Nerves are communication pathways throughout the body, transmitting electrical and chemical signals for movement, sensation, and organ function. Though generally protected, nerves can be targeted by infectious agents. While less frequent than other tissue infections, nervous system infections can lead to complex health conditions.
How Nerves Can Become Infected
Infections can reach nerves through several pathways. Direct invasion occurs when pathogens enter a nerve from a nearby injury, surgical site, or localized infection.
Hematogenous spread involves infectious agents traveling through the bloodstream from a distant infection site. Pathogens can then cross the blood-nerve barrier, a protective layer, to infect nerve tissue.
Some pathogens, especially viruses, use retrograde axonal transport. The virus enters peripheral nerve endings, like in the skin, and travels backward along nerve fibers toward the central nervous system or cell bodies. This allows latency or damage far from the entry point. Infections in surrounding structures, such as bones, joints, or soft tissues, can also spread directly to nerves via inflammation or abscesses.
Common Nerve Infections and Their Causes
Several specific infections directly affect nerve tissue, each caused by different types of pathogens. Herpes viruses frequently cause nerve issues. Varicella-zoster virus (VZV) causes shingles; it remains dormant in sensory nerve ganglia after chickenpox and can reactivate, causing painful rashes and postherpetic neuralgia. Herpes simplex virus (HSV) types 1 and 2 also establish latent infections in nerve ganglia, leading to recurrent cold sores or genital lesions.
Lyme disease, caused by Borrelia burgdorferi, can lead to neurological complications affecting peripheral and cranial nerves. Symptoms include neuropathy (nerve pain or weakness) or facial palsy. Leprosy, caused by Mycobacterium leprae, targets peripheral nerves, causing damage, especially in cooler body areas like limbs and face. The bacterium invades Schwann cells, which produce the myelin sheath, leading to demyelination and nerve thickening.
Poliovirus, now rare due to vaccination, primarily attacks motor neurons in the spinal cord and brainstem, causing muscle weakness and paralysis. Cytomegalovirus (CMV) can also affect nerves, particularly in immunocompromised individuals, leading to conditions like polyradiculopathy (affecting nerve roots) or mononeuritis multiplex (affecting multiple nerves). Localized bacterial infections can form abscesses near nerves, causing compression and inflammation that impairs nerve function.
Symptoms and Diagnosis of Nerve Infections
Symptoms of a nerve infection vary widely depending on which nerves are affected—motor, sensory, or autonomic—and the extent of damage. Sensory nerve involvement often causes severe, burning, or shooting pain, along with numbness or tingling (paresthesia). If motor nerves are compromised, weakness or paralysis can occur, potentially leading to muscle atrophy.
Heightened touch sensitivity, where light pressure causes discomfort, may also occur. If autonomic nerves are affected, symptoms like sweating abnormalities or blood pressure regulation issues can arise. Systemic symptoms, such as fever or fatigue, may also accompany nerve infections.
Diagnosis involves identifying the pathogen and assessing nerve damage. A physical and neurological assessment pinpoints affected areas. Blood tests detect pathogens or inflammation markers. Nerve conduction studies and electromyography (NCS/EMG) measure nerve and muscle electrical activity to identify damage patterns. Imaging (MRI/CT scans) visualizes inflammation, swelling, or abscesses near nerves. Cerebrospinal fluid (CSF) analysis or a nerve biopsy may also identify the infectious agent or tissue changes.
Treatment and Prevention of Nerve Infections
Treatment depends on the cause, aiming to eliminate the pathogen, manage symptoms, and prevent further damage. Viral nerve infections often require antiviral medications, like those for herpes zoster, to reduce replication and pain. Bacterial nerve infections typically need specific antibiotics based on the identified species, as with Lyme disease or leprosy.
Anti-inflammatory medications reduce swelling and pain. Pain management strategies alleviate discomfort and improve quality of life. Physical therapy and rehabilitation programs are important for regaining lost nerve function and muscle strength, aiding recovery from weakness or paralysis. Surgery may be necessary to drain abscesses compressing nerves or to decompress swollen nerves.
Preventive measures reduce nerve infection risk. Vaccinations, like the shingles vaccine (reducing VZV reactivation) and the polio vaccine (nearly eradicating the disease), are effective. Prompt treatment of other body infections prevents nervous system spread. Good hygiene, such as hand washing, reduces infectious agent transmission. Avoiding tick bites, through protective clothing and repellents, prevents Lyme disease. Managing underlying health conditions also strengthens immune defense.