Ventricular System: Anatomy

Topography and Relations of the Ventricular System

The ventricular system consists of 4 ventricles with an aqueduct connecting the 3rd and 4th ventricles. Cerebrospinal fluid (CSF) flows through the ventricles before entering the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy from the 4th ventricle:

• Lateral ventricles:
  • Body:
    • Contained in the frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy and parietal Parietal One of a pair of irregularly shaped quadrilateral bones situated between the frontal bone and occipital bone, which together form the sides of the cranium. Skull: Anatomy lobes 
    • Extends from the interventricular foramen of Monro to the splenium of the corpus callosum
  • Anterior horn Anterior horn One of three central columns of the spinal cord. It is composed of gray matter spinal laminae VIII and ix. Brown-Séquard Syndrome: in the frontal lobe Frontal lobe The part of the cerebral hemisphere anterior to the central sulcus, and anterior and superior to the lateral sulcus. Cerebral Cortex: Anatomy
  • Posterior horn Posterior horn One of three central columns of the spinal cord. It is composed of gray matter spinal laminae i-vi. Brown-Séquard Syndrome: curves posteromedially into the occipital lobe Occipital lobe Posterior portion of the cerebral hemispheres responsible for processing visual sensory information. It is located posterior to the parieto-occipital sulcus and extends to the preoccipital notch. Cerebral Cortex: Anatomy
  • Inferior horn:
    • Largest compartment of the lateral ventricle
    • Extends forward into the temporal lobe Temporal lobe Lower lateral part of the cerebral hemisphere responsible for auditory, olfactory, and semantic processing. It is located inferior to the lateral fissure and anterior to the occipital lobe. Cerebral Cortex: Anatomy
• 3rd ventricle:
  • A midline, slit-like cavity
  • Derived from the primitive forebrain forebrain The anterior of the three primitive cerebral vesicles of the embryonic brain arising from the neural tube. It subdivides to form diencephalon and telencephalon. Development of the Nervous System and Face vesicle Vesicle Primary Skin Lesions
• Cerebral aqueduct (of Sylvius): 
  • Small tube extending throughout the dorsal quarter of the midbrain Midbrain The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the pons and the diencephalon. Midbrain contains two major parts, the dorsal tectum mesencephali and the ventral tegmentum mesencephali, housing components of auditory, visual, and other sensorimotor systems. Brain Stem: Anatomy
  • Surrounded by periaqueductal gray
  • Connects the 3rd and 4th ventricles
• 4th ventricle: 
  • Between the brainstem and the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy
  • The foramen of Luschka (lateral aperture) and the foramen of Magendie (median aperture) allow newly produced CSF to enter the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage.
• Circumventricular organs:
  • Structures characterized by extensive, highly permeable capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology
  • Surround the 3rd and 4th ventricles
  • Regions do not typically contain a blood-brain barrier Blood-brain barrier Specialized non-fenestrated tightly-joined endothelial cells with tight junctions that form a transport barrier for certain substances between the cerebral capillaries and the brain tissue. Systemic and Special Circulations, which allows for communication Communication The exchange or transmission of ideas, attitudes, or beliefs between individuals or groups. Decision-making Capacity and Legal Competence between the peripheral blood and the CSF.

Choroid Plexus and Cerebrospinal Fluid

Choroid Choroid The thin, highly vascular membrane covering most of the posterior of the eye between the retina and sclera. Eye: Anatomy plexus

• Vascular pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy in all ventricles
• Location:
  • Roof of the temporal horns of the lateral ventricles
  • Floor of the body of the lateral ventricles
  • Foramen of Monro
  • Roof of the 3rd ventricle
  • Medullary of the 4th ventricle, extending through the foramen of Luschka
• Actively secretes CSF in the lateral, 3rd, and 4th ventricles

Cerebrospinal Fluid

• Clear, colorless liquid containing a small amount of protein
• Provides buoyancy and protection for the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification
• Regulates chemical concentration of neurotransmitters and metabolic waste

Subarachnoid Space and Circulation of Cerebrospinal Fluid

Subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage

• Between the arachnoid and the pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy
• Contains CSF, larger arteries and veins Arteries And Veins ACES and RUSH: Resuscitation Ultrasound Protocols, and intracranial and intervertebral portions of the cranial and spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy

Circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment of cerebrospinal fluid

• After production in the ventricles, CSF flows into the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage.
• CSF flows freely within the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy.
• CSF is reabsorbed by arachnoid granulations into the venous circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment.

Clinical Relevance

• Hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage: a potentially life-threatening condition caused by the excess accumulation of CSF within the ventricular system. The clinical presentation is nonspecific and may include headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, behavioral changes, developmental delays, or nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia. Diagnosis is confirmed with neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (ultrasound, head CT, or MRI) showing ventriculomegaly Ventriculomegaly Hydrocephalus in Children. Treatment is placement of a CSF shunt.
• Normal pressure hydrocephalus (NPH): enlargement of the ventricles without detectable elevations in intracranial pressure. Normal pressure hydrocephalus occurs most commonly in adults > 60 years of age. Symptoms include a triad of urinary incontinence, ataxia, and cognitive dysfunction and may be remembered by the mnemonic “wet, wobbly, and wacky.”
• Chronic microvascular ischemic disease: chronic atherosclerotic disease typically resulting in hypoperfusion to symmetric areas of the cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex: Anatomy and causing cerebral atrophy Cerebral Atrophy Subdural Hemorrhage or other brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification malformations. Unlike hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage, the intracranial pressure Intracranial Pressure Idiopathic Intracranial Hypertension is not elevated. 
• Chiari malformations Chiari Malformations Chiari malformations (CMs) are a group of central nervous system (CNS) conditions characterized by the underdevelopment of the posterior cranial fossa with subsequent protrusion of neural structures through the foramen magnum. Chiari Malformations (CM): a group of disorders defined by structural deficits in the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy leading to limited space in the posterior fossa and forcing cerebellar structures to protrude through the foramen magnum. Type II Chiari malformations Chiari Malformations Chiari malformations (CMs) are a group of central nervous system (CNS) conditions characterized by the underdevelopment of the posterior cranial fossa with subsequent protrusion of neural structures through the foramen magnum. Chiari Malformations are seen in combination with herniation Herniation Omphalocele of the cerebellar vermis, the brainstem, and the 4th ventricle into the foramen magnum. An association exists with myelomeningocele and multiple brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification anomalies, including hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage and syringomyelia Syringomyelia Longitudinal cavities in the spinal cord, most often in the cervical region, which may extend for multiple spinal levels. The cavities are lined by dense, gliogenous tissue and may be associated with spinal cord neoplasms; spinal cord traumatic injuries; and vascular malformations. Syringomyelia is marked clinically by pain and paresthesia, muscular atrophy of the hands, and analgesia with thermoanesthesia of the hands and arms, but with the tactile sense preserved (sensory dissociation). Lower extremity spasticity and incontinence may also develop. Central Cord Syndrome.