Learn all about Wallerian degeneration and its causes and symptoms. Wallerian degeneration is a process that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (i.e. farther from the neuron’s cell body) degenerates. This is also known as anterograde or orthograde degeneration.
A related process known as ‘Wallerian-like degeneration’ occurs in many neurodegenerative diseases, especially those where axonal transport is impaired. Primary culture studies suggest that a failure to deliver sufficient quantities of the essential axonal protein NMNAT2 is a key initiating event.
It is named after the English neurophysiologist Augustis Volney Waller (1816-1870), who had described the process in 1850 Wallerian degeneration is an important concept that is useful in mapping the anatomic components of peripheral nerves and spinal cord segments, in recognizing peripheral or central nervous system disorders microscopically, and in understanding and predicting reinnervation by peripheral nerves.
When a peripheral nerve axon is destroyed at some point in its course away from the cell body, it will completely degenerate from the point of destruction to the structure innervated. This is because the axon requires the axoplasmic flow of cytoplasmic materials from the cell body for its survival. The signs and symptoms of Wallerian degeneration are muscle weakness, limb numbness and altered sensation etc. Symptoms of the Wallerian Degeneration include acute axonal degeneration or AAD which is the rapid separation of the proximal and distal ends which usually occur within the thirty minutes of the cause or the injury. The degeneration follows swelling of the axolemma.
The axonal degeneration is usually followed by the decrease of the myelin sheath and the infiltration by the macrophages which may be accompanied by Schwann cells which serve to clear the debris from the degeneration. Treatment includes physical examination particularly the swollen affected part which may be the root or the cause of the Wallerian Degeneration.
What is Wallerian degeneration
Wallerian degeneration is the catabolic process of degeneration of a neuron or axon that occurs without influencing the main cellular body and without the affected neuron actually dying. Wallerian degeneration is a pattern of damage in nerve fibers where the axon of a nerve breaks down because of a lesion damaging the core. When lesions appear along the nerves, the opposite or distal ends can experience Wallerian degeneration. The nerve cells will attempt to grow and regenerate unless a scar or similar obstacle prevents them from doing so. In the peripheral nervous system, regrowth tends to be more rapid than in the central nervous system.
Wallerian degeneration Symptoms
Wallerian degeneration symptoms are as under;
· Muscle weakness: Muscle weakness can be the result of a neurologic diseases, disorders or conditions, which affect the nervous system. These include cerebral palsy, prolapsed disc in the back, stroke, Guillain-Barre syndrome and multiple sclerosis. Myasthenia gravis is an autoimmune disease that affects nerve function and results in muscle weakness
· Limb numbness: A pinched nerve in the back or neck can lead to numbness in the hand or arm. A herniated disk may also put pressure on a nerve that leads to the arm, causing sensation in this limb to become weakened. Animal bites which strike a nerve may also cause the arm to become numb.
· Altered sensation: The term ‘altered sensation’ covers a wide variety of symptoms experienced by many people with MS. These include numbness (people often say they feel like they’ve had a local anaesthetic) tingling or ‘electric shocks’ feeling extremities are swollen/ feeling of ’largeness’. ‘band-like’ sensation around chest or limb.
Wallerian degeneration Causes
Wallerian Degeneration usually is cause or occurs after axonal injury in both the peripheral nervous system and the central nervous system. Oligodendrocytes fail to recruit macrophages for debris removal. Macrophage entry in general into CNS site of injury is very slow. In contrast to PNS, Microglia plays a vital role in CNS Wallerian degeneration. Researchers have suggested that the delay in Wallerian degeneration in CNS in comparison to PNS is caused not due to a delay in axonal degeneration, but rather is due to the difference in clearance rates of myelin in CNS and PNS. Myelin clearance is the next step in Wallerian degeneration following axonal degeneration.
18p minus syndrome – small hands 1q deletion – small hands 2q deletion – long fingers 3-methylglutaconic aciduria, type 1 – arm weakness 46, XX chromosome 7 deletion p13 – short fingers are the causes of Wallerian degeneration.
Wallerian degeneration Treatment
Wallerian degeneration treatment consists of physical exam particularly the swollen impacted part which may be the root or the cause of the Wallerian Degeneration. Following chemotherapies may be introduced as treatment option;