Perseveration of Posture
Perseveration of posture is the maintenance, for long periods, of a posture that arose either fortuitously or because the examiner passively placed the patient's body into it. The patient allows the examiner to move their body into strange, uncomfortable positions, and then maintains the resulting posture for at least a minute, and often much longer, without being explicitly asked to hold it there.
This has traditionally been distinguished from waxy flexibility in the quality of resistance felt during the movement itself: in many cases of perseveration of posture there is no resistance at all as the examiner moves the limb, but the muscles that fix the new position can be felt to contract as the examiner releases it, which is different from the smooth, wax-like plastic resistance felt throughout the movement in true waxy flexibility.
Recognition features
- A posture, once placed there by the examiner or arising fortuitously, is maintained for at least a minute and often considerably longer, without any explicit instruction to hold it
- No resistance is typically felt while the examiner is moving the limb into position, distinguishing it from waxy flexibility
- As the examiner releases the limb, the muscles fixing it in the new position can be felt to contract, confirming active maintenance rather than passive floppiness
- May occur together with obstruction, in which case a partly completed voluntary action can also be maintained in its mid-flight position
Eliciting it at interview
- Gently move a limb into an unusual, mildly uncomfortable position and observe how long the patient maintains it once released, without giving any instruction to hold the posture
- Feel carefully for resistance during the movement itself: its absence, combined with a felt contraction on release, points toward perseveration of posture rather than waxy flexibility
- Time the duration the posture is held, since perseveration of posture is typically sustained for at least a minute and sometimes very much longer
Distinguishing features
- Differs from waxy flexibility, which involves a smooth, plastic resistance felt throughout the passive movement itself, whereas perseveration of posture involves no resistance during the movement but a felt contraction only as the examiner releases the limb
- Differs from catalepsy in current usage, where catalepsy is reserved for cases without this contraction-on-release pattern, while perseveration of posture and catalepsy are sometimes used loosely and should be distinguished carefully by this specific criterion
- Can occur together with obstruction, in which case the posture maintained is the specific mid-flight position reached when the obstructed movement stopped
Common misconceptions
- That perseveration of posture and waxy flexibility are simply two names for the same thing; they are distinguished by a specific difference in the quality of resistance felt during, versus only at the end of, the passive movement
- That the patient must be trying to hold the posture deliberately; the maintenance appears to occur without an explicit instruction or intention to do so
Related phenomena
Waxy Flexibility · Catalepsy · Obstruction (Blocking) · Motor and Verbal Perseveration · Stereotyped Posture
Practice this
An examiner passively moves a patient's arm into an unusual, uncomfortable raised position; there is no resistance felt during the movement itself, but when the examiner releases the arm, the patient's muscles can be felt to contract and actively hold the arm in that position for several minutes. What is this? · An examiner passively moves a patient's arm into an unusual position and feels a smooth, even, wax-like resistance throughout the entire movement; once positioned, the arm remains there for several minutes, with the patient not appearing to actively resist at any point. Before revealing the answer: is this perseveration of posture? · A patient's limb, once placed in an unusual position, remains there for an extended period. Before revealing the answer, decide what distinguishes perseveration of posture from waxy flexibility. · A patient maintains an unusual posture for an extended period. Before revealing the answer, decide what distinguishes a stereotyped posture from perseveration of posture. · You suspect perseveration of posture in a patient. Before revealing the answer, decide how you would assess for this. · Explain why the presence or absence of resistance specifically at the moment the examiner releases the limb is described as a useful way of distinguishing perseveration of posture from waxy flexibility.
Illustration
An examiner lifts a catatonic patient's arm into an awkward, raised position above his head, meeting no resistance at all during the movement itself, and on releasing it feels the muscles tighten to hold the arm exactly where it was placed, a posture the patient then maintains, apparently without effort or complaint, for well over five minutes.
References
- Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 8, 'Motor Disorders'.