Neurological

Spondylolisthesis: Slip, Ouch, and Wiltse

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Spondylolisthesis occurs when one vertebrae "slips" forward relative to the one below it. Spondylolisthesis is most frequently used to describe this process in the lumbar spine, but it may occur in the cervical or thoracic spine as well.

Spondylolisthesis has traditionally been divided into categories based on the underlying pathology causing the slip (ie: the Wiltse classification). These categories include: congenital, isthmic, degenerative, traumatic, pathologic, and post-surgical (aka: iatrogenic).

Regardless of the category, the end result is the same: one vertebrae slips forward relative to the one below it. Let’s talk about each category in more detail…

Congenital spondylolisthesis occurs in children. It is usually caused by malformation of the superior articulating facet of the first sacral vertebrae (S1). The facet is a portion of bone that forms a joint with the vertebrae above or below it. Therefore, in congenital spondylolisthesis the malformed S1 facet joint is unable to form a stable joint with the lowest lumbar vertebrae (L5). The end result is that the L5 vertebrae is able to slip forward relative to the sacrum.

Isthmic spondylolisthesis occurs when there is a break in the bone that connects the facet of one vertebrae to the facet of the vertebrae immediately above (or below) it. This connecting bone is known as the pars interarticularis. The defect in the pars interarticularis is known formally as spondylolysis (see image below). Spondylolysis does not necessarily cause spondylolisthesis, but when it does it is classified as "isthmic". This type of spondylolisthesis is more common in those of Inuit heritage, as well as in athletes who have had repetitive hyperextension of the lumbar spine (ie: gymnastics, tennis, football, etc).

Traumatic spondylolisthesis is exactly what it sounds like. Injury to the facet joints, pars interarticularis, or ligaments of the spine can allow one vertebrae to slip forward/dislocate relative to the one above and/or below it.

CT lumbar spondy
Pathologic spondylolisthesis occurs when the slip is caused by some underlying pathology in the bone. This category is broad and may include tumors, osteoporosis, osteopetrosis, Paget’s disease, or other diseases of bone formation or metabolism.

Post surgical (also known as iatrogenic) spondylolisthesis occurs after surgery. It most frequently develops after a laminectomy is performed. If too much bone is removed during the laminectomy it may cause instability and allow a slip to occur.

The last category, degenerative spondylolisthesis, affects people over the age of forty. It is unclear exactly what causes this type of spondylolisthesis, but it is believed to be secondary to a combination of arthritic changes in the facet joints, degenerative disc disease, and bony remodeling of the pars interarticularis. Degenerative spondylolisthesis, unlike isthmic or congenital, usually results in the fourth lumbar vertebrae (L4) slipping over the fifth lumbar vertebrae (L5).

How Do Patient’s with Spondylolisthesis Present?

Spondylolisthesis typically presents with a combination of low back pain with or without radiculopathy (ie: discomfort down the legs). The radiculopathic symptoms are due to narrowing of the intervertebral foramen and pinching of the nerves as they exit the spinal column.

Neurological symptoms such as weakness, bowel or bladder problems, or sexual dysfunction are uncommon, but can also occur. These symptoms become more common as the severity of the slip increases.

Many patient’s with spondylolisthesis also have significant hamstring tightness (ie: unable to touch their toes). Additionally, many patients will walk or stand with their torso or knees in a flexed position.

Diagnosis and Severity of Slip

Diagnosis of spondylolisthesis is based on x-rays, CT scans, and MRI imaging. X-rays and CT scans are best at delineating the bony anatomy. MRIs are frequently ordered to assess the amount of nerve compression (especially in patients with signs of neurologic dysfunction).

The severity of the slip is based on the Meyerding classification system. Type one slips occur when less than 25% of the diameter of the vertebral body slips forward relative to the one below it. Type two slips are between 26% and 50%. Type three slips are between 51% and 75% and type four slips are between 76% and 100%. If a slip is more than 100% it is referred to as a grade five slip or spondyloptosis.

Grade 1 Spondylolisthesis L5-S1

Fix Me Doc!

Initial treatment for low grade slips presenting with back pain and mild radiculopathy is usually conservative. Physical therapy, joint injections, ibuprofen (or other non steroidal anti-inflammatory medications), and bracing can be used for several months. Physical therapy should focus on lumbar flexion exercises with avoidance of lumbar extension. If symptoms continue or worsen then surgery is indicated (talk to your local spine surgeon).

Patient’s who fail conservative treatment, have high grade slips (ie: greater than 50%), or have weakness, bowel/bladder issues, or sexual dysfunction should be offered surgery. The primary goal of surgery is to prevent further slippage by fusing the vertebrae together; realigning the spine is a secondary goal, but is not absolutely necessary. In fact, attempts to realign high grade slips have been shown to increase the risk of neurological injury.

The type of surgery offered to correct spondylolisthesis may be from the front (ie: anterior), from the back (ie: posterior), or a combination of both. As of now, there is no “right” surgical approach.

The Play by Play…

Spondylolisthesis is a fancy term that describes one vertebrae slipping forward relative to the one below. There are six categories based on the underlying pathology causing the slip. These categories are congenital, isthmic, degenerative, traumatic, pathologic, and post surgical/iatrogenic. Symptoms are typically low back pain with a component of radiculopathy. Weakness, bowel/bladder or sexual dysfunction is actually uncommon unless high grade slips are present. The Meyerding system is used to determine the severity of the slip. Treatment for low grade slips is usually conservative, but surgery may be necessary for high grade slips, patients that fail conservative management, or those with hard signs of neurological dysfunction.

Additional Pathology You Might Fancy…

References and Resources

Spondylolysis and the Scotty Dog

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Spondylolysis is a fancy term for a defect in a portion of a vertebrae known as the pars interarticularis. The pars interarticularis is a section of bone that connects the superior articulating facet and the inferior articulating facet of a given vertebral body. The facets (which are joints) connect adjacent vertebrae together.

The CT scan below shows the relevant anatomy of a normal pars interarticularis and one that exhibits spondylolysis. Spondylolysis occurs about 85% of the time at the fifth (L5) lumbar segment, followed in frequency by the fourth lumbar vertebrae (L4), but it can occur elsewhere in the spine.

In spondylolysis there is a fracture/defect in the pars. Fractures of the pars interarticularis typically occur after repeated extension of the lower back. Repetitive extension causes significant pressure on the pars, which in susceptible individuals can lead to weakening of the bone.

Spondylolysis is actually quite common in gymnasts, football, and tennis players because of the repetitive back extension required of these athletes.

The importance of spondylolysis is not so much the pars defect itself, but the fact that these defects can cause one vertebrae to "slip" over the top of the one below it. When this occurs a new name is given to the condition – spondylolisthesis.

Signs and Symptoms

CT lumbar spondy
Xray Scotty Dog
The most common symptom of spondylolysis is low back pain. In fact, one of the most common causes of low back pain in individuals less than 25 years old is spondylolysis, especially in athletes. It is also important to note that spondylolysis is commonly asymptomatic.

Diagnosing Spondylolysis

Diagnosis is made by looking at an x-ray or CT scan of the spine. The classic description is a defect through the neck of the “Scotty dog”, which is seen best on an oblique x-ray of the lumbar spine.

What to do About It

Treatment starts with avoidance of the motions that caused the fracture. Occasionally a brace is used to prevent extension of the spine.

Anti-inflammatory medications like ibuprofen are commonly used if pain is significant. After a period of rest, physical therapy can be useful to strengthen muscles and prevent recurrence.

Less commonly surgical repair of the pars defect may be attempted. Surgical candidates are patients who continue to have back pain despite conservative treatment. If the patient receives significant pain relief from pre-operative bupivacaine injection into the defect, then they should be considered excellent surgical candidates.

Overview

Spondylolysis is a defect in the bony pars interarticularis of the vertebrae. It commonly occurs in the lumbar spine after repetitive extension motions. Low back pain is the most common symptom. In the absence of complications like spondylolisthesis treatment is typically conservative and involves bracing, physical therapy, and anti-inflammatories. Diagnosis is made by x-ray and/or CT scan.

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Hemangioblastoma of the Central Nervous System

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Hemangioblastomas are benign tumors that occur in the central nervous system, most commonly in the cerebellum. The exact cell from which they arise is unknown; however, they are believed to be meningeal (ie: the cells that make up the covering of the brain) in origin.

Hemangioblastomas can be solid or cystic in appearance. However, all hemangioblastomas have capillary networks that are lined by endothelial cells. Interspersed between the capillaries are pericytes and stromal cells with a polygonal appearance.

The arrangement of these various cell types can occur in three different architectures: juvenile, clear cell, or transitional. Each architecture has a specific ratio of capillaries to stroma (connective tissue), with the juvenile type having the greatest amount of capillary tissue, and the clear cell type having the greatest amount of stromal tissue.

About a quarter of cases are related to a genetic disorder known as von Hippel-Lindau syndrome. von Hippel-Lindau syndrome is the result of a genetic mutation in the VHL gene on chromosome 3. The protein product of this gene is a tumor suppressor; when mutated it is unable to suppress the abnormal growth of tumor cells. As a result, patients with von Hippel-Lindau syndrome develop hemangioblastomas of the brain and retina, renal cell carcinoma, and other tumor types.

Hemangioblastomas are most commonly found in the cerebellum, but on occassion will affect the cervical spinal cord and brainstem. They are most commonly seen in males starting at around 20 years of age.

Signs and Symptoms

Patients with cerebellar hemangioblastomas present with numerous signs and symptoms. Many patients will complain of headache, nausea, and vomiting. This is often due to the tumor compressing the cerebral aqueduct, which causes cerebrospinal fluid to “back up” in the brain leading to hydrocephalus and increased pressure inside the head.

In addition, many people with hemangioblastomas will have evidence of cerebellar dysfunction on physical exam. These signs include ataxia (ie: wobbly gait), dysmetria (ie: uncoordinated movements of the limbs), and dysdiadochokinesia (ie: difficulty repeating rapid alternating movements).

If the tumor is present in the spinal cord, symptoms may include weakness, spasticity, numbness, or other sensory changes.

Interestingly, hemangioblastomas can secrete an analogue of the hormone erythropoietin. This hormone causes bone marrow to pump out more red blood cells. As a result, some patients may have an increased number of red blood cells; this is known as polycythemia.

Diagnosis

Hemangioblastoma MRI
Hemangioblastoma Angiogram
A presumptive diagnosis can be made using epidemiology and imaging studies.

A tumor located in the cerebellum of an adult with certain characteristics on CT, MRI, and cerebral angiogram can make the diagnosis of hemangioblastoma likely.

However, the final diagnosis can only be made by looking at a sample of the tumor under the pathology microscope.

Treating These Bastards

Definitive treatment is surgical resection. However, hemangioblastomas can be highly vascular, which means they tend to bleed like stink! Therefore, preoperative embolization by an interventional neuro-radiologist can decrease the amount of bleeding that occurs during surgery.

Radiation therapy is also sometimes used as an adjunctive treatment. It may help slow the growth of the tumor, but will not cure it. Radiation therapy can be used in patients who are unable to undergo surgical resection, or if the tumor is inaccessible via traditional surgical means.

Recap It All…

Hemangioblastomas are highly vascular, but benign central nervous system tumors of undetermined origin. They are associated with von Hippel-Lindau syndrome. Signs and symptoms include headache, nausea, and vomiting, as well as cerebellar dysfunction. Diagnosis is based on imaging and pathological findings at the time of surgical resection. Surgery is the treatment of choice, although embolization and radiation therapy may also be used as an adjunct.

More Interesting Neurological Problems…

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The ACOMM Aneurysm: Balloons and Blood

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In order to understand the anterior communicating artery, we have to first appreciate the anatomy of the anterior cerebral arteries. The anterior cerebral arteries are one of the two terminal branches of each internal carotid artery (the other being the middle cerebral artery). Each anterior cerebral artery has several sections from A1 to A5.

Each A1 segment branches into an A2 segment and into the anterior communicating artery. The anterior communicating artery connects each anterior cerebral arteries’ A1 segment together to form a circle (see schematic below).

The anterior communicating artery is one of the most common sites for intracranial aneurysm formation. Patients at risk for developing aneurysms include those with atherosclerosis, those with a family history of intracranial aneurysms, those with a history of hypertension or collagen vascular disease, and those with polycystic kidney disease. Smokers are also at a higher risk of developing aneurysms.

Basilar Tip Schematic Drawing
Anterior communicating artery aneurysms form when the lining of the vessel wall is thinned and the muscular layer of the blood vessel (tunica media) becomes weakened.

This thinning allows turbulent blood flow to form out-pouchings in the vessel wall. Typically these out-pouchings occur at points where blood vessels branch.

Signs and Symptoms

Anterior communicating artery aneurysms commonly present after a subarachnoid hemorrhage, which can cause a variety of signs and symptoms. The most common being a severe headache, although cranial nerve dysfunction, stroke, coma, and death can also occur.

Less commonly, aneurysms in this location can compress the optic chiasm or optic nerves leading to problems with vision.

How Do You Diagnose Aneurysms

Anterior cerebral artery aneurysms are most commonly diagnosed after a subarachnoid hemorrhage when a patient presents with the "worst headache of their life". The best imaging methods for diagnosing these aneurysms are CT angiograms (see image below), MR angiograms, and formal cerebral angiograms.

Treatment

Like other intracranial aneurysms, anterior communicating artery aneurysms may be clipped or coiled. Clipping of an aneurysm involves an open surgical procedure where the surgeon dissects down to the aneurysm and places a clip across its neck. This excludes it from the circulation and prevents it from rupturing.

Anterior Communicating Artery Aneurysm CT Angiogram

Aneurysms may also be treated from inside the blood vessel. In this procedure a catheter is threaded from the femoral artery in the groin up towards the location of the aneurysm. Small metallic coils are placed within the dome of the aneurysm, which also excludes it from the normal circulation.

Regardless of how the aneurysm is treated – either with clipping or coiling – the end result is that the aneurysm is excluded from the normal circulation. This prevents it from rupturing.

The merits of clipping versus coiling are still under debate. Ultimately, the treatment depends on the size and location of the aneurysm, as well as other medical problems that the patient may have.

The Highlights…

Anterior communicating artery aneurysms are the most common intracranial aneurysm. They typically present after rupturing into the subarachnoid space and/or adjacent frontal lobes. They are diagnosed using CT angiograms or formal cerebral angiography. Treatment is with clipping and/or coiling.

Related Readings

Not Satisfied? More Reading on the Subject…

  • Bederson JB, Awad IA, Wiebers DO, et al. Recommendations for the management of patients with unruptured intracranial aneurysms. Stroke 2000;31:2742-2750.
    • li>Hunt WE, Hess RM. Surgical Risk as Related to Time of Intervention in the Repair of Intracranial Aneurysms. Journal of Neurosurgery 1968; 28:14-20.
  • Brisman JL, Song JK, Newell DW. Cerebral Aneurysms. NEJM 2006; 355:928-939.
  • Kumar V, Abbas AK, Fausto N. Robbins and Cotran Pathologic Basis of Disease. Seventh Edition. Philadelphia: Elsevier Saunders, 2004.
  • Frontera JA. Decision Making in Neurocritical Care. First Edition. New York: Thieme, 2009.
  • Greenberg MS. Handbook of Neurosurgery. Sixth Edition. New York: Thieme, 2006. Chapter 25.

Meningioma and the Arachnoid Cap Cell

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A meningioma is a tumor that arises from the lining of the brain or spinal cord (ie: the “meninges”). They arise from cells known as “arachnoid cap cells”. Meningiomas are usually slow growing, “benign” tumors, which means that they are not usually considered cancerous in the strictest sense of the term.

When viewed under the light microscope, meningiomas can have many different appearances. The most common type is a dense sheet-like formation of cells interspersed with closely packed blood vessels. Sometimes the sheets of cells can be separated by connective tissue.

Frequently, meningiomas will have calcium deposits in them known as “psammoma bodies”. Uncommonly, meningioma cells may take on a malignant appearance characterized by increased cellular division (ie: “mitotic figures”) and invasion of the tumor cells into surrounding brain or bone.

Meningiomas test positive for epithelial membrane antigen (EMA) and vimentin (a marker of connective tissue). Ki-67 (a marker of proliferation) can be elevated in more aggressively behaving tumors.

The most common genetic abnormality seen in patients with meningiomas is found on chromosome 22. If present, a mutation in the NF2 gene on this chromosome causes type 2 neurofibromatosis. This disease predisposes individuals to developing multiple tumor types including meningiomas. Other less common genetic abnormalities can be seen on other chromosomes as well.

Signs and Symptoms

Due to their slow growing and benign nature, many meningiomas cause no symptoms. However, if they become too large or start to compress adjacent brain tissue they can cause headache, seizures, confusion, or visual problems. Spinal cord compression can result in myelopathy.

The most common location for a meningioma is in between the two hemispheres of the brain – the so called “parasagittal” location. Parasagittal meningiomas near the portion of the brain responsible for muscle movements may cause weakness of the opposite leg.

Diagnosis

Diagnosis of meningioma can reliably be made on characteristic findings seen on CT or MRI scans. Interestingly, many meningiomas are found incidentally when a CT or MRI is done for other reasons.

Meningioma MRIs

However, like any other tumor, meningiomas can only be truly diagnosed once a specimen is sent to the pathology lab for analysis. Pathologists can reliably make the diagnosis based on typical histological features.

Meningiomas must be distinguished from a more malignant tumor known as a hemangiopericytoma. Hemangiopericytomas can look similar to meningiomas on imaging studies.

Dish Me Up Some Treatment Sir

Many meningiomas can be watched over time with repeat imaging studies; this is especially true if they are small and not causing neurological signs or symptoms.

On the other hand, large or symptomatic meningiomas require surgical resection. Many meningiomas can be removed completely. However, some meningiomas may be near vital structures such as the carotid artery, cranial nerves, or venous draining systems of the brain where complete surgical removal may be very difficult without causing significant neurologic impairment. In these cases the tumor is debulked as much as possible. The residual tumor can be followed or irradiated depending on the grade of meningioma.

Residual tumor after incomplete surgical resection, or meningiomas in difficult to access locations are candidates for radiation therapy. Many studies have shown long term growth control rates.

Overview

Meningiomas are considered “benign” tumors of the brain. They arise from arachnoid cap cells, which are located in a layer of the meninges (ie: the covering of the brain) known as the arachnoid. Symptoms include headache, weakness, vision problems, paresthesias (ie: abnormal sensations), amongst many other possible symptoms. Diagnosis can be made reliably from imaging studies such as CT or MRI. If symptomatic, or large, treatment is surgical resection. Small asymptomatic meningiomas can be managed with repeat imaging to assess for growth over time.

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Chordoma and that Pesky Notochord

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In order to understand chordomas we have to first learn a little bit about how the nervous system develops. Enter the notochord.

The notochord is a midline structure in the developing fetus that sends out various molecules (the most well known of which is “sonic hedgehog”). These molecules influence the development of the layers of embryonic cells that surround the notochord. One of these layers, the ectoderm, which is immediately behind (ie: posterior) the notochord eventually forms the brain and spinal cord. The mesoderm, which is immediately adjacent to the notochord forms the vertebral column and axial skeleton (amongst other things).

The purpose of the notochord is to ensure that each layer of tissue forms what it is supposed to. Once this occurs, the notochord ultimately becomes the nucleus pulposus of the intervertebral discs.

In some people, nests of cells that composed the fetal notochord remain (unnaturally) after birth. These collections of cells are known formally as ecchordoses physaliphora (try saying that 5 times fast). These cells can divide and turn into a slow growing tumor… What is that tumor called? You guessed it! A chordoma!

Chordomas are slow growing tumors that are most commonly located at the ends of the vertebral column. The most common place to see them is in the sacrococcygeal region, followed in frequency by a bone known as the clivus at the base of the skull. However, chordomas can occur anywhere along the vertebral column. The reason they occur most frequently at the "ends" of the vertebral column (ie: skull base and sacrum) is because these are the last areas to fuse in-utero.

Additionally, since the notochord is a midline structure in the fetus, chordomas are almost always midline in location.

Microscopically chordomas contain large polygonal shaped cells embedded in a mesh of long repetitive sugar and nitrogen containing molecules known as mucopolysaccharides.

Chordoma Highlights:
– Arise from notochord cells
– S-100 positive
– Cytokeratin positive
– Polygonal cells
– Slow growing
– Midline location
– Sacrum and clivus most
   common locations
– Worse prognosis than
   chondrosarcomas
Less than a third of chordomas will show cartilage like features. These chordomas are classically called “chondroid” chordomas because of the chondrocyte-like (ie: cartilage-like) cells and extracellular material within them. Chondroid chordomas must be distinguished from a similar looking tumor known as a chondrosarcoma.

Distinguishing chondrosarcomas from chordomas is possible with immunocytologic staining techniques. Chondromas and chondrosarcomas stain positive for a protein known as S-100. S-100 proteins have numerous intracellular functions and are commonly present in cells such as adipocytes (fat cells), chondrocytes (cartilage forming cells), melanocytes (pigment producing cells), and Schwann cells, amongst others.

So if chondrosarcomas and chordomas can look alike, and both stain positive for S-100, how the heck do we distinguish between the two? Using another molecule known as cytokeratin! Cytokeratin is a molecule that forms part of the intracellular frame for many cells. It is present in chordomas, but not in chondrosarcomas.

On to the Clinic I Say…

Chordomas are slow growing tumors and will usually start to cause symptoms in mid-adulthood. Symptoms are based on the location of the tumor.

If the tumor is located in the sacrum or coccyx then pain is the most frequent presenting symptom. If undiscovered this may progress to bowel and bladder problems as the tumor slowly envelopes the sacral nerves that go to the bowel and bladder. Additionally, patients may present with radicular symptoms such as numbness, tingling, or sharp pain in the distribution of the sacral nerves.

Clivus Chordoma
Chordomas of the clivus, the second most common location, can present with headache and if large enough symptoms of brainstem or upper cervical spinal cord compression. These symptoms may include vertigo, difficulty moving the tongue, double vision, hearing problems, spastic gait, increased reflexes, clumsiness, amongst other symptoms.

Diagnose Me McCoy

Diagnosis of chordoma can only be officially made by looking at the specimen under a microscope. However, imaging studies with x-rays, CT scans, and MRI imaging can support the diagnosis. Imaging studies will typically show a midline lytic lesion centered in the bone. Invasion of adjacent anatomical structures can occur, but is a late manifestation of the disease course.

Treating These Ugly Tumors

The gold-standard treatment for chordomas is en-bloc surgical resection with wide margins followed by radiation therapy. Complete resection is difficult, if not impossible to achieve in the skull base, but may be possible in the spine and/or sacrum with very skilled surgical teams.

Without an en-bloc surgical resection the risk of tumor re-growth and recurrence is very high. If you are planning to biopsy of a sacral lesion you should mark the biopsy tract with methylene blue so that the tract can also be resected during surgery as tumor cells can seed the tract as the needle is being pulled out.

Let’s Remix This Overview

Chordomas are slow growing, but malignant tumors that arise from notochord cells that fail to regress after birth. They are most frequently found in the sacrum and clivus (one of the bones constituing . Diagnosis is made with CT, MRI, and x-rays, as well as via tissue diagnosis at the time of surgical removal. Chordomas stain positive for S-100 and cytokeratin proteins, which helps distinguish them from chondrosarcomas that only stain positive for S-100. Symptoms are based on where the lesion is located (skull base or spine). Treatment is surgery followed by radiation therapy.

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Cerebral Cavernous Malformations: Leaky Vessels

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Cavernous malformations (aka: cavernomas or cavernous hemangiomas) can be thought of as vascular tumors. They are composed of a capillary-like network of endothelial cells (the cells that normally line blood vessels). However, unlike normal capillaries throughout the body, the capillaries of cavernomas can leak.

Interestingly, cavernous malformations do not have any brain tissue within them. This helps distinguish them from another related vascular abnormality known as an arteriovenous malformation.

The genetics of cavernous malformations have been elucidated by studying familial forms of the disorder. There are at least three known genetic defects that predispose patients to develop cavernomas. These genes appear to be important in the formation of blood vessels (a process known as "angiogenesis") and the blood brain barrier. Therefore, mutations in these genes can cause the abnormal growth of vascular tissue.

What Havock Do These Guys Cause?

Cavernomas can cause numerous signs and symptoms depending on their location within the brain. Seizures are the most common symptom. However, progressive neurological impairment such as worsening weakness can also occur.

Sometimes cavernomas can block the flow of cerebrospinal fluid leading to hydrocephalus. Hydrocephalus can cause increased intracranial pressure leading to headaches, nausea, and vomiting. However, it is important to realize that many patients with cavernomas have no symptoms at all!

If symptoms are present, they tend to progress over time. This is because cavernous malformations bleed and re-bleed resulting in an expansion of its size over time. As the malformation increases in size it can push on adjacent brain tissue causing worsening symptoms.

Unlike arteriovenous malformations, life threatening and severe hemorrhages are rare. Cavernomas bleed at an initial yearly rate of anywhere between 1% to 5%. After the first bleed, the risk of re-bleeding increases to as high as 10% per year. In other words, if a cavernoma bleeds, it is more likely to re-bleed at a later date.

How Do You Diagnose These Buggers?

Cavernoma Marked

The diagnosis of cavernous malformations are made via imaging studies. They are usually detected via MRIs that are ordered for evaluation of neurological symptoms. Cavernomas are seen best on T2 and gradient echo MRI sequences. They typically look like a piece of popcorn.

Select patients undergo a more invasive imaging procedure known as angiography. Angiography is used to rule out another similar lesion known as an arteriovenous malformation. Since cavernomas are venous malformations they are not seen on angiograms.

How Are These Treated?

Depending on the location, most cavernous malformations in the brain or spinal cord are removed surgically. Some institutions offer radiation as a means of treatment, especially in difficult to access areas (ie: where the risk of surgical removal is very high).

Let’s Recap this MoFo

Cavernous malformations of the brain are abnormal vascular growths composed of capillary networks. They are likely the result of genetic mutations in genes responsible for blood vessel growth. Depending on their location they can cause numerous neurological symptoms such as seizures and weakness. MRI often shows the characteristic “popcorn” lesion. Treatment is usually with surgical resection, although some cavernomas may be radiated depending on their location.

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Middle Cerebral Artery: A Common Site for Stroke

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Middle cerebral artery (MCA) strokes occur when the MCA or its branches are occluded. With occlusion, blood, and along with it, oxygen and nutrients fail to reach the brain. If blood flow is not restored quickly the affected brain tissue dies leading to permanent neurological injury.

Risk factors for MCA strokes are the same for other strokes. They include hypertension, diabetes, smoking, atrial fibrillation, and a whole slew of hypercoagulable states (ie: pathologic increases in the bodies’ propensity to form blood clots).

In order to understand MCA strokes we have to first appreciate the anatomy of the MCAs, as well as the brain that they serve. The MCAs are subdivided into four parts. The M1 segment is one of the terminal branches of the internal carotid artery. The MCAs then become progressively more narrow and form more and more branches as they reach out towards the cortical surfaces of the brain. The most distal portions of the MCA are deemed the M4 branches. The lateral lenticulostriate arteries are small branches that branch from the M1 segments; these small arteries feed some of the deeper structures of the brain.

Importantly, the MCAs and their branches provide blood flow to an extremely large portion of the brain. These areas include the lateral and inferior frontal lobes, superior portion of the temporal lobes, insula, and lateral parietal lobes. Branches of the first portion of the MCAs (aka: the lateral lenticulostriate arteries) also provide blood flow to the deep sections of the brain including the putamen, head and body of the caudate, external globus pallidus, and parts of the posterior limb of the internal capsule.

The segmental anatomy of the MCAs is important because strokes that occur in the outer segments (ie: M3 and M4) cause less neurological injury than the inner MCA segments (ie: M1 and M2). This is because less total brain volume is affected by outer segment strokes.

The most common cause of MCA strokes are clots that break off and travel from the heart or the carotid arteries to the MCA (aka: emboli). Less commonly, a blood clot will form directly in the MCA itself (aka: thrombus). Atherosclerotic disease is the most common cause of thrombus formation in the MCA and atrial fibrillation (an abnormal heart rhythm) is the most common cause of emboli from the heart.

Signs and Symptoms

Middle cerebral artery strokes present with one of two types of syndromes depending on which MCA – right or left – is involved, as well as which segments of the MCA are involved.

In the worst case scenario, a stroke of the right or left M1 segment of the MCA causes weakness of the opposite side of the body. This is a result of cortical damage to the primary motor cortex as well as possible infarction of the posterior limb of the internal capsule (ie: the location of descending motor tracts). MCA strokes usually present with face and arm weakness that is worse than leg weakness. Remember that the motor cortex that controls leg function is served by the anterior cerebral arteries.

M1 strokes also cause decreased ability to feel sensation on the opposite side of the body as a result of damage to the parietal lobes.

Damage to the optic radiations, which course in the parietal (Baum’s loop) and temporal lobes (Meyer’s loop) can cause problems with vision. Finally, injuries to the frontal eye fields cause the eyes to deviate towards the side of the stroke (ie: the frontal eye fields normally allow you to make fast eye movements in the opposite direction, therefore damage prevents patients from looking to the non-affected side).

Right and left sided M1 strokes will give you all of the above symptoms; however, laterality can be determined based on specific symptoms caused by only a left or a right sided strokes.

The poor patients with left M1 strokes have a decreased ability to speak and/or understand language because of damage to Broca’s area in the left frontal lobe (speech production) and Wernicke’s area in the left temporal lobe (speech comprehension). Remember this is in addition to all the other stuff above.

Right M1 strokes can cause "anosognosia", in which the patient is unaware of certain deficits they may have; these patients also often fail to recognize the left side of their body (ie: they "neglect" or fail to appreciate the entire left side of the world) and may have difficulty appreciating people or objects presented in their left visual field.

Right MCA stroke
Less "severe" cases, in which M2, M3 or M4 branches are affected can produce a variety of signs and symptoms depending on the specific branches involved.

Diagnosis

Diagnosis of MCA strokes are based on symptoms, CT scans, and MRI images. CT and MR angiograms frequently show the blocked blood vessel causing the stroke. CT perfusion scans are a newer technology that give information regarding the amount of blood flow to affected brain tissue.

Treatment

Treatment depends on the timing of the stroke. If the patient presents within 3 hours of symptom onset, and the head CT reveals no bleeding, than intravenous tissue plasminogen activator (tPA) may be given to help "break" up the blood clot causing the stroke.

Other treatments using catheter based approaches are frequently used in patients who are unable to receive tPA. Such treatments include mechanical clot removal with special catheter and wire devices. In addition, in patients more than 3 hours, but less than 6 hours out from symptom onset intra-arterial (not to be confused with intravenous) tPA may be used.

Less commonly, large "malignant" MCA strokes may cause significant swelling, which can put pressure on the brainstem. These patients sometimes undergo an open surgical procedure known as a "craniectomy", in which the bone overlying the affected brain tissue is removed. This surgery allows the edematous brain tissue to swell outwards preventing it from herniating downwards towards vital brainstem structures.

Overview

Middle cerebral artery strokes are most commonly caused by blood clots that break off from the heart or carotid artery. Symptoms of MCA strokes depend on the segment involved, as well as which MCA (right versus left) is involved. Diagnosis is made with a combination of MRI, CT, and symptomatology. Treatment consists of intravenous or intra-arterial tPA and/or mechanical clot removal depending on the time frame of the symptoms.

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Hemangiopericytoma: A Tumor of Pericytes

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In order to understand hemangiopericytomas we have to define a few terms. The first term is mesenchyma. Mesenchyma is a word used to describe the different tissues that provide structure to the bodies’ organ systems. A type of mesenchymal cell known as a “pericyte” provides structural support to blood vessels. When pericytes go haywire they form hemangiopericytomas.

Hemangiopericytomas can occur anywhere blood vessels are located, but are most commonly located in the lower extremities, pelvis, head, and neck.

Intracranial hemangiopericytomas are uncommon. They represent less than 1% of tumors within the confines of the skull. They typically arise from blood vessels adjacent to the dura (ie: lining of the brain) and often form dural attachments. They are therefore commonly lumped into the category of “dural-based tumors”, but should be distinguished from their more benign meningeal cousins (ie: meningiomas).

Since hemangiopericytomas are mesenchymal in origin, they typically have lots of reticulin (a collagen fiber) that envelopes individual cells (see pathology slide). They are highly cellular tumors, and vascular channels in the shape of "staghorns", may be seen under the microscope. Actively dividing cells (aka: "mitotic" figures) are commonly seen and are a testament to their more malignant nature. Unlike meningiomas, calcifications are absent.

Hemangiopericytomas test positive for vimentin (a marker of connective tissue), Ki-67 (a marker of proliferation), vascular endothelial growth factor (VEGF, a marker of blood vessel proliferation), CD34 (a marker of blood and vascular cell lineage), and reticulin (a collagen fiber). These tumors do not stain positive for epithelial membrane antigen. Genetic mutations have been found on different chromosomes , but the importance of these abnormalities is not well understood.

Intracranial hemangiopericytomas are considered malignant tumors. This means that they can spread to other areas of the body. In addition, hemangiopericytomas that have been removed surgically have a high recurrence rate.

Hemangiopericytoma

Signs and Symptoms

Hemangiopericytomas are relatively slow growing and often do not cause symptoms until they become quite large. However, once they start to compress adjacent brain tissue they may cause headaches, seizures, confusion, weakness, or visual problems.

Diagnosis

MRIs and CT scans of the brain typically reveal a contrast enhancing dural-based lesion. Cerebral angiograms show a highly vascular tumor with blood supply coming from the dura, as well as the underlying brain tissue.

Based on imaging alone, hemangiopericytomas are often mistaken for meningiomas. Subtle characteristics such as a lack of calcification seen on CT scans may help distinguish one from the other, but this is not reliable.

The only reliable way to diagnose hemangiopericytoma is to look at a specimen of the tumor under a microscope. Special stains and features of the tumor can help delineate it from a meningioma (see pathology section above).

Did I Hear Someone Say “Treatment”?

Intracranial hemangiopericytomas should be surgically resected when feasible. Unfortunately, even after complete resection, they frequently recur and/or spread to other areas of the body.

Because of their aggressive nature, patients with hemangiopericytomas should also have adjuvant radiation therapy. Radiation treatment after surgical removal of the tumor has been shown to lengthen survival and slows (but doesn’t appear to prevent) the time to recurrence.

The role of chemotherapy is less clear and is still being investigated. At this point, chemotherapy is typically used in patients where radiation and surgery have failed to control the disease.

Let’s Recap It…

Intracranial hemangiopericytomas are malignant dural-based tumors that arise from pericytes. They are highly vascular tumors that enhance on MRI and CT scans. Symptoms are variable and depend on the size and location of the tumor. Treatment is with surgical removal followed by radiation therapy. Recurrence rates are high despite optimal treatment.

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Spinal Shock and Neurogenic Shock: The Battle Begins

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Endless hours of studying, relentless exams, and the never-ending confusion between two perplexing phenomena: spinal shock and neurogenic shock. So, buckle up (so you don’t end up in spinal shock) and prepare for the journey through the world of spinal and neurogenic shock as we break down their differences.

The Tale of Two Shocks

Picture this: you’re in the ER, and a patient comes in with a recent spinal cord injury. You rack your brain to differentiate between spinal shock and neurogenic shock, but all you can remember is the cranial nerves mnemonic and your chief resident is about to pimp the you know what out of you… Let’s make it easy!

  • Spinal Shock: Think of it as your body’s initial reaction to “breaking up” with your spinal cord. It’s a temporary and unexpected “break-up shock” that leaves your reflexes, motor function, and sensation feeling lost and numb (physically, not emotionally) below the level of injury.
  • Neurogenic Shock: Now, imagine your body losing its balance between the sympathetic and parasympathetic nervous systems after a spinal cord injury. It’s like a tug-of-war, but the parasympathetic system wins, causing blood vessels to dilate and blood pressure to drop. Your heart, not knowing how to cope, slows down in response (bradycardia). Neurogenic shock occurs because the descending sympathetic fibers of the cord are injured, whereas the parasympathetic supply to the body provided by the vagus nerve (ie: “wandering nerve”) off of the brainstem is still intact and is now un-inhibited.

Diagnostic Dilemmas: The Hints are There You Just Have to Look

When you’re trying to diagnose spinal or neurogenic shock, look for these clues:

  • Spinal Shock: Your patient’s reflexes have gone on vacation, and they’re not telling you when they’ll be back. The muscles are flaccid, and sensations are playing hide-and-seek. But fear not, because those reflexes will eventually return. The delayed plantar response and bulbocavernosus reflex (don’t ask us how someone figured this one out!) are two of the earlier reflexes to come back from vacation. There is a lot of debate about how to define spinal shock and how long spinal shock lasts. However, you cannot prognosticate about the severity of cord injury until at least one reflex has returned.
  • Neurogenic Shock: Here, your patient’s blood pressure is lower than your motivation on a Monday morning, and their heart rate is slower than a sloth doing yoga. The skin may be warm and dry, resembling a cozy blanket you wish you were under instead of being in the ER.

Treatments: The Cures

Now that you’ve (hopefully) identified which shock you’re dealing with, it’s time to strategize and take action:

  • Spinal Shock: When faced with this shock, channel your inner superhero and protect the injured spinal cord at all costs! Immobilize the spine, maintain blood pressure, and ensure proper oxygenation to minimize further damage. Neurosurgical consultation is often indicated if the spinal column is unstable and requires surgical fixation.
  • Neurogenic Shock: Roll up your sleeves and get ready for some serious hemodynamic management. Rehydrate your patient with IV fluids, bring out the vasopressors to constrict those dilated blood vessels, and, if necessary, consider a temporary pacemaker to speed up the slow-motion heart rate.

Remember that both neurogenic and spinal shock are often occuring at the same time! Additionally, remember that neurogenic shock can also co-exist with other types of shock like hypovolemic shock in polytrauma patients.

As future health practitioners, you’ll face many confusing and challenging scenarios, like differentiating between spinal shock and neurogenic shock. But remember, amidst the stress, it’s essential to find some humor and light-heartedness. After all, laughter is the best medicine, and knowing the difference between these two conditions will not only help your patients, but also save you from those embarrassing moments during rounds. So, hold your head high, and step into the world of medicine with a smile on your face and the ability to distinguish between spinal and neurogenic shock in your ever-expanding medical knowledge toolbox.

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