Ephemeritis is a condition specific to cricketers, recently proved to be caused by unusually retarded growth of the brain, although it had previously been attributed to underdevelopment of the cerebellum or aural failure to audible stimuli.

The condition has many known variants, such as Fast Bowler, Slogger, Inzamam and No-Hands, amongst others. Of these, Fast Bowler Ephemeritis is the most prevalent.

A typical ephemeritic has a brain, on average, 7 times smaller than a healthy cricketer. For most human activity this is more than sufficient, but in a cricket context, an ephemeritic brain can only operate under close supervision and within a limited range of abilities.

Fast bowler ephemeritis:

In cricketing terms, fast bowlers are the most susceptible to the condition due to their aggressive nature and already limited mental capacity. The condition is most apparent when a fast bowler attempts to set his own field, usually after a few overs or in extreme cases, a few balls. The bowler will usually do this in response to stimuli from the brain which in turn shuts off the ability to apply the required action to the desired response. A field change to accommodate a "bouncer trap", for example, will result in a half tracker pulled for six. Fast Bowler Ephemeritis forces the blocking of any error stimuli and the sufferer will repeat the errant thought process until stopped.

The other forms of the condition are, in essence, the same as the Fast Bowler variant but subject to individual circumstances, although there are rare instances of players suffering from multiple forms of the condition. This must not be confused, however, with All Rounder Ephemeritis, which is an extreme and potentially very dangerous variant, especially to the sufferers team mates.