The posterior inferior cerebellar artery (PICA), the largest branch of the vertebral artery

Vertebral artery

The vertebral arteries are major arteries of the neck. They branch from the subclavian arteries and merge to form the single midline basilar artery in a complex called the vertebrobasilar system, which supplies blood to the posterior part of the circle of Willis and thus significant portions of the...

, is one of the three main arterial

Artery

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 supplies for the cerebellum

Cerebellum

The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...

, part of the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. Occlusion of the posterior inferior cerebellar artery or one of its branches, or of the vertebral artery leads to Wallenberg syndrome

Lateral medullary syndrome

Lateral medullary syndrome is a disease in which the patient has a constellation of neurologic symptoms due to injury to the lateral part of the medulla in the brain, resulting in tissue ischemia and necrosis.-Signs and symptoms:This syndrome is characterized by sensory deficits affecting...

, also called lateral medullary syndrome.

Course

It winds backward around the upper part of the medulla oblongata

Medulla oblongata

The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...

, passing between the origins of the vagus and accessory nerve

Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...

s, over the inferior cerebellar peduncle

Inferior cerebellar peduncle

The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle , a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.Each cerebellar inferior peduncle connects the...

 to the undersurface of the cerebellum

Cerebellum

The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...

, where it divides into two branches.

The medial branch continues backward to the notch between the two hemispheres of the cerebellum; while the lateral supplies the under surface of the cerebellum, as far as its lateral border, where it anastomoses

Anastomosis

An anastomosis is the reconnection of two streams that previously branched out, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....

 with the anterior inferior cerebellar

Anterior inferior cerebellar artery

The anterior inferior cerebellar artery arises from the basilar artery at the level of the junction between the medulla oblongata and the pons in the brainstem. It passes backward to be distributed to the anterior part of the undersurface of the cerebellum, anastomosing with the posterior inferior...

 and the superior cerebellar

Superior cerebellar artery

The superior cerebellar artery arises near the termination of the basilar artery.It passes lateralward, immediately below the oculomotor nerve, which separates it from the posterior cerebral artery, winds around the cerebral peduncle, close to the trochlear nerve, and, arriving at the upper...

 branches of the basilar artery

Basilar artery

In human anatomy, the basilar artery is one of the arteries that supplies the brain with oxygen-rich blood.The two vertebral arteries and the basilar artery are sometimes together called the vertebrobasilar system, which supplies blood to the posterior part of circle of Willis and anastomoses with...

.

Branches from this artery supply the choroid plexus

Choroid plexus

The choroid plexus is a structure in the ventricles of the brain where cerebrospinal fluid is produced...

 of the fourth ventricle

Fourth ventricle

The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...

.

Diseases

Infarction

Infarction

In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...

 of this artery due to thrombosis

Thrombosis

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

 or a stroke

Stroke

A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

 leads to lateral medullary syndrome

Lateral medullary syndrome

Lateral medullary syndrome is a disease in which the patient has a constellation of neurologic symptoms due to injury to the lateral part of the medulla in the brain, resulting in tissue ischemia and necrosis.-Signs and symptoms:This syndrome is characterized by sensory deficits affecting...

, also known as PICA syndrome or Wallenberg syndrome. Severe occlusion of this or vertebral arteries could lead to Horner's Syndrome

Horner's syndrome

Horner's syndrome is the combination of drooping of the eyelid and constriction of the pupil , sometimes accompanied by decreased sweating of the face on the same side; redness of the conjunctiva of the eye is often also present...

as well.

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