HIV and the Nervous System

HIV (human immunodeficiency virus) is the virus that causes AIDS—acquired immunodeficiency syndrome. It invades and impairs the body's immune system—parts and processes of the body that fight disease and infection. As a result, HIV-infected patients lose the ability to fight off infections, including neurological infections. In some cases, HIV can live for a long time inside of a person's body before any signs of a suppressed immune system develop.

HIV can cause damage to both the central nervous system—the brain and spinal cord—and the peripheral nervous system—the nerves leading to and from the central nervous system. Damage can vary and may be caused by HIV itself, AIDS-related cancers, or other infections that an otherwise healthy immune system would be able to prevent.

The most common HIV neurological infection is cerebral toxoplasmosis—a protazoa (type of parasite) that causes tissue damage leading to speech difficulties, seizures, confusion, and lethargy. HIV infection can cause encephalitis, swelling of the brain, or meningitis, swelling of the membranes that surround the brain. It also can cause problems with thinking (AIDS dementia complex) and changes in behavior.

Progressive multifocal leukoencephalopathy (PML) is another HIV-related disorder associated with several neurological problems such facial weakness, loss of vision, and memory loss. HIV can also lead to neuropathy (a nerve disorder) and myopathy (a muscle disorder).

Central Nervous System Symptoms of HIV

If the central nervous system is affected, patients may develop weakness, seizures, a change in mental status, headaches, and language problems. PML in particular, may cause dementia (a broad range of cognitive problems, including memory loss, poor judgment, etc.), facial weakness, visual problems, and a loss of coordination. Generally, the symptoms reflect which particular area of the brain is affected. The most common central nervous system disorder in HIV patients is the infection toxoplasmosis, followed by HIV-related brain cancer.

Peripheral Nervous System Symptoms of HIV

If the HIV infection affects the peripheral nervous system, then the nerves and muscles show various signs of dysfunction. Patients with a peripheral neuropathy (disease in the nerves that lead from the spinal cord to various parts of the body) may experience strange burning and tingling sensations, numbness, and/or pain in the arms and legs . Motor neuron involvement—nerves that lead to the skeletal muscles—may cause muscle weakness. Patients also may develop breathing or heart problems.

Types & Causes of Central Nervous System Disorders

Cerebral Toxoplasmosis

Cerebral toxoplasmosis, also known simply as toxoplasmosis, is the most common central nervous system infection in HIV patients. It is caused by a protozoa, Toxoplasma gondii, which lives in the soil and in animal feces. Most people in the United States are exposed to it at some point, but don't experience any signs of infection. In HIV patients and other people with suppressed immune systems, however, the bacteria can cause brain abscess (tissue damage and the accumulation of pus)—the symptoms of which vary depending on the location of the infection in the brain. Usual symptoms of toxoplasmosis include speech difficulties, seizures, confusion, and lethargy, which develop over the course of days to weeks.

Cryptococcal Meningitis

Cryptococcal meningitis is a type of infection that is caused by a fungus. The course of the illness is usually slow and may develop over days or months. See Meningitis for details of symptoms, diagnosis, and treatment.

Progressive Multifocal Leukencephaly (PML)

PML is an infection caused by a rare virus. A patient with PML may suffer from dementia (a broad range of cognitive problems, including memory loss, poor judgement, etc.), facial weakness, visual problems, and a loss of coordination. The symptoms vary from person to person and generally reflect which area of the brain is affected.

HIV-Related Cancer

Central nervous system lymphoma is the second most common nervous system abnormality in HIV patients. Primary lymphoma generally only develops in the central nervous system when the immune system is suppressed. Primary lymphoma—as opposed to metastatic lymphoma—is cancer that originates in the lymphatic system and has not spread from some other part of the body.

Peripheral Nervous System Disorders

Neuropathy

Neuropathy, also known as peripheral neuropathy, is disease in the peripheral nerves—the nerves that lead to and from the spinal cord and connect with all the various parts of the body. It is very common in HIV patients, usually in the later stages of HIV disease. It can manifest itself in several different ways.

Distal symmetric neuropathy is the most common form of HIV-related neuropathy. It affects the feet first and then the hands, and it affects both sides of the body equally. Patients often feel a strange tingling and painful burning sensation that can spread up the legs and arms. Some patients feel numbness or weakening in the arms and legs.

Acute Inflammatory Demyelinating Neuropathy

This type of neuropathy is very similar to Guillain-Barre syndrome. It involves the nerve root (where the root connects with the spinal cord) and the myelin sheath that surrounds and protects the nerves. The onset of this kind of neuropathy is usually very rapid, sometimes developing within hours to days.

Myopathy: Polymyositis

Myopathies are neurological disorders that involve the skeletal muscles—muscles that are connected to bones, like the biceps in the upper arm and quadriceps in the thigh.

There are many different types of myopathies (including, for example, the muscular dystrophies), but the most common type in people with HIV is polymyositis (PM). Most people with PM don't experience the intense muscular pain that other myopathies cause, but they do suffer muscular aches, cramping, and tenderness, and extreme muscle weakness. Weakness primarily affects the neck, arms, and upper portion of the legs—making it difficult to stand up from a sitting position. Many patients also experience fever, malaise (general bodily discomfort), and loss of appetite.

Diagnosis of HIV-Related Neurological Disorders

Central Nervous System Disorders

Usually, diagnoses of central nervous disorders are based on CT scan and/or MRI imaging studies—tests that provide computer pictures of the inside of the brain. Often, a dye is injected into the body that provides better tissue contrast, making it easier to detect abnormalities and brain lesions.

If an infection is suspected, a spinal tap, also known as a lumbar puncture, is performed. This test involves collecting cerebrospinal fluid so that it can be examined microscopically for the presence of bacteria or viruses. A spinal tap also provides information about the white blood cells, and glucose and protein concentrations—all of which can provide clues about what is causing the problems.

Sometimes, if the various other tests do not provide a clear diagnosis, a brain biopsy may be performed. This involves surgically removing a small sample of brain tissue which is then sent to a lab for microscopic evaluation.

Peripheral Nervous System Disorders

A complete neurological exam should be done to detect noticeable abnormalities—such as irregular muscle and eye movements—that reflect a neurological disorder.

Usually, neurophysiological tests are done to look for abnormal nerve and muscular activity. These include electromyography (EMG) and nerve conduction velocity study (NCV). EMG involves placing very tiny electrode needles into the muscles to detect abnormalities indicating that the nerve supplying the muscle is somehow damaged. NCV studies involve placing electrodes on different areas of the skin where particular nerves are located. Very small electrical shocks are administered through the electrodes and an oscilloscope (TV screen) is used to monitor nerve function and determine the speed at which an impulse travels along the nerve. One of the functions of the myelin sheath is to speed up transmission of the nervous system signals, so if the speed is slower than normal it suggests that the myelin sheath may be damaged—possibly indicating acute inflammatory demyelinating neuropathy.

Nerve and muscle biopsies are sometimes done if the various other tests do not provide a clear diagnosis.

Treatment for HIV-Related Neurological Disorders

Central Nervous System Disorders

Some neurological problems can be treated with medication(s). Anti-dementia drugs can be prescribed to relieve confusion and slow the progression of mental decline. Neurological infections can be treated with antibiotics. There is no known treatment for PML at this time. If there is an AIDS-related tumor in the brain or spinal cord, radiation therapy or steroids may be helpful, although the prognosis is poor.

Peripheral Nervous System Disorders

Treatment of the various peripheral nervous system disorders usually focuses on relieving the pain and other symptoms. Drug therapy is often used to treat neuropathic pain. Typical medications include tricyclic antidepressants such as amitriptyline (Elavil), anticonvulsants such as gabapentin (Neurontin), and analgesics such as tramadol (Ultram).

Acute inflammatory demyelinating syndrome often requires immunotherapy or plasmaphoresis as part of its treatment. Immunotherapy involves injecting a specific protein into the blood to stop the abnormal immune response that is causing the neuropathy. Plasmaphoresis involves removing some of the blood, separating the cells from the plasma, and then re-injecting the cells back into the body.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 08 Jan 2000

Last Modified: 22 Sep 2015