Which disc herniation type is central and may produce bilateral symptoms?

• A. Posterolateral disc herniation
• B. Medial disc herniation
• C. Lateral disc herniation
• D. Central disc herniation

Answer: (D)

Central disc herniation is located in the middle of the disc and projects into the spinal canal, pressing on the thecal sac. Because the thecal sac contains the nerve roots from both sides, a sizable central herniation can impinge multiple nerve roots or even the cauda equina, leading to symptoms that appear on both sides. This bilateral pattern is what makes central herniations prone to producing bilateral pain, numbness, or weakness, especially when the herniation is large.

In contrast, posterolateral herniations push against a single exiting nerve root on one side, which typically causes unilateral radicular symptoms in that root’s distribution. Lateral (far lateral) herniations affect structures more laterally, often involving a specific dorsal root or ganglion and also tend to be unilateral. Medial herniation is less commonly described, but the central location is the key factor that allows bilateral involvement.