Motor

Forced Grasping

Forced grasping is demonstrated when a patient is explicitly instructed not to shake the examiner's offered hand on future occasions, but nonetheless continues to do so every time the hand is offered, despite repeated reminders of the instruction. It is most common in catatonia, but is also seen in dementia. It should be distinguished from the grasp reflex, a genuinely neurological sign in which an object placed in the hand is automatically grasped, which points toward a different, more localising significance.

This has traditionally been elicited with a specific test: the examiner offers a hand to shake, then explains that the patient should not take it on future occasions, talks for a few minutes, and offers the hand again; forced grasping is present if the patient shakes it anyway, despite the clear prior instruction.

Recognition features

• The patient shakes an offered hand despite having just been explicitly instructed not to do so
• The behaviour persists across repeated offers, despite the instruction remaining in place throughout
• Most commonly seen in catatonia, and also occasionally in dementia
• Should be distinguished from the grasp reflex, a neurological sign with a different clinical significance

Eliciting it at interview

• Offer a hand for the patient to shake; once shaken, explain clearly that the patient should not take the hand on any future occasion; continue the conversation for a few minutes and then offer the hand again
• Note whether the patient shakes the hand again despite the clear instruction, and whether this persists on further repetition
• Distinguish carefully from the grasp reflex by checking whether the response is to a socially offered hand and an explicit instruction (forced grasping) or to any object placed directly in the palm, including outside a social context (grasp reflex)

Distinguishing features

• Differs from the grasp reflex, in which any object placed in or drawn across the palm is automatically grasped regardless of instruction or social context; a unilateral grasp reflex in a fully conscious patient points to a frontal lobe lesion on the opposite side, while a bilateral grasp reflex or one occurring with clouded consciousness suggests more widespread cerebral disorder
• Differs from the magnet reaction, in which the hand follows a stimulus (such as an examiner's withdrawing finger) as though drawn by magnetism, a specific variant of groping response related to the grasp reflex rather than to forced grasping itself
• Differs from automatic obedience in involving persistence of an action against an explicit instruction, rather than compliance with an instruction regardless of its consequences

Common misconceptions

• That forced grasping is the same as the grasp reflex; the two are explicitly distinguished in classical teaching, with different eliciting methods and different underlying clinical significance
• That forced grasping reflects the patient simply forgetting the instruction; the repeated, consistent nature of the response across multiple offers, despite reminders, points to something more specific than ordinary forgetfulness

Related phenomena

Automatic Obedience · Cooperation (Mitmachen) and Mitgehen

Diagnostically relevant to

Schizophrenia (catatonic presentations) (links open the DSM-5 Learning Lab)

Practice this

A patient is explicitly told not to shake the examiner's hand on future occasions, yet continues to shake it every single time it is offered, despite the instruction being repeated before each attempt. What is this? · An examiner asks a catatonic patient to stand on one foot for as long as possible; the patient does so despite it becoming visibly painful, and continues to comply fully each time the same uncomfortable instruction is repeated, without ever refusing or adjusting. Before revealing the answer: is this forced grasping? · A patient's behaviour does not match a given instruction. Before revealing the answer, decide what distinguishes forced grasping from automatic obedience. · You suspect a patient shows forced grasping. Before revealing the answer, decide how you would assess for this. · Explain why it matters clinically to distinguish forced grasping from the neurological grasp reflex.

Illustration

A clinician assessing a patient with catatonia offers his hand, which the patient shakes, and is then told clearly that he should not shake it again; several minutes later, when the hand is offered once more, the patient shakes it just as before, and does so again on a third attempt despite a further reminder each time.

References

• Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 8, 'Motor Disorders'.