Weakness

CHAPTER 13

Weakness

Presentation

An older patient, complaining of isolated “weakness” or an inability to carry on her usual activities or care for herself, comes to an acute care clinic or ED, often brought in by family members.

What To Do:

Obtain as much of the history as possible. Speak to available family members or friends, as well as the patient, and ask for details. Are there any new medications that can produce weakness (also consider toxins)? Is the patient weak before certain activities (suggests depression)? Is the weakness located in the limb girdles (suggests polymyalgia rheumatica when there is symmetric joint pain or painful myopathy) (see Chapter 127)? Is the weakness mostly in the distal muscles (suggests neuropathy)? Is the weakness caused by repetitive actions (suggests myasthenia gravis)? Is the weakness unilateral, with slurring of speech or confusion (suggests cerebrovascular accident)?

Obtain a thorough medical history and complete physical examination, including a review of symptoms (e.g., headaches, weight loss, cold intolerance, change in appetite or bowel habits), with a full set of vital signs; also include testing for strength of all muscle groups (graded on a scale of 1 to 5), deep tendon reflexes, and neurologic status. Do a rectal examination for occult stool blood. Order a head CT scan if there is an unexplained change in mental status or there are abnormal neurologic findings. Obtain an MRI or CT with contrast if a structural cord lesion is suspected.

Obtain a spectrum of laboratory tests that include pulse oximetry and/or arterial blood gases, chest radiograph, ECG, cardiac enzymes, urinalysis, blood cell counts, sedimentation rate, and glucose, blood urea nitrogen, and electrolyte levels, which may disclose hypoxia, hypercarbia, myocardial infarction, anemia, infection, diabetes, uremia, polymyalgia rheumatica, hyponatremia, or hypokalemia, which are the most common causes of “weakness.” Tests determining serum phosphate and calcium levels may also be valuable.

Weakness is frequently the only complaint in elderly patients with acute myocardial infarction. Weakness or fatigue is the most common atypical complaint for women with acute myocardial infarction.

Weakness is one of the most common complaints in the elderly with acute urinary tract infection.

If no cause for weakness can be found, probe the patient, family, and friends once again for any hidden agenda (i.e., no one to look after “Granny” while the family goes on vacation), and if none is found, take the patient seriously, be sympathetic, and assure her that serious illnesses have been ruled out at this time. Send the patient home and make arrangements for definite follow-up and further testing if necessary.

What Not To Do:

Do not order any laboratory tests that will not yield results quickly. Stick to tests that will return results while the patient is in the ED or clinic, and defer any long-term investigations to a follow-up physician. Obtaining laboratory results that will never be interpreted or acted on is worse than obtaining none at all.

Do not insist on making the diagnosis in the ED or acute care clinic in every case. The goals during the first visit are to rule out acute, life-threatening conditions and then make arrangements for further evaluation. The primary care physician providing follow-up may consider disorders such as hyperthyroidism, hypothyroidism, chronic fatigue syndrome (or chronic Epstein-Barr virus infection), chronic parvovirus B19 infection, and Lyme disease.

Discussion

The complaint of weakness should not be considered a “minor emergency” until all other significant causes are ruled out. Therefore approach the patient with “weakness” with an open mind, and be prepared to take some time with the evaluation. Demonstrable localized weakness usually points to a specific neuromuscular cause, and generalized weakness is the presenting complaint for a multitude of ills. In young patients, weakness may be a sign of psychological depression, whereas in older patients, in addition to depression, it may be the first sign of a subdural hematoma, pneumonia, urinary tract infection, diabetes, dehydration, malnutrition, heart attack, heart failure, or cancer.

When a patient’s weakness is suspected to be a psychiatric problem, consider the somatoform disorders, such as hypochondriasis, anxiety and sleep disorders, malingering, depression, and factitious illness (e.g., Munchausen syndrome). (These diagnoses should be avoided until all other organic causes have been ruled out.)

It is important to exclude Guillain-Barré syndrome, which is one of the critical, life-threatening causes of weakness. The pattern is not always an ascending paralysis or weakness but usually does depress deep-tendon reflexes. Botulism is another condition that must be excluded through the history or observation. Patients suffering from these sorts of neuromuscular weakness are in danger when they cannot breathe. Pulmonary function studies, such as pulse oximetry, capnography, blood gases, peak flow, or vital capacity, can be helpful in identifying patients who might be close to severe respiratory compromise.

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