A new form of herniation: the Chiari V malformation

Abstract

The Chiari malformations (CM) were first described by Hans Chiari roughly a century ago. Most of these malformations result in herniation of part of the cerebellum and brain stem into and through the foramen magnum. This herniation may cause impingement on the structures in the foramen magnum and upper part of the spinal canal with possible blockage of cerebral spinal fluid. Symptoms may include headache, neck pain, numbness of the extremities, dysphagia, nausea, and vomiting. Often the severity of the symptoms increases with the severity of the malformation [4]. Chiari malformation can be congenital or acquired. Congenital forms are thought to be caused by structural malformations early in fetal life due to either genetic mutations or nutritional deficits. Within the two different groups of CM, further classifications exist. The types are characterized by their severity of the malformation. Type 0 CM, described by Iskandar et al., represents absence of frank tonsilar herniation but syringomyelia that resolves following posterior fossa decompression [6]. Type I CM is the most common and is characterized by the protrusion of the cerebellar tonsils into the foramen magnum but without the brainstem. Type 1.5 CM has recently been described in a group of children as caudal protrusion of the brain stem and cerebellar tonsils [3]. Type II is the protrusion of both the brain stem and cerebellar vermis into the foramen magnum and is seen most often in patients with myelomeningocele and type III is the type II malformation with the addition of an occipital or high cervical myelomeningocele [4]. Type IV CM is classified when there is incomplete or underdevelopment of the cerebellum and is therefore not a form of hindbrain herniation. Herein, we describe, the first to our knowledge, a patient presenting with herniation of the occipital lobes into the neck.