subclinical disease An illness that is staying below the surface of clinical detection. A subclinical disease has no recognizable clinical findings. It is distinct from a clinical disease, which has signs and symptoms that can be recognized. Many diseases, including diabetes, hypothyroidism, and rheumatoid arthritis, are frequently subclinical before they surface as clinical diseases.
subarachnoid hemorrhage A bleeding into the subarachnoid, the space between the arachnoid and the pia mater, the innermost membrane surrounding the central nervous system. Subarachnoid hemorrhage typically occurs when an artery breaks open in the brain, such as from a ruptured aneurysm. This can require emergency neurosurgical procedures.
subarachnoid Literally, beneath the arachnoid, the middle of three membranes that cover the central nervous system. In practice, subarachnoid usually refers to the space between the arachnoid and the pia mater, the innermost membrane surrounding the central nervous system. It normally contains cerebrospinal fluid. See also cerebrospinal fluid.
subaortic stenosis Narrowing of the left ventricle of the heart, just below the aortic valve, through which blood must pass on its way up into the aorta. The narrowing restricts the flow of blood. Subaortic stenosis may be present at birth (congenital) or acquired as part of a specific form of heart disease known as…
subacute sclerosing panencephalitis A chronic brain disease of children and adolescents that occurs months to often years after an attack of measles and causes convulsions, motor abnormalities, mental retardation, and usually death. Abbreviated SSPE.
subacute Rather recent onset or somewhat rapid change. In contrast, acute indicates very sudden onset or rapid change, and chronic indicates indefinite duration or virtually no change.
stye A red, tender bump on the eyelid that is caused by an acute infection of the oil glands of the eyelid. The medical term for a stye is hordeolum.
sty See stye.
stuttering A speech disorder characterized by repetition of the sound of a word. Stuttering can usually be eliminated or significantly modified with speech therapy. See also cluttering; communication disorder; speech disorder.
Sturge-Weber syndrome A congenital, but not inherited, disorder that affects the skin, the neurological system, and sometimes the eyes and internal organs. The main sign of Sturge-Weber syndrome is a port-wine stain birthmark. Neurological symptoms of Sturge-Weber syndrome may include seizures and developmental delay. See also portwine stain.
study 1 A procedure or an examination. 2 A research project.
stroke volume The amount of blood pumped by the left ventricle of the heart in one contraction. The stroke volume is not all the blood contained in the left ventricle; normally, only about two-thirds of the blood in the ventricle is expelled with each beat. Together with the heart rate, the stroke volume determines the…