Summary
Neurology is the branch of medicine that deals with the diagnosis and treatment of neural or nerve-related disorders. Neurosurgery is a sub-discipline under Neurology which, as the name implies, has to do with incisional surgery to rectify neural disorders. In the last couple of decades, Interventional Neurology has emerged as a better alternative to Neurosurgery as it uses minimally invasive procedures to treat neural disorders. In this article, we will learn more about the same.
Introduction
The Nervous System in the human body is made up of two divisions:
- Central Nervous System (CNS) which constitutes the brain, spinal cord, and a vast network of nerves all over the body.
- Peripheral Nervous System: which constitutes the five sensory organs and various sensory receptors distributed throughout the body.
Together, CNS and PNS constitute the signalling system of the body. They generate or manage millions of signals that travel back and forth, within the Nervous System and with rest of the body, all through our day. Neurology is a branch of medicine which deals with a wide range of conditions that affect these components of the nervous system, and muscles that are controlled by the nerves.
What is Interventional Neurology
Till a few decades back, incisional or open surgery was the only alternative to treat neurological disorders that could not be treated by medication or other therapies. Incisional surgery has the drawbacks of blood loss, more pain, collateral damage to nearby tissues, long recovery times and anaesthesia-related risks. Since the 1920s, there have been various attempts at non-incisional procedures, to treat neurological disorders, in Europe and Russia. This picked up steam through the 50s and 60s.
Since the 1980s, more such successful attempts at non-incisional, neurological interventions began to be documented, recognized, and appreciated by the medical fraternity. This eventually resulted in a new sub-discipline under Neurology called Interventional Neurology. Doctors who specialize in this field are called Interventional Neurologists.
Interventional Neurology involves a wide range of minimally invasive procedures. These use a combination of Endoscopic (catheter-based) and Radiological tools and techniques to diagnose (detect and locate), as well as correct certain neurological disorders. Minimally invasive procedures come with the advantage of less blood-loss, low pain, quick recovery, no collateral damage and reduced risk of complications. Interventional Neurology is revolutionizing neuro-care as it offers hope for patients suffering from various conditions.
Conditions treated by Interventional Neurology
- Cerebral aneurysms: An aneurysm is a condition in which, the wall of a blood-vessel develops a balloon like bulge. Blood fills up in the bulge, and at a certain point of time, the bulge can burst, leading to bleeding in the brain (condition called as Intracranial Haemorrhage of which there are 4 types depending on which part of the brain – epidural, subdural, subarachnoid and intraparenchymal haemorrhage).
- Intracranial or Brain arteriovenous malformation (AVM): Arteriovenous malformation is a condition in which blood-vessels become abnormal, tangled or knotted, which can create irregular connections between the arteries and veins. Normally, arteries and veins do not connect with each other, as it can cause mixing of pure and impure blood. But in AVM, this is what happens. When AVM happens in the brain, it is called intracranial/brain/cerebral AVM.
- Extracranial (head and neck) and paraspinal vascular malformations: Here, AVM happens in the head region other than the brain, the neck, and along the spinal cord.
- Intracranial atherosclerosis: Similar to atherosclerosis in the heart. In this condition, cholesterol, and some other substances start depositing on the walls of the arteries and harden over time, and is now called plaque. Plaque deposits can constrict or narrow down the artery, thereby reducing blood-flow to the tissues served by that artery. When this condition happens inside the arteries of the brain, it’s called Intracranial atherosclerosis.
- Extracranial (brachiocephalic) atherosclerosis: In this, atherosclerosis happens inside the arteries that supply blood to the head and neck (carotid and vertebral arteries).
- Stroke: Blood-clots that originate in the brain, or originate in other parts of the body and travel to the brain, can clog up an artery in the brain, thereby reducing blood-flow to certain parts of the brain leading to loss of those functions. This is a serious condition and cannot be reversed, once a certain amount of time has elapsed. Other reasons for stroke include intracranial atherosclerosis described above.
- Carotid-cavernous fistula (CCF): In this condition, there is an abnormal shunt, or branching off, of the carotid artery to the cavernous sinus (a network of veins housed inside a cavity) inside the brain.
- Dural arteriovenous fistula (DAF): There is a tough covering over the brain and spinal cord called the Dura mater. Arteries supply pure blood to this covering while veins drain impure blood from the same. DAF is a condition in which there are abnormal connections between arteries and veins in the Dura mater.
- Traumatic vascular lesions such as Neck lesions: Lesion is an abnormal growth or mass that can develop in any part of the body. When such lesions (or masses) develop on the blood vessels, they are called vascular lesions. Vascular lesions may or may not be cancerous. They are classified as tumours, growths, bumps or lumps. Explosions and projectiles such as bullets, shrapnel, glass and metal-pieces can cause trauma (injury) to blood vessels and trigger off a lesion.
- Vasospasm: Vasospasm is a condition in which a blood-vessel in the brain narrows down, thereby reducing blood-flow. This can happen after a subarachnoid haemorrhage following a ruptured brain aneurysm.
- Tumours in the head and neck: self-explanatory
- Juvenile nasopharyngeal angiofibroma (JNA): JNA is a benign or not a cancerous type of vascular tumour that develops in the nasal cavity.
- Meningiomas: Dura Mater explained earlier is the outer-most layer in a 3-layer membrane that surrounds the brain and spinal cord, called the Meninges. Meningiomas is a tumour that arises from the meninges.
- Severe Nosebleeds: severe nosebleed can be caused by allergies, infections, nose-picking, injury, foreign bodies stuck in the nose and in rare cases a bleeding disorder.
- Paragangliomas: These are a rare kind of tumour. They can form in any part of the body, but generally form near or around the carotid artery and along the neural pathways in the head and neck.
- Vertebral body tumours: As the name implies, these are tumours that affect the bones of the spinal column, or vertebrae. They generally do not originate in the spinal cord and have metastasized from cancers in other parts of the body.
- Vertebral compression fractures (VCFs): A VCF occurs when the bony block in one or more vertebra of the spine, collapses, causing a lot of pain, deformity and eventual loss of height.
Tools and Techniques used in Interventional Neurology
Interventional Neurology uses 2D and 3D imaging techniques to precisely locate the fault and explore it in detail. Thereafter it uses endoscopy, or catheter-based interventions, to correct the problem.
A catheter is a long, thin and flexible tube that is inserted through a cut in the skin, into an artery in the groin and gently pushed or threaded all the way to the spot where the intervention has to be done. The catheter has a wired camera, a light, and surgical tools fitted at its end. The surgical tools help in the final intervention. The camera relays images to a computer kept in the room. By looking at the images on the computer, the doctor can move around the endoscope and initiate the final intervention.
There are 5 major, or common neurological interventions performed:
- Angioplasty – Similar to angioplasty done for the heart. This procedure creates a picture of blood-flow in blood-vessels of the neck and brain, to understand the type of and extent of damage, enlargement, stenosis (narrowing down) or disease in them.
- Coil Embolization – In this, a very thin, coiled wire is used to block the blood-flow to a particular part of the body. More specific to the brain, it is used to block blood-flow into an aneurysm.
- Embolectomy – This procedure involves removal of a blood-clot that has already caused a stroke, or has potential to cause a stroke. In this case, the blood-clot has clogged an artery in the brain after traveling to the brain from another part of the body. The catheter has a thin apparatus at the tip to attach to the blood-clot and pull it out of the body.
- Stenting – Similar to stenting done to open out a narrowed artery in the heart. Here, the narrowed artery lies in the brain. While a balloon is used to push out a blockage, a metal coil or stent is used to prevent the blockage from recurring at that spot.
- Thrombectomy – Similar to an Embolectomy. But the only difference is that in this case, the blood clot has originated in the brain. After the blood-clot is pulled out, blood-flow and oxygen supply to the brain are resumed immediately.
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