Arnold-Chiari syndrome

Generality

Arnold-Chiari syndrome is a collection of signs and symptoms caused by a rare malformation of the posterior cranial fossa; in the subjects who are affected, this structure is not very developed, so the cerebellum exits (protrudes) from its natural seat through the occipital hole, located at the base of the skull.

There are four different types of Chiari malformation; the parameter that distinguishes one type from another is the degree of protrusion, hence the proportion of cerebellar material involved. Type I is the least severe (sometimes it remains asymptomatic for life), while type IV is the most serious; however, starting from type II, the quality of life is compromised.

The symptoms that characterize Arnold-Chiari syndrome are numerous and range from headaches to muscle weakness etc.

To date, there is no cure that can repair the cerebellar malformation, but there are treatments that can help alleviate, at least in part, the symptoms.

What is the Chiari malformation

The Chiari malformation, or Arnold-Chiari syndrome or even more simply Arnold-Chiari, is a structural alteration of the cerebellum, characterized by a downward movement, precisely in the direction of the occipital hole and the spinal canal, of the portion basal cerebellar hemispheres.

In other words, it is a cerebellar hernia, in which part of the cerebellum protrudes from the occipital hole invading the spinal canal.

WHAT IS THE OCCITAL HOLE?

The occipital hole, or foramen magnum, is a large opening located in the lower part of the occipital bone of the skull. This hole connects the spinal canal with the cranial cavity; starting from it, in fact, the elongated marrow and then the spinal cord are placed (proceeding downwards).

Fundamental junction for the circulation of the cefalorachidian fluid (or liquor ), the foramen magno is crossed by the vertebral arteries and by the anterior and posterior spinal arteries.

ORIGIN OF THE NAME

The Arnold-Chiari syndrome takes its name from the two doctors who first described it, Julius Arnold and Hans Chiari.

It should not be confused with Budd-Chiari syndrome, which is a morbid condition affecting the liver.

Causes

Based on the severity of the protrusion and the moment of life in which it originates, the Chiari malformation can be divided into 4 different types, identified by the first four Roman numerals (I, II, III and IV).

The first two types, when compared to the second two, are more common and less serious; in fact, type III and type IV are very rare and incompatible with life.

TYPE I CLEAR MALFORMATION

The Chiari malformation of type I is asymptomatic (ie without obvious symptoms), at least until childhood or late adolescence.

Its cause of origin is to be found in the reduced cranial space: in these conditions, in fact, a part of the cerebellum (precisely the cerebellar tonsil or tonsils located on the lower side), is forced, due to lack of space, to slip into the occipital hole and to take the spinal canal.

Warning: several people with Chiari type I malformations are fine and lead a completely normal life. This is due to the fact that the cerebellar anomaly is not so severe as to cause symptoms or disorders. Therefore, very often, such subjects ignore their condition or become aware of it by pure chance.

TYPE II CLEAR MALFORMATION

The Chiari malformation of type II is a congenital disease, that is, present since birth, and always symptomatic.

Compared to type I, it is characterized by a greater protrusion, which in addition to the cerebellar tonsils also involves a portion of the cerebellum (called cerebellar vermis ) and a venous vessel known as Erofilo's torcular .

Almost always, type II Arnold-Chiari is associated with a particular form of spina bifida called myelomeningocele .

Among the various consequences of this malformation, we note: the blockage of the liquor flow through the occipital hole (which leads to the establishment of a condition called hydrocephalus ) and the interruption of nerve signaling.

Initially, the term Arnold-Chiari referred only to the Arnold-Chiari type II syndrome. Now, it is commonly used for all forms of the disease.

MALFORMATION OF TYPE III CLEARS

Present since birth, the type III Chiari malformation causes serious neurological problems, so much so that it is often incompatible with life. In these cases, in fact, the cerebellum protrusion is marked and for this reason we speak of occipital encephalocele .

Figure: syringomyelia.

From the site: mdguidelines.com

Usually, type III Arnold-Chiari is characterized by hydrocephalus and syringomyelia ; the latter represents a particular condition, characterized by the presence of one or more cysts within the spinal canal.

MALFORMATION OF TYPE IV CLARES

Type IV Chiari malformation is characterized by the lack of development of a part of the cerebellum ( cerebellar agenesis ).

This anomaly is congenital and absolutely incompatible with life.

ASSOCIATED DISEASES

Doctors and scientists have observed that the following morbid states are also common among individuals suffering from Chiari:

• Hydrocephalus
• Syringomyelia
• Rigid column syndrome
• Severe curvature of the column
• Marfan syndrome
• Ehlers-Danlos syndrome

IS IT A HEREDITARY DISEASE?

The researchers believe that the Chiari malformation may have a hereditary origin, as some recurrence has been reported in the family environment.

However, the genetic conditions that cause the appearance of the disease (ie which and how many genes are involved) and the type of transmission remain to be clarified.

Epidemiology

The precise incidence of Chiari malformation is unknown; this is because several people with type I Arnold-Chiari do not show any symptoms and appear completely normal (so the disease is underdiagnosed).

The few reliable epidemiological researches report that:

• Type I is symptomatic in one child in 100
• Type II is particularly common in populations of Celtic origin
• Women are 3 times more affected than men

Symptoms and Complications

The 4 types of Chiari malformations present different symptoms and signs.

Below is an accurate description of the symptomatology that characterizes types I, II and III.

For type IV, it is impossible to trace symptoms, as it is a condition that inevitably leads to the death of the fetus.

TYPE I CLEAR MALFORMATION

When the type I Chiari malformation is symptomatic, it can cause:

• Severe headaches, whose onset is frequent after coughing, sneezing and excessive strain.
• Neck and / or face pain
• Balance problems
• Frequent dizziness
• Speech problems, such as hoarseness
• Eyesight problems, such as double or blurred vision, pupillary dilation and / or nystagmus
• Difficulty swallowing (dysphagia) and chewing
• Tendency, when eating, to suffocation
• He retched
• Sense of numbness in the hands and feet
• Lack of motor coordination (especially in the hands)
• Restless legs syndrome
• Tinnitus (or tinnitus), that is the auditory disorder for which there is the sensation of perceiving, in the ear, non-existent noises, such as rustling, buzzing, whistling, etc.
• Sense of weakness
• Bradycardia. It is the medical term used to indicate a slowing of the heart rate
• Scoliosis associated with spinal cord disorders
• Abnormal breathing, especially during sleep (sleep apnea syndrome)

TYPE II CLEAR MALFORMATION

The Chiari malformation of type II is characterized by the same type I symptoms, with the difference that these have a more marked intensity and are always present. Furthermore, if it is accompanied by myelomeningocele, the type II Arnold-Chiari also causes:

• Intestinal and bladder disorders: the patient loses control of the anal and bladder sphincters
• Convulsion
• Huge corpus callosum
• Extreme muscle weakness and paralysis
• Deformation in the pelvis, feet and knees
• Difficulty walking
• Severe scoliosis

Spina bifida and myelomeningocele

Spina bifida is a congenital malformation of the vertebral column, due to which the meninges, and sometimes also the spinal cord, come out of their seat (normally they are confined inside the vertebrae).

Myelomeningocele is the most severe form of spina bifida: in patients who are affected, meninges and spinal cords protrude (or hernia) from their vertebral housing and form a protruding sac at the level of the back. This bag, although protected by a layer of skin, is exposed to external insults and is constantly at risk of serious and, in some cases, even lethal infections.

MALFORMATION OF TYPE III CLEARS

People with type III Chiari malformation suffer severe neurological problems (often incompatible with normal life), hydrocephalus and syringomyelia. The latter, characterized by the formation of one or more cysts within the spinal cord, may be due to:

• Weakness and muscular atrophy
• Loss of reflexes
• Loss of sensitivity to pain and environmental temperature
• Stiffness in the back, shoulders, arms and legs
• Pain in the neck, arms and back
• Intestinal and bladder problems
• Extreme muscle weakness and spasms in the legs
• Pain and numbness in the face
• Scoliosis

WHEN TO REFER TO THE DOCTOR?

Type II, III and IV Chiari malformations are visible already in the prenatal age (ie when the affected subject is still in the maternal uterus), through an ultrasound examination.

As regards, instead, the Chiari malformation of type I, it is advisable to seek medical attention as soon as the typical symptoms reported previously appear. It is important to undergo timely checks also because, from the latter, other associated disorders may emerge.

COMPLICATIONS

The complications of the Chiari malformation are related to a worsening of the cerebellar protrusion or to the morbid states associated, therefore to the hydrocephalus, to the myelomeningocele, to the syringomyelia, to the syndrome of the rigid column etc.

The worsening of the protrusion, which is due to a greater pressure of the skull to the damage of the cerebellum, obviously implies an aggravation of the symptomatology.

Diagnosis

The diagnostic tests that allow to establish the degree of protrusion of the cerebellum through the occipital hole (thus establishing the type of Chiari malformation) are:

• Nuclear magnetic resonance (or NMR ). Thanks to the creation of magnetic fields, it provides a detailed image of the cerebellum and spinal canal, without exposing the patient to harmful ionizing radiation.
• TAC . Computed tomography (CT) provides clear images of internal organs, including the cerebellum and spinal cord. During its execution, the subject is exposed to a minimum amount of harmful ionizing radiation.

TACs and MRIs, preceded by a thorough physical examination, are essential for identifying any pathologies associated with Arnold-Chiari.

Table. How and when to diagnose the Chiari malformation.

Treatment

The Chiari malformation is incurable.

Sagittal scan obtained by magnetic resonance FLAIR, showing an Arnold-Chiari malformation with a 7 mm cerebellar tonsil hernia. From the site: en.wikipedia.org

However, there are both pharmacological and surgical treatments, which make it possible to alleviate, at least in part, the symptoms.

PHARMACOLOGICAL THERAPY

Patients with type I Chiari malformation who suffer from headaches and neck and / or face pain may take pain medication .

The choice of the most suitable medicines for the individual case lies with the attending physician; therefore, it is good practice to follow its instructions.

SURGICAL THERAPY

The goal of surgical treatment is to reduce the compression exerted by the skull against the cerebellum and spinal cord.

To succeed in this, there are several procedures, such as:

• The posterior fossa decompression, during which the surgeon removes part of the posterior portion of the occipital bone.
• Spinal cord decompression, via laminectomy (or decompressive laminectomy ). During its execution, the surgeon removes the lamina of the second and third cervical vertebrae. The lamina is the vertebral portion that delimits the hole within which the spinal cord passes.

  NB: sometimes, posterior fossa decompression and decompressive laminectomy are performed simultaneously.

• The decompressive incision of the dura mater . With the incision of the dura mater, or the outermost meninge, the space available to the cerebellum increases and the pressure against it decreases. To cover and protect the crack created by the incision, the surgeon sews a piece of artificial tissue (or collected from another part of the body) onto it.
• The surgical shunt . It is, in fact, a drainage system, consisting of a flexible tube that allows the elimination of the liquor, in the case of hydrocephalus, or the emptying of the cyst, in the case of syringomyelia. Patients with hydrocephalus may have to use the surgical shunt for life.

RISKS OF SURGICAL INTERVENTION

The risks associated with surgery are different. In fact, it is possible that bleeding, damage to the encephalic structures and / or spinal cord, infective meningitis, problems with wound healing and, finally, unusual collections of fluid around the cerebellum occur.

Remember that any encephalic or spinal cord damage occurring during surgery is irreparable.

Therefore, before undergoing any type of intervention, the operating doctor will expose any risks and complications of the procedure (s) needed.

Prognosis

Type II, III and IV Chiari malformations never have a positive prognosis, as, in addition to being incurable, they can cause serious neurological deficits or even be incompatible with life.

The case of the Chiari malformation of type I is different, the prognosis of which varies according to the severity of the symptoms.