How to diagnose glioma

The diagnosis of glioma can be made based on age, gender, site of occurrence and clinical course, and the pathological type can be estimated. In addition to medical history and neurological examination, some auxiliary examinations are also needed to help with diagnostic positioning and qualitative analysis. Positron emission tomography can obtain images similar to CT, and can observe the growth and metabolism of the tumor and distinguish between benign and malignant tumors. How is glioma diagnosed?

1. Diagnosis of X-ray Films

X-rays have limitations in diagnosis. They can only show the optic nerve foramen, which has certain clinical significance, but are difficult to show the tumor itself. They are rarely used now. B-ultrasound has qualitative diagnostic significance for optic nerve gliomas.

It can clearly show the lesions in the orbit, but it is difficult to show the lesions in the canal and the brain. It can be used as a screening examination method. CT can accurately show the location, shape, boundary, orbital and intracranial conditions of the lesions.

In particular, it can more clearly show the enlargement of the optic canal and the widening of the distance between the anterior clinoid processes, making it easier to determine the nature and scope of the lesion. However, it is difficult to show smaller gliomas in the optic canal, or to accurately show gliomas of the optic chiasm or optic tract. There is also a certain limit to accurately judging the relationship between the lesion and the adjacent structures. MRI can accurately show the scope of the lesion and its relationship with the adjacent structures, especially for gliomas in the optic canal and the optic chiasm or optic tract, providing a reliable basis for clinical surgery. MRI is the best examination method for this disease, and B-ultrasound and CT can be used as auxiliary examination methods.

2. Imaging differential diagnosis

① Optic nerve meningioma: It is common in adult women and causes visual impairment, mostly behind the exophthalmos. Optic nerve sheath meningioma may be eccentric, with a high CT value, and may be accompanied by spotted, ring-shaped or irregular calcifications. MRI examinations show medium signals on both T1WI and T2WI, and a "track sign" can be seen after CT or MRI enhancement.

②Optic neuritis: Clinically, it manifests as a sharp decrease in vision, which may be accompanied by pain when the eyeballs are turned and deep orbital pain. MRI shows diffuse thickening of the optic nerve, which generally does not form a soft tissue mass. The optic nerve signal on T1WI is reduced, the signal on T2WI is increased, and the signal on STIR is high. It may be enhanced after enhancement. It is best shown by enhanced scanning combined with fat suppression sequence. It may be a change of multiple sclerosis. If MRI shows periventricular sclerotic plaques, this disease can be confirmed.

3. Pathological diagnosis and molecular biological markers

It is strongly recommended to strictly follow the WHO (2007) classification of central nervous system tumors for pathological diagnosis and grading of gliomas. In order to cooperate with the treatment, efficacy observation and prognosis judgment of glioma patients, glioma molecular biological markers should be performed as appropriate: the detection of IDH1 gene mutation and chromosome 1p/19q heterozygous loss in low-grade gliomas is of great significance for clinical prognosis judgment (level I evidence). Glioma with astrocyte differentiation characteristics and 60%~70% of oligodendrogliomas are positive for glial fibrillary acid protein (level I evidence). Oligodendrocyte-specific nuclear transcription factors have a certain reference value for distinguishing oligodendrogliomas from gliomas of astrocyte origin.

Epidermal growth factor receptor amplification and its variant III mutation are valuable for the diagnosis of primary GBM. Ki-67 proliferation index is closely related to the degree of differentiation, infiltration or metastasis and prognosis of the tumor, and is one of the important reference indicators for judging the prognosis of the tumor (level I evidence). Neuron-specific nuclear protein is of great significance in judging the neuronal components in the tumor, and is mainly used for the diagnosis and differential diagnosis of glial neuron tumors and neuroblastomas.