Imaging analysis of "pig nose sign"

Central pontine myelinolysis (CPM) is a rare acute non-inflammatory central demyelinating disease with a very poor prognosis, with most patients progressing rapidly within 3 weeks and dying
in a coma.

Early and definitive diagnosis of the disease is crucial
for the choice of treatment and the prognosis of the patient.
For brain diseases, MRI examination has an absolute advantage, but abnormal MRI of the brain of the disease is often later than the clinical manifestations, and more typical imaging manifestations
generally appear 2~3 weeks after the onset of the disease.

Trident sign is a typical imaging manifestation of central pontine myelinolysis, and its formation is mainly related
to the anatomy of the site.

The cortical pondrum fibers of the midbrain foot terminate in the pons nucleus, and the axes of these cells burst out of the pons transverse fibers, which cross the midline to intersect the corticospinal tract and the cortical nucleus tract and divide them into many small bundles
.
The transverse fibers of the pons enter the mid-foot of the cerebellum and are distributed in the cerebellar hemisphere
.
When the myelin sheath in these areas is dissolved, a trident sign can be formed (as shown in the figure below).

Fig.
1 MRI T2WI sequence in patients with central pontine myelinolysis with trident sign visible (shown on right)

Figure 2 shows a 60-year-old woman with osmotic demyelinating with trident sign

However, trident signs are more common in patients with central pontine myelinolysis about 2 weeks after onset, as shown in the case shown
in the figure below.

Figure 3 Regular MRI review of patients with central pontine myelinolysis three weeks prior to illness
.
From the second week onwards, there is a clear abnormal signal of long T1 long T2 in the pons, and obvious signs of trident can be seen in figure B
.
In the first week, T1WI (D chart) showed almost no noticeable change

In the above case, T2WI (A-figure) during the first week of illness shows a slight increase in pontine T2 signal, which is similar to the nose of a piglet, as shown
in the figure below.
This sign has been proposed in recent literature, called Piglet sign, literally translated as piglet sign, but only for the part of the pons demyelination, it may be more appropriate to translate it as "pig nose sign
".

Figure 4 shows the T2WI imaging of the first week of illness in the above case, and the figure on the right is a schematic of the "pig nose sign"

Of course, seeing this, some people will also think that the T2WI chart in the second week of illness is also similar
to the pig's nose.

Figure 5 Schematic diagram of the pig nose sign

That's right, but this time it's more like the trident sign
we mentioned earlier.
From this, we infer that perhaps the pig nose sign will become a manifestation of the trident sign as the disease progresses, that is, the pig nose sign is an early manifestation of the trident sign, do you think it's right?

If so, porcine rhinosign may be of great value
for our early diagnosis of the disease.

Of course, not only that, but in the regular review of the above patients, the Gd-DTPA enhancement sequence is also added, and the performance of this sequence is also more meaningful (see figure below).

Fig.
6 The sequence of T1WI intensification in three examinations in the above patients showed that in the first week (Figure A), the demyelinating portion was significantly inhomogeneously intensified, which closely resembled the pig nose sign, while only mild enhancement was seen in the second week and no significant enhancement in the third week

summary

The porcine rhinostrophic sign may be an early manifestation of central pontine myelinolysis, which can be found in both the T2WI sequence and the T1WI enhancement sequence, and is potentially valuable for the early diagnosis of the disease
.