Atypical Frontal Release Signs in Acute Anterior Cerebral Artery Infarction and Striatal Dopaminergic Dysfunction: A Case Report.

Introduction: Dystonic hand postures are uncommon in patients with frontal lobe infarction. Here, we report the first case of a patient with frontal lobe infarction presenting with unique dystonic hand postures-specifically, a pointing gun posture and full-finger extension posture-in combination with frontal release signs.

Case report: A 68-year-old man with a prior diagnosis of probable Parkinson disease acutely developed speech and communication impairment, along with reduced voluntary motor function in the right lower extremity. Neurological examination revealed apathy, motor and sensory aphasia, and flaccid paralysis of the right lower limb. Brain magnetic resonance imaging showed an ischemic stroke involving the left superior frontal gyrus, cingulate gyrus, and corpus callosum. Dopamine transporter single-photon emission computed tomography revealed reduced tracer accumulation in the left striatum. Ten days after stroke onset, the patient exhibited a pointing gun posture in the right hand. A repeat neurological examination revealed a grasp reflex. Removing grasped objects led to a transient index finger extension with flexion of the other fingers or a transient full extension of all fingers. The former resembled a pointing gun posture, while the latter, a newly described phenomenon, was termed the full-finger extension posture. In addition, groping movements with the pointing gun posture were observed.

Conclusion: Atypical frontal release signs, including the pointing gun posture and full-finger extension posture, may reflect specific thalamocortical excitation resulting from a combination of contralateral striatal dopaminergic denervation and frontal lobe infarction involving the supplementary motor area.