Definitions and treatments for chiari-1 malformations and its variants: Focused review

BACKGROUND: Reviewing the neurosurgical literature demonstrated that spinal neurosurgeons rarely (0.78%) diagnose chiari-1 malformation (CM-1) in adults on magnetic resonance (MR) studies defined by tonsillar descent >5 mm below the foramen magnum (FM). Children, averaging 10 years of age, exhibit CM-1 in 96/100,000 cases. According to the literature, fewer spinal neurosurgeons additionally recognize and treat the low lying cerebellar tonsil (LLCT) syndrome. METHODS: The normal location of the cerebellar tonsils on cranial/cervical MR averages 2.9 mm ± 3.4 mm above or up to 3 mm below the FM. The neurosurgical literature revealed that most neurosurgeons diagnose and treat CM-1 where the tonsils are >5 mm to an average of 12 mm below the FM. Fewer spinal neurosurgeons additionally diagnose and treat the LLCT syndrome defined by <5 mm of tonsillar descent below the FM. RESULTS: According to the neurosurgical literature, many neurosurgeons perform cranial/spinal decompression with/without fusion and/or duraplasty for CM-1. Fewer neurosurgeons perform these procedures for CM-1 and the LLCT syndrome, for which they additionally perform preoperative cervical traction under anesthesia, and the postoperative placement of occipital neurostimulators (ONS) for intractable headaches following chiari-1/LLCT surgery. CONCLUSION: Reviewing the literature revealed that spinal neurosurgeons rarely diagnose CM-1, and treat them with decompressions with/without fusions and/or duraplasty. Fewer spinal neurosurgeons diagnose/treat both the CM-1 and LLCT syndromes, perform preoperative traction under anesthesia, and place ONS for persistent headaches following CM-1 surgery.