Basilar invagination:

(basilar impression) a rare condition in which the upper portion of the second cervical vertebra (C2) migrates upward and back into the intracranial space. It can be associated with other conditions, such as rheumatoid arthritis, Chiari malformation, syringomyelia, C1-2 instability, or congenital abnormalities.

Cerebrospinal fluid (CSF):

a clear fluid produced by the choroid plexus in the ventricles of the brain. CSF bathes the brain and spinal cord, giving them support and buoyancy to protect from injury.

Cerebrospinal fluid (CSF) leak:

the fluid surrounding the brain can escape through a hole in the dura lining the skull; may require surgery to patch the leak.


the neck portion of the spine made up of 7 vertebrae.


surgical removal of a portion of the skull. Decompression: opening or removal of bone to relieve pressure and pinching of nervous tissue.

Dura mater:

the outer protective covering of the brain.

Dural patch:

(also called a dural graft, dural substitute, duraplasty) a piece of tissue used to close or extend the dura mater in surgery. Material may come from the patient’s scalp (autologous), cow, collagen, or synthetic.

Ehler-Danlos syndrome (EDS):

a rare genetic defect in collagen that affects connective tissue (e.g., joints, skin, blood vessels). Collagen is a protein, which acts as a “glue” in the body, adding strength and elasticity to connective tissue. There are six types of EDS. Types I – III cause joint hypermobility; joint dislocations and scoliosis are common.

Fibromyalgia (FM):

a chronic pain illness characterized by widespread musculoskeletal aches, pain, and stiffness; soft tissue tenderness; fatigue; and disturbs sleep, memory and mood. Many people with fibromyalgia also have tension headaches, temporomandibular joint (TMJ) disorders, irritable bowel syndrome, anxiety, and depression. Chiari is often misdiagnosed as fibromyalgia.

Glossopharyngeal neuralgia:

a painful disorder of the ninth cranial nerve (glossopharyngeal nerve). Irritation of this nerve causes intense pain on one side of the throat near the tonsil area that can radiate to the ear.
herniate: to protrude through the wall of the cavity in which it is normally enclosed.
hydrocephalus: an abnormal build-up of cerebrospinal fluid usually caused by a blockage of the ventricular system of the brain. Increased intracranial pressure can compress and damage brain tissue.

Intracranial pressure (ICP):

pressure within the skull. Normal ICP is 20mm HG.

Intrathecal space:

the space surrounding the spinal cord through which cerebral spinal fluid (CSF) flows; also called the subarachnoid space.

Marfan’s syndrome:

a genetic disorder in which patients develop skeletal defects in long bones, chest abnormalities, curvature of the spine, and circulatory defects.

Multiple sclerosis:

a chronic degenerative disease in which the body’s immune system eats away at the protective sheath (myelin) surrounding nerves in the brain and spinal cord. The symptoms often come and go and vary widely depending on the affected nerve fibers. Chiari is often misdiagnosed as MS.


a broad term referring to spinal cord dysfunction of any cause. Some processes that lead to myelopathy include transverse myelitis, injury, arthritis, vascular malformation, vertebral fracture from osteoporosis infection or malignancy, or syrinx an enlarged cyst within the spinal cord).

Paget’s disease:

also known as osteitis deformans, a bone disease in which normal bone is destroyed and then replaced with thickened, weaker, softer bone. This weaker bone easily bends and deforms. Most often affects the pelvis, thoracic and lumbar spine, skull, femur, tibia, fibula, and clavicles.


a malformation of the occipital bone (clivus), literally flattening of the skull base. It may be developmental in origin or due to softening of the skull base bone, allowing it to be pushed upward as in basilar invagination. It is associated with other congenital bone abnormalities, such as fusion of the first cervical vertebrae to the skull (atlas assimilation).


an abnormal collection of cerebrospinal fluid (CSF) that communicates with the CSF space around the brain or spinal cord. Unlike a meningocele, the fluid has no surrounding membrane but is contained in a cavity within the soft tissues.


an abnormal side-to-side curvature of the spine.


a drainage tube to move cerebrospinal fluid from inside the ventricles of the brain into another body cavity (e.g., abdomen).

Subarachnoid space:

the space between the pia and arachnoid mater of the brain and spinal cord that contains cerebrospinal fluid (CSF).


a chronic progressive disease of the spinal cord caused by an obstruction of normal cerebrospinal fluid (CSF) flow that redirects the fluid into the spinal cord to form a syrinx.
syrinx: a cavity filled with cerebrospinal fluid (CSF) that expands and elongates over time, destroying the center of the spinal cord.

Tethered cord syndrome:

a condition of the spinal cord caused by an abnormal attachment or “tether” of the cord to the bones of the spinal canal. The spinal cord gets stretched and can become damaged. The filum terminale is a fibrous thread which connects the very bottom of the spinal cord to the coccyx bone.

Trigeminal neuralgia:

a painful disorder of the fifth cranial nerve (trigeminal nerve). Irritation of this nerve can cause intense pain that usually affects one side of the face usually in the forehead, cheek, jaw, or teeth.

Ventriculoperitoneal (VP) shunt:

a tube placed in the ventricle of the brain to drain excess cerebrospinal fluid into the abdomen.

Mayfield Clinic, University of Cincinnati Department of Neurosurgery