Arnold-Chiari Malformation I (AM-I) is a congenital anomaly that manifests with cerebellar dysfunction. There is a displacement of cerebellar tonsils into the foramen magnum. Several mood disorders, personality disorders, and intellectual disabilities are associated with AM-I. Borderline personality disorder (BPD) is characterized by symptoms of mood lability, impulsivity, extreme efforts of abandonment, splitting and dysfunctional relationships.

Case Description:
The patient is an early aged adult with a past medical history of AM-I, hypothyroidism, Wolff-Parkinson-White syndrome, and diabetes mellitus type II. The patient was admitted to the hospital after ingesting foreign bodies. He/she presented with mood lability, sad mood, anhedonia, insomnia, panic attacks, ruminative worries, feelings of emptiness, and recurrent suicidal gestures and threats. The patient was eventually diagnosed with borderline personality disorder. This case suggests a possible connection between AM-I and BPD.

Emerging from contemporary research involving the cerebellum, it is important to acknowledge that the current definition of control of fine motor and balance is inadequate. Symptoms associated with AM-I and BPD may be better explained by Cerebellar Cognitive Affective Syndrome (CCAS), a condition that ties the cerebellum with the higher cognitive functioning in the brain.