To the Editor: Arnold–Chiari malformation is a congenital brain anomaly that was first described by the Austrian pathologist Hans Chiari in the late 19th century.¹ It is categorized into three types based on the degree of herniation. Type I malformation is characterized by downward displacement of the cerebellar tonsils through the foramen magnum; while in type II the cerebellar vermis and possibly the fourth ventricle and pons are involved. Type III malformation is the most severe and rarest form and consists of an encephalomeningocele that contains the brainstem and cerebellum.² The malformation is known to produce variable clinical signs and symptoms of cerebellar, cervical and brainstem dysfunction.

There is a paucity of literature pertaining to the neuropsychiatric illnesses associated with Arnold–Chiari malformation. To our knowledge, the only neuropsychiatric disorder reported in humans, in association with Arnold-Chiari malformation is anxiety. We now summarize a case of 53-year-old woman with Arnold–Chiari type I malformation who presented with dementia.

Mrs. A. is a 53-year-old woman who graduated high school and worked for 20 years in administration. She was married and has one daughter. She was able to care for self and her family, and to maintain her social and occupational life.

The patient was generally asymptomatic during childhood, but often manifested with headaches and dizziness. Her brain MRI indicated Arnold–Chiari type I malformation. One year ago, she was admitted to a psychiatric hospital for depression and agitation where her neuropsychological testing suggested frontal dementia with executive dysfunction. She was discharged on citalopram 40mg daily and donepezil 10mg daily.

She was readmitted to the hospital within one year for increased irritability and depression in the context of medications noncompliance. There were no psychotic symptoms. Her Mini Mental State Exam score was 20/30. Montreal Cognitive Assessment score was 14/30. Her orientation, recall, attention, abstraction and trail making were impaired. She was unable to make any denotation of time on the Clock Drawing Test. She scored low on Dementia Rating Scale. Her laboratory tests were all negative. EEG was normal. Her medical history was unremarkable except for complaints of impaired coordination and vertigo. She denied history of substance abuse. The family history was notable for her mother’s dementia. The patient was restabilized on the same medications and discharged with services in the community.

Two case reports of two women, in their early thirties, with type I malformation were described.^{3, 4} Symptoms of anxiety preceded the diagnosis of the malformation in both cases. Grosso et al. reported an association of mental retardation, speech delay, and epilepsy with Arnold–Chiari type I malformation.⁵ In veterinary medicine literature, Shamir et al described symptoms of progressive ataxia, tremors, and dementia in a female African lion. The symptoms appeared at age of 3 months and the lion died 6 months later. Postmortem examination revealed Arnold–Chiari type II malformation.⁶

In our patient, diagnosis of Arnold–Chiari type I malformation is made through a combination of patient history, neurological examination, and Magnetic Resonance Imaging. Her memory impairment and functional decline are consistent with diagnosis of dementia. Symptoms of dementia succeeded the diagnosis of the malformation. Development of early dementia in association with Arnold–Chiari malformation in this patient has been a clinical dilemma. It is likely that Arnold–Chiari malformation and dementia have two separate course of illness. However, the possibility that the malformation might have triggered the neuropathological process of dementia cannot be ruled out. It is reasonable to hypothesize that the neuroanatomical anomaly itself might have caused memory impairment, particularly in a predisposed patient, or traction on the brain might have directly induced memory decline.