Psychotic and major neurocognitive disorder secondary to arnold-chiari type II malformation.

Arnold-Chiari malformations (ACM) represent a constellation of related congenital anomalies at the base of the brain. ACM is a very rare disorder with displacement of the cerebellar tonsils caudally into the foramen magnum. To date, the cause of this malformation is unknown, however, there is some evidence for a defect of the paraxial mesoderm resulting in a shallow posterior cranial fossa and brainstem as well as herniation through the foramen magnum (Caldwell et al. 2009). ACM is characterized by four subtypes. A) type I represents a herniation of the cerebellar tonsils into the foramen magnum, B) type II is associated with a myelomeningocele and hydrocephalus, herniation not only of the tonsils, but also the vermis, fourth ventricle, and pons. Morphologically, aqueductal stenosis, hydromelia and cortical dysplasia occur. C) type III is characterized by an encephalocele, the descent of both cerebellum and brainstem into the spine and internal sac, and D) type IV is associated with cerebellar atrophy (Caldwell et al. 2009). There are many somatic complications caused by ACM such as a pain, motor deficits, hand muscular atrophy, lower cranial palsy, cerebellar ataxia, nystagmus, sensory deficits, dysphagia, and dysphonia (Caldwell et al. 2009). In addition, psychiatric comorbidities such as anxiety and mood disorders occur and affect the functioning and quality of life (Bakim et al. 2013, Mestres et al. 2012). To date, only two case reports describe the association with psychosis (Del Casale et al. 2012, Ilankovic et al. 2006) and only one case mentions a secondary major neurocognitive disorder (Mahgoub et al. 2012).