Examination of the skull and brain using an MRI

introduction

Magnetic resonance imaging (MRI) is also known as magnetic resonance imaging. If the tomography is carried out in the area of ​​the head, it is called cranial magnetic resonance imaging. It is carried out to accurately represent structures in the skull and brain and, if necessary, to discover pathological processes.

Read more on the subject at: Magnetic resonance imaging

application areas

Magnetic resonance tomography is used for detailed imaging of the structures of the head. It is used to detect or rule out various diseases. These include above all diseases that affect the soft tissue structures of the head area, such as tumor diseases or inflammation.
Inflammations and tumors can affect many structures in the head area, so the MRI is used to clarify:

• Meningitis (meningitis)
• Encephalitis (Encephalitis)
• Sinus infections
  Read more on the subject at: MRI of the sinuses
• Tumors
• Inflammation of the salivary glands
• Inflammation of the throat
• Inflammation of the larynx

Cerebral infarctions can also be detected by an MRI of the head, as can cerebral hemorrhage and changes in the blood vessels of the brain (aneurysm), such as calcification (atherosclerosis) or aneurysm formation.
Injuries that affect the cranial nerves can be recognized on an MRI image, for example a functional impairment of the auditory and equilibrium nerves can also be recognized.
Since bony structures are also shown, malformations of the skull, injuries to the temporomandibular joint and the eye socket can be detected. A cranial brain trauma (TBI) can also be seen on an MRI image.

Read more on the subject at: MRI of the skull

Preparations for an MRI of the head

An MRI examination of the head, like any other MRI examination, does not require any special preparation.
In the preliminary discussion with the doctor, possible allergies to contrast media should be clarified and if there is claustrophobia, the administration of a sedative should be discussed.
If there is a pronounced claustrophobia, options must be considered to perform an MRI.

Please read our relevant topic: MRI for claustrophobia - what can you do?

On the day of the MRT examination, the patient must take off all metal parts that he is wearing on the body, as these are magnetically attracted by the examination device and can lead to injuries. Above all, this includes jewelry such as bracelets, watches, necklaces, earrings and piercings. But clothing with metal parts such as buttons or buckles should also be removed. Keyrings and purses should be removed from pockets, and removable dentures should also be taken out. In addition, wires or screws that have been surgically inserted into the bones should be mentioned in the educational discussion.

Read more on the subject at: Clothing in the MRI - what should I wear?

Electronic devices, such as cell phones or MP3 players, should not be taken into the examination room, as well as EC or credit cards, as they influence the magnetic field and can also be damaged as a result.

Do I have to be sober for the MRI?

For head MRI imaging, the patient must usually not sober be. There is no effect on the picture quality. The normal intake of food and drink is possible.
A exception represents the planned administration of Contrast media The contrast agent is injected into the patient through an access placed in the crook of the arm. In order to avoid possible aspiration (vomit gets into the lungs via the airways) in the case of a contrast medium intolerance, food should be supplied to the for safety reasons 4 hours before the examination be waived.

procedure

After all metallic objects have been put down, the magnetic resonance tomography can be started. The normal examination device is constructed as a tube into which a bed can be inserted. The patient lies down on this couch and is driven with his head into the tube. People who suffer from claustrophobia are given a sedative before the examination. Since very loud technical knocking noises occur during the examination, the patient is given either soundproof headphones or earplugs through which music can be heard.

In addition, the patient is given a switch that he can press to call the medical staff. Because this leaves the room during the examination and takes place behind a pane of glass. The medical-technical radiology assistants can observe the patient from here.

Depending on the purpose of the examination, it may be necessary to take a series of images with contrast medium in addition to the normal MRI examination. This then has to be injected into the patient in between. When the examination is complete, the patient is driven out of the tube on the couch and does not have to observe any further precautionary measures. There is an exception if the patient was given sedatives before the examination. Then he is not allowed to drive a vehicle himself that day.

The images are evaluated by a radiologist and the patient is then asked for a meeting.

Further information on the subject can be found at: Procedure of an MRI

Duration of the investigation

The actual MRI scan of the head takes about 15 to 20 minutes.
Added to this are the waiting time, preparation time, positioning of the patient and the subsequent final discussion. Depending on whether the MRI is carried out with or without contrast agent, additional time must be planned for.
You must plan between 60 - 75 minutes for all preparatory and follow-up measures and the head MRI.

Read more on the subject at: Duration of various MRI examinations.

Contraindications to an MRI

In patients with a pacemaker or with an implantable defibrillator (ICD) an MRI scan cannot be performed in most cases. Magnetic resonance tomography should also not be performed with other metallic foreign bodies, such as mechanical artificial heart valves, since otherwise both the patient and the implant can be damaged.
Also insulin pumps and an artificial inner ear (Cochlear implant) are contraindications to MRI.In the meantime, however, there are also MRI-compatible cardiac pacemakers, about which the attending physician should nevertheless be informed in the preliminary discussion.

In addition, there are restrictions for which magnetic resonance imaging should be avoided, but the administration of contrast media. These are functional restrictions of the kidneys (Renal failure) or pregnancy in the first three months.

Also read: MRI and piercing - is that possible? and MRI in pregnancy

MRI with claustrophobia

With MRI imaging of the head, the skull and neck are fixed with pillows and special frames. In addition, a coil is placed around the head to record the radio waves required for imaging. This makes the tube, which is normally 60 to 70 cm wide, appear even narrower when imaging the head. If necessary, the patient can be given a Sedatives administered. In addition, the patient receives a button in his hand that he can press during the examination if he or she becomes increasingly unwell.
In exceptional cases, an examination in one is an alternative open MRI possible. This is a C-shaped magnet that gives the patient an all-round view during the examination.

Cost of a head MRI

The costs for one MRI scan of the head are usually used by the statutory and private health insurance companies if indicated by the doctor.
Depending on the effort and place of implementation, they amount to about 400 to 1,000 euros for privately insured persons.
If the MRI is performed on the head with a contrast medium, the costs are higher than with a simple MRI.

MRI of the head in children

Magnetic resonance imaging of the head can also be performed on children.
Since there is no radiation exposure, it is less of a concern than computed tomography or X-rays. An MRI of the head may be necessary in children if malformations of the head are to be detected or excluded during the growth phase.
An MRI scan is also suitable for identifying the possible consequences of injuries from a fall or another accident, as it can be used to detect cranial brain trauma, for example, and reveal any bleeding.

In children, the head MRI is also used to identify the degree of maturity of the brain and to be able to draw conclusions from this about age-appropriate development or a possible developmental disorder.

In the case of small children, it is helpful for one of the parents to stay in the examination room during the examination and possibly lie on their stomach on the couch that is moved into the MRI tube. This can relieve the child of possible fear and ensure that meaningful pictures can be taken, as the child has to lie very still for this.

Complications

As in magnetic resonance tomography in contrast to computed tomography no radiation is used, the consequences of the investigation are very minor.
At Take all precautionary measures and Discard all metallic foreign objects There are no side effects to fear from a normal MRI scan. However, it can with Tattoos or with makeup on the skin too Heat development and the following slight skin irritation come.

In the first three months of pregnancy, expectant mothers should only have an MRI scan performed in an emergency due to possible complications.

When using contrast media, allergic skin reactions or malaise and circulatory problems can rarely occur.

Side effects

After removing all metallic objects and items of clothing usually persist no risks for the patient through the magnetic field and the radio waves. The studies carried out so far have not found any side effects for humans.
Any side effects that occur during or after an examination can be attributed to the administration of contrast media. Even if the occurrence of the side effects is rare, they are Temperature sensation disorders, a tingling sensation on the skin, headache, nausea and a general malaise are possible. However, these symptoms do not last longer than a few hours, as the contrast agent is quickly excreted via the kidneys.

MRI with contrast agent

Since the MRI images are only shown in black and white, many tissues look very similar and are difficult to distinguish from one another. Here a contrast agent helps to increase the contrast between different tissues.
For example, muscles and blood vessels can be better distinguished from one another. Usually the contrast agent is injected into the vein. This distributes the contrast agent in the blood and ensures that the blood vessels stand out from the rest on the MRI images.
The contrast agent also accumulates in tumors and their metastases. Therefore, in addition to tumor diagnosis, a contrast medium MRI of the head also enables the detection of brain aneurysms, cerebral infarctions and bleeding in the head area.

Learn more about the MRI for a stroke.

MRI contrast media are very well tolerated and can also be used if you are allergic to X-ray contrast media, as they do not contain iodine. Gadolinium-GTPA is often used as a contrast medium. This is a metal associated with an acid.

The contrast agent is completely excreted in the urine within 24 hours. Therefore caution is advised in patients with severe kidney disease (renal insufficiency), as they cannot excrete the contrast medium optimally.
In very rare cases, the contrast medium can cause a change in the connective tissue, a so-called nephrogenic systemic fibrosis, which affects not only the skin but also the connective tissue of the internal organs.

Read more about this under MRI with contrast media.

When is the contrast agent injected?

First, the imaging is performed without the administration of contrast agent. If the examining doctor determines during these recordings that the administration of contrast medium is necessary or helpful, the examination is briefly interrupted and the contrast medium is injected into the patient.
The main purpose of the contrast agent is to improve the display of structures with a high blood flow and metabolic activity. These are mainly Foci of inflammation and some Tumors. Due to the enrichment of the contrast agent, these structures appear white in the MRT image and are thus clearly differentiated from their surroundings.

MRI without contrast agent

An MRI scan of the head without countermeasures almost brings no side effects with himself. It can also be used in patients with Kidney disorder or in patients with a Allergy to MRI contrast media be performed.
In some areas of application, MRI images without contrast medium are very informative, but they are often not sufficient for diagnoses that require detailed images of the blood vessels. Also in the Tumor diagnostics usually becomes a MRI with contrast agent carried out.

White spots on the MRI - what can they mean?

There are two different procedures for MRI imaging (T1 / T2 weighting). As a result, structures that are displayed as white in one method appear black in the other. The color is therefore of no essential importance without considering the method (T1 / T2). In T1-weighted images, fatty tissue appears light or white (including the Brain marrow), while in T2-weighted images liquids (including the Liquor) is displayed brightly.
Clearly demarcated spots in MRI imaging can be based on different diseases. Sometimes it is also one old, healed inflammation in the brain and is not pathological.

Typically round-oval white spots occur under the Multiple sclerosis on. These foci of inflammation are mainly found at the edge of the ventricles filled with liquor. For better representation, delimitation and differentiation of the individual spots one can give the patient Contrast media administer.
Also Tumors (benign / malignant) may appear as white spots on the MRI image. Due to the high blood flow in metabolically active tumors, a lot of contrast agent accumulates in the tumor tissue, which makes the tumor appear white in the imaging. In addition, white spots can appear on the MRI on a T2-weighted image for free liquid, Liquor (e.g. with Cysts) or Scarring indicate in the area of ​​the brain.

Tests, usually done by a neurologist, are needed to further differentiate between the causes of the spots.

MRI of the head in various diseases

MRI for multiple sclerosis

An MRI of the head can be helpful to confirm the diagnosis of multiple sclerosis (MS). After the doctor has asked about the patient's complaints and MS is suspected, an MRI scan can provide information about the changes in the brain.
In 85% of cases, multiple sclerosis can be detected in the early stages by an MRI of the head. This disease has a typical appearance on the MRI images.
Round to oval white spots (foci) appear in several parts of the brain. These can preferably be seen at the edges of the brain chambers. In some cases these spots allow a clear diagnosis, in other cases they cannot be distinguished from small areas with reduced blood flow.

Young people sometimes have white spots in the area of ​​the external brain, but they are usually completely harmless.

Read more about this in our topic: MRI in multiple sclerosis and MRI of the brain

MRI for migraines

Migraines are a form of chronic headache. These typically occur on one side and are often accompanied by nausea, vomiting, and sensitivity to light and noise.
Apart from a few triggering factors, the exact cause and development has not been clarified. Because of this, migraines can easily be confused with other causes of chronic headaches. MRT imaging represents an additional form of diagnosis that serves to differentiate the cause of unclear chronic headaches. Among other things, it serves to rule out life-threatening causes (e.g. subarachnoid hemorrhage or brain tumors).

You might also be interested in that: Therapy of migraines

Detect intracranial pressure signs on an MRI

Magnetic resonance tomography (MRT) provides detailed sectional images of the brain and the liquor spaces. The liquor spaces are a chamber system in the brain that is filled with the cerebral water, the so-called liquor. Increased intracranial pressure is usually shown by various indirect signs. The increased pressure leads to an expansion of the liquor spaces, especially the inner in rare cases also the outer. As a result, the venous drainage of the brain can narrow and become blocked. In addition, certain structures of the brain tissue, which are usually rounded, can be flattened. Another sign is a prominent optic nerve papilla. However, the signs should always be viewed as a whole under the existing symptoms and compared with previous recordings.

Read more on the subject here Intracranial pressure sign

MRI for vasculitis

Vasculitis is inflammation of the blood vessels that can appear anywhere in the body. The individual diseases are divided according to the size of the affected vessels (including Wegener's granulomatosis, Henoch-Schönlein purpura, polyarteritis nodosa, giant cell arteritis).
In some cases the vessels of the head are also affected. Involvement of the central nervous system is also possible in rare cases.
The administration of contrast media during an MRT examination serves to better visualize the vascular inflammation. The foci of inflammation surrounding the vessels appear as wide white lesions along the vessels. The MRI findings, however, are often unspecific and suggest several clinical pictures - further examination is required.

MRI if a tumor is suspected

If there is a suspicion of a tumor in the head area, an MRI examination is carried out to detect it. This allows tumors and metastases to be recognized very well and their size and location to be assessed. For this purpose, an MRI with contrast agent is carried out, as this is particularly concentrated in tumors and metastases and these can thus be distinguished from the surrounding tissue. Performing an MRI offers better options in the area of ​​tumor diagnosis than computed tomography.

In addition to the fact that the tumors in the head differ from the surrounding tissue in their coloring on the MRI images, it is also the case with larger tumors that they displace the surrounding tissue. The resulting pressure compresses the brain chambers and the entire brain mass is shifted. Despite these often unambiguous features, when a brain tumor is first diagnosed, it is necessary to confirm the diagnosis of a tumor by taking a tissue (biopsy).

MRI for epilepsy

Epilepsy can either be genetic or it can be acquired over a lifetime. Both forms can be differentiated using MRI images. Genetically caused epilepsy does not usually show any changes in the brain structure on MRI images. An electroencephalogram (EEG) is required for this, in which typical changes can be recognized.

In contrast, acquired epilepsies are based on structural changes in the brain that can be seen on MRI images of the head. These structural changes are mostly localized and can affect either one or both hemispheres of the brain. Sometimes, however, the changes are so small that they are barely noticeable, so post-processing of the images with the computer is necessary.

Epilepsies can also result from structural changes, so scarring caused by a previous illness can cause epilepsy in the further course.

Procedure

The MRT procedure is used for imaging diagnostics and is based on the application of a magnetic field. This aligns certain particles in the body with the magnetic field. If the magnetic field is switched off, the particles orient themselves again in their original position and the respective speed to reach the position is measured.
Since this is different for all particles, images can be created from the measurement data. No rays like X-rays or CT are used here.
With an MRT, cross-sectional images of the head are created that allow various structures to be assessed very precisely. An MRI of the head can reveal the brain, skull, blood vessels, ventricles (Ventricle) with nerve water (Liquor) are filled and the remaining soft parts of the skull are shown.