Aging of the Spinal Nerve Root

There is a loss of the protective fatty lining around nerve fibers within the spinal nerve root with advancing age.  There is also a gradual loss (drop out) of nerve fibers with age. The loss of nerve fibers in the spinal nerve root begins after age 30.  Age related changes include an increase in the amount of connective tissue in the nerve root.  The lumbosacral nerve roots in adult humans are estimated to lose approximately 350 nerve fibers per decade, as a consequence of a loss of anterior horn cells within the spinal cord, although, there is considerable variation within each advancing decade of life.

Magnified Effects of Aging in a Deconditioned Patient:

There are many factors that can cause disturbances of musculoskeletal function in aged individuals.  The aging spine can lead to loss of adaptability and to varying degrees of physical disability.  Occupational factors such as repetitive microtrauma and spinal postures can contribute to degeneration of the spine.  Sudden stress or athletic trauma can also have long-lasting musculoskeletal repercussions on the spine, which may  manifest in the form of incapacitating symptoms later in life.

The capacity of spinal tissues to accept a load is altered secondary to the deconditioning and degeneration associated with aging.  For some individuals, declining mobility of the spine may lead to a loss of independence and loss of effective interaction in both social and recreational settings.  Combined system compromise resulting in extremity weakness, impaired equilibrium, and loss of joint positions, orthostatic hypotension, and impaired vision in the elderly increases the risk for falls.  The elderly person with weak back muscles and delayed reaction time is much more prone to suffer more severe injury to the spine.

The Aging Spine and the Risk for Falls:

Falls in the elderly are a leading cause for non-fatal injury and represent one of the most common causes of unintentional injury leading to death in elderly in United States.  Approximately 40% of patients over 80 years will fall at least one time per year.  The increase incidence of falling also suggests advancing frailty and disability in the elderly.  The incidence of falling increases substantially, when multiple risk factors are present such as sedative use or overmedication for cognitive impairment.  The risk of falling can often be reduced by recognizing and eliminating one or more risk factors such as environmental hazards, environmental obstacles, overmedication, and vision correction.

Spinal conditions can contribute to increased risk for falling.  Spinal stenosis in the neck can lead to compromise of the cervical spinal cord referred to as spondylotic myelopathy.  This leads to lower extremity weakness, incoordination as well as unsteadiness of gait, which can lead to risk for falling.  This is becoming a more prevalent condition in the aging population.  Low back degeneration and disc herniation

can also cause pressure on nerves that go to various muscles of the leg.  This can lead to weakness.  Upper as well as lower leg muscle weakness can increase the risk for falling while walking, descending, or ascending stairs.  A common condition referred to as foot drop is associated with weakness of muscles that control and power the foot.  This is most commonly associated with compromise of the L4 and/or L5 spinal nerves secondary to disc herniation.  Foot drop leads to alteration in gait, which also increases the risk for falling.  Elderly individuals are also more prone to have generalized neuropathy combined with varying degrees of spinal stenosis. These to conditions taken together, further complicate the capacity to walk normally and increase the risk for falls.