Cerebellar Tonsillar Ectopia

What is Cerebellar Tonsillar Ectopia?

An un-uniform term used to describe both asymptomatic tonsillar ectopia and Chiari I malformations, Cerebellar Tonsillar Ectopia indicates an inferior position of the cerebellar tonsils. Cerebellar Tonsillar Ectopia denotes all cases including congenital and acquired in which the cerebellar tonsils are below the base of the skull. Cerebellar Tonsillar Ectopia includes asymptomatic and symptomatic cases of all degrees of severity.

What conditions can be encompassed in “Cerebellar Tonsillar Ectopia”?

Low-Lying Tonsils: Low-Lying Tonsils lay slightly below the base of the skull, less than approximately 5mm. In Low-Lying Tonsils, the cerebellar tonsils have a slight downward descent through the foramen magnum. Low-Lying tonsils may also be referred to as Benign Tonsillar Ectopia, but the preferred term is Low-Lying Tonsils, as not all cases with protrusion greater than 5 mm are malignant and not all cases with protrusion under 5mm are asymptomatic.

Chiari I Malformation:

The most common variant of the Chiari Malformations, Chiari I Malformation is characterized by a caudal descent of the cerebellar tonsils through the Foramen Magnum. Diagnosed through the use of an MRI, Chiari I Malformations are more common in females than males and symptoms typically reflect the degree of descent.

Acquired Tonsillar Ectopia:

Often considered a subgroup of Cerebellar Tonsillar Ectopia, Acquired Tonsillar Ectopia is the downward displacement of the cerebellar tonsils. The Caudal displacement of the cerebellar tonsils is secondary to another defined pathological process. This sets Acquired Tonsillar Ectopia apart from Chiari I Malformations and Low-Lying Tonsils.

Tonsillar Herniation:

A type of cerebral herniation, Tonsillar Herniation is characterized by the inferior descent of the cerebellar tonsils below the foramen magnum. Clinicians may often refer to the presence of tonsillar herniation as “coning”.

What are the most common symptoms of Cerebellar Tonsillar Ectopia?

In patients with Cerebellar Tonsillar Ectopia, the most common symptom presented is occipital headaches. Occipital headaches are felt near the base of the skull and can radiate, or spread, to the neck and shoulders. The pain can be described as sharp, brief, throbbing, or even pulsating. Patients often have symptoms worsened by coughing, sneezing, or straining.

Additional symptoms include posterior cervical pain, balance issues, difficulties with speaking or swallowing, or tingling and burning sensations within the fingers, toes, or lips.

In certain cases of Cerebellar Tonsillar Ectopia, primarily in individuals diagnosed with a Chiari I Malformation, a cyst may form in the spinal cord (syrinx), a condition known as syringomyelia. A syrinx can expand over time and cause symptoms of muscle weakness, loss of muscle mass, muscle spasms, abnormal curvature of the spine, and decrease sensations. A syrinx can form due to both congenital or acquired causes.

Congenital causes of a syrinx include:

• Myelomeningocele
• Chiari I Malformation and Chiari II Malformation
• Dandy-Walker Malformation
• Klippel-Feil Syndrome

Acquired causes of a syrinx include:

• Post-Trauma
• Cervical Canal Stenosis
• Post-Inflammatory
• Secondary to a hemorrhage or spinal cord tumor
• Following Vascular Insufficiency

How are conditions of Cerebellar Tonsillar Ectopia treated?

Treatment of conditions associated with Cerebellar Tonsillar Ectopia is directed towards the specific symptoms exhibited by the patient. Treatment plans must be patient specific and typically require a team of physicians from multiple specialties. These physicians may include neurologists, pediatricians, and ophthalmologists. Patients whom exhibit no symptoms typically are regularly monitored by a neurologist to ensure the condition is not progressing. If mild symptoms are present, a neurologist may prescribe pain medications, massage therapy, or reducing the patient’s activities.

Symptomatic Cerebellar Tonsillar Ectopia’s are often treated by surgery. The most common surgery to treat Cerebellar Tonsillar Ectopia is posterior fossa decompression surgery. This procedure relieves pressure and compression on the brainstem by removing small pieces of bone in the posterior skull, and in turn enlarges the foramen magnum.