Arnold Chiari malformation: types, symptoms and main causes

Rare or infrequent diseases (RD) are those that have a low prevalence in the population. To be considered rare, a disease has to affect fewer than 5 out of 10,000 inhabitants at any given time and place.

These data somewhat contradict the reality observed at a practical level, since the World Organization of Health (WHO) estimates that there are about 7,000 rare diseases that affect 7% of the population global. Of course, we are facing a not inconsiderable figure.

Today we bring you one of these rare pathologies that, at the beginning of the 20th century, was estimated to have a prevalence of 1 in every 1,000 newborns. This figure has not remained valid over time because, unfortunately, with new diagnostic techniques it has been shown that it is much more common than previously believed. Immerse yourself with us in the world of patients with Arnold Chiari malformation.

• Related article: "Lissencephaly: symptoms, causes and treatment"

What is the Arnold Chiari malformation?

Arnold Chiari malformation is a generally congenital disease, which consists of

an anatomical abnormality at the base of the newborn's skull. This pathology is characterized by the descent of a part of the cerebellum or almost entirely through the foramen magnum (foramen magnum) to the cervical canal.

In other words, when a part of the skull is smaller than normal or deformed, the cerebellum is pushed into the foramen magnum and the spinal canal. This causes a series of characteristic symptoms in the patient, which are due to the following reasons:

• As part of the cerebellum moves towards the cervical canal, it produces pressure on all nerve endings, a fact that causes several symptoms.
• This cerebellar descent acts as a "plug", which causes an accumulation of cerebrospinal fluid and triggers other pathologies.

This rare disease, of a disabling and progressive nature, affects 0.5% of the world population, 80% of patients being female. Beyond the seriousness of the most pronounced cases, various informative portals affirm that many children with this anomaly do not realize that they have it, since they never present symptom.

Types

Talking about the symptoms of the Arnold Chiari malformation is practically impossible without differentiating the different degrees in several blocks, since It is estimated that this group of malformations in the central nervous system group more than 100 different clinical signs. Therefore, below we show you the different types of the disease, classified according to the parts of the brain that extend into the spinal cavity. Go for it.

Type 0

Patients with syringomyelia fall into this category (a fluid-filled cyst within the spinal cord) with minimal or no evidence of tonsillar herniation (i.e., sliding of the cerebellum). The appearance of this liquid mass responds to a hydrodynamic alteration of the cerebrospinal fluid (CSF) at the level of the foramen magnum.

Type I

Type I is characterized by a dislocation of the cerebellar tonsils (the inner part of the cerebellum) through the foramen magnum (more than 5 millimeters). We are dealing with the most common type of all and, luckily, the patient may not present any obvious symptoms.

Although the general incidence of this type of malformation is not well known, it is estimated that 50 to 70% of the patients present an associated syringomyelia and 10% of the cases are also associated with hydrocephalus, namely, an excessive accumulation of cerebrospinal fluid within the skull. It should be noted that this characteristic type is usually diagnosed from the second-third decade of the patient's life, since symptoms do not usually appear during childhood.

Among the most common signs and symptoms of type I Arnold Chiari malformation we find the following:

• Headaches.
• Loss of balance and dizziness.
• Neck Pain.
• Vision problems and poor motor coordination.
• Difficulty swallowing and hoarseness.
• Change of habits when going to the bathroom.

Anyway, it should be noted that 15 to 30% of patients with Chiari type I have no symptoms at any time but, even so, symptomatic cases can go to medical specialists who address the pathology through surgery.

Type II

We advance on the scale of pathological severity, since type II Chiari malformation usually shows more obvious symptoms and these develop during childhood. In this case a caudal herniation occurs through the foramen magnum of the cerebellar vermis, brainstem, and fourth ventricle, that is, a decrease in cerebellar tissue more pronounced than that of type I. This pathology can be the cause of death during infancy or early childhood and, unlike the two previous variants, requires surgery.

In addition to the symptoms already listed previously, patients with this type present syringomyelia and hydrocephalus in 90% of cases, but a pathology appears accessory: almost 15% of those affected may have spina bifida, that is, a series of defects in the spine and spinal cord due to poor closure and development of the neural tube. Most newborns with severe spina bifida end up dying prematurely.

Type III

We are facing the rarest and most serious type of Arnold Chiari malformation of all. On this occasion, the herniated cerebellum and brainstem enter the cervical spinal canal (often accompanied by the fourth cerebral ventricle) and compress the spinal cord. In addition to all the symptoms mentioned in type I and II, this variety has serious neurological signs associated with it: severe mental and physical decline and seizures, among others.

Type IV

This is the most recently described type. Also known as cerebellar hypoplasia, characterized by underdevelopment of the cerebellum, that is, it is located in its normal position, but some parts are missing. In this case there is no associated tissue hibernation.

• You may be interested in: "Dandy Walker Malformation: Causes, Symptoms, and Treatment"

Other pathologies associated with the Arnold Chiari malformation

As we have already seen in previous lines, syringomyelia and hydrocephalus are pathologies of joint presentation with this malformation, spina bifida being of exceptional appearance. Despite this, we have left ourselves in the inkwell some physiological imbalances associated with this very specific clinical picture. We show them briefly:

• Volume alterations of the posterior fossa: This small space in the skull is usually smaller in Chiari patients.
• Bone alterations: among many others, an example of this is the empty sella turcica, when the pituitary shrinks or becomes flattened.
• Alterations in the ventricles, that is, the four anatomical cavities through which the cerebrospinal fluid circulates. The hydrocephalus already mentioned is an example.
• Meningeal alterations: Several bands of dura mater (outer meningeal) are frequently found, compressing the foramen magnum.
• Brain abnormalities in all types except 0 and I.

As we can see, the Arnold Chiari malformation presents with multiple signs, symptoms and accessory conditions. In general, depending on the severity of the clinical picture, cranial, spinal, ocular, otorhinolaryngological signs, scoliosis, sleep problems, fatigue, axial skeletal pain may appear and all the disorders that we have named you in previous lines. Unfortunately, if there is something lacking in Chiari type II and III patients, it is aggressive and clear symptoms.

Resume

Rare diseases are those that affect less than 5 people per 10,000 inhabitants and, despite being considered as such in several medical portals, the malformation of Arnold Chiari seems to affect 0.5% of the global population, that is, one in every 200 inhabitants, all this without counting the mild type I pathological pictures that will never be diagnosed.

It is impressive to put these results into perspective because, if we take them into account, it is possible that more than one of the Readers who have been interested in this space have met someone with this malformation and have not given account. Of course, the more diagnostic tools advance, the more we realize that a rare disease may not be so rare.

Bibliographic references:

• Chiari Malformation, mayoclinic.org. Picked up on November 13 at https://www.mayoclinic.org/es-es/diseases-conditions/chiari-malformation/symptoms-causes/syc-20354010
• Chiari malformation, National Institute of Neurological disorders and Stroke. Picked up on November 13 at https://espanol.ninds.nih.gov/trastornos/malformaciones_de_chiari.htm
• Chiari Malformation, Radyschildren.org. Picked up on November 13 at https://www.rchsd.org/health-articles/malformacin-de-arnold-chiari/
• Chiari malformation type I, Kidshealth.org. Picked up on November 13 at https://kidshealth.org/es/parents/chiari-esp.html
• Arnold-Chiari malformations, RGS Neurosurgery Unit. Picked up on November 13 at https://neurorgs.net/docencia/sesiones-residentes/malformaciones-de-arnold-chiari/#Chiari_0
• Chiari Malformations, Medlineplus.gov. Picked up on November 13 at https://medlineplus.gov/spanish/chiarimalformation.html
• Martínez-Sabater, A. (2014). Arnold-Chiari malformation: loss of smile. Nursing Index, 23 (4), 256-259.
• Ruiz Hernández, I., & Cano Soler, A. (2010). Arnold Chiari type I malformation. Presentation of a case. Electronic Medical Journal, 32 (5), 0-0.