Bma Illustrated Medical Dictionary

myectomySurgical removal of part or
all of a muscle. Myectomy may be per-
formed to treat severely injured and
infected muscles or to remove a fibroid
in an operation called a myomectomy.
myel- A prefix that denotes a relation-
ship to bone marrow (as in multiple
myeloma) or to the spinal cord (as in
myelitis). The prefix myelo- has the
same meaning.
myelinThe fatty material made of lipid
(fat) and protein that forms a protective
sheath around some nerve fibres and
increases the efficiency of nerve impulse
transmission. (See also demyelination.)

myelitisInflammation of the spinal cord,
often caused by a viral infection. In trans-
verse myelitis, the spinal cord becomes
inflamed around the middle of the back.
Common symptoms are back pain and
gradual paralysisof the legs, which, in
some cases, becomes permanent.
myeloceleAnother name for myelo-
meningocele(see neural tube defect).
myelofibrosisAn alternative term for
myelosclerosis.
myelographyX-rayexamination of the
spinal cord, nerves, and other tissues
within the spinal canal after injection of
a contrast medium (a substance that is
opaque to X-rays).
The procedure has now been replaced
by CT scanningand MRI.
myeloma, multipleSee multiple myeloma.
myelomatosisSee multiple myeloma.
myelomeningoceleA protrusion of the
spinal cordand its meninges(protective
membranes) under the skin due to a con-
genitaldefect (see neural tube defect).
myelopathyAny disease or disorder of
the spinal cord.

MYELIN

myelosclerosisAn increase of fibrous

tissue within the bone marrow(also

known as myelofibrosis), in which the

marrow’s ability to produce blood cells

is impaired. Myelosclerosis may be pri-

mary (occurring with no obvious cause)

or secondary (resulting from another

bone marrow disease).

The main symptoms of myelosclerosis

are those of anaemia. Enlargement of the

spleen, night sweats, loss of appetite,

and weight loss also commonly occur.

In secondary myelosclerosis, the under-

lying disease may cause other symptoms.

Treatment of primary myelosclerosis

includes blood transfusionsto relieve

symptoms. A few patients may develop

acute leukaemia. Treatment of second-

ary myelosclerosis depends on the

underlying cause.

myiasisAn infestation by fly larvae,

which is primarily restricted to tropical

areas. In Africa, the tumbu fly lays eggs

on wet clothing left outside; the larvae

hatch and penetrate the skin to cause

boil-like swellings. Other flies may lay

eggs in open wounds, on the skin, or in

the ears or nose. Sometimes, larvae

penetrate deeply into the tissues. Intes-

tinal infestation can occur after eating

contaminated food. Preventative mea-

sures include keeping flies away from

food, covering open wounds, and ironing

clothes that have been dried outdoors.

Myiasis of the skin is treated by plac-

ing drops of oil over the swelling. The

larva comes to the surface, where it can

be removed with a needle. In deeper tis-

sues, surgery may be needed. Intestinal

myiasis is treated with a laxative.

myo-A prefix denoting a relationship to

muscle (as in myocarditis).

myocardial infarctionSudden death

of part of the heart muscle due to a

blockage in the blood supply to the

heart. The disorder is popularly known as

a heart attack. It is usually characterized

by severe, unremitting chest pain. Myo-

cardial infarction is the most common

cause of death in developed countries.

Men are more likely to have a heart

attack than women, and smokers are at

greater risk. Other risk factors include

increased age, unhealthy diet, obesity,

and disorders such as hypertensionand

M

Nucleus

Nerve-cell

ending

NERVE CELL

Myelin

sheath

Nerve cell body

Axon

(nerve

fibre)

MYECTOMY MYOCARDIAL INFARCTION