Having oriented the above discussion to imply that many cases of chronic fatigue have a psychologic, or asthenic basis, it should be emphasized that previously healthy individuals, may have persistent fatigue for years after a severe febrile viral infection. Most of these cases, in our experience, have arisen suddenly, mostly in adolescents and young men, and less often women, who experience overwhelming fatigue during a well-documented and prolonged viral infection. They continue to take interest in activities in which they are able to participate, do not show anxiety or major depressive symptoms, and have the best prognosis, although complete recovery may take up to 5 years. Often these patients are able to define the date on which the illness began. The term postviral fatigue state is most appropriate for this group. Impressive in some of our cases have been severe headaches and orthostatic hypotension, with wide swings in blood pressure resulting in syncope as well as intermittent hypertension. Alcohol intolerance may develop. It would seem that the more ambiguous and less-severe cases of chronic fatigue, particularly those with fibromyalgia, may have a different basis, but this cannot be stated with certainty.
At the present time, the status of the chronic fatigue syndrome is undetermined. The possibility of an obscure endocrine, metabolic or immunologic derangement secondary to a viral infection cannot be dismissed, as discussed by Swartz, but the majority of cases lack such a history and no evidence of a virologic cause has so far held up. Certainly, high levels of cytokines, such as occur after many types of illness and with cancer, and some of the numerous endocrine aberrations are capable of causing fatigue and lethargy. From a neurologic perspective, the hypothalamus is the structure most implicated by the loss of endurance and the presence of associated symptoms such as orthostatic intolerance, tachycardia and some of the endocrine changes enumerated later in the chapter. Treatment, largely unsatisfactory, is discussed further on.
Differential Diagnosis of Fatigue
If one looks critically at patients who seek medical help because of incapacitating exhaustion, lassitude, and fatigability, it is evident that the most commonly overlooked diagnoses are anxiety and depression as described in Chap. 47. The correct conclusion can usually be reached by keeping these illnesses in mind as one elicits the history from patient and family. Difficulty arises when symptoms of the psychiatric illness are so inconspicuous as not to be appreciated; one comes then to suspect the diagnosis only by having eliminated the common medical causes. Repeated observation may bear out the existence of an anxiety state or gloomy mood. Reassurance in combination with a therapeutic trial of antidepressant drugs may suppress symptoms of which the patient was barely aware, thus clarifying the diagnosis. The best that can be done is to assist the patient in adjusting to the adverse circumstances that have brought him under medical surveillance.