What is the Difference Between Axonal and Demyelinating Neuropathy?
🆚 Go to Comparative Table 🆚Axonal and demyelinating neuropathies are two types of peripheral neuropathies that affect the nerves supplying muscles and the skin. The main differences between them are the affected nerve components and the clinical manifestations.
- Axonal Neuropathy:
- Affects the axons, which are the cores of nerve fibers responsible for signal transmission.
- Caused by a broad spectrum of systemic illnesses, toxic, ischemic, metabolic, or genetic conditions.
- Characterized by a reduction in amplitude of compound muscle action potentials (CMAPs).
- Nerve conduction study (NCS) shows relatively normal conduction velocities when recording from proximal and distal muscles.
- Demyelinating Neuropathy:
- Affects the myelin, which is the fatty tissue that ensheathes axons and is required for rapid signal transmission.
- May be seen in compressive neuropathies, hereditary neuropathies, and acquired immune-mediated neuropathies like Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy.
- Characterized by a reduction in conduction velocity and prolongation of distal and F-wave latencies.
- NCS shows marked slowing of conduction at both proximal and distal sites.
A nerve conduction study is necessary to determine whether a nerve injury is primarily demyelinating or axonal, or both, and is essential in the assessment of peripheral nerve injury. The choice of treatment and prognosis depend on the specific type of neuropathy.
Comparative Table: Axonal vs Demyelinating Neuropathy
Axonal and demyelinating neuropathies are two distinct types of peripheral neuropathies that affect the nerves differently. Here is a comparison of their characteristics:
| Feature | Axonal Neuropathy | Demyelinating Neuropathy |
|---|---|---|
| Definition | Characterized by the degeneration of axons (nerve fibers) | Characterized by the degeneration of myelin, the protective covering around nerve fibers |
| Nerve Conduction Study Findings | Reduction in amplitude of nerve action potentials | Reduction in conduction velocity and prolongation of distal and F-wave latencies |
| Recovery | Often incomplete, as the injury is at the level of the cell body | Often rapid (weeks to months) and complete, as the injury is at the level of the myelin sheath |
| Causes | Can be caused by toxic, ischemic, metabolic, or genetic conditions | Can be caused by compressive neuropathies, hereditary neuropathies, and acquired immune-mediated neuropathies like Guillain-Barré syndrome (GBS) |
To differentiate between axonal and demyelinating neuropathies, nerve conduction studies can be performed. Comparing conduction velocity obtained from proximal versus distal muscle recordings provides a reliable aid for differentiating between chronic axonal and demyelinating polyneuropathies, especially in cases with conduction velocity slowing and low compound muscle action potential (CMAP) amplitudes.
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