Schemazia Distortion
Schemazia distortion is a general term for a family of experiences in which the felt size of a body part, or of the whole body, no longer matches its actual physical size. A limb, or the body as a whole, can feel much larger or much smaller than it is, or in more severe cases can lose any distinct felt sense of size at all.
This has traditionally been framed as a distortion of the size dimension specifically within the body's internal working map, distinguishing it from disturbances that affect ownership or spatial location rather than felt size.
Also known as
- Hyperschemazia
- The felt size of a body part is exaggerated, most often to feel much larger than it actually is.
- Hyposchemazia
- The felt size of a body part is diminished, most often to feel much smaller than it actually is.
- Aschemazia
- A body part or, in its most extreme form, the whole body loses any felt sense of size or shape at all, rather than being felt as merely bigger or smaller.
Recognition features
- A felt mismatch between the actual size of a body part and how large or small it feels to the person experiencing it
- Can affect a single limb, one side of the body, or the body as a whole
- May fluctuate over minutes or hours rather than being constant
- The person usually retains insight that the distortion is a subjective sensation rather than a real physical change
Eliciting it at interview
- Ask specifically and concretely: "Does any part of your body ever feel like it has changed size — bigger, smaller, or somehow lost its usual shape — even though you know looking at it that it hasn't actually changed?"
- Establish which body parts are affected and whether the distortion is constant, intermittent, or tied to particular triggers such as migraine or fatigue
- Clarify insight directly, since retained awareness that the sensation is not literally true is an important distinguishing detail
Distinguishing features
- Differs from a delusion about body size in that the person usually recognises the felt change as a subjective distortion rather than holding it as a fixed, unshakeable belief
- Differs from paraschemazia, which involves the sense of an extra or altered body part rather than a change in the felt size of an existing one
- Differs from anosognosia, which concerns unawareness of a genuine deficit rather than a distorted sense of size
Common misconceptions
- That these experiences always indicate a severe or progressive brain disease; transient versions are well described alongside migraine and are not necessarily signs of serious underlying pathology
- That hyperschemazia and hyposchemazia are opposite disorders rather than two ends of the same underlying disturbance of the felt sense of body size
Related phenomena
Practice this
A patient reports that her right leg suddenly feels enormous, several times its actual size, though she knows objectively that it looks and measures the same as always. What is this? · A patient with left-sided paralysis following a stroke insists nothing is wrong with her arm and offers a vague, confident explanation for why she is not moving it when asked, showing little concern about the situation. Before revealing the answer: is this schemazia distortion? · A patient describes a felt change in how large a body part seems. Before revealing the answer, decide what distinguishes schemazia distortion from anosognosia. · You suspect schemazia distortion in a patient. Before revealing the answer, decide how you would assess for this. · Explain why schemazia distortion is described as a family of experiences rather than one single, fixed pattern.
Illustration
During the aura preceding a migraine, a 24-year-old woman reports that her right hand suddenly feels as though it has swollen to twice its normal size, filling her entire field of awareness, even though she can see it looks completely normal. The sensation fades within twenty minutes as the headache sets in.
References
- Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 3, 'Disorders of Perception'.