Arnold Chiari malformation: types, symptoms and main causes

Rare or rare diseases are those that have a low prevalence in the population. To be considered rare, a pathology must affect less than 5 inhabitants in 10,000 at a given time and place.

These data somewhat contradict the practical reality, since the World Health Organization (WHO) estimates that there are around 7,000 rare diseases that affect 7% of the world’s population. Of course, we are faced with a sizeable figure.

Today, we present to you one of these rare pathologies which, at the beginning of the 20th century, was estimated at a prevalence of 1 per 1000 newborns. This figure has not retained its validity over time because, unfortunately, new diagnostic techniques have turned out to be much more common than previously thought. Immerse yourself with us in the world of patients with Arnold Chiari malformation.

    What is Arnold Chiari’s malformation?

    Arnold Chiari’s malformation is a generally congenital disease, which consists of an anatomical change at the base of the newborn’s skull. This pathology is characterized by the descent of part or all of the cerebellum through the large foramen (occipital foramen) to the cervical canal.

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

    • By moving part of the cerebellum towards the cervical canal, it puts pressure on all of the nerve endings, causing several symptoms.
    • This cerebellar descent acts as a “plug”, which causes an accumulation of cerebrospinal fluid and triggers other pathologies.

    This rare disease, debilitating and progressive, affects 0.5% of the world’s population, Be 80% of patients. Beyond the severity of the most pronounced cases, several informative portals indicate that many children with this anomaly do not realize that they are suffering from it because they never show symptoms.


    Talking about the symptoms of Arnold Chiari’s malformation is practically impossible without differentiating the different degrees into several blocks, such as this group of malformations in the central nervous system group is estimated to have more than 100 different clinical signs. Therefore, below we show you the different types of diseases, cataloged according to the parts of the brain that extend into the spinal cavity. Let’s do this.

    type 0

    Patients with syringomyelia fall into this category (A fluid-filled cyst inside the spinal cord) with minimal or no tonsillar hernia (i.e., the appearance of this fluid mass responds to a hydrodynamic alteration of the cerebrospinal fluid (CSF) at the level of the large foramen.

    Type I.

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

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

    The most common signs and symptoms of Arnold Chiari type I malformation are:

    • Headache.
    • Loss of balance and dizziness.
    • A sore throat.
    • Vision problems and poor motor coordination.
    • Difficulty swallowing and hoarseness.
    • Change of habits when going to the bathroom.

    Either way, it should be noted that 15-30% of patients with type I Chiari have no symptoms at any time but, nevertheless, symptomatic cases can go to specialist doctors who treat the pathology with surgery.

    Type II

    We move up the pathological severity scale because Chiari malformation type II usually has more obvious symptoms and these develop during childhood. In that case a complete hernia occurs through the large foramen of the cerebellar vermis, brainstem, and fourth ventricleThat is, a more pronounced decrease in cerebellar tissue than that of type I. This pathology can lead to death in infancy or infancy and, unlike the previous two variants, requires surgery.

    In addition to the symptoms already listed above, patients with this type present with syringomyelia and hydrocephalus in 90% of cases, but an ancillary pathology appears: nearly 15% of affected people can have spina bifida, that is, that is, a series of defects in the spine. and the spinal cord due to poor closure and poor development of the neural tube. Most newborns with severe spina bifida eventually die prematurely.

    type III

    We are dealing with the rarest and most serious type of Arnold Chiari malformation. On this occasion, the cervical hernia and the brainstem are introduced into the cervical medullary canal (often accompanied by the cerebral ventricular chamber) and compress the spinal cord. In addition to all of the symptoms mentioned in types I and II, this strain exhibits associated severe neurological signs: decreased mental and severe physical capacities and seizures, among others.

    Type IV

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

      Other pathologies associated with Arnold Chiari’s malformation

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

      • Posterior fossa volume changes: This small space in the skull is usually smaller in Chiari patients.
      • Bone alterations: among others, the empty Turkish chair, when the pituitary gland shrinks or flattens.
      • Alterations of the ventricles, that is to say of the four anatomical cavities through which cerebrospinal fluid circulates. The hydrocephalus already mentioned is an example.
      • Meningeal changes: There are often several bands of dura mater (outer meninges) that compress the large foramen.
      • Brain abnormalities of all types except 0 and I.

      As we can see, Arnold Chiari’s malformation has multiple incidental signs, symptoms and conditions. In general, depending on the severity of the clinical picture, cranial, spinal, ocular, otolaryngologic, scoliosis, sleep disturbances, fatigue, axial skeletal signs may appear and all the troubles that we have named to you in the previous lines. Unfortunately, if Chiari type II and III patients do not have anything, it is aggressive and clear symptoms.


      Rare diseases are those that affect less than 5 people per 10,000 population, and although they are seen as such in various medical portals, Arnold Chiari’s malformation appears to affect 0.5% of the world’s population. this without counting the benign pathological conditions of type I which will never be diagnosed.

      It’s impressive to put these results into perspective because, if you take them into account, it’s possible that more than one of the readers who took an interest in this space encountered someone with this defect and didn’t. Note. Of course, the more advanced the diagnostic tools, the more we realize that a rare disease may not be so common.

      Bibliographical references:

      • Chiari malformation, Retrieved November 13, from
      • Chiari malformation, National Institute of Neurological Disorders and Stroke. Collected November 13 at
      • Chiari malformation, Retrieved November 13, from
      • Chiari malformation type I, Retrieved November 13 from
      • Arnold-Chiari malformations, RGS neurosurgery unit. Collected November 13 from
      • Chiari malformations, Retrieved November 13, from
      • Martínez-Sabater, A. (2014). Arnold-Chiari malformation: loss of smile. Nursing Index, 23 (4), 256-259.
      • Ruiz Hernández, I., and Cano Soler, A. (2010). Arnold Chiari type I malformation. Presentation of a case. Electronic Medical Journal, 32 (5), 0-0.

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