The grasp reflex and related prehensile phenomena were investigated in two studies. In Study 1, 491 patients consecutively admitted to the neurological wards of our department were tested with a standardized procedure. Grasping was found in 8% of brain-damaged patients and occurred predominantly in patients with single (14 cases) or multiple (10 cases) hemispheric lesions, accompanied by stable neurological symptoms. The locus of the lesion was either in the frontal lobe or in the deep nuclei and subcortical white matter. Grasping never occurred when the disease was confined to the retrorolandic regions.

Study 2 was designed to identify the frontal structures responsible for grasping. Forty-four patients who either showed grasping or had CT scan documentation of frontal damage were investigated. Grasping was found in 70% of patients who had involvement of the medial areas and was always associated with damage to the cingulate gyros; the supplementary motor cortex was less consistently encroached upon. It also occurred following damage to the lateral motor and premotor areas, but only in 26% of cases. A few patients with grasping had deep lesions.

The clinical analysis of the symptom showed that it usually affected both hands, even when the lesion was unilateral, and that in most patients it did not manifest itself as a forced phenomenon, but could be modified by will, although it showed up again as soon as the patient's attention was diverted. Groping was more rarely found and the so-called grasp reaction was unusual. No hemispheric asymmetry in the occurrence of this set of phenomena was apparent.

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