Neurological Diagnosis: Timing and Significance

The capacity of the spinal cord to recover from compressive injures is limited.   A timely diagnosis is critical and positively influences outcome.  Peripheral nerves and spinal nerve root have a greater potential for repair and recovery than the spinal cord.  Bone and muscle have a broader therapeutic window than spinal nerves and peripheral nerves.  If a compressed spinal nerve or peripheral nerve is decompressed before permanent injury has occurred, the nerve will begin to recover immediately when the microcirculation and blood flow is returned to the nerve.  However, spinal cord tissues respond and recover very differently.  In cases of rapid onset compression, the spinal cord may undergo very little recovery after relief from compression. 

Surgical approaches performed to decompress the spinal cord may help prevent further neurological compromise but may still not allow for full recovery.  The spinal cord has a greater potential for recovering in younger individuals.  Spinal cord recovery occurs very slowly, often taking a year or two or more before the level of deficit is considered permanent.  Individuals who have other existing conditions such as heart disease, peripheral artery disease and diabetes, are less likely to have the same pattern of neurological recovery as someone in better health. 

The use of advanced imaging such as MRI or CT may reveal risk for spinal cord compromise or actual compression of the spinal cord in the absence of signs and symptoms.  An MRI study may reveal abnormal signal changes within the compressed area of the spinal cord.  Theses changes may represent ischemic or inflammatory compromise of nerve fibers.  In this case, neurosurgical consultation is typically warranted.  If a CT or MRI study confirms displacement and/or compression of a spinal nerve in the absence of associated signs or symptoms, surgical consultation is rarely warranted. A watch and wait approach in conjunction with conservative treatment would be appropriate. 

Timing: Nerve Damage and Muscle Atrophy

Within 1-2 hours after a nerve becomes significantly compromised, degenerative changes within the nerve can be observed on microscopic studies.  Within 24-48 hours, fibroblasts begin to proliferate at the site of injury.  Early degeneration at nerve connections (synapses) can be identified as early as 24‑48 hours after nerve compromise.  Within approximately 5-10 days after a muscle loses its nerve connection, muscle fiber atrophy begins to develop.  After 4 months without its nerve supply, the muscle and muscle fibers begins to degenerate.  Once muscle fibers degenerate full recovery of the muscle may not occur.

Recovery and Repair of Nerves in the Spinal Cord

There are many potential causes of neurological compromise in the spine that include: inflammation, compression, blunt or concussive trauma, stretch, or a lack of blood supply (ischemia).  The first symptoms of mild neurological compromise are often intermittent and are usually characterized by a disturbance in sensation.  Unusual sensations are often referred to as paresthesia, although the term is currently used to describe numbness and/or tingling.  The symptoms associated with more severe nerve compromise are generally characterized by persistent and more intense symptoms.  Continued progression of neurological compromise leads to varying degrees of muscle weakness.  The presence of pain, numbness, tingling, weakness, or loss of normal function, should cause an individual to seek medical attention.  The primary goal of the initial evaluation is to determine the location and cause of the neurological compromise.  The workup will also serve to identify the cause of the symptoms.