Table 2.

Proportions of ‘present’ and ‘indefinable’ ratings per observer for each feature of Chiari II malformation

Feature	Present			Indefinable			Non-applicablea
	A	B	C	A	B	C
Sagittal plane
Downward herniation cerebellum	35	33	35	−	−	−
Downward herniation vermis	25	28	35	3	3	−
Downward herniation tonsil	33	30	26	1	1	6
Upward herniation cerebellum	13	17	6	−	6	3
Downward displacement medulla	30	26	20	−	−	3
Downward displacement pons	26	26	13	−	3	3
Downward displacement fourth ventricle	25	23	20	−	4	1
Medullary kinking	17	14	14	1	1	6
Flattened pons	25	38	23	−	−	−
Abnormal width fourth ventricle	25b	25	29b	−	−	1
Hypoplastic tentorium	26	22	22	−	13	3
Abnormal course straight sinus	23	23	29	9	4	3
Beaked tectum	25	28	23	−	−	−
Enlarged massa intermedia	43	62	10	−	−	4
Stenogyria	19	7	9	3	22	12	+
Axial plane
Cerebellum in cervical spinal canal	21	21	19	10	19	12	+
Vermis in cervical spinal canal	2	2	14	26	36	16	+
Tonsil in cervical spinal canal	7	5	16	24	34	16	+
Cerebellum wrapped around brainstem	29	24	3	−	5	2
Abnormal fissural pattern of cerebellum	29	59	47	7	7	5	+
Small fourth ventricle	26	28	26	−	3	−
Enlarged fourth ventricle	3	2	3	−	9	−
Beaked tectum	19	26	19	7	7	7	+
Enlarged massa intermedia	17	12	−	−	3	98	+
Gyral interdigitation	22	31	17	5	7	5	+
Stenogyria	17	9	7	7	91	12	+
Coronal plane
Downward herniation cerebellum	35	26	24	8	8	4	+
Downward herniation vermis	10	69	14	18	31	6	+
Downward herniation tonsil	35	24	24	8	10	2	+
Upward herniation cerebellum	26	12	8	2	6	6	+
Indentation	12	12	6	2	4	−
Hypoplastic tentorium	26	2	14	4	61	2
Gyral interdigitation	18	26	14	2	10	4

Data are percentages

A observer A, B observer B, C observer C

^aAt least two observers considered the feature as indefinable in more than 5 % of the MR images

^bAll abnormally small fourth ventricles, except for one dilated fourth ventricle