Peripheral Neuropathy: Causes, Classification, and Symptoms

1. What Is Peripheral Neuropathy?

Peripheral neuropathy is a chronic disease characterized by varied sensory, motor, and autonomic symptoms. It often appears as a systemic illness, with complications linked to metabolic, toxic, infectious, nutritional, neoplastic, and immunologic factors.

2. What Is Axonal Degeneration?

In response to injury, nerves may undergo axonal degeneration. When the axon's continuity is interrupted, it loses its connection to the cell body and the ability to receive necessary nutrients. Consequently, the myelin bands degenerate secondarily.

3. What Is Demyelination?

Demyelination is a primary reaction where the myelin sheath degenerates. This process leads to:

• Slowing of nerve conduction
• Nerve conduction block
• Initiation of remyelination, which usually allows for quick and complete recovery

4. Classification by Evolution Time

• Acute Neuropathy: Evolution from days to 4 weeks; typically inflammatory in origin.
• Subacute Peripheral Neuropathy: Evolution over several weeks; often caused by drugs, environmental toxins, or nutritional deficiencies.
• Chronic Peripheral Neuropathy: Evolution over months to years; associated with metabolic, cancerous, autoimmune, or hereditary diseases.

5. Classification by Nerve Involvement

Neuropathies are categorized based on the type of nerves affected:

• Predominant motor neuropathy
• Predominant sensory neuropathy
• Sensorimotor neuropathy
• Autonomic neuropathy

Note: These can be further classified as demyelinating or axonal, and acute or chronic.

6. Classification by Distribution

• Mononeuritis: Affectation of a single nerve.
• Mononeuritis Multiplex: Injury to multiple noncontiguous nerves.
• Polyneuritis: Diffuse, distal, and symmetric affectation of nerves.

7. Causes of Peripheral Neuropathy

Acquired Peripheral Neuropathy

Common causes include physical injury, tumors, toxins, infections, autoimmune disorders, nutritional deficiencies, alcoholism, and metabolic diseases.

Hereditary Peripheral Neuropathy

The most common group is Charcot-Marie-Tooth disease. Clinical features include:

• Extreme muscle weakness
• Wasting of lower limb and foot muscles
• Abnormal gait
• Loss of tendon reflexes
• Numbness in the lower limbs

8. Clinical Manifestations

Sensory signs are the most common clinical manifestations observed in patients with peripheral neuropathies.