Onset may be sudden and without apparent cause, for example a sudden attack of acute vertigo. There is usually a history of infection of the upper respiratory tract or, occasionally, the gastrointestinal tract. All cases have low grade pyrexia (up to 38 deg C) usually subsiding within a week.
Subsequently there is persistent and profound fatigue, accompanied by a medley of symptoms such as headache, giddiness and a number of muscle symptoms such as pain, cramp, twitching, tenderness and weakness (especially after exercise). Other symptoms include paraesthesia, frequency of micturition [urination], blurred vision and/or diplopia, hyperacusis (sometimes alternating with deafness or normal hearing), tinnitus, fainting attacks which may be the result of hypoglycaemia and a general sense of "feeling awful".
The Established Syndrome
Once the syndrome is fully established there are three groups of symptoms:
Muscle fatiguability. Even after a minor degree of physical excercise, 3 or more days may elapse before full muscle power is restored. This feature is unique and is the "sheet anchor" of diagnosis. In moderate cases there may be normal muscle power in remission.
Muscle spasm and twitching. In severe cases there may be swollen and very tender bands of muscle including minute focii of exquisite tenderness in trapezii and gastrocnemii (the muscle groups most commonly involved).
Hypersensitivity to climactic change.
Ashen grey facial pallor, 20 to 30 minutes before patient complains of being ill
Impairment of memory
Impairment of powers of concentration
Other Common Features
Using the wrong words
Alteration to sleep rhythm or vivid dreams
Frequency of micturition