Table 2.

Morphometric characterization and other mechanisms of hindbrain ptosis in CM-I type A, and the corresponding surgical intervention.

	Instability of CCJ	Tethering	Hydrocephalus	Intracranial Mass	Pressure Dissociation
VPCF	normal	normal	normal	normal	normal
VAFM	normal	normal	normal	normal	normal
VBPCV/VPCF	normal	normal	normal/large	normal/large	normal
Brainstem and Cerebellum	normal	elongation and downward displacement		normal	normal
Cause	cranial settling	traction	pressure coning		Hypotension of intraspinal canal
Intervention	CCF	untethering/SFT	VPS	resection of mass or FMD	others

Abbreviations: CM-I: Chiari malformation, CCJ = craniocervical junction, VPCV: volume of the posterior cranial fossa, VAFM: volume of area of surrounding foramen magnum, PFBV: volume of brain in posterior cranial fossa, CCF: craniocervical fixation, SFT: section of filum terminale, VPS: ventriculo-peritoneal shunt.