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Infectious Diseases

HIV & the Nervous System, Signs and Symptoms, Diagnosis, Treatment

Physician-developed and -monitored.

Original Date of Publication: 09 Jan 2000
Reviewed by: Stanley J. Swierzewski, III, M.D.
Last Reviewed: 01 Dec 2007

Original Source: http://www.neurologychannel.com/infectiousdiseases/hiv.shtml

Home » Infectious Diseases » HIV & the Nervous System, Signs and Symptoms, Diagnosis, Treatment

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, that is, all the parts and processes of the body that fight disease and infection. As a result, HIV-infected patients lose their ability to protect the body from various infections, including neurological infections. HIV can live for a long time inside of a person's body before any signs of a suppressed immune system begin to show.

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HIV can cause damage to both the central nervous system, the brain and spinal cord, and the peripheral nervous system, all the nerves leading to and from the central nervous system. The damage varies from person to person. It is caused by either the HIV virus 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 lead to encephalitis, a swelling of the brain, or meningitis, a swelling of the membranes that surround the brain. It can cause problems with thinking (AIDS dementia complex), and it can cause 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).

Signs and Symptoms

Central Nervous System
If the central nervous system is affected, patients may develop weakness, seizures, a change in their mental status, headaches, and language problems. If they have PML in particular, they may suffer from 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 what particular part 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
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 all the various parts of the body) may feel strange burning and tingling sensations, may experience numbness, or their arms and legs may ache. If the motor neurons in particular are involved (the nerves that lead to the skeletal muscles), a patient's muscles may weaken. Patients 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 in their life but don't suffer any of the signs of infection. In HIV patients and other people with suppressed immune systems, however, the bacteria can cause brain abscesses (tissue damage and the accumulation of pus), the symptoms of which vary depending on where in the brain the infection is located. The usual symptoms of toxoplasmosis include speech difficulties, seizures, confusion and lethargy. Symptoms usually develop over the course of days to weeks.

Cryptococcal Meningitis
Cryptococcal meningitis is a type of meningitis 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 what particular part of the brain is affected.

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HIV-Related Cancer
Central nervous system lymphoma is the second most common nervous system abnormality in HIV patients after toxoplasmosis. Primary lymphoma generally develops in the central nervous system only in people, like HIV patients, who have suppressed immune systems. Primary lymphoma, as opposed to metastatic lymphoma, is cancer that actually 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. The most common form of HIV-related neuropathy 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.

See also: More on Neuropathy

Acute Inflammatory Demyelinating Neuropathy
This 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 that affects HIV patients is polymyositis, or PM. Most people with PM don't feel the intense muscular pain that other myopathies cause, but they do suffer muscular aches, cramping and tenderness. The muscle weakness, on the other hand, is quite intense. It is often worse in 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 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 lesions in the brain.

If an infection is suspected, a spinal tap, also known as a lumbar puncture, is done, which 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. A biopsy is sometimes necessary to confirm a cancer diagnosis, for example.

Peripheral Nervous System Disorders
A complete neurological exam should be done to look for any 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 the electromyography (EMG) and nerve conduction velocity study (NCV). An EMG involves placing very tiny electrode needles into the muscles, and if there are any abnormalities evident, it is likely that the nerve supplying the muscle is somehow damaged. The NCV involves placing electrodes on different places on the skin where particular nerves are known to be located. Very small electrical shocks are given, and using an oscilloscope (a TV screen monitor), the nerve function can be monitored and the speed at which an impulse travels along the nerve can be determined. 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, which indicates that the disorder may be acute inflammatory demyelinating neuropathy.

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

Treatment

Central Nervous System Disorders
Some neurological problems can be treated with medication or antibiotics. Antidementia 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 steroid use 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 the tricyclic antidepressants such as amitriptyline (Elavil), anticonvulsants such as gabapentin (Neurontin), and analgesics such as tramadol (Ultram).

Acute inflammatory demyelinating syndrome is caused by abnormal immune system proteins attacking the myelin sheath, just as in Guillain-Barre syndrome. It often requires immunotherapy or plasmaphoresis as part of its treatment. Immunotherapy involves injecting a specific protein into the blood that plays an important role in protecting the body from infection. The protein stops the abnormal immune response that is causing the neuropathy. Plasmaphoresis involves removing some of the blood, separating the cells from the plasma, and then reinjecting the cells back into the body.