Precision grip in congenital and acquired hemiparesis: similarities in impairments and implications for neurorehabilitation

Abstract

Background: Patients with congenital and acquired hemiparesis incur long-term functional deficits, among which the loss of prehension that may impact their functional independence. Identifying, understanding, and comparing the underlying mechanisms of prehension impairments represent an opportunity to better adapt neurorehabilitation.

Objective: The present review aims to provide a better understanding of precision grip deficits in congenital and acquired hemiparesis and to determine whether the severity and type of fine motor control impairments depend on whether or not the lesions are congenital or acquired in adulthood.

Methods: Using combinations of the following key words: fingertip force, grip force, precision grip, cerebral palsy, stroke, PubMed, and Scopus databases were used to search studies from 1984 to 2013.

Results: Individuals with both congenital and acquired hemiparesis were able to some extent to use anticipatory motor control in precision grip tasks, even if this control was impaired in the paretic hand. In both congenital and acquired hemiparesis, the ability to plan efficient anticipatory motor control when the less-affected hand is used provides a possibility to remediate impairments in anticipatory motor control of the paretic hand.

Conclusion: Surprisingly, we observed very few differences between the results of studies in children with congenital hemiplegia and stroke patients. We suggest that the underlying specific strategies of neurorehabilitation developed for each one could benefit the other.

Keywords: cerebral palsy; fingertip force; grip force; precision grip; stroke.

Figure 1

To achieve a precision grip movement, the goal of the task is sent to an inverse model (1) that generates a motor command. Due to this motor command, a movement of the upper limb is generated. In parallel, a forward sensory and motor model (2) is generated. This forward model predicts the movement induced by the motor command and estimates the sensory feedback of the new state of the hand and arm. It allows comparison with actual feedback (4) and consequently there is an updating of the motor command. Actual feedback emanates from sensors and is transmitted to the feedback controller (4) after sensory processing (3). The red dotted frame represents the feedforward components, and the green frame denotes the feedback components. Both can be affected at different levels in unilateral brain lesions, with consequential impairment to precision grip.

Figure 2

Representation of the grip (red) and load (blue) forces applied on a handheld object during a grip–lift task, as well as the vertical position (lower panel) of the handheld object. The different phases of the grip–lift task are highlighted with dotted lines. T0–T2, the contact between fingers and the object is initiated in a quick succession. T2–T3, preload phase, GF increases prior to LF onset. T3–T4, loading phase, GF and LF subsequently increase in parallel. T5–T6, static phase, followed by the release of the object including a replacement phase (T6–T7) of a subsequent rapid decrease in the grip and load forces (T7–T8) until the thumb and index fingers are released from the object (T8–T9).

Figure 3

Representation of typical traces on the paretic hand of (A) a child with congenital hemiparesis and (B) a stroke patient. T2–T3, preload phase, T3–T4, loading phase, T5 start of static phase.