MR Imaging Features of Acute Mastoiditis and Their Clinical Relevance

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Fig 1.
Image examples of each scoring category according to signal intensities. Categories are displayed in columns from left to right in increasing severity.
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Fig 2.
Obliteration degree in different temporal bone subregions (n = 31).
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Fig 3.
MR images of bilateral AM with duration of symptoms of 12 days on the left and fewer than 6 days (3–6 days) on the right side. T2 FSE image (A) shows total obliteration of middle ear and mastoid air spaces. SI is comparable with that of brain parenchyma. Especially on the right side, delineation of intramastoid bony septa is no longer detectable. On the left, outer cortical bone is destroyed (arrow) with subperiosteal abscess formation (asterisk). Intramastoid signal decrease, compared with CSF, becomes even more evident in CISS (B). In postgadolinium T1 MPRAGE (E), intense, thick enhancement surrounds the fluid-filled mastoid antra (a) and fills the peripheral mastoid cells. On the left, intense soft-tissue enhancement around the subperiosteal abscess and, on the right, periosteal enhancement surrounding the mastoid are visible. DWI b=1000 (C) and ADC (D) show diffusion restriction in the whole mastoid region bilaterally with foci of markedly elevated SI inside both antra (a) and the left subperiosteal abscess (asterisk).

Table 1:

Distribution of intramastoid signal intensity and enhancement

	No.	No. of Patients per Category (Valid %)
SI in T2 FSE and CISS		Isointense to CSF	Hypointense to CSF, hyperintense to WM	Iso- or hypointense to WM
CISS	25	1 (4)	14 (56)	10 (40)
T2 FSE	31	3 (10)	24 (77)	4 (13)
SI in T1 SE		Isointense to CSF	Hyperintense to CSF, not to WM	Hyperintense to WM
T1 SE	31	0 (0)	22 (71)	9 (29)
SI in DWI (b=1000)		Hypointense to WM	Isointense to WM	Hyperintense to WM
	27	2 (7)	9 (33)	16 (59)
SI in ADC		Not lowered	Lowered
	26	10 (38)	16 (62)	–
Enhancement		None	Faint, thin	Intense, thick
	31	3 (10)	12 (39)	16 (52)

Note:—No. indicates the number of patients with a specific sequence available.

Table 2:

Prevalence of AM complications detected on MRI (N = 31)

Complication	No. (%)
Complication	All	Children	Adults
Septal destruction	11 (35)	5 (45)	6 (30)
Inner cortical bone destruction	4 (13)	2 (18)	2 (10)
Outer cortical bone destruction	9 (29)	7 (64)^{^a}	2 (10)^{^a}
Intratemporal abscess	7 (23)	3 (27)	4 (20)
Subperiosteal abscess	6 (19)	5 (45)^{^a}	1 (5)^{^a}
Labyrinth involvement	5 (16)	0 (0)	5 (25)
Epidural abscess	2 (6)	2 (18)	0 (0)
Soft-tissue abscess	2 (6)	1 (9)	1 (5)
Generalized pachymeningitis	2 (6)	1 (9)	1 (5)
Leptomeningitis	2 (6)	1 (9)	1 (5)
Sinus thrombosis	1 (3)	1 (9)	0 (0)
Subdural empyema	0 (0)	0 (0)	0 (0)