Table 9.

Radiologic criteria for the os petrosum in patients with CHARGE syndrome

Mastoid and vascular structures
Mastoid	Observation: pneumatisation of one or more cells Measurement: AP size: minimal distance from external meatus wall to sigmoid sinus taken at the middle of the meatus in the axial plane Measurement: LM size: minimal distance from cortex to sinus at the most anterior border of the sinus perpendicular to the mastoid AP size
Emissary veins	Observation: emissary veins through temporal squama, persistent petro-squamosal sinus [13] Measurement: >1 and <1 mm
Jugular bulb	Observation: high if at the level or cranial of the round window in axial plane
Middle ear
Ossicles	Observation: dysplasia
Windows	Observation: stenotic
Facial nerve	Observation: normal with present SCC: in transverse plane caudal of the LSCC and lateral and superior of the oval window. In coronal plane lateral and medial of the SCC Normal with absent SCC: coronal plane cranial of the oval window, posterior of the axis of the basal turn of the cochlea at the level of the anterior rim of the round window
Cochlear vestibular system
Cochlea	Measurement: angle basal turn and midline skull (54.6 degrees (range 46.8°–63.8°; standard deviation, 3.5) [24] Observation: dysplasia [31] with separate judgment of modiolus.
SCC	Absent, dysplastic, normal
Vestibulum	Measurement length: maximum longitudinal extension, width maximum transversal diameter, perpendicular to the length [22]. (normal (6.18–6.42) × (3.44–3.59) mm, interval)
Vestibular aqueduct	Measurement: diameter at midpoint (normal 1.5–2 mm) Observation: course
IAC	Measurement: Midline in axial plane(normal 2–8 mm)
Cochlear aperture	Observation: present or bony stenosis
Nerves in IAC	Observation on MRI: normal, hypoplastic or aplastic

AP anterior-posterior, LM lateral-medial, SCC semicircular canal, LSCC lateral semicircular canal, IAC internal auditory canal