Twelve patients with lumbar arachnoiditis were investigated by means of magnetic resonance imaging. The results showed three groups of different anatomic features: The group I showed conglomeration of nerve roots residing centrally within the thecal sac. The group II demonstrated clumped nerve roots attached peripherally to the meninges. The group III showed increased soft tissue signal within thecal sac. The overall clinical manifestations and electromyographic findings were also investigated; Ten(83%) patients complained of increased, non-radicular, leg pain with activities, such as standing or walking. There were muscle spasms and cramps in the legs in seven(58%). There appears to be no specific clinical and electromyographic findings characteristic to each of the three groups, except that the group III showed more prominent clinical symptoms than those of the other two.

In conclusion, MRI is useful in establishing the diagnosis of lumbar arachnoiditis, as well as seperating three different anatomic features. And we found that increased, non-radicular pain with activities and muscle spasms and cramps appeared to be characteristic to lumbar arachnoiditis, and the group III showed more prominent clinical symptoms than the other two groups.