Chiari malformation is a comprehensive term that covers various structural defects in cerebellum, part of brain responsible for maintaining balance. They often develop due to structural defects of brain and spinal cord during fetal development. Rarely chiari malformations may develop later in life due to injury, increased exposure to toxic substances or infection that result in excessive draining of cerebrospinal fluid. Structural defects often disturb the relationship between cerebellum, upper cervical cord, brain stem and boney cranial base.
Types of Chiari malformation
Four types of chiari malformation are observed. Of the four types type I and type II are more commonly observed:
- Type I: This disorder commonly observed in children can be inherited from parents. In this type of malformation cerebellum extends in to an opening present at the bottom of the brain. Brain stem remains intact.
- Type II: This type of malformation is observed in children born with disorder Spina bifida (incomplete development of spinal cord or the protective layers). Type II chiari malformation is also termed as classic chiari malformation or Arnold chiari malformation. In these patients both cerebellum and brain stem extend in to the opening present at the base of skull (foramen magnum).
- Type III: This malformation is characterized by protrusion of cerebellum and spinal cord in to the foramen magnum and also in to the spinal cord. Though this type of malformation is rarely observed it is serious and results in severe neurological defects.
- Type IV: This is also a rare type of chiari malformation characterized by incomplete formation or underdevelopment of cerebellum. In few people parts of skull and spinal cord may be exposed. Children born with this malformation rarely survive.
Other categories of chiari malformation include Hydrocephalus characterized by fluid buildup in brain, Syringomyelia characterized by cyst formation in central canal of spinal cord and Tethered cord syndrome, a progressive disorder in which spinal cord joins to the bony spine.
Chiari Malformation Symptoms
Chiari malformation symptoms vary depending on the nature of brain tissue that is shifted in to the spinal canal. All patients with chiari malformations do not suffer with symptoms. Few Children born with structural defects of cerebellum may start to experience the symptoms in either adolescence or adulthood. Commonly observed chiari malformation symptoms
- Vision problems which can be blurred or double vision.
- Trouble balancing and coordination resulting in shaky walk and poor motor skills.
- Weakness of neck muscles.
Depending on the extent of severity of the condition and type of malformation numerous other problems are experienced by the patients.
Type I chiari malformation symptoms
Unless the defect is severe type I chiari malformation does not cause any symptoms. Symptoms observed in severe cases include:
- Pain in the lower back of head that radiates in to the neck. Pain intensifies with activities such as sneezing and coughing that exert pressure on brain.
- Dizziness and trouble balancing.
- Poor coordination.
- Sleep apnea.
- Difficulty to swallow.
Rarely observed symptoms include
- Tinnitus characterized by ringing sound in ears.
- Trouble controlling bladder.
- Chest pain.
- Irregular breathing.
Type II chiari malformation symptoms
- Pain in the head: Activities such as coughing, sneezing, straining during bowel movement and strenuous physical activities cause pain in the head.
- Poor functioning of the nervous system: Problems in functioning of nerves associated with brain stem results in breathing abnormalities, difficulty in swallowing, weakness of vocal cords and change in functioning of nerves of tongue and throat.
Chiari malformation Treatment
Chiari malformations are corrected by performing a surgery. However, surgery is performed only when chiari malformation symptoms are not manageable with medications. If the physician suspects of malformations of cerebellum basing on the symptoms then he will check the functions regulated by spinal cord and cerebellum. Motor skills, balance, touch, sensation and reflexes of the patient are examined. Diagnostic tests such as CT scan, MRI scan and X-ray are performed to pinpoint the type of malformation.
Treatment plan is made depending on the severity of the disease. If the patient does not complain of any symptoms and is able to continue with daily activities normally then no treatment is given. Otherwise, medications such as indomethacin are used to control chiari malformation symptoms such as severe pain in head. Muscle relaxants may also be recommended to relax neck muscles. These medications help to delay or even avoid surgery.
Surgery as Chiari malformation treatment
If the defects are worse, surgery is done either to correct the defects or to arrest the progression of damage to central nervous system. Surgery is performed to correct the fluid circulation process through and around the affected area and thus, relieve pressure on spinal cord and brain.
Different types of surgery are performed in children and adults.
- Posterior fossa decompression surgery: Small part of the bottom of skull and if necessary portion of spinal column is also removed to rectify irregular bony structure. To create extra space for the circulation of cerebrospinal fluid a film covering the brain and spinal cord (Dura) is opened and widened.
- Electrocautery: Lower part of cerebellum is shrunken using high energy electric currents.
- Spinal laminectomy: Part of bony roof of spinal canal is removed to increase the size of canal and reduce pressure on spinal cord and nerve roots.
Based on the research of the results of surgery, about 50% of the children do not show any chiari malformation symptoms after surgery. Of the remaining 50% children 45% show reduction in the symptoms while in rest of 5% symptoms get stabilized.