Head pathology on a CT scan

CT in traumatic hemorrhages

A direct consequence of a head injury is a brain contusion, accompanied by hemorrhage. Acute hemorrhage appears as an area of increased density with swelling of surrounding tissues and displacement of adjacent brain structures. In patients with anemia, the hematoma appears less dense and may even be isodense (equal in density) to normal brain tissue.

If the vascular wall damage occurs secondary to decreased perfusion due to edema of a brain region, signs of hemorrhage may not be detected for several hours or, much more rarely, days after the head injury. Therefore, a CT scan of the head performed immediately after the head injury and showing no pathological changes does not exclude the development of intracranial hemorrhage in the future. Therefore, if the patient's condition worsens, a repeat scan should be performed. After complete resorption of the hematoma, a clearly defined defect with a density equal to (isodensity) CSF is determined.

Brain contusion often results in epidural, subdural, or subarachnoid hemorrhage, possibly extending into the ventricles. A complication of such extension, as with subarachnoid hemorrhage, is disruption of cerebrospinal fluid circulation due to obstruction of the pacchionian granulations (arachnoid membrane), the foramen of Monro, or the fourth ventricle. This may result in hydrocephalus with increased intracranial pressure and transtentorial brain herniation.

Epidural and subdural hematomas can also lead to significant displacement of brain tissue and midline structures. Very often, this is the cause of obstruction of the opposite foramen of Monro and, accordingly, unilateral enlargement of the lateral ventricle of the brain on the side opposite to the bleeding.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ]

Computed tomography in intracranial hemorrhages

If the hemorrhage extends into the ventricular cavity, physiological calcifications of the choroid plexuses in the lateral and third ventricles, epithalamic cord, and pineal gland must be distinguished from fresh hyperdense blood clots. Note the edema surrounding the hemorrhage.

When performing a CT scan with the patient in the supine position, a horizontal blood level may be seen in the posterior horns of the lateral ventricles due to sedimentation. If the ventricles are dilated, the patient is at real risk of transtentorial herniation.

[ 7 ], [ 8 ], [ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ], [ 15 ], [ 16 ]

Subarachnoid hemorrhage (SAH)

Obstructive hydrocephalus caused by SAH is easily identified by the dilation of the temporal horns and lateral ventricles. In such cases, it is important to assess the width of the SAP and pay attention to the convolutions of the brain - the lack of clarity indicates diffuse cerebral edema.

Intracranial hemorrhages

Since children have a very narrow FAS, the presence of a SAH may not be noticed. The only sign is a small area of increased density adjacent to the falx. In adults, a small SAH appears as a limited area of increased density.

Subdural hematoma

Bleeding into the subdural space occurs as a result of a brain contusion, damage to the vessels of the pia mater, or rupture of the emissary veins. Initially, the hematoma appears as an extended structure of increased density located along the inner edge of the cranial vault. Unlike an epidural hematoma, its outlines are usually uneven and slightly concave on the side of the adjacent cerebral hemisphere. This type of intracranial bleeding is not limited to the sutures of the skull and can spread along the entire surface of the hemisphere.

A subdural hematoma can cause a noticeable displacement of brain structures, disruption of cerebrospinal fluid circulation, and wedging of the brainstem into the tentorial notch. Therefore, to select further treatment tactics, it is not as important to establish the nature of the hematoma (subdural or epidural) as to determine the size (dimensions) of the hemorrhage. Hematomas with a tendency to spread, especially with a threat of cerebral edema, should be removed surgically.

A chronic subdural hematoma appears as a homogeneous area of low density or a non-homogeneous area with blood sedimentation. Minor venous bleeding is especially dangerous due to the patient's asymptomatic period and gradual development of somnolence - up to coma. Therefore, a patient with a head injury and suspected bleeding should always be under observation so that deterioration of the condition can be noticed in time.

[ 17 ], [ 18 ], [ 19 ], [ 20 ], [ 21 ], [ 22 ], [ 23 ], [ 24 ]

Epidural hematomas

Bleeding into the epidural space usually occurs due to damage to the middle meningeal artery and rarely from the venous sinuses or pacchionian bodies (granulations). They are most often found in the temporoparietal region or the posterior cranial fossa, where there is a risk of herniation of the cerebellar tonsils. Arterial bleeding separates the dura mater from the inner surface of the cranial vault and is visualized in section as a biconvex zone of increased density with a smooth edge on the side of the adjacent hemisphere. The hematoma does not extend beyond the sutures between the frontal, temporal, parietal or occipital bones. In the case of small epidural hematomas, the biconvex shape is not clearly defined, and in this case it is difficult to distinguish it from a subdural hematoma.

It is important to differentiate between a closed skull fracture with an intact dura mater and an open skull fracture with the risk of secondary infection. A characteristic sign of an open skull fracture is the presence of air bubbles in the cranial cavity, which prove the presence of communication between the intracranial space and the external environment or paranasal sinuses.

[ 25 ], [ 26 ], [ 27 ], [ 28 ], [ 29 ], [ 30 ]

CT scan for stroke

Along with cardiovascular and oncological diseases, stroke is one of the most common causes of death. Thrombotic occlusion of a cerebral artery leads to irreversible necrosis of the area of its blood supply. The causes of occlusion are atherosclerotic changes in the cerebral vessels or, less commonly, arteritis. Embolism from the left heart and from thrombi on atherosclerotic plaques of the bifurcation of the common carotid artery can also be the cause of cerebral vessel occlusion.

Typical for embolism is the presence of small infarct zones of low density, located diffusely in both hemispheres and basal ganglia. Later, the embolic zones appear as small, clearly defined areas with a density equal to (isodense) the density of the cerebrospinal fluid. They are called lacunar infarcts. Such diffuse brain damage is an indication for duplex sonography or angiography, as well as echocardiography to exclude atrial thrombosis.

If a stroke is suspected, it may take up to 30 hours for the swelling to become clearly visible as a low-density area that is distinct from normal brain tissue. Therefore, a CT scan should be repeated if the initial scan is normal even though the patient has neurological symptoms and these symptoms do not resolve. Relief of symptoms indicates a transient ischemic attack (TIA) - in this case, there are no visible changes on CT.

In contrast to TIA, in cases of prolonged reversible ischemic neurological deficit, CT sections often reveal areas of edema with low density.

If the infarction zone corresponds to the blood supply area of the cerebral artery, one should think about occlusion of the corresponding blood vessel. Classic infarction of the branches of the middle cerebral artery is manifested by a zone of ischemic edema of low density.

Depending on the extent of the lesion, an infarction may cause a pronounced mass effect and cause a shift in the midline. Small infarctions usually do not cause a shift in the midline. If the integrity of the arterial wall is compromised, bleeding may occur, which manifests itself as areas of increased density covering the nearest convolutions.

[ 31 ], [ 32 ], [ 33 ], [ 34 ], [ 35 ]

Computed tomography for tumors and metastases

Although differential diagnosis of cerebral infarction and intracranial hemorrhage can be performed without the use of contrast, detection of brain metastases is significantly improved by intravenous contrast agents. Even the smallest areas of BBB disruption are visible. On non-contrast-enhanced images, large metastases of the same density (isodense) with surrounding tissues are sometimes accompanied by perifocal edema (and may be misinterpreted as tissue edema due to infarction.

After the introduction of a contrast agent, it is much easier to perform a differential diagnosis of a brain tumor.

[ 36 ], [ 37 ], [ 38 ], [ 39 ], [ 40 ], [ 41 ], [ 42 ], [ 43 ]

Computer tomography for inflammatory processes

Another example of the advantage of using a contrast agent is the diagnosis of inflammatory processes, since this pathology is accompanied by a violation of the BBB and is not always clearly visible without enhancement. Contrast enhancement confirms the presence of an inflammatory process. Bacterial infection of the aortic valve was the cause of septic embolism of the left occipital lobe.

Inflammation of the paranasal sinuses and middle ear can always be diagnosed on regular sections by the presence of effusion, for example, in the cells of the mastoid process, which are normally filled with air. Edema of the mucous membrane of the external auditory canal is well visualized without the introduction of a contrast agent. As the process progresses and an abscess forms, it is necessary to examine the images in the bone window to search for areas of possible erosion of the surrounding bone formations.

A retention cyst, which is often found in one of the paranasal sinuses, should be differentiated from inflammatory changes. It is characterized by a wide base on the sinus wall, spreading into its lumen, and a rounded upper contour. Cysts are clinically significant only if they cause obstruction of the maxillary sinus funnel or semilunar canal, which leads to accumulation of secretion in the sinus.

In patients with chronic sinusitis, it is important to ensure that the lumen of the semilunar canal is not obstructed and that there are no other restrictions for the movement of secretion by the ciliated epithelium. The most vulnerable structures in this regard are Heller cells, the middle nasal concha, and the uncinate process. Changes in these structures can lead to obstruction of the semilunar canal and cause chronic recurrent sinusitis.

[ 44 ], [ 45 ], [ 46 ], [ 47 ], [ 48 ], [ 49 ], [ 50 ]

Eye sockets

Any formation inside the orbit must be quickly diagnosed and effectively treated, otherwise serious consequences for vision are possible. To exclude tumor invasion into the wall of the orbit, it is necessary to use a bone window.

Endocrine ophthalmopathy

When viewing CT images, minor changes may be missed. Endocrine ophthalmopathy often manifests as a sign of Graves' disease (diffuse thyrotoxic goiter) and in the early stage can be diagnosed based on thickening of the eye muscles, especially the inferior rectus muscle. Myositis should be considered in the differential diagnosis.

If this early sign of endocrine ophthalmopathy, which is autoimmune in nature, is missed, orbital tissue damage will progress in the absence of adequate therapy.

The pattern of damage changes as the disease progresses. First, an increase in the volume of the inferior rectus muscle is detected. Then the medial rectus muscle and the superior rectus muscle respond. The remaining eye muscles are the last to increase in size. Therefore, when analyzing CT images of the orbits, you should always monitor the symmetry of the muscles surrounding the eye.

[ 51 ], [ 52 ], [ 53 ], [ 54 ], [ 55 ], [ 56 ], [ 57 ], [ 58 ], [ 59 ], [ 60 ], [ 61 ]

Bones of the facial skull and paranasal sinuses

Unlike retention cysts, malignant neoplasms of the paranasal sinuses often cause contact destruction of the facial bones and may extend to the orbit, nasal cavity, or even the anterior cranial fossa. Therefore, sections should be viewed in both the soft tissue and bone windows. Planning surgery to remove a space-occupying neoplasm usually requires obtaining CT sections in several projections. The following example shows such a tumor of the paranasal sinuses in axial and coronal projections. Beginning in the mucous membrane of the right maxillary sinus, the tumor extends to the nasal cavity and the ethmoid cells.

In addition to determining the prevalence of chronic sinusitis, the main reason for performing coronal scans is to diagnose fractures. Fractures of the orbital floor are often accompanied by dislocation of the fat or inferior rectus muscle into the fracture area, or even into the inferior maxillary sinus. This must be established before surgical treatment. It is also important to detect indirect signs of a fracture, such as slight step-like contours of the bones and post-traumatic bleeding into the nasal cavity or the frontal and maxillary sinuses. It is also important to establish whether there is a fracture of the head of the mandible? Is there a violation of the integrity of the bones of the maxilla with displacement of fragments from the sphenoid bone?

[ 62 ], [ 63 ], [ 64 ]

Fractures of the facial bones according to Le Fort

• Type I The fracture line passes through the maxilla and maxillary sinus.
• Type II The fracture line passes through the zygomatic process of the maxilla, into the orbit to the frontal process of the maxilla, where it passes to the opposite side. The maxillary sinus is not involved in the process.
• Type III The fracture line passes through the outer wall of the orbit and the frontal process of the maxilla to the opposite side, involving the ethmoid cells, the zygomatic bone, and often extending to the base of the skull.