detected prior to surgery with a repeat MRI. So an unwanted surgery was avoided. The probable mechanism of shrinkage may be either dehydration or resorption by inflammation, since the axial T2-weighted image shows a hypointense wrinkled fragment (Fig. 2c.). The knowledge of shrinkage of the extrusion helped in improvement of her symptoms, since psychological factors seem to play a major role in the outcome of low back pain as in the literature8.