Congenital malformations of spine are defects or disorders of spine that are present from birth. These malformations may be mild or severe and are often corrected by surgery.
The various types of congenital malformations of spine
Chiari malformation is a congenital anomaly whose acquired forms are also known. The anomaly is categorized in order of severity as; types I, II, III, and IV. These malformations are closely associated with syringomyelia and hydromyelia. The majority of these cases are asymptomatic and are often detected coincidently among patients who have undergone diagnostic imaging for unrelated reasons.
Types of Chiari Malformations
Type I Chiari Malformation
This malformation occurs during intra-uterine development and is characterized by downward displacement of the cerebellar tonsils beneath the foramen magnum into the cervical spinal canal by more than four millimeters. This displacement may block the normal pulsations of CSF between the spinal canal and the intracranial space. This form of Chiari malformation may be associated with syringomyelia/hydromyelia. It is diagnosed usually in growing children or young adults.
Abnormities of the base of the skull and spine (Cranio – Vertebral Junction) like basilar invagination, Klippel-Feil deformity etc. is present in 30-50 percent of patients suffering from Chiari I malformation.
Symptoms of Chiari I malformation
Although most of the people with Chiari I malformation has no symptoms but some may show any of the following symptoms:
Severe head and neck pain which worsens on coughing and sneezing.
Loss of pain and temperature sensation of the any of the combination of limbs, more so in upper limbs
Loss of muscle strength in the hands
Sudden collapsing due to muscle weakness or insufficient blood supply to brain
Combination of spasticity and wasting of muscles
Problems with balancing while walking
Visual issues like double or blurred vision
Type II Chiari malformation
This malformation is characterized by further downward displacement of lower brain and brain stem into the cervical spinal canal, as well as elongation of the upper brain stem. This type occurs almost exclusively in patients with myelomeningocele which is a congenital condition in which the spinal cord and column do not close properly during foetal development, resulting in an open spinal cord defect at birth. Other abnormalities commonly associated with myelomeningocele include hydrocephalus, cardiovascular abnormalities, as well as gastrointestinal abnormalities, and genitourinary abnormalities.
Symptoms of Chiari II malformation
Altered pattern of breathing, including periods of brief periods of cessation of breathing
Difficulty in swallowing
Involuntary, rapid and downward eye movements
This is a surgical emergency needing multidisciplinary approach in Neonatal ICU.
Type III Chiari malformation
This includes a form of dysraphism with a portion of the cerebellum and/or brainstem pushing out through a defect in the back of the head or neck.
Type IV Chiari malformation
This is the most severe form and the rarest. The cerebellum fails to develop normally. There may be other associated malformations of the brain and brainstem.
Associated Malformations of Chiari malformation
When CSF forms a cavity or cyst within the spinal cord, it is known as syringomyelia or hydromyelia. These are progressive disorders that involve development, expansion or extension of the spinal cord. As the fluid cavity expands, it displaces and/ or injures the nerve fibers inside the spinal cord. A wide variety of symptoms can occur, depending upon the size and location of the syrinx.
Hydromyelia is usually defined as an abnormal widening of the central canal of the spinal cord.
Encephalocele: a congenital malformation characterized by herniation of the brain and/or meninges through a defect in the skull.
Arachnoid Cysts: are congenital lesions that occur as a result of the splitting of the arachnoid membrane. The cysts are fluid-filled sacs, not tumors, appearing in one of the three layers of tissue covering the central nervous system.
Diagnosis of Spinal Congenital Malformations
There are several tests that can help diagnose and determine the extent of Chiari malformation and syringomyelia including:
Magnetic resonance imaging (MRI)
Computed tomography scan (CT or CAT scan)
Brainstem auditory evoked potential (BAER)
Somatosensory evoked potentials (SSEP)