Bma Illustrated Medical Dictionary

baby’s head is large in relation to the
size of the mother’s pelvis, a forceps
deliveryor vacuum extraction may be
required. If a vaginal delivery is impos-
sible or dangerous to the mother or the
baby, a caesarean sectionis necessary.
deltoidThe triangular muscle of the
shoulder region that forms the rounded
flesh of the outer part of the upper arm,
and passes up and over the shoulder
joint. The wide end of the muscle is
attached to the shoulderblade and the
collarbone. The muscle fibres meet to
form the apex of the triangle, which is
attached to the humerus (upper-arm
bone) halfway down its length. The cen-
tral, strongest part of the muscle raises
the arm sideways. The front and back
parts of the muscle twist the arm.

delusionA fixed, irrational idea not
shared by others and not responding to
reasoned argument. The idea in a para-
noid delusion involves persecution or
jealousy. For instance, a person may
falsely believe that he or she is being
poisoned (see paranoia). Persistent del-
usions are a sign of serious mental
illness, most notably schizophreniaand
manic–depressive illness. (See also hal-
lucination; illusion.)
dementiaA condition characterised by
a deterioration in brain function. Demen-
tia is almost always due to Alzheimer’s
disease or to cerebrovascular disease,
including strokes. Cerebrovascular dis-

ease is often due to narrowed or blocked

arteries in the brain. Recurrent loss of

blood supply to the brain usually results

in deterioration that occurs gradually

but in stages. A small proportion of

cases of dementia in people younger

than 65 have a underlying treatable

cause such as head injury, brain tumour,

encephalitis, or alcohol dependence.

The main symptoms of dementia are

progressive memory loss, disorienta-

tion, and confusion. Sudden outbursts

or embarrassing behaviour may be the

first signs of the condition. Unpleasant

personality traits may be magnified;

families may have to endure accusa-

tions, unreasonable demands, or even

assault. Paranoia, depression, and delu-

sionsmay occur as the disease worsens.

Irritability or anxiety gives way to indif-

ference towards all feelings. Personal

habits deteriorate, and speech becomes

incoherent. Affected people may even-

tually need total nursing care.

Management of the most common

Alzheimer-type illness is based on the

treatment of symptoms. Sedative drugs

may be given for restlessness or para-

noia. Drugs for dementia, for example

donepezil, can slow mental decline in

some people with mild to moderate

Alzheimer’s disease (see acetylcholines-

terase inhibitors).

dementia praecoxAn outdated term

for severe schizophrenia, especially that

affecting adolescents or young adults.

De Morgan’s spotsHarmless red or

purple raised spots in the skin, consist-

ing of a cluster of minute blood vessels.

About 2 mm across, the spots usually

affect middle-aged or older people.

With increasing age, the spots become

more numerous but do not increase in

size. They may bleed if injured. Treat-

ment is unnecessary.

demyelinationBreakdown of the fatty

sheaths that surround and electrically

insulate nerve fibres. The sheaths pro-

vide nutrients to the nerve fibres and

are vital to the passage of electrical

impulses along them. Demyelination

“short-circuits” the functioning of the

nerve, causing loss of sensation, coordi-

nation, and power in specific areas of the

body. The affected nerves may be within

DELTOID DEMYELINATION

D

DELTOID

Trapezius

Shoulderblade

Deltoid

Triceps

of arm

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