Childhood tumor

Medulloblastoma is a malignant glioma of the posterior cranial fossa in children. The cell morphology of medulloblastoma resembles that of embryonic medulloblastoma, hence the name. Medulloblast cells are primitive, non-polar cells. It is found only in the posterior medullary velum in human embryos, which is consistent with the tendency of medulloblastoma to occur in the inferior vermis of the cerebellum. Medulloblastoma is the most malignant intracranial glioma. So, how to check the diagnosis of medulloblastoma? The diagnosis can be confirmed by examination based on clinical manifestations, laboratory and imaging.

1. Lumbar puncture

In addition to increased pressure, protein volume and white blood cell count can increase. Because tumor cells can be shed and spread, it is easy to find tumor cells, so the examination of cerebrospinal fluid tumor cells is very important. Due to increased intracranial pressure in most patients with medulloblastoma, preoperative lumbar puncture should be used with caution to avoid inducing cerebral hernia. In addition to routine tests, shed cells can be found in cerebrospinal fluid. Usually, multiple lumbar puncture indicates increased intracranial pressure, while increased protein and white blood cells in cerebrospinal fluid are only 1/5.

2. Plain X-ray of the head

Skull X-ray showed signs of intracranial hypertension such as widening of cranial suture, and tumor calcification was extremely rare.

3.CT examination

It can be seen that the cerebellar vermis or the four ventricles have uniform or slightly high density occupying space, which is mostly demarcated with the bottom of the four ventricles, and the brain stem is pushed forward. There is a thin low-density edema band around the tumor, which is obviously uniform enhancement, and the tumor calcification sac is less common. Typical medulloblastoma is generally larger than 3.5cm in diameter and is located in the cerebellar vermis of the midline of the posterior fossa. The tumor involving the upper vermis extends above the tentorial notch of the cerebellum. The tumors on plain CT scan mostly showed uniform high or equal density lesions with clear boundaries. The enhanced examination showed uniform and consistent enhancement. When there are small necrotic foci in the lesion, the plain scan can also show uneven mixed density, enhanced after injection. Calcification of the tumor is common, sometimes with a thin band of low-density edema surrounding the lesion. The fourth ventricle is often pushed forward and may be accompanied by obstructive hydrocephalus. It is distinguished from ependymoma mainly by medulloblastoma calcification and cystic degeneration, and uniform lesion density. When there is a downdraft of the ventricle membrane, there can be a complete or incomplete slightly high-density image around the ventricle, which is banded and has obvious enhancement.

4.MRI

The tumor parenchyma showed long T1 and long T2 signals, and the sagittal position could better show the tumor originated from the vermis of the cerebellum and the relationship between the tumor and the floor of the fourth ventricle. Generally, the signal intensity of medulloblastoma is uniform, and when necrosis or cystic change occurs, the internal focal area is longer than the tumor T1 and T2. Gd-DTPA enhanced scan showed significant enhancement of tumor parenchyma. Sagittal or coronal MRI scan is more valuable for the examination of medulloblastoma with disseminated implantation along cerebrospinal fluid, and the implanted lesion can also be significantly enhanced by Gd-DTPA.

5. Ventriculography

The ventricular system above the aqueduct was uniformly enlarged, and the inferior aqueduct and the fourth ventricle were seen to shift forward, but rarely to the side, and the fourth ventricle may have filling defects or even no filling. The filling of aqueduct and fourth ventricle is of great value for preoperative evaluation of the size and location of the tumor. The main manifestations are as follows: (1) If the tumor protruded the aqueduct and did not develop, it was manifested as aqueduct obstruction, which could only be distinguished by clinical manifestations and CT examination. ② The upper vermis tumor can shorten the aqueduct and bend downward at right angles, and there is no left-right displacement of the aqueduct in the upper Towne position. (3) When the tumor was located in the lower vermis, the aqueduct expanded in a trumpet shape, and the fourth ventricle did not have lateral displacement.