Instruct: Given a question, retrieve documents that can help answer the question.
Query: Can you cut a nerve fiber?
Surgery can be done in case a nerve has become cut or otherwise divided. Recovery of a nerve after surgical repair depends mainly on the age of the patient. Young children can recover close-to-normal nerve function. In contrast, a patient over 60 years old with a cut nerve in the hand would expect to recover only protective sensation, that is, the ability to distinguish hot/cold or sharp/dull. Many other factors also affect nerve recovery. The use of autologous nerve grafting procedures that involve redirection of regenerative donor nerve fibers into the graft conduit has been successful in restoring target muscle function. Localized delivery of soluble neurotrophic factors may help promote the rate of axon regeneration observed within these graft conduits.
Electromyographic (EMG) nerve-conduction studies may be required. X-rays may be needed to exclude bone abnormalities that might put pressure on the nerve; likewise CT or MRI scans to exclude soft tissue causes such as a tumor.
Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system. In most jellyfish the nerve net is spread more or less evenly across the body; in comb jellies it is concentrated near the mouth. The nerve nets consist of sensory neurons, which pick up chemical, tactile, and visual signals; motor neurons, which can activate contractions of the body wall; and intermediate neurons, which detect patterns of activity in the sensory neurons and, in response, send signals to groups of motor neurons. In some cases groups of intermediate neurons are clustered into discrete ganglia.
Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system. In most jellyfish the nerve net is spread more or less evenly across the body; in comb jellies it is concentrated near the mouth. The nerve nets consist of sensory neurons that pick up chemical, tactile, and visual signals, motor neurons that can activate contractions of the body wall, and intermediate neurons that detect patterns of activity in the sensory neurons and send signals to groups of motor neurons as a result. In some cases groups of intermediate neurons are clustered into discrete ganglia.
Another area of research for HSV treatment or a potential cure is the use of genome editing. It is thought that by cleaving the DNA of HSV that infects neurons, thereby causing destruction or mutational inactivation of the HSV DNA, the virus can be greatly treated or even cured.
Nervous systems are found in most multicellular animals, but vary greatly in complexity. The only multicellular animals that have no nervous system at all are sponges, placozoans, and mesozoans, which have very simple body plans. The nervous systems of the radially symmetric organisms ctenophores (comb jellies) and cnidarians (which include anemones, hydras, corals and jellyfish) consist of a diffuse nerve net. All other animal species, with the exception of a few types of worm, have a nervous system containing a brain, a central cord (or two cords running in parallel), and nerves radiating from the brain and central cord. The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants.
One is the neuroscientists' "objective" way. They dissect the brain with scalpel and microscope or look at it with brain scans and then trace neurochemical pathways. Neurology observes "mind" from outside, that is, by means of the neurological examination: questionnaires, the Boston Naming test or Wisconsin Sorting, bisecting lines, acting out how you use a screwdriver, and so on. Neurologists can compare the changes in psychological function that the neurological examination shows with the associated changes in the brain, either post mortem or by means of modern imaging technology.
Functional MRI analyses of the anterior cingulate cortex have also led to the introduction of bilateral cingulotomy for the treatment of chronic pain. Such application was introduced since the anterior cingulate cortex has been found to be related to the processing nociceptive information input. In particular the role of the anterior cingulate cortex is in the interpretation of how a stimulus affects a person rather than its actual physical intensity.
In all cases, illness is caused by the botulinum toxin produced by the bacterium "C. botulinum" in anaerobic conditions and not by the bacterium itself. The pattern of damage occurs because the toxin affects nerves that fire (depolarize) at a higher frequency first.
In 1985, American paleontologist William Akersten suggested the shearing bite. This method of killing is similar to the style of killing seen in hyenas and canines today. A group of machairodonts captured and completely subdued a prey item, holding it still while one from the group bit into the abdominal cavity, pulled back and tore open the body.
Some studies have found that safer needles attached to syringes reduce injuries, but others have shown mixed results or no benefit. The adherence to "no-touch" protocols that eliminate direct contact with needles during use and disposal greatly reduces the risk of needlestick injuries. In the surgical setting, especially in abdominal operations, blunt-tip suture needles were found to reduce needle stick injuries by 69%. Blunt-tip or tapered-tip suture needles can be used to sew muscle and fascia. Though they are more expensive than sharp-tipped needles, this cost is balanced by the reduction in injuries, which are expensive to treat. Sharp-tipped needles cause 51-77% of surgical needlestick injuries. The American College of Surgeons (ACS) and the Food and Drug Administration (FDA) have endorsed the adoption of blunt-tip suture needles for suturing fascia and muscle. Hollow-bore needles pose a greater risk of injury than solid needles, but hollow-bore needle injuries are highly preventable: 25% of hollow-bore needle injuries to healthcare professionals can be prevented by using safer needles. Gloves can also provide better protection against injuries from tapered-tip as opposed to sharp-tipped needles. In addition, the use of two pairs of gloves (double gloving) can halve the risk of needle stick injury in surgical staff. Triple gloving may be more effective than double gloving, but using thicker gloves does not make a difference. A 2014 Cochrane review, updated in 2017, found low quality evidence showing that safety devices on IV start kits and venipuncture equipment reduce the frequency of needlestick injuries. However, these safety systems can increase the risk of exposure to splashed blood. Education with training for at-risk healthcare workers can reduce their risk of needlestick injuries. The National Institute for Occupational Safety and Health (NIOSH)as a campaign (Stop Sticks) to educate at-risk healthcare workers.
Neuroplastic surgery has adapted reconstructive principles from the fields of craniofacial surgery, and plastic and reconstructive surgery and refined them in order to address challenging deformities which result from Neurosurgical Procedures. The first center for Neuroplastic and Reconstructive Surgery was started at Johns Hopkins University Hospital in Baltimore, Maryland by a formal collaboration between the Department of Plastic and Reconstructive Surgery, under the guidance of plastic surgeon Chad Gordon, and the Department of Neurosurgery under the guidance of neurosurgeon Judy Huang. Upon arrival to Johns Hopkins Hospital, Dr. Chad Gordon formed a multi-disciplinary team of physicians, scientists and engineers. The team’s unified goal was to develop techniques and devices to treat neurosurgical patients. These advances led to several publications and patents, and allowed for the establishment of the first formal fellowship training program in Neuroplastic and Reconstructive Surgery. In March 2018, Dr. Gordon was appointed the Director of Neuroplastic and Reconstructive Surgery at Johns Hopkins.
Sponges have no cells connected to each other by synaptic junctions, that is, no neurons, and therefore no nervous system. They do, however, have homologs of many genes that play key roles in synaptic function. Recent studies have shown that sponge cells express a group of proteins that cluster together to form a structure resembling a postsynaptic density (the signal-receiving part of a synapse). However, the function of this structure is currently unclear. Although sponge cells do not show synaptic transmission, they do communicate with each other via calcium waves and other impulses, which mediate some simple actions such as whole-body contraction.
This implied neuroplasticity during the critical period. However, Merzenich argued that neuroplasticity could occur beyond the critical period. His first encounter with adult plasticity came when he was engaged in a postdoctoral study with Clinton Woosley. The experiment was based on observation of what occurred in the brain when one peripheral nerve was cut and subsequently regenerated. The two scientists micromapped the hand maps of monkey brains before and after cutting a peripheral nerve and sewing the ends together. Afterwards, the hand map in the brain that they expected to be jumbled was nearly normal. This was a substantial breakthrough. Merzenich asserted that, "If the brain map could normalize its structure in response to abnormal input, the prevailing view that we are born with a hardwired system had to be wrong. The brain had to be plastic." Merzenich received the 2016 Kavli Prize in Neuroscience "for the discovery of mechanisms that allow experience and neural activity to remodel brain function."
Phantom limb pain is a type of tactile hallucination because it creates a sensation of excruciating pain in a limb that has been amputated. In 1996, VS Ramachandran conducted a research on several amputees to pinpoint the neural reasons behind these illusionary pains. Most of these amputees that had an unbearable phantom limb pain are reported by patients whose limb was paralyzed before amputation. VS Ramachandran proposed the "learned paralysis" hypothesis. The hypothesis suggested that every time the patients tried to move their paralyzed limb, they received sensory feedback (through vision and proprioception) that the limb did not move. This feedback hardwired itself into the brain circuitry, so that, even when the limb was no longer present, the brain had learned that the phantom limb was paralyzed. As a treatment for phantom limb pains, VS Ramachandran devised a mirror box that would superimpose the mirror image of the normal arm in place of the missing arm and the patient would immediately be relieved of the pain. This suggested that the brain had a plastic nature in the somatosensory system and the brain had reorganized its somatosensory region to accommodate for this new change. Patients that experience this phantom limb pain are very important in research studies for their role in determining brain plasticity. The vivid tactile sensation of the arm that is no longer present suggest the highly complex nature of the brain to reorganize different functions which were once thought to be hardwired to specific regions (localization).
Due to more recent Medical, Rehabilitation and ongoing results 'neuroplasticity' within the mechanics of our brains lead to re-arrangement of the brain's workings. These often result in the synapses arranging alternate routes, to achieve previous habits. Neuroplasticity is the brain's ability to reorganise itself by forming new neural connections throughout life. Neuroplasticity allows the neurons (nerve cells) in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment.
In 1820, Justinus Kerner, a small-town German medical officer and romantic poet, gave the first complete description of clinical botulism based on extensive clinical observations of so-called “sausage poisoning”. Following experiments on animals and on himself, he concluded that the toxin acts by interrupting signal transmission in the somatic and autonomic motor systems, without affecting sensory signals or mental functions. He observed that the toxin develops under anaerobic conditions, and can be lethal in minute doses. His prescience in suggesting that the toxin might be used therapeutically earned him recognition as the pioneer of modern botulinum toxin therapy.
Needlestick injuries are a common event in the healthcare environment. When drawing blood, administering an intramuscular or intravenous drug, or performing any procedure involving sharps, accidents can occur and facilitate the transmission of blood-borne diseases. Injuries also commonly occur during needle recapping or via improper disposal of devices into an overfilled or poorly located sharps container. Lack of access to appropriate personal protective equipment, or alternatively, employee failure to use provided equipment, increases the risk of occupational needlestick injuries. Needlestick injuries may also occur when needles are exchanged between personnel, loaded into a needle driver, or when sutures are tied off while still connected to the needle. Needlestick injuries are more common during night shifts and for less experienced people; fatigue, high workload, shift work, high pressure, or high perception of risk can all increase the chances of a needlestick injury. During surgery, a surgical needle or other sharp instrument may inadvertently penetrate the glove and skin of operating room personnel; scalpel injuries tend to be larger than a needlestick. Generally, needlestick injuries cause only minor visible trauma or bleeding; however, even in the absence of bleeding the risk of viral infection remains.
Phantom limbs are a phenomenon which occurs following amputation of a limb from an individual. In 90–98% of cases, amputees report feeling all or part of the limb or body part still there, taking up space. The amputee may perceive a limb under full control, or paralyzed. A common side effect of phantom limbs is phantom limb pain. The neurophysiological mechanisms by which phantom limbs occur is still under debate. A common theory posits that the afferent neurons, since deafferented due to amputation, typically remap to adjacent cortical regions within the brain. This can cause amputees to report feeling their missing limb being touched when a seemingly unrelated part of the body is stimulated (such as if the face is touched, but the amputee also feels their missing arm being stroked in a specific location). Another facet of phantom limbs is that the efferent copy (motor feedback) responsible for reporting on position to the body schema does not attenuate quickly. Thus the missing body part may be attributed by the amputee to still be in a fixed or movable position.
Kean begins the chapter with the sad tale of George Dedlow. George Dedlow had fought in the Civil War and in turn had both his arms and both his legs amputated for various reasons. These amputations brought on another neurological phenomenon: phantom limbs. George Dedlow, amongst millions of other war amputees, felt pain in limbs that he did not have.
Nakiri bōchō (, translation: knife for cutting greens) and usuba bōchō (, thin knife) are Japanese-style vegetable knives. They differ from the "deba bōchō" in their shape, as they have a straight blade edge suitable for cutting all the way to the cutting board without the need for a horizontal pull or push. These knives are also much thinner. While the "deba bōchō" is a heavy blade for easy cutting through thin bones, the blade is not suitable for chopping vegetables, as the thicker blade can break the vegetable slice. The "nakiri bōchō" and the "usuba bōchō" have a much thinner blade. This does not help with cutting small bones in fish or meat, but is useful for cutting vegetables.
A neurolytic block is the deliberate injury of a nerve by the application of chemicals (in which case the procedure is called "neurolysis") or physical agents such as freezing or heating ("neurotomy"). These interventions cause degeneration of the nerve's fibers and temporary interference with the transmission of pain signals. In these procedures, the thin protective layer around the nerve fiber, the basal lamina, is preserved so that, as a damaged fiber regrows, it travels within its basal lamina tube and connects with the correct loose end, and function may be restored. Surgically cutting a nerve severs these basal lamina tubes, and without them to channel the regrowing fibers to their lost connections, a painful neuroma or deafferentation pain may develop. This is why the neurolytic is preferred over the surgical block.
A neurolytic block is a form of nerve block involving the deliberate injury of a nerve by freezing or heating ("neurotomy") or the application of chemicals ("neurolysis"). These interventions cause degeneration of the nerve's fibers and temporary (a few months, usually) interference with the transmission of nerve signals. In these procedures, the thin protective layer around the nerve fiber, the basal lamina, is preserved so that, as a damaged fiber regrows, it travels within its basal lamina tube and connects with the correct loose end, and function may be restored. Surgical cutting of a nerve (neurectomy), severs these basal lamina tubes, and without them to channel the regrowing fibers to their lost connections, over time a painful neuroma or deafferentation pain may develop. This is why the neurolytic is usually preferred over the surgical block.
Ephaptic transmission is when two nerves communicate with each other via an artificial synapse between nerves. Healthy peripheral nerves are insulated with a myelin sheath that helps to both enhance electric transmission and to prevent cross-talk between parallel nerves. After a lesion, it has been observed that regenerating nerves might not be myelinated effectively. Consequently, the two nerve fibers can come into contact and provide a means for an impulse to be directly conducted through the nerve membrane. An analogy for this is having two uninsulated electrical wires placed adjacent to each other. Thus, the two nerves are able to “cross-talk” and send action potentials in both directions.
After the sensory nerves are exposed, each sensory nerve root is divided into 3-5 rootlets. Each rootlet is tested with electromyography, which records electrical patterns in muscles. Rootlets are ranked from 1 (mild) to 4 (severe) for spasticity. The severely abnormal rootlets are cut. This technique is repeated for rootlets between spinal nerves L2 and S2. Half of the L1 dorsal root fibers are cut without EMG testing.