Formula Medical Group
Apple Valley, CA

James Krider, MD

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Lethargy - Hypersomnia

Lethargy is a condition of drowsiness or indifference that is usually a sign of chronic fatigue or weakness after a prolonged illness. It may sometimes indicate the beginning of a state of stupor, a more serious condition that is defined as partial unconsciousness.

Causes of lethargy

Brain cancer and tumors
If there is a tumor on the brain, whether or not it is cancerous, the pressure it causes as it grows can produce a wide variety of symptoms. In addition to lethargy and drowsiness, these may include headaches, vomiting, muscle weakness that is often limited to one side of the body, failing vision, a lack of balance and coordination, double vision, and personality changes.

Cerebral palsy
Because of damage to the motor centers of the brain, a child with cerebral palsy has little control over his or her muscular motions. Many children have other related complications, including lethargy; mental retardation; hearing, vision, and speech defects; learning disorders; and behavioral problems. Symptoms in infants may include convulsions, twitching, spasticity of the arms and legs, lethargy, excitability, high-pitched crying, partial facial paralysis, lack of awareness and alertness, and slow development.

Down's syndrome and retardation
There are many causes of mental retardation, which can range from profound to mild. Down's syndrome, a congenital abnormality that may be accompanied by other problems and birth defects, is one of the more common. It is often difficult to diagnose mental retardation until a child reaches school age, unless there are characteristic facial and other abnormalities as in Down's syndrome, or the retardation is severe. A mentally retarded infant may be lethargic, and feeding and other skills may develop more slowly than usual.

Sometimes called "sleeping sickness," encephalitis is an infection (usually viral) that produces brain inflammation and is characterized by lethargy, drowsiness, and stupor. There also may be a high fever and severe

Infections such as mononucleosis or encephalitis produce lethargy.

headache. The encephalitis may result from another infection such as measles, mumps, or chickenpox, or it may be caused by some other virus or infectious agent. It is a serious disease that may require hospitalization, but early treatment, often with antiviral drugs, has substantially reduced mortality from encephalitis.

Head injuries
Concussions, skull fractures, and other serious head injuries often result in lethargy or extreme drowsiness. The lethargy often results from bleeding into the brain or brain swelling — conditions that require immediate treatment to prevent permanent brain damage or even death. Drowsiness or an inability to rouse a person to full alertness after a head injury is a warning sign to seek emergency care.

Mononucleosis, a viral illness, affects mostly adolescents and young adults. Its symptoms range from barely noticeable to severe, and may include fever, headache, sore throat, and swelling of the lymph nodes. Most people who have mononucleosis also feel listless and lethargic.

Reye's syndrome
Reye's syndrome is a serious illness that strikes children and adolescents. It usually occurs during recovery from a viral illness, such as chickenpox or a bout of the flu, and is characterized by brain inflammation and swelling as well as development of fatty streaks in the liver and other internal organs. Initial symptoms include persistent vomiting and aggressiveness or other mental changes. As the brain swelling progresses, the child becomes lethargic and may lapse into a coma.

Also known as German measles, rubella is a mild viral illness in children, but in pregnant women it can result in serious birth defects in the unborn baby. Besides the characteristic rash, adults may

experience slight lethargy and headache. Vaccination can prevent rubella.

This is a medical emergency involving a failure of the blood to circulate adequately enough to keep the body functioning. Shock can be the result of trauma, such as severe wounds, broken bones, massive bleeding, or extensive burns. It can also be caused by dehydration, an allergic reaction to an insect sting, an overwhelming infection, a heart attack, or poisoning. Symptoms include pallor, dry mouth, and cold, clammy skin. The lips, nails, and fingertips may turn blue. The person may be anxious at first but then becomes lethargic.

Thyroid deficiency
When the thyroid gland fails to produce adequate thyroid hormone, a condition called hypothyroidism results. It is marked by a slowdown in all metabolic and bodily functions. Lethargy, apathy, and sluggishness, along with constipation, dry skin, brittle hair, a husky voice, and a slow pulse rate and reflexes, are characteristic symptoms. Some patients also develop a goiter. The condition is readily treatable with thyroid replacement hormone.

Advice about lethargy

  • Don't attempt to diagnose and treat lethargy on your own. Many people mistakenly think their lack of energy is a sign of a vitamin deficiency and resort to self-treatment. This can delay proper treatment.
  • Anyone who has sustained a head injury or blow to the head should report it to a doctor, especially if there is drowsiness or lethargy.
  • If you think your baby is lethargic or slow to develop, discuss it with your pediatrician. All children develop at different rates, and some are more active than others. But the lethargy also may be a warning sign.
This article was last reviewed November 8, 2005 by Dr. James Krider.
Reproduced in part with permission of Home Health Handbook.
Cancer, brain
Cerebral palsy
Down's syndrome
Encephalitis, viral
Head injuries

Reye's syndrome
Thyroid deficiency

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