Paranasal sinus hypoplasia is a clinical manifestation of craniosynostosis. Craniosynostosis is the premature closure of one or more cranial sutures resulting in cranial deformity, increased intracranial pressure, impaired intellectual development, and may have ocular symptoms. It is characterized clinically by premature closure of a single or multiple cranial sutures. The etiology of this disease is unknown and there is no satisfactory explanation. Some scholars have found that the disease is familial, so it is thought to be genetically related. The lesions are mostly concentrated in the coronal suture or multiple sutures of bone ossification. Some scholars refer to cranial suture ossification of unknown origin, which is present at birth, as primary sarcopenia, while early ossification of the cranial sutures secondary to other diseases of the body is referred to as secondary sarcopenia, such as early cranial suture ossification in patients with cretinism accompanied by overuse of thyroid hormone replacement therapy. Common tests for paranasal sinus hypoplasia: Cranial CT examination: CT examination of the skull is a method of examining the skull through CT. Cranial CT is a new examination method that is convenient, rapid and safe, painless and non-invasive. It can clearly show the anatomical relationship between different cross-sections of the skull and the specific brain tissue structure. Thus, it greatly improves the detection rate of lesions and the accuracy of diagnosis. In general, CT has better visualization of human hard tissues than soft tissues. Cranial CT examination is important for the diagnosis of most diseases in the skull, cranium and scalp (including trauma, tumor, inflammation, vascular lesions, poisoning, degenerative and metabolic diseases, etc.). Cranial MRI: Cranial MRI is an MRI examination of the brain, which is used to observe whether there are lesions in the brain and can clarify whether the patient is due to structural changes in the brain. Intracranial tumors often cause epilepsy, and MRI has an extremely high diagnostic confirmation rate for low-grade astrocytomas, ganglia, gliomas, arteriovenous malformations and hematomas in the brain. Cranial transillumination test: The cranial transillumination test is performed on newborns and infants with thin cranial bone plates and unclosed fontanelles, and when there is a large amount of fluid under the dura, some of the light can be transmitted and diffracted to the surrounding area.