A spinal cord injury often leads to spinal shock, a temporary physiological response. This condition immediately follows damage to the spinal cord, impacting the body below the injury site. Its resolution is an important step in understanding the long-term effects of the injury.
Understanding Spinal Shock
Spinal shock is a temporary state where reflex activity, motor control, and sensation are depressed below the level of a spinal cord injury. It is a physiological response, not a structural injury, meaning the spinal cord’s function is temporarily suppressed. This condition often results from direct trauma or ischemia.
Immediate symptoms include flaccid paralysis, a limp and unresponsive state of the muscles, and a loss of reflexes. Individuals may also experience an absence of sensation in affected areas. Additionally, changes in blood pressure and heart rate can occur, particularly if the injury is at the T6 level or higher.
Stages and Duration of Spinal Shock
Spinal shock progresses through distinct phases, and its exact duration varies significantly among individuals, depending on the severity and location of the spinal cord injury. While it can range from hours to several weeks, it often resolves within a few days to a few months, with a mean duration around 4-6 weeks.
The first phase, lasting 0 to 1 day, is characterized by areflexia or hyporeflexia and flaccid paralysis due to spinal neuron hyperpolarization. During this initial period, there is a loss of descending facilitation, meaning signals from the brain do not effectively reach the spinal cord below the injury.
The second phase occurs 1 to 3 days post-injury, marked by the initial re-emergence of reflexes. This return is attributed to denervation supersensitivity and receptor upregulation. Polysynaptic reflexes, which involve signals traveling from sensory to motor neurons, are often among the first to return.
The third phase spans 4 days to 1 month, where early hyperreflexia begins to appear. This stage involves axon-supported synapse growth, leading to overactive reflexes. The final phase, lasting 1 to 12 months, sees continued hyperreflexia and the development of spasticity. This prolonged stage is due to soma-supported synapse growth and more extensive changes in neuronal cell bodies.
What Happens After Spinal Shock Resolves
The resolution of spinal shock is indicated by the return of reflexes below the level of the injury. This often begins with the reappearance of superficial reflexes before deep tendon reflexes. The bulbocavernosus reflex, involving the anal sphincter contracting in response to stimulation, is often one of the first reflexes to return and is sometimes used by clinicians to mark the end of spinal shock.
Once spinal shock resolves, the temporary physiological suppression of the spinal cord lifts, allowing for a more accurate assessment of the permanent neurological deficit. The return of reflexes does not signify a full recovery of function, but rather the end of the initial temporary suppression. Instead, it indicates that the true extent of the damage can now be determined, distinguishing between temporary functional loss and lasting impairment.