Natural History, Neuroradiological Workup, and Management Options of Chronic Atlantoaxial Rotatory Fixation Caused by Drug-Induced Cervical Dystonia

Table 1

AARF classifications.

Fielding and Hawkins AARF classification [4]
Type 1	Rotatory fixation with no anterior displacement
Type 2	Rotatory fixation with anterior displacement of 3 to 5 millimeters
Type 3	Rotatory fixation with anterior displacement of more than 5 millimeters
Type 4	Rotatory fixation with posterior displacement
Pang AARF classification [9, 17]
Type 1	AARF patients show essentially unaltered (“locked”) C1-C2 coupling regardless of corrective counterrotation
Type 2	AARF patients show reduction of the C1-C2 separation angle with forced correction, but C1 cannot be made to cross C2
Type 3	AARF patients show C1-C2 crossover but only when the head is cranked far to the opposite side