Posterior epidural migration of herniated lumbar disc fragment.

OBJECT: Posterior epidural migration of a free disc fragment in the lumbar region is a very rare condition that has only been reported in isolated cases to date. Patients with this condition present with radiculopathy or major neurological deficits. Difficulties in diagnosis and the choice and timing of surgical treatment are important in these cases. In this clinical case series, features of cases with posterior epidural migration of free lumbar disc fragments accompanied by cauda equina syndrome are discussed.

METHODS

Eight cases (0.27%) of posterior epidural migration of disc fragments were detected among 2880 patients surgically treated for lumbar disc herniation between 1995 and 2008. Seven of these patients had cauda equina syndrome. The mean duration of symptoms in the 8 cases was 4.2 days (range 1-10 days). The group included 6 men and 2 women, with a mean age of 48 years (range 34-72 years). The sequestered disc fragments were at the L3-4 level in 6 patients (75%) and the L4-5 level in 2 (25%). Magnetic resonance imaging showed tumor-like ring contrast enhancement around sequestered fragments in 5 patients. The patients' motor, sensory, sexual, and urological functions were evaluated postoperatively, and modified Odom criteria and a visual analog scale were used in the assessment of postoperative outcomes.

RESULTS

A microsurgical approach was used in all cases. Sequestrectomy with minimal hemilaminotomy and removal of the free segments were performed. The patients were followed up for a mean period of 28.5 months. Three patients (37.5%) had excellent results, 3 (37.5%) had good results, 1 patient (12.5%) had fair results, and only 1 patient had poor results according to the Odom criteria. The main factors affecting the long-term outcomes were the presence of cauda equina syndrome and the time period between onset of symptoms and surgery.

CONCLUSIONS

Patients with posterior migration of a disc fragment present with severe neurological deficits such as cauda equina syndrome. Because the radiological images of disc fragments may mimic those of other more common posterior epidural space-occupying lesions, definite diagnosis of posteriorly located disc fragments is difficult. All of these lesions can be completely removed with hemilaminotomy and sequestrectomy, and early surgical treatment is important as a first choice to prevent severe neurological deficits.