Smooth-Pursuit Eye Movement - A Convenient Bedside Indicator for Evaluating Frontal Lobe and Intellectual Function

We hypothesized that smooth-pursuit eye movement is related to higher brain functions and that its impairment (iSPEM) could be useful in diagnosing neurological dysfunctions. We prospectively examined 305 patients and studied the relations between iSPEM and five items that reflect intellectual and/or frontal lobe function (dementia, sucking, snouting, hand grasping, elbow flexion response). We divided these patients into four subgroups: group A, patients with cerebellar ataxia as the presenting manifestation and with main lesions in the cerebellum; group B, patients with main lesions in brain regions other than the cerebellum; group C, patients with main lesions in the spinal cord, peripheral nerves, and muscles; and group D, patients with non-organic functional disorders, such as paroxysmal attacks and physical pain. Consequently, iSPEM was significantly (p<0.01) related to impairment in intellectual and frontal lobe functions in patients with cerebral lesions, and it also can be regarded as being equivalent to primitive reflexes. In patients with intellectual or frontal lobe dysfunction, handling (rapid and slow manipulation) of the forearm during daily neurological observations has been found to induce a spontaneous, involuntary, and gradual flexion of the elbow, which we termed as 'elbow flexion response' (EFR), speculating that it could be used as another primitive reflex for diagnosing neurological dysfunction (1). On the basis of clinical observations, we speculated that impairment in smooth-pursuit eye movement (iSPEM) is similarly related to higher brain function and considered that it may also be similar to the primitive reflexes. Here, we tested this hypothesis by prospectively studying the patients who participated in our daily rehabilitation program to identify the relationship between iSPEM and other items reflecting intellectual and/or frontal lobe function.