Intradural Lumbar Disc Herniation From the Lateral Inner Surface of the Dura Without a Penetration Hole: A Case Report

Intradural disc herniation (IDH) is usually diagnosed during surgery when a herniated mass is found to have penetrated the ventral dura. We experienced a case of IDH that entered the dura from the lateral side with no penetrating hole. A 61-year-old man presented to our institution with left leg pain of two months' duration. Plain x-ray imaging showed degeneration of the lumbar spine, and a magnetic resonance imaging (MRI) scan revealed a suspected tumor at the L3-L4 level. Two weeks later, the patient suffered from acute cauda equina syndrome. A gadolinium-enhanced MRI showed an enlarged lesion with no enhancement visible, and emergency surgery was performed. The lesion originated from the left side of the dura. Despite the white debris suggesting a herniated disc, no penetrating hole was found in the dura. Pathologically, the lesion was found to be an intervertebral disc and was diagnosed as an intradural lumbar disc herniation. The patient’s neurological symptoms improved, but he did not recover his left ankle dorsiflexion. In a degenerated lumbar spine, IDH may not always originate from the ventral dura and may not be accompanied by a penetrating hole.