SCI Explanation (Spinal Cord Injury, SCI)

More is Possible, 25.03.2024

Spinal Cord Trauma

Something breaks. Tissue is scarred. Neurons die. The hours after a spinal cord injury are often described as a war zone -  as the body attempts to shield itself from trauma, the delicate cord bears the brunt of the damage. As if physical scars are not enough, we have all heard bedside horror stories of medical “professionals” who say, in those early, dark days: “Here’s your chair. Here’s what you can expect from life with a spinal cord injury. Get used to it. And by the way, what you get back in the first few months is all you can expect for the rest of your life.” Nonsense. 

When it comes to research, spinal cord injury is often compared with disease. Retrofitting a spinal cord injury into a standard classification of a disease is not fair to the complexity of this injury or to what people living with spinal cord injury face daily. Every spinal cord injury is different, which means that there can never be a one-size-fits-all cure, but rather a series of significant breakthroughs that will eventually combine to solve this puzzle.[1]

These few sentences talk straight out our hearts and we can imagine we are not the only ones which feel that way.

It shows two very important things - the suffering and the complexity of what spinal cord injuries entail. - So let’s start to support those who are working on solutions rather than those who are part of the problem themselves.

A Spinal Cord Injury (SCI) can affect the CNS as well as the autonomic nervous system

Central nervous system (CNS)

The central nervous system consists of the brain (encephalon) and the spinal cord (medulla spinalis) [2]

It is the control center where all signals converge and are processed.

SCI_Explanation_Picture_003

Peripheral Nervous System (PNS)

Your peripheral nervous system (PNS) is that part of your nervous system that lies outside your brain and spinal cord. It plays key role in both sending information from different areas of your body back to your brain, as well as carrying out commands from your brain to various parts of your body.[4]

Somatic nervous system

The somatic nervous system (soma, Greek = body) controls all processes that we are aware of and that we can influence voluntarily.

Autonomic Nervous System

Failure in spinal cord injuries (RMV), especially at paralysis levels above the T6 segment. In the event of damage above T6, the connection between the spinal cord and the brain stem and brain is interrupted. The brain's control over sympathetic innervation is thus lost. This leaves only and predominantly parasympathetic innervation via the cranial nerves, primarily via the vagus nerve (vagus nerve is the 10th cranial nerve, which emerges directly from the brain stem and not from the spinal cord).

The autonomic nervous system is responsible for regulating the internal organs (glands, stomach, intestines, sexual organs) and maintaining vital bodily functions (respiration, circulation, digestion, metabolism). It works autonomously, i.e. it is not or only slightly under our voluntary control. It consists of the sympathetic, parasympathetic and enteric nervous system (nerve plexus within the intestinal wall) [3].

SCI_Explanation_Picture_001

Parasympathicus

The parasympathetic nervous system originates from the brain (cranial nerves III, VI, IX and X) and the sacral spinal cord (S2-S4) [3].

Sympathicus

The sympathetic nervous system originates from the thoracic and lumbar spinal cord (T1-L2). It is switched off in cases of high complete paraplegia.

Paraplegia or tetraplegia?

Paraplegia

Paraplegia is an injury to one or more neurological segments of the spinal cord in the thoracic and/or lumbar vertebrae.

Tetraplegia

In tetraplegia (also quadriplegia), there is an injury to the spinal cord in the area of the neck, i.e. in the area of the cervical vertebrae, in one or more neurological segments from C1 to C8. Damage in the area of the upper thoracic (thoracic vertebra segment) T1 also causes paralysis of the arms and is therefore also part of tetraplegia.

If all four extremities (both legs and both arms) are affected by the paralysis, this is referred to as tetraplegia. Tetra is Greek and means four, plegia means paralysis, i.e. a "paralysis of four extremities". [3]

Motoric and sensory paralysis

SCI_Explanation_Picture_002

Due to the impact of a Spinal Cord Injury very often motoric (descending, i.e. efferent, fibers) and sensory (ascending fibers, i.e. afferent, fibers) of the spinal cord are affected by the  incident. The Spinal Cord consists of hundreds of thousands of fibers which are very close to each other - so this fact comes as no surprise.

Motoric system

SCI_Explanation_Picture_004

The motoric system are the nerve pathways (consisting of lots of fibers) between the brain and the  skeletal muscles, and are responsible for the movement (contraction) of the muscles.

Sensory system

SCI_Explanation_Picture_005

The sensory system are the nerve pathways (consisting of lots of fibers) between sense organs (skin, eyes, etc.) and the brain. The sense organs send all the information which they receive from the outside world such as, touch, pain, temperature, vibration and proprioception (position of the body in space/position of the joints) to the Central Nervous System (CNS) and are processed there.

→ The damage of the motoric and sensory system is the result of paraplegia and thus causes the corresponding restriction for the person affected

motor neuron damage due to Spinal Cord Injury

If you want to do a movement, the signal flow goes over your upper motor neuron to the lower motor neuron all the way to the muscle(s) you want to use (contract) - if this connection is disturbed/damaged we are talking about a motor neuron damage.

Upper Motor Neuron Lesion, UMNL (Damage)

→ a damage of the upper motor neuron

If the first motor neuron is damaged, spastic paralysis develops. [3]

Lower Motor Neuron Lesion, LMNL (Damage)

→ Injury to the second or lower motor neuron is referred to as LMNL. This type of injury results in flaccid paralysis of the muscles. Either the nerve cell in the spinal cord may be destroyed or the nerve conduction axon (peripheral nerve) leading to the corresponding muscle may be interrupted. [3]

→ regardless of damage to the upper and/or lower motor neuron, in the vast majority of cases part of the sensory system is also affected in some way

Citation Source Information

[1] Kate Willette, Don’t call it a miracle, 2014, Christopher & Dana Reeve Foundation

[2] Picture, AdobeStock_188786817

[3] Koch Hans Georg and Geng Veronika. Leben mit Querschnittslähmung (Band 2). Schweizer Paraplegiker-Vereinigung and Manfred-Sauer-Stiftung , 2021.

[4] Clevland Clinic, 2024, https://my.clevelandclinic.org/health/body/23123-peripheral-nervous-system-pns