About Chiari-related Syringomyelia
The spinal cord holding the tubular cavitation is known as Syringomyelia. Syringomyelia may be present from birth though it may not show symptoms until adulthood or it can be developmental during life in extremely rare cases. It is a caused by the effect of malfunctioning where a fluid-filled cavity develops at the spinal cord which is also known as syrinx. It is chronic and a syrinx can grow over time. It is one of the most common causes of Chiari malfunctioning. This form is sometimes referred to as adult Chiari malfunctioning. It is the action of different pathologic processes. The area where the brain and the spinal cord connect which is the lower posterior of the skull gets affected in Chiari malformation. It is generally a group of complex brain abnormalities. Generally, Chiari malfunction is classified and defined by the level of cerebellar tonsils that protrude through the foramen magnum. It is reported in 50-60% of cases.
Causes of Chiari-related Syringomyelia
Usually, the cavity at the base of the skull (posterior fossa) opening is too narrow compared to the size of the cerebellum. Sometimes the developing brains especially the brainstem and the cerebellum is forced downwards because of the small size of the posterior fossa. The normal opening which is found at the occipital bone at the base of the skull which is known as the foramen magnum may allow a part of the cerebellum also known as the cerebellar tonsils to protrude inside. Thus there will be an accumulation of the cerebral spinal fluid in the subarachnoid spaces of the spine and brain as the tonsil may interfere in the flow of the cerebral spinal fluid to and fro from the brain and the skull. Though the actual or direct cause is unknown, the flow to the foramen magnum being obstructed by the cerebellar tissue which causes the interference of the normal CSF pulsation is thought to be the reason of syringomyelia. Complications of trauma, tumor, meningitis, tethered spinal cord or arachnoiditis can cause the syrinx to form in the spinal cord which gets damaged by the disorder. Increased Cases of post-traumatic syringomyelia are being diagnosed in people surviving spinal cord injuries.
Symptoms of Chiari-related Syringomyelia
A wide variety of symptoms can arise due to Chiari malfunction which may cause by the pressure in the brain due to excessive cerebrospinal fluid, the condition which is known as hydrocephalus. Sometimes there may not be any symptoms for the Chiari malfunctioning or sometimes the symptoms can be highly variable which may affect each individual differently or sometimes the symptoms can be life-threatening such as neurological deficits. It generally reflects dysfunction of the cerebellum, the spinal cord, the brainstem, and the lower cranial nerves. Syringomyelia can consist of several of symptoms depending on the position of the syrinx developed. Symptoms includes muscle weakness, non-sensitivity to heat and coldness, loss of muscle mass, scoliosis which is the abnormal curvature of the spine, chronic pain, loss of bladder and bowel control, ataxia which is regarded as uncontrollable movement, muscle contraction, and spasticity which is regarded as the tightening of the muscles of the leg. Initial symptoms include sensory disturbances and pain.
A related disorder to syringomyelia is hydromyelia which is the widening of the central canal of the spinal which are filled with cerebrospinal fluid, where hydromyelia cavities are usually connected to the area in the brain that normally contains the cerebrospinal fluid which is also known as the fourth ventricle and is mainly seen in infants or children with or without brain abnormalities. Syringomyelia does not connect to any fluid-filled cavities and is mainly seen in adults. It usually may not be related to brain or neurological abnormalities although compression of the brainstem and the spinal cord can cause neurological symptoms. Individuals who have syringomyelia are found to have Chiari malfunction with or without herniation of the cerebellar tonsils through the foramen magnum. The abnormalities in the flow of the cerebrospinal fluids can produce symptoms such as occipital headaches.
In posttraumatic syringomyelia, in which there is an initial traumatic injury followed by the injury of the spinal cord, chronic pain is associated. Although it is not possible to determine whether the pain is due to primary pathological condition or syrinx, it appears that the treatment of the syrinx help from the relief of the pain which may be said that the pain is related to the previous spinal cord injury.
Symptoms may arise when the syrinx extends to the brainstem area which consists of the dysfunction of the lower cranial nerve associated with aspiration, coughing and dysphagia. Symptoms may also arise due to a cervical syrinx which includes sensory loss and motor weakness. A thoracic syrinx may also cause sensory disturbances and motor weaknesses of the trunks followed by the legs.
Treatment for Chiari-related Syringomyelia
Individuals with this disorder can improve after having a decompression surgery in spite of the response to therapy being highly variable. Some may be treated whereas others may experience persistence of the symptoms such as loss of sensation, muscle weakness, and residual pain. Leakage of Cerebrospinal fluid or infection is the risks that may arise due to surgery. Usually, the treatment of syringomyelia is related to the treatment of Chiari malfunctioning. The surgery to improve Chiari malfunctioning toilet also improve syringomyelia because the normal flow of cerebrospinal fluid is restored. The surgery is though not safe in older age because of arachnoiditis and long tract impairment syndrome. Tumor resection provides a good outcome for patients having tumor-related syringomyelia. The neurological outcome depends on the pre-operative neurological status.
Diagnosis of Chiari-related Syringomyelia
The size and condition of the syringomyelia after the surgery as seen through MRI is usually classified as improved, increased or unchanged. Sometimes aseptic meningitis and nonspecific headache can persist in patients of syringomyelia even after surgery. MRI is the only way to demonstrate the CSF flow abnormalities in patients with symptoms of posterior fossa compression. A sleep study is considered as one of the ways to diagnose in where a person is kept under check while sleeping by monitoring snoring, breathing, seizure activity, and oxygenation to determine if there is any symptom of sleep apnea. To check the proper working of the brainstem, an electrical test known as the Brainstem auditory evoked potential (BAER) is used. Somatosensory evoked potentials (SSEP) which are used to take information about the spinal cord, brain, and the peripheral nerve. The outcome depends largely on the pathology for post-traumatic patients. While going for surgical treatment, one should be informed that people who have gone for surgery and failed, do experience worse outcome.
Patients who are not experiencing symptoms of syringomyelia but with small syrinx cavities and without any cause are managed with several Magnetic Resonance Images and watchful waiting. The management of patients showing symptoms or with large syringomyelia is basically treated by focusing on and identifying the conditions defining the underlying causes of the syrinx. Through MRI research, it is observed that there is no relation between the syringomyelia and the size of the CSF pathway along with the foramen magnum. The result of the surgery depends on the degree of Chiari malfunctioning and the extent of any brain or spinal cord injury before the treatment. 85 to 95 % of the patients experience relief in symptoms. If the injury in the spinal cord is permanent, then surgery won’t fix the damage. However, patients may proceed to receive symptoms from syringomyelia. The syrinx is allowed to dry on its own after decompression surgery. The CSF flow and the syrinx site are needed to be monitored. The progress can be reported after 1year by MRI.
Chiari is often misdiagnosed so it is important to be evaluated and treated by professionals who can decipher the ambiguous and confusing symptoms. As for the treatment some people need only monitoring whereas many others need decompression surgery to restore the circulation of normal fluid around the brain, to enlarge the opening, and to restrict a syrinx. Obstructed flow of the CSF to the foramen magnum is the result of a failed surgery. A new trauma, inadequate removal of bone, scarring of tissue, brain pressure increased surgical complications such as spinal instability or cerebellar slumping can cause reoccurrence of Chiari related syringomyelia after surgery though it is a very rare case.
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- Hekman, K., Aliaga, L., Straus, D., Luther, A., Chen, J., Sampat, A., & Frim, D. Positive and negative predictors for good outcome after decompressive surgery for Chiari malformation type 1 as scored on the Chicago Chiari Outcome Scale. Neurological Research, (2012). 694-700. doi: 10.1179/1743132812y.0000000066