What is normal Atlantodental interval?
The atlantodental interval (ADI) is a measurement used to evaluate the atlanto-axial relationship. This distance, described by Hinck et al,6 is conventionally held to be normal when it is less than 3 mm in men and 2.5 mm in women.
How is Atlantodens interval measured?
The Atlantodens Interval is the distance between the backside of the C1 bone and the front of the C2 bone. It is measured in milimeters (mm). To accurately assess the presence of Atlantoaxial Instability it is important that the radiographic study includes both flexion and extension images.
What is atlanto-occipital instability?
Atlantoaxial instability (AAI) is characterized by excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bony or ligamentous abnormality. Neurologic symptoms can occur when the spinal cord or adjacent nerve roots are involved.
What is a normal ADI?
In adults, an ADI of 3-5 mm indicates that the transverse ligament is insufficient. In children, this value may be as large as 4.5 mm and still be considered normal. An ADI of greater than 5 mm is indicative of misalignment of the alar ligaments.
What is occipital dislocation?
Atlanto-occipital dislocation involves complete disruption of all ligamentous relationships between the occiput and the atlas. Death usually occurs immediately from stretching of the brainstem, which causes respiratory arrest. Radiographically, disassociation between the base of the occiput and the arch of C1 is seen.
What is Atlantodental?
Measurement. The atlantodental interval is the horizontal distance between the posterior cortex of the anterior arch of the atlas (C1) and the anterior cortex of the dens in the median (midsagittal) plane.
What movement does the atlas allow?
The atlas and axis are specialized to allow a greater range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head. The atlanto-occipital joint allows the head to nod up and down on the vertebral column.
Is Craniocervical instability an emergency?
Cervical instability is a medical condition in which loose ligaments in your upper cervical spine may lead to neuronal damage and a large list of adverse symptoms. If you have cervical instability, you may be experiencing migraines, vertigo, or nausea. Fortunately, this condition is treatable, though not curable.
What is CCI AAI?
CCI stands for craniocervical instability and AAI means atlantoaxial instability. Before we get into what these terms mean, let’s review the anatomy of the craniocervical junction, or where the cervical spine meets the skull. The upper neck where the spine meets the head is called the craniocervical junction or CCJ.
How is Adi space measured?
The ADI is determined by measuring the distance between the posterior edge of the anterior arch of C1 and the anterior edge of the dens. A value less than three mm is considered normal in adults and a value less than 4.5 mm is considered normal in children.
Can you survive a dislocated head?
Prognosis. The injury is immediately fatal in 70% of cases, with an additional 15% surviving to the emergency room but dying during the subsequent hospital stay. A basion-dental interval of 16mm or greater is associated with mortality. In those with neurologic deficits, survival is unlikely.
What is the normal range of basion dens interval?
Basion-dens interval. It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the dens in the median (midsagittal) plane. Normal values are <12 mm on plain radiographs and <8.5 mm on CT 1.
What is the normal distance from the basion to superior aspect?
It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the dens in the median (midsagittal) plane. Normal values for adults are <12 mm on plain radiographs and <8.5 mm on CT 1. In children, >10 mm suggests atlanto-occipital dissociation 2.
What is the basion cartilaginous dens interval (BCDI)?
In their study, this novel distance was coined as the “basion-cartilaginous dens interval” (BCDI). They measured the BCDI in 86 children between 0–24 months of age and calculated the upper limit of normal to be 4.4 mm. 8
What is the basion-dens interval (BDI)?
The basion-dens interval (BDI) is the distance between the basion and the tip of the dens, used in the diagnosis of atlanto-occipital dissociation injuries. It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the dens in the median (midsagittal) plane.