The spinal cord carries motor commands and sensory information between the brain and the periphery. Damage to the posterior spinal cord--whether due to disease, tumor, or injury--can result in devastating consequences because these connections are interrupted. Posterior spinal cord injury produces the condition called posterior cord syndrome. The syndrome is characterized by particular symptoms, the hallmarks of which are differences in the extent of sensory and motor impairments below the level of the lesion.
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The posterior spinal cord carries mainly sensory information from the periphery to the brain. This is critical information to the brain and includes sensations about the position of the body and limbs in addition to vibration sense and the ability to finely discriminate touch sensations. Destruction of neurons in the posterior spinal cord results in loss of these sensations below the level of involvement. Neuron destruction can be accompanied by other odd sensations on the skin, as well as shooting or burning pain, prickling and a feeling like that produced by insects crawling on the skin. Pain and temperature sensation, however, are preserved below the involved area.
Preserved Motor Function
Injury to the posterior spinal cord generally does not produce motor deficits of the severity produced in other areas of the spinal cord. This is because the posterior spinal cord carries primarily sensory information to the brain. Therefore, motor function is preserved below the area of involvement, even in the presence of profound sensory deficits.
When the posterior columns are damaged, patients often display L’Hermitte’s sign. This is also called the "barber chair phenomenon." It is characterized by the sensation of electric shocks running down the back and into the limbs. It occurs when bending the head far forward or backward: Compromised nerve fibers are irritated by stretching the neck. L’Hermitte’s sign usually occurs with lesions in the cervical spinal cord, such as would arise from compression, multiple sclerosis and disc degeneration.