Chiari malformations is a very common disease condition and occurs in every 1 out of 1000 births. Chiari malformations are caused due to structural abnormalities in the cerebellum which is present at the opening of skull and allows the spinal cord to pass through an area of the brain called foramen magnum. Chiari malformation occurs when cerebellum extends abnormally below the foramen magnum and into the upper segments of the spinal cord. This malformation is likely to happen in people who have a small skull size which forces the cerebellum to push outside into the foramen magnum and then into the spinal canal. The pressure exerted onto the cerebellum and brain stem due to this abnormality affects various functions controlled by these brain areas. The cerebrospinal fluid (CSF) responsible for cushioning the brain and spinal cord is unable to reach the damaged structures of the brain in Chiari malformation processes. CSF is essential for circulating nutrients and chemicals which are filtered from the blood to the brain, and for removal for waste products from the brain (Buell, Heiss & Oldfield, 2015).
Chiari malformations could happen from genetic mutations and structural defects in the fetus might be due to lack of vitamins and nutrients in the mother’s diet. This type of genetic or structural malformation is known as primary or congenital Chiari malformation. Chiari malformation does not only occur in the fetal development stages but might happen in later stages in life. This abnormality could also happen in cases of a traumatic brain injury or brain infection which causes excessive spinal fluid drainage from the lumbar or thoracic area. This type of disease or trauma related abnormality in the cerebellum and brainstem areas is known as acquired or secondary Chiari malformation. Prominent symptoms of Chiari malformation are headache, neck pain, balance and hearing problems, numbness, difficulty in swallowing, ringing in the ears, vomiting, problems in coordination and motor skills, insomnia etc. (Buell, Heiss & Oldfield, 2015).
Primary Chiari malformation are more common as compared to secondary Chiari malformations. It is observed that infants with this abnormality may have difficulty in swallowing milk, arm weakness, stiffness in neck, breathing problems, gagging or vomiting, developmental delays, and excessive drooling. Patients who acquire Chiari malformations later in life may have slight symptoms depending on the compression of cranial nerves and CSF pressure (Shweikeh, Sunjaya, Nuno, Drazin & Adamo, 2015).
Chiari malformations are also classified on the basis of severity and extent of abnormality caused by this defect. Chiari malformation type I occurs when the lower part of the cerebellum extends into the foramen magnum and only the spinal cord function is affected. Hence, this type of malformation does not cause symptoms and is usually noticed in the adolescent years. Chiari malformation type 2 is more severe and symptoms start to appear in early childhood. Type 2 malformations have the potential to cause life-threatening malformations during infancy and early childhood years. Type II is also called classic chiari malformation and it is caused when both cerebellum and brain stem tissue extends into the foramen magnum. Hence, nerve tissue connecting the two halves of the cerebellum is either absent or partially developed. Type II abnormality often occurs with Spina bifida defect in which the spinal canal and backbone does not close before birth. Spina bifida is related to incomplete development of brain and spinal cord during fetal growth (Shweikeh, Sunjaya, Nuno, Drazin & Adamo, 2015).
Chiari malformation Type III is another most serious and rare form of abnormality which is characterized as sticking of the cerebellum to some area of the brainstem and protrusion of this herniated area from the back of the skull. This abnormal sticking and protrusion results in life-threatening complications such as neurological defects, cognitive and physical delays, seizures etc. Chiari malformation Type IV results in the development of an incomplete cerebellum and this condition is also known as cerebellar hypoplasia. This form of malformation is extremely rare and is observed as missing parts of cerebellum in the brain. Chiari malformations is also associated with developing fatal clinical complications such as hydrocephalus, Syringomyelia, Spina bifida, tethered cord syndrome etc. (Shweikeh, Sunjaya, Nuno, Drazin & Adamo, 2015).
Hydrocephalus occurs with the excessive buildup of CSF because chiari malformations blocks the normal flow of CSF and increases the cranial fluid pressure. This excessive pressure buildup known as hydrocephalus results in enlarged skull and other mental defects, Spina bifida is caused due to incomplete closure of the membranes around the spinal cord which causes severe neurological deficits in infants such as paralysis of spine, scoliosis, muscle weakness etc. Syringomyelia is another neurological disorder which occurs because of Chiari malformations and is associated with development of tubular cyst within the spinal cord. These cysts or syrinx are filled with CSF and it destroys the center of the spinal cord. Symptoms of Syringomyelia are stiffness and pain in the back, shoulders, arms or legs. Tethered cord syndrome occurs when the spinal cord abnormally attaches to the tissues of the spinal cord. Hence, the spinal cord is unable to move freely or bend in any direction thus causing a permanent damage to the lower body and leg muscles (Lei, Wu, Zhang, Han, Wang, Li & Shu, 2018).
To date, no specific test is present to diagnose Chiari malformations before birth of the child. However, it causes birth defects such as spina bifida which might be seen on ultrasound images before the birth of the child. Chiari malformations which are not so severe and asymptomatic might be diagnosed during a physical exam in adolescence or adulthood. Physical exams for memory, cognition, balance, touch reflexes, motor skills, sensation etc. might help in the diagnosis of Chiari malformations. Diagnostic tests including magnetic resonance imaging (MRI) and Computed Tomography (CT) scan shall be ordered by the physician in case the patient shows abnormalities in cognitive and motor skills during physical exam. Surgical treatment such as posterior fossa decompression surgery is recommended in patients of chairi malformation with cognitive and motor skills defects. This surgical procedure creates space for the cerebellum and relieves the CSF pressure on the spinal cord. Infants and children with spina bifida are treated with a surgery to reposition the spinal cord and close the opening of surrounding membranes (Lei, Wu, Zhang, Han, Wang, Li & Shu, 2018).
Buell, T. J., Heiss, J. D., & Oldfield, E. H. (2015). Pathogenesis and cerebrospinal fluid hydrodynamics of the Chiari I malformation. Neurosurgery clinics of North America, 26(4), 495.
Lei, Z. W., Wu, S. Q., Zhang, Z., Han, Y., Wang, J. W., Li, F., & Shu, K. (2018). Clinical Characteristics, Imaging Findings and Surgical Outcomes of Chiari Malformation Type I in Pediatric and Adult Patients. Current Medical Science, 38(2), 289-295.
Shweikeh, F., Sunjaya, D., Nuno, M., Drazin, D., & Adamo, M. A. (2015). National trends, complications, and hospital charges in pediatric patients with Chiari malformation type I treated with posterior fossa decompression with and without duraplasty. Pediatric neurosurgery, 50(1), 31-37.
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