Sunday, March 7, 2021

How surgery to repair spinal injuries works


Jenny Weast is a teacher in California who is very good at her job—so good that her salary has grown and she doesn’t qualify anymore for assistance that pays for caregivers to come to her house and help her get out of bed for work. Ms Weast, you see, is a quadriplegic, the Sacramento Bee reports.

The 30-year veteran math teacher at Oakmont High School became paralyzed in a skiing accident when she was 16. She’s now 56 and earns a six-figure salary, which effectively disqualifies her from receiving payments that help her get to work in the first place. Her situation is rare, but it underscores a gap in our laws.

“The way the laws are, the majority of the disabled don’t go to work for fear of losing their benefits or they stop midway because they will lose their benefits, or they work part-time,” the Bee quoted her as saying. “My goal has always been to be independent and to pay my own bills and to have my own health care. I pay those all myself.”

Without her caregivers, she can’t take a shower, get out of bed, or get to work to earn that six-figure salary or teach math to Oakmont’s students. “We aren’t just doing stuff that is inconvenient or tougher for her to do,” the paper quoted Cassie Crooms-Young, who has worked for Ms Weast for 20 years, as saying. “She can’t do that at all. She can’t prepare a meal.”

The veteran educator completely dismisses the idea of quitting her job. “It gives you a purpose. You go in there and every day you are challenged,” she said. “You have a reason to be excited. You have a reason to work really hard. You laugh every day. You are amazed every day by what the kids say and do.”

Although she has returned to the slopes on a bi-ski, new research endeavors to find a way to repair spinal cord injury, at least for sensory neurons, with surgery. Now scientists in the UK and Sweden, who previously developed a surgical technique to reconnect sensory neurons to the spinal cord after injury, say they have gained new insight into how the technique works at a cellular level by recreating it in rats with implications for designing new therapies for injuries where the spinal cord itself is severed.

The brain and the neurons (nerve cells) in the rest of our body are connected in the spine. Here, motor neurons, which control muscle movement, and sensory neurons, which relay sensory information such as pain, temperature and touch, connect with the spinal cord.

Where the neurons connect with the cord, motor neurons bundle together to form a structure called the motor root, while sensory neurons form a sensory root. In patients with traumatic injuries, these roots can be torn, causing areas of the body to lose neural control.

Surgeons can implant motor roots at the area from which they are torn, and they will usually successfully reconnect, as motor neurons can regrow out of the spinal cord and into the motor root. However, this does not apply to the more troublesome sensory root, which surgeons couldn’t reconnect properly until recently. “Doctors previously considered this type of spinal cord injury impossible to repair,” says Nicholas James, a researcher at King’s College London. “These torn root injuries can cause serious disability and excruciating pain.”

Happily, Thomas Carlstedt, also at King’s College London, recently helped to develop a new surgical technique to reconnect the sensory root. It involves cutting the original sensory nerve cells out of the root and implanting the remaining root directly into a deeper structure in the spinal cord. This area is called the dorsal horn, and it contains secondary sensory neurons that don’t normally directly connect to sensory roots. When the team tried the technique in patients, certain spinal reflexes returned, indicating that the implanted neuron had integrated with the spine to form a functional neural circuit.

In a new study recently published in Frontiers in Neurology, James, Carlstedt and other collaborators set out to understand how the implanted sensory root was connecting with the spinal cord in the dorsal horn. By understanding the mechanism, they hope to develop new treatments for patients with other types of spinal injuries.

The scientists used a rat model of spinal injury to study the process at a cellular level. During surgery, they produced a similar spinal injury in the rats and then reattached the sensory root using the new technique. At 12–16 weeks after surgery, the researchers assessed the spinal repair by passing electricity along the neurons to see if they formed a complete neural circuit. They then sacrificed the rats and analyzed the neural tissue under a microscope.

The electrical tests showed that the neural circuit was complete, and that the root had successfully integrated with the spinal cord. When they examined the tissue, they found that small neural offshoots had grown from structures called dendrites (branched projections at the end of neurons) in the dorsal horn. These thin offshoots had extended all the way into the implanted sensory root to create a functional neural circuit.

So, what does this teach us about spinal cord repair? The researchers hope that this type of neural growth could also be used to repair other types of spinal cord injury. “The strategy of encouraging new growth from spinal neurons could potentially be of use in other injuries of the nervous system,” says Carlstedt. For example, scientists could capitalize on this mechanism when designing new therapies for injuries where the spinal cord itself is severed, by implanting grafts that encourage or facilitate this type of nerve growth.

Press Release
This information was provided in a press release.

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