Cerebellar Tonsillar Ectopia

What is a Cerebellar Tonsillar Ectopia?

Cerebellar tonsillar ectopia, an un-uniform term used synonymously with tonsillar descent or low-lying tonsils 1. This term usually shows an inferior location of the cerebellar tonsils below the margins of the foramen magnum 2. Many authors use cerebellar tonsillar ectopia as a descriptive term for all cases including congenital and acquired where the cerebellar tonsils locate below the base of the skull. This disorder can cause severe, life-threatening complications during childhood. Cerebellar tonsillar ectopia encompasses some conditions such as low-lying tonsils, asymptomatic tonsillar ectopia, Chiari I malformations, and tonsillar herniation.

Low-lying tonsils usually locate slightly below the base of the skull and measure less than 5 mm. This refers to a subtype of Cerebellar Tonsillar Ectopia in which the cerebral tonsils descend through the foramen magnum. Some authors prefer saying Low-lying Tonsils over benign tonsillar ectopia since not all cases with protrusion cross 5 mm become malignant or asymptomatic. The most common variant of the Chiari Malformations includes Chiari malformation type I, also characterized by a caudal descent of the cerebellar tonsils through the Foramen Magnum.

As a subgroup of Cerebellar Tonsillar Ectopia, Acquired Tonsillar Ectopia describes the downward displacement of the cerebellar tonsils. Another defined pathological process apart Acquired Tonsillar Ectopia from Chiari I Malformations and Low-lying Tonsils. Finally, Tonsillar Herniation describes the inferior descent of the cerebellar tonsils below the foramen magnum.

What Are The Common Symptoms And Causes of Cerebellar Tonsillar Ectopia?

Most patients with Cerebellar Tonsillar Ectopia usually present occipital headaches as a common symptom. Patients usually feel this pain near the base of the skull. This headache may radiate to cause pain in the neck and shoulder. Patients usually describe this pain as sharp, throbbing, brief, or pulsating. These symptoms even get worse by sneezing, straining, or coughing. Additional symptoms of Cerebellar Tonsillar Ectopia may include 3:

  • Posterior Neck Pain
  • Poor coordination
  • Problems with balance
  • Difficulties swallowing and speaking (dysarthria)
  • Fainting episodes
  • Sleep disorders
  • Tingling and burning sensation in the finger, lips, and toes.

The signs and symptoms of patients with Chiari malformation can differ from one person to another. Some individuals may not produce any symptoms or remain asymptomatic while others may develop serious manifestations like neurological deficits. Patients with Chiari malformation can produce abnormalities in the eyes such as double vision, blurred vision, nystagmus, abnormal sensitivity to light or photophobia, and pain behind the eyes.

Individuals diagnosed with a Chiari I Malformation may develop a cyst in the spinal cord (syrinx) called syringomyelia. This cyst can expand over time and produce additional symptoms such as muscle spasm, muscle weakness, abnormal spinal curvature, loss of sensation, loss of muscle mass, etc. A series of causes ranging from congenital to acquired can cause syrinx 4.

Congenital causes of a syrinx include both Chiari I Malformation and Chiari II Malformation, Klippel-Feil Syndrome, Myelomeningocele, etc. Acquired causes of a syrinx include trauma, spinal cord tumor, hemorrhage, vascular insufficiency, spinal stenosis, etc.

How Do Spinal Specialists Diagnose

Cerebellar Tonsillar Ectopia?

Diagnosis of Cerebellar Tonsillar Ectopia depends upon the symptoms of patients and further examinations. Neurosurgeons usually observe abnormal findings upon the neurological examinations. Neurosurgeons may perform several imaging techniques, such as magnetic resonance imaging (MRI), cine MRI and Xrays, to confirm the diagnosis. This condition affects individuals of every race and ethnicity. A study found a more frequent occurrence of Chiari malformation in females than males and symptoms typically reflect the degree of descent 4.

How Do Neurosurgeons Treat a Cerebellar Tonsillar Ectopia?

Treatment of conditions associated with Cerebellar Tonsillar Ectopia usually depends upon the symptoms exhibited by the patient. This requires a patient-specific treatment by a professional medical team from multiple specialties. This team may include neurosurgeons, pediatricians, and ophthalmologists. Patients with asymptomatic Chiari I Malformations do not need treatment. But physicians recommend monitoring this condition regularly to check the progress. Most patients with mild symptoms respond well to non-surgical and conservative treatment. Other treatment protocol includes 5:

  • Medications: This includes the administration of nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants to relieve symptoms of muscle pain.
  • Physical therapy: This includes stretching and light exercises that can reduce pressure on your nerves and relieve minor pains.

Reducing the patient’s activities can also help to recover from mild symptoms. Neurosurgeons usually treat Chiari malformations with headaches with analgesia to control pain. When a patient with Chiari malformation does not respond to conservative treatment, the treating physician will then recommend surgery. Symptomatic Cerebellar Tonsillar Ectopia often requires surgery. The most common surgical procedure for treating Cerebellar Tonsillar Ectopia includes posterior fossa or Chiari decompression surgery. Almost 80% of patients with Cerebellar Tonsillar Ectopia experience a significant improvement in their headaches or neck pain after this surgery.

This procedure includes the removal of a piece of the skull (craniectomy) to relieve pressure and compression on the brainstem. Also, this involves the removal of part of the bony covering of the spinal canal, called a laminectomy, to provide more room for CSF circulation. Ultimately, this enlarges the foramen magnum and improves the patient’s condition.

References

 

  1. Tubbs, R. S., Wellons, J. C. & Oakes, W. J. Asymmetry of tonsillar ectopia in Chiari I malformation. Pediatr. Neurosurg. 37, 199–202 (2002).
  2. Aiken, A. H., Hoots, J. A., Saindane, A. M. & Hudgins, P. A. Incidence of cerebellar tonsillar ectopia in idiopathic intracranial hypertension: A mimic of the Chiari I malformation. Am. J. Neuroradiol. 33, 1901–1906 (2012).
  3. Furuya, K., Sano, K., Segawa, H., Ide, K. & Yoneyama, H. Symptomatic tonsillar ectopia. J. Neurol. Neurosurg. Psychiatry 64, 221–226 (1998).
  4. Lawrence, B. J. et al. Cerebellar tonsil ectopia measurement in type i Chiari malformation patients show poor inter-operator reliability. Fluids Barriers CNS 15, 11–13 (2018).
  5. Freeman, M. D. et al. A case-control study of cerebellar tonsillar ectopia (Chiari) and head/neck trauma (whiplash). Brain Inj. 24, 988–994 (2010).