| Neurogenic shock | |
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| Cervical spine MRI of a patient withSCI: C4 fracture and dislocation, spinal cord compression | |
| Specialty | Neurology  |
Neurogenic shock is adistributive type ofshock resulting inhypotension (low blood pressure), often withbradycardia (slowed heart rate), caused by disruption ofautonomic nervous system pathways.[1] It can occur after damage to thecentral nervous system, such asspinal cord injury andtraumatic brain injury. Low blood pressure occurs due to decreasedsystemic vascular resistance resulting from loss ofsympathetic tone, which in turn causes blood pooling within theextremities rather than being available to circulate throughout the body. The slowedheart rate results from avagal response unopposed by asympathetic nervous system (SNS) response.[2] Suchcardiovascular instability is exacerbated byhypoxia, or treatment withendotracheal orendobronchialsuction used to preventpulmonary aspiration.[3]
Neurogenic shock is a potentially devastating complication, leading toorgan dysfunction and death if not promptly recognized and treated.[2]
It is not to be confused withspinal shock, which is not circulatory in nature.[2]
Neurogenic shock can result from severe central nervous system damage (brain injury,cervical or highthoracicspinal cord).[1] In simple terms, the trauma causes a sudden loss of background SNS stimulation to the blood vessels. This causes them to relax (vasodilation)[4] resulting in a sudden decrease in blood pressure (secondary to a decrease in peripheral vascular resistance).
Neurogenic shock results from damage to the spinal cord above the level ofthe 6th thoracic vertebra.[5] It is found in about half of people who have a spinal cord injury within the first 24 hours, and usually persists for one to three weeks.[5]
Neurogenic shock may be caused by severe brain injury.[6] However, in case of increasedintracranial pressure, according to theCushing triad, blood pressure will beincreased (unless decreased fromhypovolemia), respirations will be irregular and bradycardia will also be a feature.
Neurogenic shock is diagnosed based on a person's symptoms and blood pressure levels.
Neurogenic shock's presentation includes:[7][8]
- warm and pink skin
- labored breathing
- low blood pressure
- dizziness
- anxiety
- history of trauma to head or upper spine.
- if the injury is to the head or neck, hoarseness or difficulty swallowing may occur.
Symptoms of neurogenic shock are differentiated from other forms of shock by the lack of signs of thecompensatory mechanisms triggered by the SNS, usual in other forms of shock. 'This SNS response is effected via release ofepinephrine andnorepinephrine, and signs of theseneurotransmitters' activity are typically absent where shock is of neurogenic origin. Those signs - in non-neurogenic shock - would include: tachycardia (increased heart rate),tachypnea (increased breath rate), sweating, and adaptivevasoconstriction, which serves in other forms of shock to shunt blood away from the extremities and to the vital organs.
In neurogenic shock, the body loses its ability to activate the SNS so that only parasympathetic tone remains. The resulting loss of sympathetic tone, which plays a major role in other forms of shock, is responsible for the unique and atypical features mentioned above.[7][9]
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