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sacrum
Triangular-shaped bone composed of three fused vertebrae located caudal to the lowest lumbar vertebrae; strengthens and secures the pelvis.
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sagittal sulcus
See longtitudinal fissure.
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sarcoma
Malignant neoplasia growing from connective tissue (cartilage, fat, blood vessels, muscle or bone).
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Schwann cell
Form of neuroglial cell of the peripheral nervous system responsible for the synthesis and maintenance of the myelin sheath that insulates axons.
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seizure
A discrete event due to sudden, transient neuronal discharge that disturbs the brain’s normal electrical activity and causes a temporary change in behavior, consciousness, bodily movements or sensation. A seizure can have any one to three phases: preictal, ictus, and/or postictal. Seizures are the main symptoms of epilepsy, but can be caused by a wide variety of conditions.
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semicircular canals
Three half-circular, interconnected tubes in the inner ear that measure the body's orientation. This information is used by the vestibular system to maintain balance.
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sensory nerve
A nerve composed of sensory nerve fibers.
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sensory neuron
A nerve cell that conducts action potentials from sensory organs about changes in the external or internal environments toward the central nervous system; also called an afferent neuron.
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serum
The fluid that is left after whole blood is allowed to clot; also defined as plasma that lacks fibrinogen or any other clotting factors.
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sharp wave
EEG pattern consisting of a transient electrical discharge with a pointed peak and a duration of 70-200 milliseconds that stands out from ongoing background activity; has a strong association with epilepsy.
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shock
Condition where the tissues in the body do not receive enough oxygen and nutrients to allow the cells to function due to an acute derangement of circulatory control or loss of circulating fluid. This can ultimately lead to cellular death and progress to organ failure, whole body failure and then death.
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sign
An indication of the existence of a disease that is perceptible to an examining veterinarian; it is objective evidence, as opposed to the subjective sensations (symptoms) of the patient.
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simple partial seizure
A partial seizure that is primarily due to abnormal motor discharges and may appear as head/body turning, facial/muscle twitches, limb flexion or episodic tremors.
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small dog encephalitis
Immune-mediated disease causing severe inflammation of the brain; believed to be breed specific: common to Yorkshire Terriers, Maltese, and Chihuahuas.
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somatic nervous system
Division of the peripheral nervous system which carries messages to the muscles that move the skeleton either voluntary or by reflex; both the somatic and autonomic nervous systems utilize motor neurons.
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spike
EEG pattern consisting of a transient electrical discharge with a pointed peak and a duration of less than 70 milliseconds that stands out from ongoing background activity; has a strong association with epilepsy.
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spike-and-wave complex
Generalized synchronous pattern seen on EEG, consisting of a sharply contoured fast wave followed by a slow wave; seen in generalized epilepsy which is characterized by tonic-clonic seizures.
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spina bifida
A developmental anomaly characterized by defective closure of the vertebral arch; the spinal cord and/or meninges may or may not protrude through the defect.
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spinal canal
The space that houses the spinal cord throughout the length of the spinal column and provides openings for the exit of paired spinal nerves from the spinal cord; also called the vertebral canal.
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spinal cord
Part of the central nervous system, a column of nervous tissue that runs from the base of the skull down the back. It is surrounded by three protective membranes (i.e. meninges) and is enclosed within vertebrae that compose the spine. It carries most of the messages between the brain and the rest of the body. ►click here to learn more-link provided by: University of Minnesota, College of Veterinary Medicine
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spinal infarct
Sometimes called a spinal "stroke", a spinal cord infarction occurs when one of the three major arteries that supply blood to the spinal cord is blocked. Therefore, the spinal cord is deprived of oxygen, resulting in injury and destruction of the nerve fibers. The resulting disability depends on where the spinal cord was injured and the extent of the blockage. Everything below the occlusion will be affected.
►click here to learn more-link provided by: University of Pennsylvania, School of Veterinary Medicine
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spinal tap
A procedure in which a needle is inserted into the subarachnoid space and cerebrospinal fluid (CSF) is withdrawn; a cisternal tap is performed in the upper cervical area called the cerebellomedullary cistern and a lumbar tap is performed in the patient's lower back region.
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splenium
Thickened caudal border of the corpus callosum.
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spondylosis deformans
Noninflammatory condition associated with degeneration of the annulus fibrosus of the intervertebral disk leading to the formation of bony spurs and bridges at the intervertebral spaces along the ventral spine. The ossification is frequently present in the caudal thoracic and caudal lumbar vertebrae. Spondlylosis does not cause degeneration of the center (nucleus pulposus) of the disk or disk protrusion and rarely causes any neurological signs; occasionally it can cause spinal pain.
►click here to learn more-link provided by: University of Pennsylvania, School of Veterinary Medicine
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staggering disease
See feline nonsuppurative meningoencephalomyelitis.
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status epilepticus
Medical emergency generally considered to be more than 7 minutes of either continuous seizure activity or two or more sequential seizures without full recovery of consciousness in between them.
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stenosis
Narrowing or stricture of a duct or canal.
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storage diseases
Metabolic disorders characterized by the accumulation of certain substances in various tissues in abnormal amounts; two commonly reported in veterinary medicine are lysosomal and glycogen storage disease.
►click here to learn more-link provided by: www.petplace.com
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stroke
Sudden loss of neurological function caused by a blockage or rupture of a blood vessel to the brain or spinal cord; includes infarction and hemorrhage subtypes.
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strychnine poisoning
Caused by a chemical found in Strychnos (a genus of tropical trees) that results in excitation of all parts of the central nervous system by blocking postsynaptic inhibition of neural impulses.
►click here to learn more-link provided by: www.merckvetmanual.com
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stupor
Condition of unresponsiveness from which the patient can only be aroused by vigorous and repeated stimuli; once stimulus ceases, patient lapses back into unresponsiveness.
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subcortical
Portion of the brain immediately below the cerebral cortex.
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subluxation
An incomplete or partial luxation; partial dislocation.
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suppurative
Producing pus.
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suture
Fibrous joint between bones of the skull which allows very little movement.
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sylvian aqueduct
See cerebral aqueduct.
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symptom
Any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease; it is subjective evidence, as opposed to objective indicators (signs) that a doctor finds upon examination.
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synapse
The junction between neurons and their target cells at which an impulse is transmitted by either electrical or chemical means; the two cells are separated by a small gap called the synaptic cleft.
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syncope
Temporary loss of consciousness (fainting) that results from inadequate blood supply to the brain.
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syndrome
A condition based on a set of signs/symtpoms that occur together.
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syrinx
A divirticulum that forms in the spinal cord due to obstruction of the normal flow of cerebrospinal fluid.
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