Archive for the ‘NEUROSURGERY’ Category

Video shows how Stretchable, Long-Term Neural Implant on the Spinal Cord Could Restore Walking

Tuesday, March 10th, 2015

So-called “surface implants” have reached a roadblock. They can’t be applied long-term to the spinal cord or brain, beneath the nervous system’s protective envelope (known as the dura mater), because when nerve tissues move or stretch, they rub against the rigid devices. Repeated friction causes inflammation, scar tissue buildup, and rejection. Scientists from the Swiss Federal Institute of Technology in Lausanne (EPFL) now introduce the e-Dura implant, which is designed specifically for implantation on the surface of the brain or spinal cord. The neural implant combines electrical and chemical stimulation and has successfully made paralyzed rats walk again. Soft and stretchable, it is the first of its kind that can be implanted directly on the spinal chord without damaging it. Its silicon substrate is covered with cracked gold electric conducting tracks, and the electrodes are made of an innovative composite of silicon and platinum microbeads. They can be deformed in any direction, while still ensuring optimal electrical conductivity. A fluidic microchannel enables the delivery of pharmacological substances that will reanimate the nerve cells beneath the injured tissue.
Henry Sapiecha

Non-surgical procedure repairs severed nerves in just a few minutes

Thursday, August 14th, 2014

U.S. researchers have developed a nonsurgical technique to repair severed nerves in minutes instead of months (Image

U.S. researchers have developed a nonsurgical technique to repair severed nerves in minutes instead of months Image

Professor George Bittner and his colleagues at the University of Texas at Austin Center for Neuroscience have developed a simple and inexpensive procedure to quickly repair severed peripheral nerves.

Professor George Bittner of the University of Texas at Austin image

The team took advantage of a mechanism similar to that which permits many invertebrates to regenerate and repair nerve damage. The new procedure, based on timely application of common chemicals to the severed nerve ends, could help patients to recover nearly full function in days or weeks.

Peripheral nerves connect the central nervous system to the muscles and sensory organs. Nerves contain a bundle of cylindrical sheaths called axons, within which reside individual nerve cells. The axons are surrounded by Schwann cells which coat the axons with myelin.

Trauma to peripheral nerves is relatively common. A nerve that has been damaged by pressure or stretching generally has a severed nerve fiber inside an intact axon. A severed nerve occurs when both the nerve fiber and the axon are cut in two. Either injury can prevent muscles from working and result in loss of feeling from the area of the body served by that nerve, often for years thereafter.

Why is nerve repair in mammals such a slow process?

When a nerve fiber breaks within its axon, the broken end of the nerve fiber which is no longer connected to the central nervous system dies, leaving an empty axonal tube from the point of injury. The nerve fiber will slowly grow within the empty tube, at a rate of about an inch per month. Thus, even minor nerve injuries commonly take months or years to heal. Even then the regrown nerves rarely meet up perfectly with the original muscles and sensory organs, so that a significant amount of function is permanently lost.

In what is known as Grade V neurotmesis, the axon is severed along with the nerve fiber. The growth of the regenerating nerve fiber is not constrained, and can form a twisted ball of nerve fiber at the cut in the axon. Such nerve scars are called neuroma, and can be extremely painful. Recovery from Grade V nerve injury is never rapid, usually taking months or years for even partial recovery.

In current medical practice, a cut nerve is repaired by using microsutures to reconnect the cut ends of the axon in an extraordinarily delicate operation (imagine sewing together two limp strands of angel hair pasta).

The object is to provide a continuous axon to guide the regrowth of the nerve fiber. Again, the regrowth process takes months or years to be completed, and typically the function of the original nerve will remain impaired.

A new approach

Professor Bittner’s team had discovered earlier that when a plasma membrane is damaged, a calcium-mediated healing mechanism starts to draw small vesicles toward the site of the injury. Vesicles are small sacks made of lipid membranes which provide the material needed to repair an injured plasma membrane. However, when the vesicles are attracted to the site of a severed axon, both ends of the axon are sealed off by this repair mechanism, preventing regrowth of the nerve.

To avoid this problem, the first step of the Texas group’s nerve repair procedure is to bathe the area of the severed nerve with a calcium-free saline solution. By removing calcium from the injured axons, premature healing of the axon ends by this vesicle-based repair mechanism is prevented and even reversed. The damaged axons remain open, and can more easily be reattached. The calcium-free solution also contains antioxidants (e.g., methylene blue) to prevent degenerative changes in the axon and nerve.

In standard methods, the two ends of the severed axon would be reattached surgically. In contrast, Bittner’s procedure does not require such difficult microsurgery. Instead, the severed ends of the axon are pulled to within a micron of each other, whereupon a small amount of a solution containing polyethylene glycol (PEG) is injected. The PEG removes water from the axonal membranes, allowing the plasma membranes to merge together, thereby healing the axon.

At the same time, the nerve fibers are brought into close enough proximity that they receive chemical messengers from each other making them believe they are still whole, thereby preventing the death of the disconnected nerve fiber. The severed nerve fibers can then grow together in a short period of time and with relatively good fidelity to the original connectivity of the nerve fibers.

The final step of the procedure is to inject the area with a calcium-rich saline solution, which restarts the vesicle-based repair mechanism, thereby repairing any residual damage to the axonal membrane. At this point, the nerve is structurally repaired, and use of the affected area begins to return within a few hours.

Indeed, tests of Bittner’s procedure on rats have indicated an amazing level of success. The sciatic nerve of the rats was cleanly severed, resulting in paralysis of the affected limb.

Within minutes of awaking from Bittner’s procedure, many of the rats were immediately able to move the limb containing the severed nerve. The normal function of the limb was partially restored within a few days, and 80-90% of the pre-injury function was restored within two to four weeks. Control rats subjected to sciatic nerve cutting followed by a sham procedure permanently lost nearly all (95-98%) function in the affected limb.

The chemicals used in Bittner’s procedure are common and well understood in interaction with the human body. PEG is on the FDA’s GRAS (generally recognized as safe) list, and methylene blue is an aromatic dye used for staining histological samples, as well as in fabric stains and paints. Because of this, there is no clear obstacle to beginning human clinical trials of the procedure. Indeed, teams at Harvard Medical School and Vanderbilt Medical School and Hospitals are currently conducting studies aimed at gaining approval for such trials. While the procedure developed by Bittner’s group will not apply to the central nervous system or spinal cord injuries, the procedure offers hope to people whose futures include accidents involving damaged nerves.

Sources: University of Texas, News in Physiological Sciences

Henry Sapiecha


Thursday, May 23rd, 2013


When a nerve in the peripheral nervous system is torn or severed, it can take a long time to regenerate – if it does so at all. Depending on the location of the injury, it can leave the affected part of the patient’s body numb and/or paralyzed for years, or even for the rest of their life. Now, however, scientists from Israel’s Tel Aviv University have created a gel and an implant that they claim could vastly aid in the healing of damaged nerves.

The implant is a tiny pliable biodegradable tube, that is placed around the two cut ends of the nerve. It serves to line them up with one another and hold them together end-to-end, plus its inner surface is coated with the gel.

Known as Guiding Regeneration Gel (GRG), the substance supports the growth of new nerve fibers via three key components – anti-oxidants, synthetic laminin peptides (amino acid compounds), and hyaluronic acid. The anti-oxidants help prevent inflammation, the peptides provide a sort of guiding line for the nerve fibers to grow along in the gap between the two cut ends, and the hyaluronic acid – which is typically found in the human fetus – keeps everything from drying out. As a result, nerves reportedly heal “quickly and smoothly.”

The implant/gel system has already been successfully tested on lab animals, with clinical use on humans said to be only a few years away. GRG could also be used on its own in the field of cell therapy, as a means of preserving cells for transplantation.

Source: American Friends of Tel Aviv University


Henry Sapiecha


Wednesday, May 2nd, 2012


Researchers at Northwestern University have developed a neuroprosthesis that restores complex movement in the paralyzed hands of monkeys. By implanting a multi-electrode array directly into the brain of the monkeys, they were able to detect the signals that generate arm and hand movements. These signals were deciphered by a computer and relayed to a functional electrical stimulation (FES) device, bypassing the spinal cord to deliver an electrical current to the paralyzed muscles. With a lag time of just 40 milliseconds, the system enabled voluntary and complex movement of a paralyzed hand.

The experiments were carried out on two healthy monkeys, whose electrical brain and muscle signals were recorded by the implanted electrodes when they grasped, lifted and released a ball into a small tube. Using these recordings, the researchers developed an algorithm to decode the monkeys’ brain signals and predict the patterns of muscle activity that occurred when they wanted to move the ball.

The monkeys were then given an anesthetic to locally block nerve activity at the elbow, resulting in temporary paralysis of the hand. The multi-electrode array and FES device – which combine to form the neuroprosthesis – allowed the monkeys to regain movement in the paralyzed hand and pick up and move the ball with almost the same level of dexterity as they did before the paralysis.

“The monkey won’t use his hand perfectly, but there is a process of motor learning that we think is very similar to the process you go through when you learn to use a new computer mouse or a different tennis racquet. Things are different and you learn to adjust to them,” said Lee E. Miller, the Edgar C. Stuntz Distinguished Professor in Neuroscience at Northwestern University Feinberg School of Medicine and the lead investigator of the study.

Dr. Miller’s team also performed grip strength tests, and found that the neuroprosthesis enabled voluntary and intentional adjustments in force and grip strength – key factors in successfully performing everyday tasks naturally.

The multi-electrode array implant detects the activity of about 100 neurons in the brain, which is just a fraction of the millions of neurons involved in making the hand movements. However, Miller points out that the neurons they are detecting are output neurons normally responsible for sending signals to the muscles.

“Behind these neurons are many others that are making the calculations the brain needs in order to control movement. We are looking at the end result from all those calculations,” Miller said.

Miller added that, while the temporary nerve block used in the study is a useful model of paralysis, it doesn’t replicate the chronic changes that occur after prolonged brain and spinal cord injuries. For this reason, the next test for the system will be in primates suffering long-term paralysis to study how the brain changes as it continues to use the device.

However, the ultimate aim for the team is for the system to restore movement in human paralysis sufferers. “This connection from brain to muscles might someday be used to help patients paralyzed due to spinal cord injury perform activities of daily living and achieve greater independence,” said Miller.

The results of the Northwestern University team’s study, which was funded by the National Institutes of Health (NIH), appears in the journal Nature.

Sourced & published by Henry Sapiecha