Essentially, the spinal column is made of vertebrae that are separated by cartilage called discs. Within each disc is a soft, gelatinous center that acts as a cushion during vertebral movement.
To help understand why symptoms vary between people with herniated discs, let me introduce another medical term called dermatome. A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve. In the diagram on the left, the body is split in two parts. The right side of the body provides the names and locations of nerves. The left side of the body illustrates corresponding dermatomes. The letters before the numbers represent the different sections of the spine. (C=cervical spine, T=thoracic spine, L=lumbar spine, S=sacral spine). The numbers indicate the disc level of the spine. The colors represent the dermatome, or "path," that symptoms (like pain, tingling or numbness) typically follow when a nerve root is affected. This helps illustrate why someone with a nerve impingement from a herniated cervical disc has different location of symptoms than someone with an impinged nerve due to a herniated lumbar disc.
Symptoms from spinal nerve compression typically occur only on one side of the body and individuals may also experience motor and sensory loss in the affected dermatome. Overtime, if left untreated this can cause weakness and atrophy of the affected muscles.