Patient Information
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PATIENT INFORMATION
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This site contains information for patients who wish to learn more about the diagnostic and therapeutic possibilities of Neuroradiology. We have attempted to present the information in generally understandable, not too-technical medical language. The information is not intended to make personal discussion with the doctor unnecessary, but rather to present basic information as a foundation for each patient’s personal questions and needs.
The contents of the website are continuously updated to reflect modern developments, and this section is presently still in the set-up phase.
CONTENTS DIAGNOSTICS
- X-ray
- Computed tomography
- MAGNETIC resonance tomography
- Angiography (vascular imaging)
- Temporay carotid occlusion test
- Wada-test
- Venous blood collection in the Sinus cavernosus
- Myelography
THERAPY
- Endovascular Interventions / Minimal Invasive Therapy
- CT-guided controlled Pain Therapy
- CT-guided Treatment of Pain
X-ray
Traditional X-ray pictures of the head and spine have lost their importance these days. They are mainly used now following accidents, in chronic diseases of the spine, tumours arising in the bones or following surgery. They have largely been replaced by computer tomography and magnetic resonance tomography.
Computed tomography
Computed tomography (CT) is an X-ray procedure: during the examination, an X-ray tube circles the supine patient while at the same time detectors opposite the tube and rotating with it measure the radiation. These radiation values are converted in computer calculations to layered images. The patient lies on a special table, which is placed in the CT unit to the level of the body part to be examined. Numerous cross-sections only a few millimeters thick of the area to be examined are imaged. Unlike traditional X-ray examinations, the organs can be imaged without the overlying structures and are thus better visible. Even slight differences in tissues become visible and can be made additionally clearer by injection of contrast agent. The “fathers” of computer tomography, G.N. Hounsfield and A.M. Cormack were awarded the Nobel Prize in 1979 for this method, which was first used in humans in 1973.
The CT is a quick and reliable examination method which is eminently suitable for both emergency diagnostics and the diagnostics of several diseases of the nervous system (head, spine, spinal cord or nerves), for example in stroke, cerebral bleeding, accidents, malformations, tumours, vertebral disc prolapse. The use of multislice-CT sets new improved standards in the imaging of vessels, brain perfusion and 3-D-Reconstruction.
Additional application of contrast agent enables direct imaging of blood vessels and of blood flow in the brain: thus stroke can be accurately diagnosed, when brain tissue can be saved by prompt initiation of therapy. Narrowing of blood vessels (“stenoses”) or vessel occlusion, which may be causes of stroke, can be detected. After cerebral bleeding, the pathological changes in vessels (vascular bulging = aneurysms) can also be detected quickly and with high spatial resolution.
Moreover, the CT is used to guide numerous procedures: for example, local anaesthetic is injected under CT guidance in nerve root blockade in the treatment of pain syndromes. Tissue samples are taken under CT guidance in the case of tumours or inflammations, which must be clarified by tissue examination.
The advantages of the CT are the widespread use of the equipment, making the examination readily available, the short examination time, the reliability of results in emergency examinations; moreover, the units are generously constructed so that even people who are fearful in closed spaces can be examined, and unlike the magnetic resonance tomography (MRT), patients with pacemakers and other metal foreign bodies can be examined.
The disadvantages of the CT are based on the exposure to radiation (although this is slight and further minimized by current technical developments), and the lower tissue contrast compared to MRT. In applying the contrast agent, allergic reactions or critical overfunction of the thyroid (“thyreotoxic crisis”) may occur in very rare cases.
In summary, computed tomography is the first choice in a number of emergency and routine examinations, making MRT unnecessary in these patients.
Here are some examples of the use of computed tomography in Neuroradiology:
CT Fig. 1: CT following a stroke during contrast agent administration to measure blood flow in the brain (“perfusion CT”). Left the grey-scale picture, the stroke area is dark grey compared to healthy brain tissue (arrows). Right the colour-coded image of blood flow in the brain, areas of reduced flow are red.
Fig. 2:
CT vessel image (“Angio-CT”) during contrast agent administration. Three-dimensional reconstruction of the base of the skull with the large brain arteries. The left middle cerebral artery is occluded (arrow).
Fig. 3:
Left: normal finding of a cranial CT, right: extensive subarachnoid bleeding (light grey edge, see arrows) after a burst aneurysm).
Fig. 4:
CT of the cervical spine after injection of contrast agent into the spinal canal (CT-“myelography”). Tearing of a nerve root after a traffic accident with leaking of agent into the torn root pocket (arrow). Other side normal.
Fig. 5:
CT of the transition between the lumbar spine and the sacrum. CT guided so-called root blockage in pain syndrome. The patient is lying on his stomach. A fine puncture needle (long arrow) is inserted through the back muscles to the nerve root. Anaesthesia mixed with contrast agent is injected (short arrow) and the proper position controlled by CT.
What is magnetic resonance tomography?
Magnetic resonance tomography (MRT or MRI) is a medical imaging procedure to depict organs and tissues using magnetic fields and radio waves. Unlike computer tomography, in which slice images are also produced, the MRT can be used to produce not only horizontal views, but also other levels without changing the position of the patient.
Magnetic resonance tomography has a number of advantages over other imaging procedures, such as computed tomography:
No exposure to radiation.
Very high soft-tissue contrast, even in the vicinity of bones. This makes it possible, for example, to image small pathological processes in the spinal cord, which cannot be recorded in computer tomography due to the adjacent spinal column. Images of any desired level and view without changing the patient’s position
In addition to images of tissues, MRT special procedures also enable visualization of brain functions (see below).
However, the MRT is not generally “better” than CT. There are questions which can be better answered by CT, such as bone lesions, for example at the skull base, bone fractures (breaks), fresh blood. Moreover, monitoring and examining is simpler in unconscious patients. Also, patients with pacemakers can usually not be examined because of possible disruption caused by the magnetic field in the magnetic resonance tomography. Finally, an MRT examination is considerably more expensive than a CT examination.
Fig. 1:
View of an MR tomograph. The patient is lying on his back and is wearing a sort of motorcycle helmet (so-called “Coil”) for examination of the head (as in this case).
Magnetic resonance tomography can be used for various special examinations using special techniques. These are described briefly and examples of images are given below.
Functional MRT (fMRT)
The basis of the fMRT is the fact that the activity of nerve cells results in local changes in the blood flow in the brain. These can be made visible using special examination sequences, since blood containing oxygen has other magnetic properties than blood from which brain activity has depleted the oxygen (the so-called BOLD effect). This makes it possible to visualize the activation area in the brain in a wide variety of motor, sensory and cognitive processes without using contrast agent. This procedure is performed, for example, prior to neurosurgical operations in which tumours are located near functionally-important areas of the brain (for example for movement or speech) which must be spared during the operation.
Diffusion and perfusion imaging:
In so-called diffusion-weighted examinations, the diffusion (molecular movement) of water in the tissues can be made visible. In stroke, there is an early disruption in this diffusion in brain tissue without blood flow. Thus, diffusion-weighted MRT is a very sensitive procedure to diagnose stroke. When the diagnosis is made early enough, destruction of brain tissue can be prevented or limited by means of appropriate therapy.
The flow of blood in the brain can be imaged with perfusion imaging, which also provides additional information, for example in stroke.
MR angiography
Here, special examination sequences are used which are particularly sensitive to movements of small particles, such as flowing blood. This enables direct visualization of vessels through which blood is flowing, without the use of contrast agent. Correspondingly, narrowing or blockage of arteries and veins is also visible. Some of the examinations which used to be performed only invasively, using catheter angiography, can be replaced with this less-stressful MR angiography.
MR spectroscopy
Brain metabolic products in the living body can be determined with this procedure. The procedure is useful for example for preoperative characterization of brain tumours, and also in the diagnostics of metabolic diseases of the brain.
Where is magnetic resonance tomography uses in neuroradiology?
MRT is especially well-suited for examination of the brain and spinal cord. Flowing blood in the arteries and veins can be imaged, as can e.g. diseases of the spinal column and vertebral discs.
Thus, for example, in stroke, the brain tissue in which blood flow in interrupted, as well as the vessels leading to the brain and possible occlusions in these vessels can be imaged by MR angiography .
Fig. 2:
Acute stroke with occlusion of the right middle cerebral artery (arrow in the right-hand picture) and image of the infarction area (light in the left-hand picture).
Inflammation foci in multiple sclerosis can also be almost exclusively imaged using MRT.
Fig. 3:
Fresh episode in multiple sclerosis, in which newly-formed inflammatory foci appear bright (see arrows).
In brain tumours, images of the tumour at various levels and imaging of the displacement of arteries and veins are important to be known for surgery.
Fig. 4:
Benign tumour (meningeoma) in the tentorium cleft. A vein, the so-called straight sinus, is displaced by the tumour (double arrow).
Diseases of the spinal column or vertebral discs are imaged well in the MRT by imaging at several levels and soft-tissue contrast.
Fig. 5:
Prolapsec disc in the lowest segment of the lumbar spine (arrow). Image in sagittal direction (spinal axis, left) and horizontal direction (cross-section, right).
However, magnet resonance tomography can be used not only for anatomical-pathological imaging, but also to image brain function (so-called functional imaging) and metabolic processes (MR spectroscopy).
Fig. 6:
Brain tumour (arrow) in the left temporal lobe near the speech centre of a right-handed patient. The speech regions (dotted arrows) are imaged in colour by means of functional imagi ng. Their position near the tumour is taken into account in planning surgery.
Especially in hard-to-treat epilepsy, MR spectroscopy can often provide additional information about metabolism in the diseased tissue.
Fig. 7:
Epileptic focus in the right temporal lobe (so-called hippocampal sclerosis, white arrow) and spectroscopy of regions defined with the boxes in the left image. Reduction of the so-called N-acetyl-aspartate (NAA, black arrow), a marker molecule for neurons, can be seen.
How is magnetic resonance tomography performed?
This depends essentially on the type of equipment and the purpose of the individual examination. Usually, the patient is placed on a gurney and pushed into a “tube” with a diameter of about 60 cm. During the examination, taps can be heard which are caused by the electromagnetic switches (gradient fields). In order to exclude excessive noise, the patient wears hearing protection (headset, ear-plugs, small pillows at the ears). The average examination lasts about 15-30 minutes. It is sometimes necessary to administer a contrast agent.
What must you do if you are to undergo magnetic resonance tomographic examination?
1.Do you have a pacemaker, insulin ump, artificial heart valve or other implants?
2. Do you know of any metal parts remaining in your body after surgery or accident? (for example after broken bones, clips, spirals, metal splinters in the eye, gunshots?)
3. Do you have any allergies or intolerance to medications?
4. Did any problems arise after other examinations with contrast agents?
5. Do you suffer from a disease of the kidney?
If any of these apply to you, a magnetic resonance tomography may not be possible, or only possible without contrast agent!
Angiography (vascular imaging):
Angiography is a routine procedure with which vessels supplying the brain or spinal cord can be imaged. The classical angiography via catheter has been replaced in part in recent years by computed tomographic or magnetic resonance tomographic angiography techniques which are non-invasive. The catheter angiography is used these days in a computer-supported form, the so-called digital subtraction angiography, in which only arteries and veins are imaged and bone is not visible and does not cover the vessel. Modern angiography equipment can make images at two planes simultaneously (view from the side and from the front) (Fig. 1).
Fig. 1:
Modern biplane angiography. Thanks to simultaneous recording of frontal and lateral series, the quantity of contrast agent needed can be cut in half and the time is shorter.
Usually, angiography is used in preparation of an intervention, that is it precedes a minimally-invasive or surgical therapy, for which planning requires very precise knowledge of the details of the vascular system.
Diagnostic angiography is mainly used when one of the following diseases is suspected
• Narrowing of the neck arteries which supply the brain (stenosis of the vertebral or carotid artery) or vessels in the brain itself (anterior, middle or posterior cerebral artery, basilar artery).
• Occlusion of the carotid or cerebral arteries, for example in stroke, venous and venous sinus thromboses, clarification of unexplained cerebral bleeding if magnetic resonance or computed tomography does not definitely reveal an aneurysm, vascular malformations (arterio-venous vascular malformation, arterio-venous fistula).
• Inflammatory diseases of the cerebral vessels (so-called vasculitis).
• Vessel-rich tumours prior to embolisations (obliteration of tumour vessels).
On the day before the procedure, laboratory tests are performed of the function of thyroid and kidneys in order to rule out a disease to these organs. In preparation of angiography, the groin – usually on the right side – is shaved and desinfected. Then the patient is covered with sterile cloths and local anaesthetic is applied. The femoral artery in the groin is punctured with a hollow needle, through which a guide wire and than a so-called introduction sheath – a temporary access – is pushed into the artery. The process is largely pain-free (Fig. 2).
Fig. 2: The sheath has already been positioned in the right groin artery (arrow, left side of the picture. A catheter 90 cm long can now be introduced and pushed into the artery to be examined (right side of the picture).
Under fluoroscopy, the catheter is navigated through the pelvic and aortic trunk artery into the vessel relevant to diagnosis of the disease. In addition to the less-often examined spinal cord arteries, these are usually the anterior and posterior neck arteries which supply the brain (Fig. 3, so-called carotid artery and vertebral artery), which arise from the aorta immediately above the heart (from the aortic arch).
Fig. 3: 3D reconstruction image of the carotid arteries from a left oblique view (upper image).
Aortic arch model with the course of the guiding catheter in the right carotid artery (lower left half of the image) and view of several differently-formed catheters for navigation in the carotid arteries.
Arteries and veins of the brain can be imaged from the position of the catheters in the carotid arteries (Fig. 4). If further details are to be examined, single brain arteries can be selected and made visible in the X-ray image by pushing a small catheter (microcatheter) about 1 mm thick through the larger guiding catheter. The patient must hold his breath for about 10 seconds while the contrast agent is injected so that the blood vessels can be clearly imaged without movement artefacts. At the same time, there is a feeling of warmth or heat in the neck or head, sometimes with flashes before the eyes, which lasts seconds
When the examination has been completed, the catheter and then the introducer sheath are removed, pressure is applied to the puncture site until it no longer bleeds, and a pressure bandage is applied for several hours. The patient must remain quietly in bed for this time, after which the puncture site has become sealed with a stable tissue clot.
Fig. 4:
Three-dimensional image of the vessels in one half of the brain, obtained by rotation angiography. The arteries (left half of the image) and veins (right half of the image) can be visualised independent of each other.
As complications, allergies to the contrast agent may occur, which are fatal in extremely rare cases (in one of 10 to 20,000 examinations). The average risk for persistent damage due to embolisms in the form of, for example, paralysis, is 0.3% of the examinations. The risk for patients with serious arteriosclerosis may be as high as nearly 1%.
Angiography enables imaging and evaluation of, for example, narrowing in the neck arteries (stenoses), vascular occlusion (for example in stroke), aneurysms in the neck or brain vessels, vascular malformations (fistulas, arterio-venous malformations) or tumours. This may be necessary for diagnosis and planning of possibly required operations or minimal-invasive treatment (see chapter on Endovascular Interventions).
A. Temporary Carotid Occlusion Test
In this test, the internal carotid artery is occluded on one side for 20 minutes with a balloon. At the same time, an ultrasonic examination of the cerebral vessels (TCD = transcranial Doppler sonography) is performed to evaluate whether sufficient blood flows in the cerebral vessels dependent on the occlusion. This must be sufficient to prevent a stroke which may occur due to insufficient blood flow. The patient is continuously neurologically examined.
The temporary occlusion test is necessary if there is to be surgical or endovascular closure of a vessel. The test enables considerably better estimate of the risk of stroke and its results influence planning of the intervention.
B. Wada Test
In the Wada test, medication is injected into a vessel which causes the brain in the area supplied by the vessel to “go to sleep” for a few minutes. Usually, this medication is administered through a normal catheter into the internal carotid. Rarely, and only in very carefully defined examinations, the medication is introduced superselectively into a cerebral vessel through a microcatheter. These examinations are performed under local anaesthesia, since the aim is to examine the effect of the medication administration on brain function. These examinations are performed especially to clarify epilepsy prior to a planned operation.
In recent years, these examinations have continuously become less frequent, since functional magnetic resonance (fMRI) combined with neuropsychological testing has largely replace these invasive examinations, which are now justified only in special cases.
C. Venous blood collection in the Sinus cavernosus
Thanks to modern imaging with thin-layer and dynamic MR examinations of the pituitary, most pituitary tumours can be detected, even those extremely small in diameter (microadenoma). Nonetheless, in rare cases, imaging is not able to provide definite proof of a tumour, although for example the hormone constellation indicates a tumour. In order to clarify whether the hormone-active tumour is located in the pituitary, it is possible to position a microcatheter in a vein immediately next to the pituitary (cavernous sinus). Blood is drawn through this catheter before and after medical stimulation of the pituitary from which the presence of a tumour can be determined.
Myelography
Myelography is used to examine the spinal canal. X-ray dense contrast agent is injected into the "nerve water" (cerebro-spinal fluid), which thus makes the fluid space visible. This is performed through a puncture in the lower spine, a procedure by which neurologists also examine the cerebro-spinal fluid. Local anaesthetic can be administered for the puncture. Usually contrast imaging is combined with a computer-tomographic examination after the X-ray agent has dispersed, since the two methods together provide the best diagnostic results. In order to be able to examine all segments of the spine, the contrast agent is transported to the area to be examined by changing the position of a tilting-table.
Usually, spinal column diagnostics with magnetic resonance tomography or computer tomography are sufficient, for example in the case of tumour or disc prolapse, so that many myelographies can be avoided these days. If myelography is performed, it is usually in preparation of surgery. Its great advantage is that functional examinations of the spine, such as slipped disc under static stress and with testing of the movement which causes pain, can be simulated. Additional weights, held by the patient with outstretched arms, are used for this loading myelography. This enables examination of diseases caused by a lack of stability in the spine.
Headache may be a side effect of the examination, but this usually subsides after a short time. Complications like infections or injury to nerve structures are very rare.
THERAPY
Therapy with neuroradiological methods has become increasingly widespread in the last two decades. Treatment procedures have become standard today which were hardly developed 20 years ago, such as the treatment of aneurysms via catheter. All procedures use a non-surgical access via catheters inserted in arteries or veins or via puncture of pathological processes through the skin. This neuroradiological interventional therapy is called minimally-invasive therapy because entry into the body is limited and thus less stressful in character for the patient. The various possibilities for use are described below.
ENDOVASKULARY VESSEL INTERVENTIONS
MINIMALY- INVASIVE THERAPY
The area of interventional Neuroradiology has developed at a very fast pace over the past 30 years and has become an established form of treatment. Without requiring open surgical access, use is made of the paths of access available, such as arteries and veins (endovascular = through the vascular system). Access usually proceeds via puncture of a vessel in the groin. Under fluoroscopic control, the catheter (2 mm in diameter) can be inserted all the way into e.g. the carotid artery. A second thinner microcatheter is inserted through the first catheter to the site of therapy. These minimally-invasive methods can be used in the treatment of vessels in the brain and head-neck area, and in the spinal cord. The procedures are performed under local anaesthetic or full general anaesthesia, depending on the site of treatment, the disease and the patient’s age.
In principle, we differentiate between:
1.V essel occluding therapies: Closure (embolisation) of wall bulges in vessels (aneurysms), or vascular malformations (arterio-venous or venous vascular malformations) and pathological vessels in tumour diseases.
2. Vessel reopening therapies: Closure (embolisation) of wall bulges in vessels (aneurysms), or vascular malformations (arterio-venous or venous vascular malformations) and pathological vessels in tumour diseases.
3.D agnostic procedures prior to surgery or endovascular treatment: temporary blocking of an artery supplying the brain for 20 minutes (temporary occlusion test), administration of medications (barbiturates) to evaluation brain function prior to epilepsy-surgical procedures (WADA test), or venous blood collection from venous brain leads in pituitary tumours.
A. Embolisation of aneurysms
Wall bulges in vessels (aneurysms) often become symptomatic by a subarachnoid bleeding (SAB) and must be treated because of the associated high morbidity and mortality and the danger of repeated bleedings. Aneurysms detected by chance, which have not bled, are called “incidental aneurysms”.
Indication for treatment of these aneurysms is given if they have exceeded a certain size or if they cause clinical complaints, such as paralysis of brain nerves.
Since 1991, aneurysm therapy with platinum coils has become established as an alternative to surgical therapy (clipping). The aneurysm sack is filled with platinum spirals (coils) and thus closed. The technique is constantly improving thanks to new developments. Among these are various material thicknesses and degrees of softness, coated platinum spirals and also vessel-restoring methods, such as the technique called “remodeling”, with balloon-assisted filling of the aneurysm or insertion of stents.
The results of numerous series of cases and a large randomized multicentre study (Interntional Subarachnoid Aneurysm Trial, ISAT) confirm the efficacy and safety of endovascular treatment of aneurysms. The absolute risk reduction is 8.7%, the relative risk reduction is 26.8% in favour of patients undergoing endovascular treatment (ISAT trial). As a result of these studies, the number of aneurysms treated with endovascular methods is increasing and at most centres offering both surgical and endovascular treatments, even exceeds the number of aneurysms treated surgically. Nonetheless, treatment of an aneurysm must be performed individually by a neuroradiologist or neurosurgeon experienced in endovascular or surgical techniques and the advantages and disadvantages of the two methods must be weighed. Optimal treatment is thus only guaranteed when the two disciplines are available on site.
Tab.1: Distribution across treatment of aneurysms since 2003 in Freiburg (H&H = Hunt&Hess-classification related to the grade of bleeding)
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Case 2: Incidental, broad-based aneurysm (A: image with 3D rotation angiography; B: conventional image in lateral projection), which was completely closed. To prevent bulging of platinum spirals into the vessel lumen the aneurysm neck was protected by a stent (Neuroform, Boston Scientific). Fig. C shows a sketch of the treatment principle based on the patient treated. Figures D and E show the follow up after 6 and 24 months, which reveal complete aneurysm closure and also no stent reaction in the parent vessel. The open arrow in Fig. F shows the platinum spirals, the closed arrow the stent marker.
B. Embolisation of arteriovenous malformations
Cerebral arteriovenous malformations are short-circuit connections of arteries and veins. Direct short-circuits are called fistulas. Depending on the supply type, these are called dural arteriovenous fistula (dAVF – fistulas of the hard brain membrane = dura mater) or pial arteriovenous fistulas (pAVF – fistulas of the cerebral cortex). If there are short-circuit vessels between arteries and veins which are formed like grapes, this is termed a nidus. This vascular malformation is termed AVM (arterio-venous malformation) or angioma.
While fistulas usually develop because of craniocerebral trauma or thrombosis of the venous sinus, the AVMs are usually present at birth, whereby angioneogenetic factors appear to play a role.
Traumatic fistulas with vascular tears between the internal carotid artery and the cavernous sinus (complex large veins) should be treated in any case, but dural fistula only when they have bled, when there is danger of bleeding (for example in drainage into brain veins) or if the patient complains of an unbearable pulse-synchronous ringing in the ears (tinnitus). Treatments are performed with fluid adhesives or platinum spirals through the arteries or veins. Sometimes, the internal carotid artery (A. carotis interna = ACI) must be closed. An operation is only necessary if endovascular closure is not possible.
Case: 64-year-old woman with pulsating exophthalmus (protruding of the eyeball) and paralysis of all three eye muscle nerves. This is an indirect fistula supplied by branches of the internal and external carotids on both sides. (Figs. A-C, upper row, before treatment). Complete closure of the fistula by embolisation of the venous lead with platinum spirals (Fig. E: embolisate marked with arrows). The control angiography after 6 weeks (D+E) confirms complete closure. The clinical symptoms had meanwhile abated
Among the intracerebral vascular malformations, arteriovenous malformations (AVM) have an incidence between 0.04 and 0.52%. In the USA, about 10 cerebral AVM per 1 million residents are diagnosed every year. AVM often become symptomatic between the ages of 20 and 40. Bleeding is the most frequent initial symptom at 50% and may occur in up to 90% in deep central AVM. A seizure is initially indicative for further clarification in about 25% of patients. Headache is less frequent and it rarely occurs that AVM are discovered by chance in clarifying other queries.
Usually, treatment is surgical, endovascular (embolisation) or radiosurgical (single radiation), whereby the treatments are often combined. Spontaneous closure of cerebral arteriovenous malformations is rare. The surgical risk depends on the size, venous drainage and localization, so that an individual treatment concept must be worked out for each patient. This is only possible when all 3 potentially possible treatment options are available and the appropriate specialists in the individual disciplines are involved in the discussion.
Example AVM: 39-year-old man who became symptomatic due to seizures. Embolisation of the AVM in 2 sessions with complete closure of the AVM. Control angiography after 3 months.
Example AVM: Same patient as above with 3D image of the AVM. The arrows mark the individually probed vessels, which were closed with liquid adhesive.
C. Embolisation of venous malformations
Venous angiomas of DVA (developmental venous anomaly) are the most frequent among vascular malformations, whereby the term “malformation” is confusing and it would be better to speak of a developmentally-related anomaly or venous variant. Treatment is usually not indicated, since these veins are important for the normal venous drainage of the brain.
Vein of Galen malformations (VGM) with tremendous enlargement of this vein are rare malformations which require treatment. These malformations are often observed before or at birth. Treatment is performed by transarterial or transvenous embolisation, as for other vascular malformations.
Example: Vein of Galen malformation in a female patient who became symptomatic with cerebral bleeding. Angiography before and after embolisation, after which she was treated with transarterial liquid adhesive and transvenous with platinum spirals (in the figure, the platinum spirals are shown at the lower right).
Capillary-cavernous, venous, arteriovenous and lymphatic malformations of the skin and soft tissues occupy a special position. An interdisciplinary team of pediatricians, plastic surgeons, orthodontists, dermatologists, lymphologists and neuroradiologists have to deal especially with these disease patterns, as well as with the usually spontaneously-healing hemangiomas and cutaneous malformations.
In capillary-cavernous and venous malformations, sclerosing treatment can be performed in which the vascular change is directly punctured with a thin needle.
Case: 23-year-old man with capillary-cavernous malformation of the right forehead (thin arrow), which was sclerosed by several direct percutaneous punctures. Prior to sclerosing treatment, the vascular malformation is imaged with contrast agent (thin arrows mark the needle and the puncture site on the forehead).
D. Embolisation of vessel-rich tumours
This treatment is made primarily in benign tumours of the hard brain membrane (meningeoma), in glomus tumours lying at the bifurcation of the carotid artery, in the middle ear or at the internal jugular vein, and in fibromas of the neck or throat. Treatment is made immediately prior to surgery to dry the tumour out. Particles which do not provide permanent closure are usually used as embolisation material. For this reason, surgery should be performed within 10 days.
One exception is meningeomas which can no longer be operated and which have already undergone radiation. As a final possible treatment in these cases, permanent vascular closure can be achieved with particles which result in permanent closure thanks to their material composition.
Case: 46-year-old woman with a large meningeoma before (upper row) and after embolisation (lower row; the MR was performed 3 days later and shows large dead areas in the tumour which no longer take up contrast agent, dark centre). The tumour was supplied primarily by an artery supplying the brain covering membrane, which was fed as a variant from the ophthalmic artery (arrow upper left in image). Angiographically complete drying out (devascularisation) and surgical removal on day 4 after embolisation.
A. Recanalisation in acute cerebral strokes
Stroke is the third-most frequent cause of death after cardiac infarction and cancers. About 80% of strokes are ischemic (no blood supply due to vascular blockage = non-bloody) and 20% hemorrhagic (bloody). In order to guarantee successful treatment of strokes, an infrastructure must be available which functions without a hitch under the motto “Time is Brain”. Early reopening of an occluded cerebral vessel is the decisive factor in preventing or at least limiting brain damage which increases with time, and thus to improve the end status following the stroke.
Decisive for therapy is the early diagnosis which, in addition to the clinical symptoms, is based on rapid and professionally-competent imaging with CT and/or MR. It can determine the extent of infarction, the severity of the stroke, and the localisation of the vascular blockage. Early reopening of an occluded artery may occur spontaneously (rarely) or by systemic (intravenous) or interaarterial thrombolysis therapy. The indication for local intraarterial lysis treatment (LIF) via a microcatheter inserted at the site of occlusion depends on the time window between the onset of stroke and possible treatment. LIF should begin, namely, within 6 hours after vessel occlusion in the anterior and within 24 hours in the posterior circulation.
Endovascular treatment has now become an established method which requires recanalisation times of 1-2 hours, despite local application of the fibrinolytic. Multimodal treatment strategies using mechanical procedures make it possible to shorten this further. These procedures, such as mechanical manipulation with a microwire, vessel dilation with balloon and stent or laser resolution of a blood clot, may be used primarily or secondarily after unsuccessful local fibrinolytic treatment.
Graphic: Interaarterial lysis were accomplished since 1986 in the center of neuroradiology of Freiburg. The graphic shows the progress of since the launch of the stroke unit with an obvious increase of the inverventions. This is due to the fact among other things that the infrastructure with better clarification of the population leads to the fact that the patients appear most early possibly and on the shortest way in the medical center, because a treatment is possible only in a narrow time window of few hours.
Example: mechanical recanalisation with balloon without fibrinolytic treatment.
Example: 36-year-old man with occlusion of the brainstem artery (basilar artery), which could be mechanically recanalised with a laser catheter. The laser treatment time was 5 minutes and 11 seconds. MR angiographies (magnetic resonance angiography) after 24 hours and after 30 days are shown in the lower row.
B. Recanalisation of a central retinal arterial occlusion with acute blindness
Sudden loss of sight (blindness in one eye) may be caused for example by occlusion of the central artery in the eye. Local intraarterial lysis treatment (LIF) is one possibility for treatment which has the advantage that the fibrinolytic (medication to dissolve the blood clot) can be administered directly to the site of the blockage. As with a stroke in the brain, the success of restoring sight in a stroke in the eye is closely related to the time between the onset of symptoms and start of treatment. The shorter this time is, the better the chances that sight can be restored.
This treatment possibility is presently being tested in an international multicentre study (EAGLE Study), to compare endovascular treatment with conventional treatment methods.
C. Reopening of a narrowed vessel (Stent-supported PTa, vessel dilatation)
TEA (thrombendarterectomy) is presently still the gold standard in the treatment of high-grade symptomatic carotid stenoses (narrowing of the internal carotid artery), against which endovascular treatment with stents (metal endoprostheses) and dilation (PTA, expanding the vessel with a balloon) must be measured. The first successful use of recanalisation (reopening) was described nearly 40 years ago by Dotter and Judkins. In the past years, an increasing number of studies has been published in which endovascular treatment was performed because an operation was either not possible or refused by the patient. The complication rate is 3-5% when the treatment is performed by doctors experienced in neuro-interventions. Studies have shown that surgical and endovascular treatments bring similar success and are associated with comparable complications.
Endovascular treatment of carotid stenosis is performed under local anaesthesia and usually takes between 45 and 120 minutes. In rare cases, a blood clot may block a cerebral vessel and cause a stroke. Local anaesthesia makes it possible to perform the procedure on the conscious patient and thus continuously evaluate his brain function. A stroke can thus be recognized promptly and treated directly with the thrombolysis described above.
In addition to the carotid stenosis, which occurs most frequently, stenosis of other brain-supplying vessels can also be treated with stents.
In recent years, stents are increasingly used also in acute vascular occlusion in those cases when stenosis can be considered as the cause of the blockage. Stents are used not only in the internal carotid artery in the neck but also in cerebral arteries with more than 2 mm diameter.
early 10% of the atherosclerotic stenoses of cerebral arteries are responsible for cerebral infarctions. For this reason, these stenoses are treated with stents as a preventive measure when treatment with blood-thinning drugs is unsuccessful. Since the intervention in brain vessels requires very precise navigation of the catheter system, such procedures are performed under general anaesthesia.
Example: Irregularly-defined carotid stenosis before (A) treatment with stent, after 8 months (B) and after 26 months (C). Slight thickening of the intima in the stent. The external carotid artery is covered by the stent in the branching area, but this is has no influence on blood flow.
Example: 70-year-old man with acute stroke with high-grade intracranial stenosis of the carotid artery (arrows, top row), which was reopened with a stent (4 mm diameter, 9 mm long). Magnetic resonance tomographic image of the extent of stroke before the stent (upper right) and constant extent of infarction after 2 days (lower right). Additional spread with complete infarction of the right brain hemisphere could be prevented by prompt treatment.
CT Guided Pain Therapy
65-80% of the population develop back pain at some point in their lives, whereby 14% report complaints lasting more than 14 days. 74% of the patients can return to work within 4 weeks and 7% of the population develop a chronic pain syndrome lasting more than 3-6 months. This epidemiological analysis of numbers published makes clear the importance of this medico-sociological and occupational-medical health problem, which can be rated the “Nr. 1 disease in the population” in western industrial countries.
Percutaneous pain therapy as a minimally-invasive method has proven valuable as a supplement to conservative therapy, but also in the differential diagnosis of unexplained pain. Still, this form of pain therapy is an invasive method and may only be used in selected patients for that reason. In order to guarantee this, extensive pre-examinations are necessary in Pain Centres by a team of neurosurgeons, neurologists, neuroradiologists, anaesthetists and psychiatrists. This procedure facilitates the correct evaluation of therapeutic success and the decision concerning further therapy.
Radiological findings are largely unimportant in unspecific simple back pain. Findings of imaging procedures are included more in the therapy decision when there is a combination of clear symptoms, such as nerve root-related pain, paralysis or sensitivity impairments. Two-thirds of spinal pains are in the lumbar spine and sacrum and do not require surgical or invasive-therapeutic measures, since the rate of spontaneous healing is nearly 90%.
Invasive treatment of back pain requires stricter indication than non-invasive procedures. Consequently, patient selection must occur which can only be achieved by a team as described above.
CT-Controlled pain treatments
I. Facet blockade (drug infiltration of the vertebral joints)
Back pains originate in the vertebral joints in about 15-40% of patients. These pains, called pseudoradicular, arise exclusively in the facet joints in only 7%.
I. Facet blockades
Facet blockades are undertaken for diagnostic and therapeutic reasons, for example in postnucleotomy syndrome (= pains after vertebral disc operations), improper facet-joint position, instability of the spinal column or degenerative changes in the vertebral joints.
Although there are no rules concerning Fig. 1: CT (left) and by fluorescopy-controlled (right) needle position prior to instillation of local anaesthetic.the methodical procedure, CT-controlled positioning of the needle appears to be advantageous over fluoroscopic-controlled method, as far as reproducibly correct needle position is concerned. The exact positioning of the point of the needle enables keeping the application volume of the medicine low and avoiding unspecific joint flooding with medication.
Fig 1: CT (left) and by fluorescopy-controlled (right) needle position prior to instillation of local anaesthetic.
II. Nerve root blockade
Diagnostic root or nerve blockage is very important in differential diagnosis in order to be able to definitely assign apparently divergent clinical and morphological findings of a nerve root. By blocking a root which is clinically assumed to be affected, the diagnosis can be proven and further therapy decided on.
Fig. 2: Nerve root blockade in the thoracic spine in a woman with Herpes zoster. First, planning of the access (left top) and after positioning of the needle, control of the needle position (top right). Final control to evaluate the mixture of contrast agent and long-term local anaesthetic applied (lower left, arrow) and to rule out injury to the lungs (lower right).
III. Sympathetic Trunk Blockades
The spontaneous burning character of the pain with surface localisation is typical of sympathic-related pain in the arms and legs, sometimes accompanied by changes in sensitivity and trophic disturbances in the hand. Classical indications are, for example, complex regional pain syndrome (CRPS) and sympathic reflex dystrophy (SRD), Sudecks atrophy, causalgia, algodystrophy and a number of other things.
Inactivating the sympathetic system by means of temporary or long-term drug blockade improves both the pain and the perfusion in the arms and legs.
Fig. 3: Sympathetic blockade at the level of the third lumbar vertebral body (= LVB3). Patient with “open leg” of the left lower calf (ischemic ulcer) due to peripheral arterial occlusive disease and impaired venous flow. Sympathetic blockade at the level of LVB3 left. First needle control (upper left), then application of 7 mL of a mixture of 10 mL carbostesin 0.5% and 1 mL contrast agent (upper right). 90 minutes later, control of success with thermography (lower left, view of the forefeet and lower right the soles of the feet). A few days later, neurolysis (“killing” of the nerve) was performed with 96% alcohol.
IV. Vertebroplasty
Specific forms of back pain caused by bony processes like fractures, bone tumours, metastases, serious osteoporosis or infections can be differentiated from unspecific back pain. Percutaneous vertebroplasty is an alternative to major operative interventions to stabilize bones. In addition to the stabilisation effect, vertebroplasty at the same time serves as treatment of pain, which differs in effectiveness depending on the underlying process.
In vertebroplasty, larger bony defects are first filled with liquid, quick-setting bone cement (methylmetacrylate). Under local anaesthesia or full narcosis, needles 2-3 mm in diameter are inserted in the vertebral body. Cement leaks in the spinal canal with narrowing of the spinal canal and rarely venous dispersion with the danger of pulmonary embolism can occur as complications, and this requires careful injection control under fluoroscopy or CT monitoring. The best results can be expected in osteoporosis and in vertebral body haemangiomas with freedom from pain in about 90%, while success in the treatment of vertebral body metastases or plasmocytom vertebrae is lower at 70% freedom from pain.
Fig. 4: 75-year-old woman with pronounced therapy-resistant back pain (lumbago) with haemangiom vertebra LV. Magnetic tomographic image of the haemangioma (arrows) in fat-suppressed T2 (left) and T1 (middle). Typical changes in vertebral body in the CT (upper right) and status after cement insertion with direct puncture of the haemangioma. Treatment was performed in the prone position. The patient was pain-free after treatment.
