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. Vessel 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. Diagnostic 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.
1.Vessel occluding therapies
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.
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.
2. Vessel reopening therapies
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.
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.
Indications for pain 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.
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.
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.
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.
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.
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.
V. Percutaneous treatment of lumbar disc protrusions