Hands-on will teach you to read the film 05: acute disseminated encephalomyelitis

OVERVIEW: Acute disseminated encephalomyelitis (ADEM) is a rare central nervous system demyelinating disease, most of which have a history of viral infection or vaccination days to weeks before onset, and a small number have no clear cause
.
Clinical manifestations are diverse and uncharacteristic
.
MRI has important diagnostic value
for this disease.

Etiology and pathogenesis: ADEM, also known as immune-mediated encephalomyelitis, is a less common autoimmune disease
of the central nervous system.
Clinical diagnosis mainly depends on the medical history (predisposing factors), clinical manifestations and cerebrospinal fluid examination, among which the development of the history and course of the disease are particularly important
for diagnosis.
Most patients with ADEM have a history of viral infection or vaccination at the onset week, and a few may have no clear precipitating factors
.

Pathological features: ADEM brain pathological changes are demyelination of the white matter along the vein, there is peripheral vascular inflammatory cell infiltration, edema and even hemorrhage in the lesion area, and axons are not affected
.
Since there is no evidence of viral detection in the lesion, it is thought to be a demyelinating disorder due to autoimmune injury rather than viral encephalitis
.

Image features:

Typical MRI findings of ADEM:

(1) Location and distribution of lesions: mainly located around the lateral ventricles and in the frontal, parietal, temporal and occipital white matter areas, partially involving the cortex, thalamus, brainstem and cerebellar white matter, the lesions are of different sizes and asymmetrical, and can show the distribution characteristics of "vertical unsheathing sign";

(2) Tumor morphology and signal: mostly spotted or patchy, a few are round and oval, manifested as T1WI low signal, T2WI and FLAIR high intensity;

(3) Enhancement: the lesion showed multiple uneven annular strengthening or dotted piece strengthening;

(4) MR review: After hormone therapy or immunosuppressant treatment, the scope and number of abnormal signals will be reduced, reduced or absorbed
to varying degrees.

Typical cases

Female, 3 years old, with a history of
vaccination 4 days before onset.

Typical ADEM imaging findings:

Fig.
1 A) Plain MR scan 8 days after onset, FLAIR showed multiple spotty or patchy high signals of varying size in the white matter area around the lateral ventricle and some cortex, and the distribution was asymmetrical
.
B) After 20 days of treatment, FLAIR showed that the white matter area around the lateral ventricle and some of the intracortical patchy hypersignal were significantly absorbed and improved without new lesions
.
C) After 3 months of treatment, FLAIR showed that the patchy hypersignal in the white matter area around the lateral ventricle had been basically completely absorbed, and only a few patchy hyper-signal
remained.

Male, 35 years old, with a history of
upper respiratory viral infection 10 days before onset.

Typical ADEM imaging findings:

Fig.
2 A) 14 days after the onset of the disease, plain MR scanning, T2WI showed multiple patchy and strip-like hyperintensity in the white matter area around the lateral ventricle, and some lesions were arranged perpendicular to the lateral ventricle, that is, "vertical unsheathing sign"
.
B) T2WI shows lesion involving the right thalamus and left basal ganglia
.
C) Enhanced scanning, showing multiple uneven annular enhancement or dotted enhancement
of the lesion.

Hands-on reading: The following images are in line with the characteristics of the disease:

1.
Clinical history: female, 32Y Progressive change of consciousness with limb weakness for 7 days
.

2.
MRI performance:

The above figure T1WI shows that the lesions are low-intensive, multiple episodes of unequal size and asymmetrical distribution, the distribution area is mainly white matter area, spotty or patchy, and a few are round-like and oval
.

FLAIR above shows that multiple spots, patches or round-like hyperintensity of varying sizes in the white matter area around the lateral ventricle and some cortex, with asymmetric distribution, and some lesions are arranged perpendicular to the lateral ventricle, that is, "vertical dissheathing sign" (red vertical line).

MR enhancement in the figure above shows that the lesion shows multiple uneven annular reinforcements (red arrows) or dotted reinforcements (blue arrows).