1. Acute epidural hematoma: it is characterized by a localized spindle-shaped uniform high-density area under the skull inner plate, and the contact edge with the brain is clear. The seat occupation performance is slight.
2. Acute subdural hematoma: it is a crescent-shaped thin-layer uniform high-density area under the skull inner plate. The shape of subacute phase is unchanged, but most of them are high or mixed density or equal density. Isodensity hematoma should be determined according to the displacement of ventricle and sulcus. Hematoma in chronic stage is low density or isodensity.
3. Acute intracerebral hematoma: it is a round or non-plastic uniform high-density area in the brain with clear outline and brain edema around it. When it enters the ventricle or subarachnoid space, you can see the high-density shadow at the hematocele.
4. Brain contusion and laceration: It is characterized by a large area of low-density edema with clear boundaries and patchy high-density bleeding foci in the area. Simple brain contusion only manifests as a well-defined low-density edema area, which appears within a few hours to three days after injury, and 12 ~ 24 hours is the most obvious and lasts for several weeks.
5. Chronic subdural effusion: It shows crescent or half moon shape near the low density area of cerebrospinal fluid under the skull inner plate. It is more common in frontotemporal region, involving one or both sides, with no or only slight occupying performance. Chronic subdural effusion is more common after traumatic brain injury, and it may also be one of the manifestations of chronic subdural hematoma. The location and quantitative diagnosis of brain tumor by CT is quite reliable, and the qualitative diagnosis is superior to other methods. The third and fourth generation CT can also clearly show lesions with a diameter of not less than 0.5cm. According to the development position of lesions and the changes of ventricles and cisterns, it is not difficult to determine the location of tumors. Combined with the reconstruction of coronal and sagittal images, the position of tumor in three-dimensional space can be displayed, which makes the localization diagnosis more accurate.
Most common tumors have typical CT manifestations, and 70 ~ 80% cases can be diagnosed qualitatively. For example, meningiomas usually show high density, clear boundary, spherical or lobulated lesions, which are connected with skull or cerebellar tentorium or cerebral falx. It is obviously strengthened after enhancement. Brain metastases are mostly located in cortical and subcortical areas, showing small low, high or mixed density lesions, and ring-shaped enhancement or uniform enhancement after enhancement. Multiple lesions are of great significance for diagnosis. Most suprasellar lesions with low density or mixed density enhancement are craniopharyngiomas. Acoustic neuroma is a low-density or slightly high-density lesion in cerebellopontine angle area, which is enhanced and the internal auditory canal is enlarged and destroyed. The characteristic signs of intracranial tumors are extensive edema of tissues around the tumor and deviation of adjacent brain structures and midline structures. Tumors located in the midline of the brain, especially those located in the posterior cranial fossa, can cause signs of moderate and severe hydrocephalus even if the tumors are small. Because common tumors sometimes have atypical CT manifestations, some rare tumors can also have typical manifestations of common tumors, so the qualitative diagnosis of intracranial tumors by CT is limited. 1. Hypertensive intracerebral hematoma: CT findings are related to the disease stage of hematoma. Fresh hematoma is a high-density area with clear edge and uniform density. The CT value is about 50 ~ 70 Hu. After 2 ~ 3 days, edema zone appeared around the hematoma. After about a week, the absorption density of the periphery began to fade. After about 4 weeks, it became a low-density softening focus with neat edges. Hematomas are mainly located in basal ganglia and thalamus, and the probability of breaking into ventricles is high. Intracerebroventricular hematoma can buffer increased intracranial pressure caused by hematoma to varying degrees, but intraventricular hemorrhage can also block cerebrospinal fluid circulation, lead to hydrocephalus and aggravate increased intracranial pressure. But hydrocephalus caused by intraventricular hemorrhage is rare after all. The hematocrit in the ventricle is absorbed faster than the hematoma in the brain parenchyma, and it is completely absorbed and dissipated in more than a week.
2. Cerebral infarction: Ischemic cerebral infarction mostly occurs in the blood supply area of the middle cerebral artery, and arterial trunk occlusion mostly involves the cortex and medulla of multiple cerebral lobes, which are fan-shaped or wedge-shaped, with unclear boundaries and occupying space. Brain gyrus or patchy enhancement appeared after enhancement. Lacunar infarction caused by terminal arteriolar occlusion is mostly found in basal ganglia and radial coronal region of parietal lobe, showing low-density lesions with clear boundaries and diameter less than 1cm, without occupying effect. Hemorrhagic cerebral infarction is characterized by irregular bleeding spots with slightly higher density in a large low density area.
3. Arteriovenous malformation and aneurysm: Obviously, CT is not as reliable as MRI and DSA in diagnosing arteriovenous malformation and aneurysm. But CT diagnosis of its complications is very accurate. Some cases can also be diagnosed qualitatively by CT. Aneurysms usually occur in basilar artery ring or communicating artery. Plain scan shows a slightly circular high-density shadow with clear boundary and no occupying effect, which is obviously enhanced after enhancement. Arteriovenous malformations are mostly characterized by punctate calcification in irregular low-density lesions without occupying space. Enhanced scan showed obvious and abnormal enhancement around the lesion, and the vascular shadow was tortuous and thick. Abnormal rupture and bleeding of aneurysm can be seen in subarachnoid space, brain or ventricular hemorrhage. Lesions can occur in intervertebral disc space and bilateral posterior intervertebral joints. The examination range of each intervertebral space should be from the pedicle of the previous vertebral body to the pedicle of the next vertebral body, and the scanning plane should be parallel to the intervertebral space. Spinal degeneration is more common in lumbar vertebrae and cervical vertebrae, with a wide range of activities. Vertebral hyperplasia, disc herniation, posterior longitudinal ligament hyperplasia and ossification, ligamentum flavum hypertrophy and posterior facet joint hyperplasia can be seen in the diseased spine. Lumbar degeneration is the most common. The early change was the radial "tearing" of the fiber ring. Because there is no broken ring, it leads to a weak point, and the nucleus pulposus in this area expands around. Although it is still contained in the posterior edge of the intervertebral disc, it can protrude to the weakest place. The protruding part consists of a thinned ring and a nucleus pulposus in the ring. When one or more tears spread to the posterior edge of the intervertebral disc, the ring can really rupture, which will lead to the compression of nearby nerves. Posterior disc herniation and rupture caused by lateral deviation of midline (kyphosis or hernia) or midline (central type) are the most common, and rupture of lateral margin is the least common.
There are two types of clinical syndrome that must be clearly distinguished. The first type is cauda equina compression syndrome, which manifests as back pain and radiates to both lower limbs. The pain increases when standing, especially when walking. Surprisingly, the neurological examination was negative. When walking weakness occurs, it is bilateral symmetry, and the inhibition of deep tendon is also bilateral. The second is nerve root compression syndrome caused by nucleus pulposus protrusion, which causes sciatica and may be accompanied by back pain. Pain radiates along the involved nerve root pathway, and the cavity may be accompanied by the disappearance of sensation, muscle strength and deep tendon reflex in the nerve root distribution area. Positive straight leg elevation sign and positive Lasegue test also suggest nerve root compression. Protrusion of the nucleus pulposus often compresses the nerve roots from the intervertebral foramen in one plane of the ruptured intervertebral disc. When the protruding disc fragments are large, the knife tail will also be compressed, and the two syndromes coexist and have clinical signs and characteristics. Similarly, when disc herniation is accompanied by spinal stenosis, there are two kinds of syndromes coexisting in clinic.
The CT manifestations of spinal degeneration are as follows: ① the posterior edge of intervertebral disc is deformed; ② Epidural fat displacement; ③ soft tissue density of epidural space; ④ deformation of dural sac; ⑤ Nerve root sheath is compressed and displaced; ⑥ Protruded calcification of nucleus pulposus; ⑦ "vacuum" phenomenon (pneumatosis) in intervertebral disc or bony spinal canal. Some congenital deformities of spine and spinal cord, spinal structure, etc. It shows well on CT film.
CT diagnosis is due to its special diagnostic value. It has been widely used in clinic, but CT can not show tumors or other lesions with a diameter less than 65438±0cm. In some cases, it can only provide the location, size and number of lesions, but can not determine the nature of lesions.