Neural degeneration

Any time there is damage to the cell body, the result is cell death. If there is damage to the axon, death is not certain.

• Anterograde degeneration – Breakdown of an axon from the point of damage back toward the terminal button
• Retrograde degeneration – Breakdown of an axon from the point of damage back toward the cell body
• Chromatolysis – Retrograde degeneration can spread toward cell body
• Transneuronal degeneration – Spreads to neighboring cells

Neuron regeneration

What kind of recovery can we expect? Neuron regeneration will occur in the Peripheral Nervous System (PNS), but not the CNS (brain and spinal cord). And in the PNS, even if neurons do regenerate, there is no guarantee that they will connect. Just because the potential is there, it does not mean that things will “hook up” correctly.

Why no regeneration in the Central Nervous System?

• No glycoproteins – Growth-promoting glycoproteins are present in the PNS only.
  • Laminin and fibronectin – Necessary for development of growth cone/neuron
  • Oligodendrocytes – Glycoproteins that inhibit growth are present in the CNS. Remember, oligodendrocytes are a type of CNS glial cell responsible for forming myelin sheath. Schwann cells do this in the PNS.

This is seen in transplant studies. When you transplant a PNS cells to the CNS, they do not regrow. When you transplant CNS cells to PNS, they can regrow. Therefore, the ability for these cells to regenerate is dependent on the cellular environment.

Brilliant Blue G

Studies have found that Brilliant Blue G dye (found in M&Ms) may be beneficial in reducing inflammation, swelling and the formation of scar tissue following a spinal cord injury, allowing more time for treatments. Unfortunately, one of the side effects of Brilliant Blue G is that it turns you blue, as seen in this rat. Testing is still in progress to determine if this treatment can be used effectively in humans.

Spinal cord research

Lesions on spinal cord… Looking for drugs that encourage regeneration by neutralizing growth-inhibiting proteins (MAG and No-Go). Today, we are able to recover some functions, but they are reflexive in nature and happen at the level of the spinal cord, not the brain. For example, increases in stride length versus limb placement (picking up a limb in response to sensory input). This is demonstrated when a paraplegic’s body’s is suspended (body weight supported) and placed on a treadmill using Lokomat system. This activates a reflex as if you are falling, causing you to step forward. With practice, this can be refined, so steps do not appear so robotic. Today, advances in technology have led to robotic exoskeletons that make it possible for some paraplegics to walk again. A sensor is placed on the body that reads signals from the brain transmitted to the nerves, that then activate the exoskeleton to move as desired.

Neural reorganization

Collateral sprouting is when a neighboring cell and move in and form new cell connections, fill vacant cell receptor sites. You see things like Mirror Box Treatments for Phantom Limb Pain, the visual input allows people to feel relaxation. The parts of the brain that process the missing limb are still being activated, where are they getting their information from?

6 Causes of Brain Damage

There are 6 causes of brain damage: 1) Brain tumors; 2) Cerebrovascular Disorders; 3) Closed Head Injuries; 4) Brain Infections; 5) Neurotoxins; and 6) Genetic Factors. The behavioral consequences of brain damage depend on where the damage is taking place in the brain.

1) Brain tumors

• Neoplasm – A neoplasm is a new growth in the brain. Some may be cancerous, some may not.
• Meningiomas – About 20% of brain tumors are meningiomas, or tumors that grow between the 3 membranes in the central nervous system. Because they occur on the outside layers of the brain, they are easier to remove. They do not invade brain tissue. All meningiomas are encapsulated tumors.



• Encapsulated tumors – Encapsulated brain tumors are ones that grow within their own membrane. These types of brain tumors are usually easily to identify on a CT scan – and benign, meaning they are not cancerous. Because encapsulated brain tumors are clearly defined, they are also typically easier to remove than other types of brain tumors. However, damage may have been to the surrounding tissue, causing the death of neurons, which may have permanent consequences.



• Infiltrating tumors – Infiltrating tumors invade the surrounding brain tissue. They have undefined edges, and are most often malignant (cancerous).
• Metastatic brain tumors – About 10% of brain tumors originate elsewhere in the body. These types of brain tumors occur when pieces of a tumor break off and spreads to the brain through the bloodstream. Most metastatic brain tumors originated from a lung cancer. Once cancer spreads into brain, fragments often break off and invade the lymphatic system, and easily spread to other parts of the body. (The lymphatic system is the system of nodes and capillaries.)

Each year, about 150,000 people are diagnosed with a metastatic brain tumor in the U.S.

2) Cerebral vascular disorders

Strokes – the 3rd leading cause of death in the U.S. – are sudden-onset disorders that cause brain damage. There are two main types:

• Cerebral hemorrhage – Bleeding in the brain caused by a ruptured blood vessel
  • Aneurysm – Balloon-like dilation in the vessel wall which can be congenital or due to exposures to infection or toxins
• Cerebral ischemia – Medications can be used to dissolve blockages in the brain. The blood vessels are too small to use the same types of procedures used in other parts of the body.
  • Thrombosis – Blocks blood supply
  • Embolism – Comes from another location, and travels through the blood stream after breaking off from another site

3) Closed head injuries

• Cerebral contusions – Includes damage to the circulatory system, like hemotomas (clotted blood) and concussions (consciousness is disrupted, but there is no structural damage)

Chronic Traumatic Encephalopathy (CTE)

This is a long-term condition due the the result of multiple concussions (closed head injuries) often seen in professional and even amateur football players. Also often referred to as “Punch Drunk Syndrome” in relation to the brain damage incurred by professional boxers. This is a progressive disease in that those with CTE will end up needing cared for.

4) Brain infections

• Bacterial infections of the brain – Meningitis, syphilis
• Viral infections of the brain – Rabies, herpes simplex 1 (can lead to swelling of the brain/encephalitis)

5) Neuropsych diseases

Parkinson’s Disease

Parkinson’s is caused by insufficient dopamine biosynthesis in the dopaminergic neurons of the brain that result in communication problems between the substantia nigra and basal ganglia. Parkinson’s is a progressive disease that eventually causes rigidity of the limbs and tremors at rest. During the early stages, L-Dopa may be given to “super-charge” the remaining neurons. However, it does not stop the long-term progression of the disease. Embryonic stem cell (plurypotent neurons) implants in the substantia nigra done outside the U.S. are showing some promise/success in the treatment of Parkinson’s disease. Deep brain stimulation (DBS) in which an electrode is implanted in the brain near the substantia nigra also shows some success in treating symptoms of the disease, which slows, but does not stop the progression of the diease. Michael J. Fox has Parkinson’s disease, as seen in the video below.

Huntington’s Disease

Is the result of damage to the caudate nucleus and putamen that causes uncontrollable jerky movements. Symptoms typically begin to appear around age 40, and children who have a parent with Huntington’s have a 50/50 chance of inheriting the disease. Genetic testing is available for early diagnosis of Parkinson’s disease. Woody Guthrie died in 1967 as a result of Huntington’s disease, and Carol Carr made national news for killing her sons that were also affected by the disease.

6) Neurotoxins

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