WHAT IS MICROVASCULAR NEUROSURGERY?

Special skills are required to utilize these techniques. In all of these instances, the Neurosurgeon is using a sophisticated Neurosurgical Operating Microscope to magnify vision, as well as delicate instruments designed specifically for this type of endeavor.

Microvascular Neurosurgical Operations that address blood vessel problems include those that are conducted for:

1. Microvascular Decompression Operations (MVD)

   Trigeminal and Glossopharyngeal Neuralgias as well as Hemifacial Spasm. In these conditions, cerebral arteries and/or their branches impinge upon one or more of the specialized Cranial Nerves that enter or emerge from the Brain Stem. As they beat synchronously with the heart, they tend to wear out a portion of the insulating material (Myelin) of these nerves resulting in a "short circuit" and the symptoms of each of these afflictions. Using Microvascular Decompression (MVD) Techniques the Neurosurgeon is able to reposition the offending vessel while placing some form of permanent padding to retain the vessel in a new and transposed position relative to its previous noxious one.

   Figure 1: Operative Photo Left Retromastoid "Keyhole" Craniectomy for Trigeminal Neuralgia. Superior Cerebellar Artery (Upper Slender Arrows) Compare the Artery to Figure 2 below. The Left Trigeminal Nerve root entry Zone (Lower Broad Arrow) is compressed by a tortuous and redundant Superior Cerebellar Artery.

   Figure 2: Operative Photo Microvascular decompression (MVD) of the Left Trigeminal Nerve (Same patient as Figure 1). The Superior Cerebellar Artery (Upper Left Arrow) has been transposed and held in the new position by a permanently implanted Ivalon sponge (Lower Left Arrow).

2. Skull Base Tumors

   Skull Base Tumors are tumors that involve the bone in the region of the Base of the Skull and often have an intimate relationship with delicate and vital structures (Cranial Nerves, Cerebral Arteries and Veins) which must be preserved both anatomically and functionally in order to have a fully satisfactory outcome. The Microvascular Neurosurgeon's special dissection techniques are often invaluable when addressing these difficult circumstances.

   Figure 3A (Left): MRI Scan (Sagittal View-Gadolinium enhanced) of a large Anterior Cranial Fossa SKULL BASE TUMOR that extends into the Posterior Cranial Fossa and involves multiple vital arteries at the Skull Base. Figure 3B (Right): MRI Scan (Coronal View) of the same patient. The tumor involves both Frontal Lobes of the Brain and both Orbits as well as major vessels such as both Anterior Cerebral and Internal Carotid Arteries and their branches. Microvascular dissection principles and techniques reduce the risk of injury to the vital structures in this area.

3. Intracranial Arterial Reconstruction

   Microvascular techniques are utilized in order to prevent Strokes from occurring in patients with certain types of Obstructive Cerebrovascular conditions that do not respond to other therapies. Examples of this include extensive multivessel atherosclerosis (hardening of the arteries) that results in decreased blood supply to the Brain. An example of this is Extracranial to Intracranial Arterial Bypass Grafting as illustrated in Figures 5 through 8.

   These operations are referred to as Cerebral Revascularization (or Extracranial-Intracranial [EC-IC] Bypass Graft). Patients requiring the reconstruction of the arterial blood supply to their Brain (either to deal with an obstructive blood vessel problem that would lead to Stroke, or where tumor removal requires the sacrifice of a major cerebral artery) will understand the requirement to have a Neurosurgeon with special skills, knowledge and expertise to undertake this extremely delicate task.

   Several techniques are available including the repair and or bypass of larger vessels such as the Intracranial Internal Carotid Artery as well as bypass of somewhat smaller caliber arteries such as the Middle Cerebral Artery. Figures 5, 6 & 7 concern a "large" vessel bypass graft using a vein graft technique to create a "new" Carotid Artery. Figures 8 A & B concern the creation of a smaller vessel bypass graft using a scalp artery (the Superficial Temporal Artery) to supply the Brain's Middle Cerebral Artery blood requirements.

   Figure 5: Diagram of Extracranial to Intracranial Carotid Artery Bypass Graft. This technique is used to bypass a major obstruction in the Carotid Artery where conventional treatments are not appropriate. A vein, harvested from the patient's leg, is inserted between the Carotid Artery in the neck (Arrow) and passed under the skin to enter the skull cavity where it is sutured to the Intracranial Carotid Artery. NOTE: The concepts and techniques described in this section were initially elaborated in: "Microsurgical Cerebral Revascularization: Concepts and Practice. Surgical Neurology 1:355-359, 1973. (Lazar, M.L., and Clark, W.K.)

   Figure 6: Post-operative Cerebral Angiogram of an Extracranial to Intracranial (EC-IC) Carotid Artery Bypass Graft. A vein graft (Broad Arrow) has been sutured in place from the Right Common Carotid Artery in the neck and brought in through a Craniotomy and sewn to the Intracranial Carotid Artery. This "new" vessel" now supplies the ENTIRE Right and Left Anterior & Middle Cerebral Artery distribution. This patient had a high grade obstruction of his Left Carotid Artery at the Carotid Siphon with Complete Occlusion of his EXTRACRANIAL Right Carotid Artery. Post-operatively the patient was found to have experienced an ASSYMPTOMATIC complete occlusion of the Left Carotid Artery with the "new" Bypass Graft supplying the Anterior and Middle Cerebral Arterial Circulation to BOTH Cerebral Hemispheres (Small Arrows.)

   Figure 7: Post-operative Cerebral Angiogram (Lateral View- Same Patient as Figure 6) The vein graft extends from the Extracranial Carotid to the Intracranial carotid Artery (Arrows)

   Figure 8A (Left): Pre-operative Left Carotid Angiogram. The entire Left Middle Cerebral Artery (MCA) circulation (Arrow) is absent secondary to MCA occlusion. Figure 8B (Right): Left Common Carotid Artery Angiogram. Post-operative EC-IC Bypass Graft (Superficial Temporal Artery to Middle Cerebral Artery). The entire MCA distribution is now supplied by the "new" vessel. This EC-IC Bypass involved suturing a 2 millimeter Superficial Temporal Artery to a 1 millimeter MCA Cortical Arterial Branch.

4. Aneurysms & Arteriovenous Malformations

   Exquisite Microvascular dissection techniques are required when surgically confronting Intracranial vascular problems such as Aneurysms and Arteriovenous Malformations.

   The majority of these aneurysms are located around the "base" of the Brain. As such they may have intimate relationships with other vital structures such as Cranial Nerves, adjacent major Cerebral Arteries and Veins as well as Brain structures. The Microvascular dissection techniques are useful in preserving these structures and their function while eradicating the threat to life that the aneurysm represents.

   Figure 9A (Left): Left Carotid Angiogram (Lateral View). Left Internal Carotid Artery Aneurysm (Arrow) Figure 9B (Right): Left Carotid Angiogram (Anterior-Posterior Oblique View) Left Carotid Artery Aneurysm (Arrow)

   Figure 10A (Left): Operative Photo. Left Internal Carotid Artery Aneurysm (Slender Arrows) arises from the Left Internal Carotid Artery (Broad Arrow) (Note: The Left Optic Nerve is just to the RIGHT of the Carotid artery and is partially obscured by the Arrow in each photo.) Figure 10B (Right): Operative Photo. The Aneurysm has been successfully obliterated by placing an aneurysm clip around the "neck" (Slender Arrow) to stop any blood from flowing to the aneurysm while maintaining the patency of its parent Left Carotid Artery Broad Arrow).

   Figure 11: Left Carotid Angiogram (Lateral View) Left Posterior Frontal AVM demonstrates the tangle of vessels that make up the AVM. Enlarged arteries "feed" the AVM (Left Arrows) and enlarged Veins "drain" the AVM (Top Arrow)

   Figure 12: Operative Photo. After Microvascular Resection Part of the challenge of this surgery is to remove the AVM while preserving normal adjacent Brain and the vital vessels that supply the Brain. For the most part the AVM does not incorporate functioning Brain; however, it is intimately and intricately involved with the contiguous Brain elements. A "cavity" is left where the AVM previously resided.

5. Spinal Cord Arteriovenous Malformations (AVM) & Spinal Cord Tumors

   These same delicate techniques Microvascular dissection techniques and surgical principles are required for Intraspinal Vascular problems and Spinal Cord Tumors.

   Figure 13: Operative Photo of Spinal Cord Arteriovenous Malformation. The "feeding artery" (Upper Arrow) supplies the tangle of vessels that comprise the Arteriovenous Malformation-AVM- (Bottom Arrow) The AVM obscures the Spinal Cord from view. A portion of the Spinal Cord (white tissue-Middle Arrow) is visible.

   Figure 14: Operative Photo of Intradural Spinal tumor (Middle Arrow). Compressed Intradural Spinal Nerves have been displaced by the tumor (Upper & Lower Arrows).

   Figure 15: Operative Photo (Same patient as Figure 14.) The Intradural Spinal Tumor has been completely removed (using Minimally Invasive Microvascular Dissection techniques) with preservation of the Spinal Nerves and their blood supply.

6. Deep-seated Brain Tumors

   Microvascular dissection techniques are often used for surgical procedures that address pathological conditions in very confined areas such as Tumors located deep within the Ventricles of the Brain, Tumors within and around the Brain Stem and Tumors within the Orbit of the Skull.

   Figure 16A (Left): MRI Scan (Transaxial View). A deep-seated Tumor (Arrow) fills the posterior aspect of the Third Ventricle. Figure 16B (Right): MRI Scan (Sagittal View-Gadolinium Enhanced). The tumor (Left Arrow) has an intimate relationship with vital vascular structures including the Vein of Galen (Right Arrow) and its branches (Top Arrow).

   Figure 17: Operative Photo A 3rd Ventricular Tumor has been approached through a Right Occipital Craniotomy (in a direction indicated by the "Right Arrow" in Figure 16B above). The Vein of Galen (Lower Arrow) has been carefully dissected allowing access to the Tumor that filled the 3rd Ventricle (Top Arrow).

7. Optic Nerve & Orbital Tumors

   Microvascular dissection techniques are often required when dealing with the delicate structures within the Orbit of the Skull. Tumors of the Optic Nerve or those that are directly adjacent to the Nerve and Globe require very delicate management in order to preserve useful vision. (An example of this is illustrated in the case of an Optic Nerve Meningioma in Figures 18 A & B.)

   Figure 18A (Left): CT Scan ("Dye-Enhanced" Transaxial View of Orbits). A Right Optic Nerve Meningioma widens the appearance of the Optic Nerve (Arrow) Figure 18B (Right): Operative Photo of this Right Optic Nerve Meningioma AFTER MOST OF THE TUMOR HAS BEEN REMOVED. The Meningioma had partially encircled the Nerve. It is a daunting technical task to preserve the tiny Optic Nerve vessels while removing the tumor. Remnants of tumor (Arrows) remain in this photo and must be removed in order to prevent a recurrence. A COMPLETE REMOVAL WITH PRESERVATION OF VISION WAS ACCOMPLISHED.

This page last edited on 2/22