Neurological diseases and peripheral neuropathy

Multiple sclerosis

The axon of a nerve cell is covered with a myelin sheath to protect and insulate electrical stimulation as it passes to the terminal end of the neuron. Multiple sclerosis (MS) is an autoimmune disease that causes progressive inflammation and deterioration (demyelination) of the myelin sheath; this leaves nerve fibers uncovered, which results in scattering of the nervous message as it passes down the axon. Myelinated axons are commonly called white matter. Researchers have learned that MS also damages the nerve cell bodies, which are found in the brain’s gray matter, in addition to the axons themselves in the brain, spinal cord, and optic nerve. The term multiple sclerosis refers to the distinctive areas of scar tissue (sclerosis, or plaques) present in the white matter of people who have MS. These areas are visible on MRI brain scans.

There is no single test used to diagnose MS. Diagnosis is difficult because the signs and symptoms of the disease mimic those of other neurologic disorders. Diagnostic studies include a complete history and physical with a detailed neurologic examination and an MRI of the brain and spinal cord to look for distinctive plaques and areas of sclerosis from scar tissue at the inflammation sites. MS frequently is diagnosed by the exacerbation and remission of neurologic symptoms characteristic of the condition. Patients cycle through remission and relapse with an ever-increasing degree of dysfunction after each episode.

Early symptoms may include numbness, paresthesia, diplopia, ataxia, and bladder control problems. As the disease progresses, patients experience increased spasticity, vertigo, depression, gait problems, joint pain, fatigue, and varying degrees of paralysis. MS most commonly begins in women between the ages of 20 and 40. The cause remains unknown; however, the common belief is that it is due to a combination of genetic and environmental factors, including family history, living in a Northern climate, low vitamin D levels, smoking, and viral infection.

MS has no cure; therefore, treatment focuses on alleviating symptoms and delaying the progression of the disease. Medications used to treat the disease include corticosteroids during periods of exacerbation: interferon (Betaseron, Avonex) and glatiramer acetate (Copaxone) to reduce the frequency and severity of relapses; fingolimod (Gilenya) for relapsing forms of MS, and additional medications to treat fatigue, pain, spasticity, and bladder control problems. Some patients live an essentially normal life with only occasional attacks, whereas others experience rapidly progressive incapacitation.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, is a rapidly progressive, ultimately fatal neurologic disease that destroys the motor neurons responsible for voluntary muscle control. Without stimulation from motor neurons, muscles cannot function and gradually weaken and atrophy. The cause is unknown. The disease is more common among white males 60 to 69 years of age, but younger and older people also can develop the disease. In about 5% to 10% of individuals with ALS, the disease is inherited, with one parent carrying the faulty gene. The diagnosis is primarily based on symptoms and signs, and a series of tests to rule out other diseases.

ALS usually begins with small, local, involuntary muscle contractions in the forearms and hands. As the disease progresses, the patient has difficulty with speech, chewing, swallowing, and breathing. In most cases, the disease does not affect a person’s personality, intelligence, or memory, nor does it affect the ability to see, smell, taste, hear, or recognize touch. The first drug treatment for the disease is riluzole (Rilutek), which reduces damage to motor neurons and prolongs survival, especially in patients with difficulty swallowing. Other palliative treatments include attempts to keep the individual as comfortable as possible and to help with pain, depression, sleep disturbances, and constipation. Death from failure of the respiratory muscles usually occurs within 3 to 5 years after the onset of symptoms.

Bell’s palsy

Bell’s palsy is a temporary facial paralysis. It results from inflammation and edema of cranial nerve VII, which in turn are caused by a viral infection (e.g., herpes simplex or Epstein-Barr virus). The condition occurs suddenly, and symptoms reach their peak within 48 hours. The disorder usually subsides spontaneously over several weeks to months. Symptoms range in severity from mild weakness to complete paralysis on the affected side, depending on the degree of nervous involvement. The patient can experience facial twitching, eyelid drooping, excessive tearing of the affected eye, and drooping of the mouth with drooling of saliva. The patient is unable to close the eye on the affected side completely and may have taste disturbances. The antiviral drug acyclovir may be prescribed, in addition to prednisone to reduce the inflammation and control edema. The physician recommends an eye patch to protect the exposed eye, especially at night, to prevent corneal abrasions.

Peripheral neuropathy

Peripheral neuropathy is not a disease in itself, but rather a condition of peripheral nerve dysfunction that can have more than 100 different known causes. It can be cryptogenic or idiopathic, which means that the underlying cause cannot be identified. Conditions that can cause peripheral neuropathy include diabetes mellitus, human immunodeficiency virus (HIV) infection, nutritional deficiencies, and neurologic side effects of some medications. Symptoms usually affect the legs and arms and can include muscular weakness and pain or sensory disturbances such as burning, numbness, and tingling.

Symptoms can vary widely from person to person in both number and severity. Patients often feel extremely frustrated when they try to explain to the physician the abnormal sensations they are experiencing. Peripheral neuropathies can result from damage or injury to any portion of the neuron. Treatment of peripheral neuropathy is most effective when the causative condition is diagnosed and then treated successfully. Encouraging a healthy lifestyle, including weight control, exercise, a nutritious diet, and limiting or avoiding alcohol, helps control the physical and emotional effects of peripheral neuropathy.