F95 vs F98
F98.4 — Stereotyped movement disorders
Distinguish a tic (F95) from a stereotyped movement (F98.4), using the character of the movement — sudden, rapid, non-rhythmic, and involuntary versus rhythmic, sustained, and voluntary-seeming — rather than the movement's severity or social visibility.
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Show overlap — what both share
Both tics and stereotyped movements are repetitive, non-purposeful-looking movements that can appear in the same age group and can both be exacerbated by stress or excitement, so surface repetitiveness alone does not distinguish them.
Show decisive evidence
- F95 tics are sudden, rapid, and non-rhythmic, experienced as involuntary though they can often be suppressed briefly with effort, and characteristically diminish during absorbing activity and disappear during sleep.
- F98.4 stereotyped movements are rhythmic, sustained, and often self-soothing (such as body-rocking or head-banging), appearing more voluntary in character and not sharing a tic's sudden, non-rhythmic quality.
- A movement that is abrupt, brief, and non-rhythmic, worse with stress and absent in sleep, favours F95.
- A movement that is rhythmic, sustained over a longer period, and appears to serve a self-soothing function favours F98.4.
What weakens F95: A rhythmic, sustained, voluntary-seeming quality weakens F95 in favour of F98.4; a sudden, non-rhythmic, suppressible-but-involuntary quality weakens F98.4 in favour of F95.
Show duration / course
F95's fourth character is decided partly by duration (under versus at least 12 months) together with type (motor, vocal, or combined); F98.4 instead requires a persistent, not transient, rhythmic pattern without the same duration-based subdivision.
Show exclusions / context
Per each category's own exclusions_distinctions entries, a genuinely tic-like presentation (sudden, non-rhythmic, involuntary) is directed to F95 rather than F98.4, and a rhythmic, sustained, voluntary-seeming pattern is directed to F98.4 rather than F95.
Show information still needed
Whether the movement's character is sudden and non-rhythmic (favouring F95) or rhythmic and sustained (favouring F98.4), independent of how severe or socially noticeable it is.
Show the common trap
Classifying any repetitive childhood movement as a tic without checking whether its rhythmic, sustained, self-soothing character actually fits a stereotyped movement disorder instead.
Mini challenge — practise this distinction
Apply the discriminating evidence above to a fresh case before checking the full feedback.