Title : Surgical approach to the management of chiari i malformation in adults
Abstract:
Chiari 1 Malformation (CIM) is defined as the degree of fall of the cerebellar tonsils below the foramen magnum. The degree of dip below the cerebellar tonsil involves >3 mm in children and >5 mm in adults. An extension of greater than five mm of the cerebral tonsil below the foramen magnum is considered pathological. The prevalence CIM is approximately 0.9 % in adults and 0.6 % in the pediatric population. The treatment for Chiari 1 has improved over the years with the advancement of Magnetic Resonant Imaging (MRI) and the understanding of the pathophysiology and natural history of CIM. CIM is further subdivided into primary or congenital and secondary. Primary CIM is theorized to be caused by the overcrowding of the posterior fossa (small posterior fossa) while secondary is due to tumor/space occupying lesion or condition causing intracranial hypertension and hydrocephalus. The most common symptom of CIM is headache in the occipital or cervical region. Headache is reported in approximately 60-80% of the patients with CIM. This headache is exacerbated by Valsalva type activities such as coughing, sneezing, or laughing and or neck movement. If brain stem or spinal cord involvement, the symptoms may include difficulty swallowing, spasticity, myelopathy and motor or sensory loss. It is important to differentiate the CIM headache from that of migraine or tension headache. About 30-70 % of CIM patients present with unrelated headaches, however, CIM patient’s headache response to surgery in approximately sixty percent of the cases. MRI is the gold standard imaging in this patient population. MRI of entire cranio-spinal axis for evaluation of cord compression, intramedullary edema, and evaluation the narrowing of the cranio-vertebral junction. MRI findings that suggest surgery: Tonsillar herniation, cerebrospinal fluid disappearance at level of foramen magnum along with the following symptoms of myelopathy and syrinx. Initially surgery had no treatment role for these patients and now CIM is considered a disorder with surgery as an option to provide quality of life to those who were once destined for disability. Treatment approach for CIM is based on whether the patient is symptomatic. Asymptomatic patients are monitored with imaging. The goal of surgery is symptom reduction, prevent further damage to the central nervous system, and restore the usual flow of cerebral spinal fluid. Surgical approach may vary but commonly include dural opening with bony decompression with shunting or fourth ventricular–cervical subarachnoid stenting, a more aggressive approach. Ongoing monitoring of CIM patients neurologically and with imaging is important post decompression because there is still a possibility of recurrent syrinx and return of neurological symptoms.
Audience Take Away Notes
- Define Chiari 1 Malformation (CIM).
- Discuss the prevalence of CIM.
- Review the common symptoms of CIM.
- Discuss the role of surgery.
