Obstruction (Blocking)
Obstruction is an irregular, unpredictable hindrance to voluntary movement, in which a person may be unable to begin or continue an action at one moment and then carry it out with no difficulty shortly afterward. It is the motor equivalent of thought blocking, and gives movement a stiff, halting, disjointed quality rather than the smooth, steady slowing seen in psychomotor retardation.
This has traditionally been distinguished from psychomotor retardation by its irregular, unpredictable quality: retardation is like a steady, uniform slowing of movement, while obstruction is like an intermittent hindrance that can appear and disappear even within a single attempted action.
Also known as
- Sperrung
- The German term for the same phenomenon, used interchangeably with obstruction and blocking.
Recognition features
- A person may begin a movement, stop partway through, and either resume or abandon it, in an unpredictable, irregular pattern
- Can affect not only voluntary actions but also habitual and reactive movements, such as failing to brush away an insect or turn toward a speaker
- A characteristic delayed response pattern, in which the person answers a question only at the very last moment, sometimes just as the examiner is about to give up and turn away
- The effort needed to overcome an obstructed movement does not correspond to any change in muscle tension, suggesting the difficulty lies in initiating the act itself rather than in the muscles involved
Eliciting it at interview
- Ask the person to carry out a simple voluntary movement and observe carefully for hesitation, stopping partway, or unpredictable delay before completion
- Note whether an apparently stuck movement suddenly completes quickly, as though breaking through a barrier, which is a recognised pattern
- Ask a question and wait patiently rather than repeating it immediately, since a delayed answer arriving only as the examiner is about to move on is a specific and useful sign to watch for
Distinguishing features
- Differs from psychomotor retardation, which is a steady, uniform slowing of all movement, whereas obstruction is an irregular, unpredictable hindrance that can come and go within a single action
- Differs from negativism, in which the failure to act reflects an apparently motiveless resistance, whereas obstruction reflects a genuine difficulty in carrying the act through rather than active opposition
- Its motor pattern closely parallels thought blocking, the equivalent disturbance affecting the flow of thought rather than movement
Common misconceptions
- That obstruction reflects deliberate non-cooperation; the difficulty appears to be involuntary and unrelated to the person's underlying willingness to engage
- That obstruction is the same as simple slowness; its hallmark is the irregular, unpredictable, start-stop quality rather than a uniformly reduced pace
Related phenomena
Disorders of Reactive Movements · Thought Blocking · Psychomotor Retardation · Ambitendency · Catalepsy · Perseveration of Posture · Stupor
Practice this
A patient begins to reach for a cup, stops abruptly partway through the movement for no apparent reason, and then completes the action with no difficulty a few moments later, this pattern occurring unpredictably across several different actions during the interview. What is this? · A severely depressed patient moves, speaks, and thinks noticeably slowly and consistently throughout the entire interview, with no sudden stops or unpredictable interruptions, simply a uniform, steady slowness across everything he does. Before revealing the answer: is this obstruction? · A patient's movements are slowed or hindered. Before revealing the answer, decide what distinguishes obstruction from psychomotor retardation. · You notice a patient's movements are being interrupted in an unusual way. Before revealing the answer, decide how you would assess whether this is obstruction. · Explain why obstruction is described as closely paralleling thought blocking, and why this parallel is clinically useful.
Illustration
Asked to raise his arm, a 36-year-old man with catatonia lifts it partway, stops completely for nearly a minute with his arm suspended in mid-air, and then suddenly completes the movement in one quick motion, as though something had abruptly stopped blocking it.
References
- Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 8, 'Motor Disorders'.