CT cisternography is a layer-by-layer scanning X-ray visualization of the cerebrospinal fluid spaces of the brain. It is carried out after endolumbal administration of an iodine-containing contrast agent. First, a scan is performed in a lateral projection, then the required number of frontal sections is performed. CT cisternography is informative for the diagnosis of posttraumatic basal liquorrhea, since it allows to assess the state of the cerebrospinal fluid pathways and cerebrospinal fluid dynamics. In addition, the study helps to detect tumor processes in the area of the cerebellar bridge angle and the chiasmal cell region, hydrocephalus, Arnold-Chiari anomaly, arachnoid cysts.
Technique for performing
Water-soluble contrasts are injected into the cerebrospinal fluid by puncture endolumbally in a certain part of the back. Together with the cerebrospinal fluid, the compounds enter the ventricles, brain cisterns, and subarachnoid spaces.
The distribution of the drug is monitored by performing tomography at certain intervals – in the arterial and venous phases of contrast. The scanning intervals are determined individually depending on the speed of movement of the cerebrospinal fluid, the presence of obstacles to progress (cysts, adhesions, tumors).
Subsequent scans are carried out via 1, 3, 6, 12, 24, 48 hours after endolumbal injection.
Criteria for evaluating results:
- Physiologically, after 12 hours, part of the contrast is absorbed by gray and white matter, cortex, and periventricular areas;
- After absorption, the visualization of the brain structure increases, even small pathological foci are detected in which contrast does not accumulate;
- Normally, approximately 1 hour after contrast, the amnipac fills 4 ventricles, the interhemispheric gap, and the cisterns of the brain;
- To study cranial nerves (5,7,9 pairs), the scan steps should not exceed 2 mm;
- Convexial furrows are traced after 2-3 hours;
- Tissue contrast saturation decreases after 4-5 hours, which indicates the absorption of the drug by gray matter;
- After 24 hours, the cerebrospinal fluid is cleared of the contrast agent. The drug is preserved in small areas of the large hemispheres, parasagital zones.
When the cerebrospinal fluid circulation slows down after the specified time intervals, an increased accumulation of the drug is noted. Due to the puncture of the spinal canal, the procedure of CT cisternography is invasive, requires anesthesia. The appointment is justified by diagnostic purposes – the identification of dangerous diseases
- Tumors of the chiasmosellar zone;
- Inflammation of the meninges (arachnoiditis);
- Arnold-Kiara disease;
- Hydrocephalus (normotensive);
- An empty Turkish saddle (with the absence of the pituitary gland).
The relative limitation to CT cisternography of the brain is epileptic seizures.
Types of CT-cisternography
An alternative to the study is pneumocysternography– a method of filling the subarachnoid space with air. The combination of an iodine-containing preparation with a gas increases the spraying effect, which increases the visibility of the wall of the cavity structures. The method is used to study the flow of contrast into the pyramids of the temporal bone, the paranasal sinuses, to study the condition of the cerebellar angle, visualization of basal cisterns.
Dynamic scanning is a procedure for administering a contrast agent with an automatic syringe or through a dropper with simultaneous tomography. The method is used to analyze the patency of the cerebrospinal fluid between the subarachnoid cavities and the main cisterns. CT ventriculography and CT cystography are used to analyze individual anatomical formations.
After the introduction of carbon dioxide or nitrous oxide under the meninges, the structure of bridge tanks is monitored using CT cisternography of the internal auditory canal. Two-dimensional and three-dimensional reconstruction after CT of ventriculo-, cisterno-, myelo-, cystography is used for spatial assessment of brain structures. In conclusion, we will describe the indications for cisternography:
- Study of the movement of cerebrospinal fluid, identification of obstacles, narrowing or expansion of brain cisterns;
- Detection of swelling of the cerebral parenchyma;
- Monitoring of cerebrospinal fluid leaks in the paranasal sinuses or in the middle ear;
- Detection of neoplasms.
Special preparation for the procedure is not required. Before performing, you need to make sure that you are not allergic to iodine.