Bma Illustrated Medical Dictionary

the adrenal medulla is the central

region of an adrenal gland. The term

“medulla” is also sometimes used to

refer to the medulla oblongata.

medulla oblongataAlso known as the

medulla, the lowest part of the brain-

stem. The medulla oblongata lies in the

skull just above the spinal cord.

medulloblastomaA type of cancerous

brain tumourthat occurs mainly in chil-

dren. The tumour usually arises from the

cerebellum, which is concerned with

posture, balance, and coordination. It

grows rapidly and may spread to other

parts of the brain and to the spinal cord.

A morning headache, repeated vomiting,

and a clumsy gait develop. There are

also frequent falls. The tumour is diag-

nosed by CT scanningor MRIand often

responds to radiotherapy. Surgery and

anticancer drugsmay also be needed.

mefenamic acidA nonsteroidal anti-

inflammatory drugused to relieve pain

and inflammation. Possible adverse ef-

fects are typical for this group of drugs.

mefloquineA drug used for prevention

and treatment ofmalariain parts of the

world where the parasite that causes it

is resistant to chloroquine. Mefloquine is

one of the preferred treatments for fal-

ciparum malaria. Side effects include

nausea, vomiting, and diarrhoea. Rarely,

there may be panic attacks, halluci-

nations, and psychosis.

MEDULLA OBLONGATA

mega-A prefix meaning very large, as in

megacolon, a condition in which the

colon is greatly enlarged. The prefix

megalo- has the same meaning.

megacolonA gross distension (enlarge-

ment) of the colon, usually accompanied

by severe, chronic constipation.

In children, the main causes of mega-

colon are anal fissures, Hirschsprung’s

disease, and psychological factors that

may have arisen during toilet-training.

In elderly people, causes include the

long-term use of strong laxative drugs.

People suffering from chronic depression

or schizophreniaoften have megacolon.

Other, rarer causes include hypothy-

roidism, spinal injury, and drugs such as

morphineand codeine.

Megacolon causes constipation and

abdominal bloating. Associated loss of

appetite may lead to weight loss. Diar-

rhoea may result if semi-liquid faeces

leak around the obstructing hard faeces.

Diagnosis is made by proctoscopy,

barium X-ray examination, and tests of

bowel muscle function. If Hirschsprung’s

disease is suspected, biopsyof the large

intestine may be performed. Impacted

faeces are often removed using enemas.

In severe cases, the faeces must be

removed manually.

megaloblastic anaemiaSee anaemia,

megaloblastic.

megalomaniaAn exaggerated sense of

one’s own importance or ability that

often occurs in mania. Megalomania

may take the form of a delusionof

grandeur, or of a desire to organize

activities that are expensive, large in

scale, and involve many people.

-megalyA suffix meaning enlargement,

as in acromegaly, a condition in which

there is enlargement of the skull, jaw,

hands, and feet due to excess produc-

tion of growth hormone.

megestrolA progestogen drugused to

treat certain types of breast cancerand

uterine cancer (see uterus, cancer of). It

may be prescribed when a tumour can-

not be removed by surgery, if a tumour

has recurred after surgery, or when

other anticancer drugsor radiotherapy

prove ineffective.

Possible adverse effects of megestrol

include swollen ankles, weight gain,

MEDULLA OBLONGATA MEGESTROL

Medulla

oblongata

Spinal

cord

Midbrain

Pons

Thalamus

M LOCATION

Brainstem