The complex circuitry interconnecting different areas in the brain, known collectively as white matter, is composed of millions of axons organized into fascicles and bundles. Upon macroscopic examination of sections of the brain, it is difficult to discern the orientation of the fibers. The same is true for conventional imaging modalities. However, recent advancements in magnetic resonance imaging (MRI) make such task possible in a live subject. By sensitizing an otherwise typical MRI sequence to the diffusion of water molecules it is possible to measure their diffusion coefficient in a given direction1. Normally, the axonal membrane and myelin sheaths pose barriers to the movement of water molecules and, thus, they diffuse preferentially along the axon2. Therefore, the direction of white matter bundles can be elucidated by determining the principal diffusivity of water. The three-dimensional representation of the diffusion coefficient can be given by a tensor and its mathematical decomposition provides the direction of the tracts3; this MRI technique is known as diffusion tensor imaging (DTI). By connecting the information acquired with DTI, three-dimensional depictions of white matter fascicles are obtained4. The virtual dissection of white matter bundles is rapidly becoming a valuable tool in clinical research.

Our journey begins with a transverse section of tightly packed axons as seen through light microscopy. Although represented as a two-dimensional "slice", we see that these axons in fact resemble tubes. A simulation of water molecules diffusing randomly inside the axons demonstrates how the membranes and myelin hinder their movement across them and shows the preferred diffusion direction --along the axons. The tracts depicted through DTI slowly blend in and we ride along with them. As we zoom out even more, we realize that it is a portion of the corpus callosum connecting the two sides of the brain we were traveling on and the great difference in relative scale of the individual axons becomes evident. The surface of the brain is then shown, as well as the rest of the white matter bundles--a big, apparently chaotic tangle of wires. Finally, the skin covers the brain.

With the exception of the simulated water molecules, all the data presented in the animation is obtained through microscopy and MRI. Computer algorithms for the extraction of the cerebral structures and a custom-built graphics engine make our journey through the brain's anatomy possible in a living person.

Micrograph courtesy of Dr. Christian Beaulieu, University of Alberta.
Music by Mario Mattioli.

References:
1. Stejskal, E.O., et al., J. Chem. Phys., 1965. 42:
2. Beaulieu, C., NMR Biomed., 2002. 15:435-55.
3. Basser, P.J., et al., J. Magn. Reson. B, 1994. 103:247-54.
4. Mori, S., et al., NMR Biomed., 2002. 15:468-80.

Nystagmus is a condition of involuntary (or voluntary, in rare cases) eye movement, acquired in infancy or later in life, that may result in reduced or limited vision. Due to the involuntary movement of the eye, it has been called "dancing eyes"

Bone Marrow Aspiration

A ventricular septal defect (VSD) is an opening or hole in the wall that separates the two lower chambers of the heart. This wall is called the ventricular septum. The hole causes oxygen-rich blood to leak from the left side of the heart to the right side. This causes extra work for the right side of the heart, since more blood than necessary is flowing through the right ventricle to the lungs. The hole is usually closed with surgery. However, in certain situations, your child's cardiologist and surgeon may think it is best to close the hole with a special device. This procedure is done in the heart catheterization lab.

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A brain (cerebral) aneurysm is a bulging, weak area in the wall of an artery that supplies blood to the brain. In most cases, a brain aneurysm causes no symptoms and goes unnoticed. In rare cases, the brain aneurysm ruptures, releasing blood into the skull and causing a stroke. When a brain aneurysm ruptures, the result is called a subarachnoid hemorrhage. Depending on the severity of the hemorrhage, brain damage or death may result. The most common location for brain aneurysms is in the network of blood vessels at the base of the brain called the circle of Willis. What causes a brain aneurysm? A person may inherit the tendency to form aneurysms, or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled, and others can't. The following risk factors may increase your risk for an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing: Family history. People who have a family history of brain aneurysms are more likely to have an aneurysm than those who don't. Previous aneurysm. People who have had a brain aneurysm are more likely to have another. Gender. Women are more likely to develop a brain aneurysm or to suffer a subarachnoid hemorrhage. Race. African Americans are more likely than whites to have a subarachnoid hemorrhage. High blood pressure. The risk of subarachnoid hemorrhage is greater in people who have a history of high blood pressure. Smoking. In addition to being a cause of high blood pressure, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.

Guillain-Barre syndrome is a rare disorder in which your body's immune system attacks your nerves. Weakness and tingling in your extremities are usually the first symptoms. These sensations can quickly spread, eventually paralyzing your whole body. In its most severe form Guillain-Barre syndrome is a medical emergency. Most people with the condition must be hospitalized to receive treatment. The exact cause of Guillain-Barre syndrome is unknown. But it is often preceded by an infectious illness such as a respiratory infection or the stomach flu. There's no known cure for Guillain-Barre syndrome, but several treatments can ease symptoms and reduce the duration of the illness. Most people recover from Guillain-Barre syndrome, though some may experience lingering effects from it, such as weakness, numbness or fatigue.

Surgical procedure of Tonsillectomy and Adenoidectomy

To understand congenital heart defects, it's helpful to know how a healthy heart works. Your child's heart is a muscle about the size of his or her fist. The heart works like a pump and beats 100,000 times a day. The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. The left side of the heart receives the oxygen-rich blood from the lungs and pumps it to the body. The heart has four chambers and four valves and is connected to various blood vessels. Veins are blood vessels that carry blood from the body to the heart. Arteries are blood vessels that carry blood away from the heart to the body.

Not every woman undergoes a traditional vaginal delivery with the birth of her child. Under conditions of fetal or maternal distress, or in the case of breech presentation (when a baby is turned feet first at the time of delivery), or if the woman’s first baby was born by cesarean delivery, a procedure called a cesarean section may be required. During a cesarean, a doctor will make either a lateral incision in the skin just above the pubic hair line, or a vertical incision below the navel. As the incision is made, blood vessels are cauterized to slow bleeding. After cutting through the skin, fat, and muscle of the abdomen, the membrane that covers the internal organs is opened, exposing the bladder and uterus. At this time the physician will generally insert his or her hands into the pelvis in order to determine the position of the baby and the placenta. Next, an incision is made into the uterus and any remaining fluids are suctioned from the uterus. The doctor then enlarges the incision with his or her fingers. The baby’s head is then grasped and gently pulled with the rest of its body from the mother’s uterus. Finally, the abdominal layers are sewn together in the reverse order that they were cut. The mother is allowed to recover for approximately three to five days in the hospital. She will also be quite sore and restricted from activity for the following several weeks. There are several potential complications associated with this procedure that should be discussed with a doctor prior to surgery.

Epidermoid cysts, also called sebaceous, keratin, or epithelial cysts, are small, hard lumps that develop under the skin. These cysts are common. They grow slowly. They do not cause other symptoms and are nearly never cancerous. Epidermoid cysts are often found on the face, head, neck, back, or genitals

Osteochondral Allograft

Pharyngitis is caused by swelling in the back of the throat (pharynx) between the tonsils and the voice box (larynx). Most sore throats are caused by colds, the flu, coxsackie virus or mono (mononucleosis). Bacteria that can cause pharyngitis in some cases: Strep throat is caused by group A streptococcus.

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Tracheotomy is a surgical procedure which consists of making an incision on the anterior aspect of the neck and opening a direct airway through an incision in the trachea (windpipe). The resulting stoma (hole), or tracheostomy, can serve independently as an airway or as a site for a tracheostomy tube to be inserted; this tube allows a person to breathe without the use of his or her nose or mouth. Both surgical and percutaneous techniques are widely used in current surgical practice. It is among the oldest described procedures.

Sialadenitis is an infection of the salivary glands. It is usually caused by a virus or bacteria . The parotid (in front of the ear) and submandibular (under the chin) glands are most commonly affected. Sialadenitis may be associated with pain, tenderness, redness, and gradual, localized swelling of the affected area.

Laparoscopic varicocellectomy Surgery

Physical Examination of the abdomen

Transmetatarsal Amputation for Gangrene

Symptoms Burning stomach pain Feeling of fullness, bloating or belching Fatty food intolerance Heartburn Nausea The most common peptic ulcer symptom is burning stomach pain. Stomach acid makes the pain worse, as does having an empty stomach. The pain can often be relieved by eating certain foods that buffer stomach acid or by taking an acid-reducing medication, but then it may come back. The pain may be worse between meals and at night. Nearly three-quarters of people with peptic ulcers don't have symptoms. Less often, ulcers may cause severe signs or symptoms such as: Vomiting or vomiting blood — which may appear red or black Dark blood in stools, or stools that are black or tarry Trouble breathing Feeling faint Nausea or vomiting Unexplained weight loss Appetite changes