Bma Illustrated Medical Dictionary

Genetic factors play a part in neural
tube defects, which show multifactorial
inheritance. Couples who have had an
affected child or who have a family his-
tory of neural tube defects should seek
genetic counselling. The risk of a neural
tube defect occurring can be substant-
ially reduced if the mother takes folic
acidsupplements for a month before
conception and during the early part of
the pregnancy.
Ultrasound scanningand amniocen-
tesisallow accurate antenatal testing for
neural tube defects.
neurapraxiaA type of nerve injuryin
which the outward structure of a nerve
appears intact, but some of the con-
ducting fibres have been damaged or
have degenerated and thus do not
transmit signals normally.
neurastheniaAn outdated term that
literally means “nervous exhaustion”. It
was once used to describe a number of
physical and mental symptoms, includ-
ing loss of energy, insomnia, aches and
pains, depression, irritability, and re-
duced concentration.

neuritisA term that literally means

inflammation of a nerve. True nerve in-

flammation may be caused by infection

(for example by a virus in herpes zoster

or by a bacterium in Hansen’s disease).

The term neuritis is also often applied

to nerve damage or disease from causes

other than inflammation. It has become

virtually synonymous with neuropathy.

neuroblastomaA tumour of the adre-

nal glandsor the sympathetic nervous

system (which is part of the autonomic

nervous system). Most neuroblastomas

develop in the adrenal glands or in the

sympathetic nerves along the back wall

of the abdomen. Less commonly, tum-

ours develop in the sympathetic nerves

of the chest or neck.

Neuroblastomas are the most com-

mon extracranial (outside the skull),

solid tumour of childhood. Most cases

develop during the first 10 years of life,

especially in the first 5.

Common symptoms include a lump in

the abdomen, tiredness, weight loss,

aches and pains, paleness, and irritabil-

ity. Diarrhoea, high blood pressure, and

flushing of the skin sometimes occur.

The diagnosis of a neuroblastoma is

from MRIand CT scanning, blood tests,

urine tests, and biopsyof the bone

marrow and any accessible tumours.

Treatment consists of surgical removal

of the tumour, followed by radiotherapy.

Anticancer drugsand a bone marrow

transplantmay also be required. The

outlook varies because neuroblastomas

range from being relatively harmless to

aggressively cancerous.

neurocutaneous disordersA group

of conditions characterized by abnor-

malities of the skin and of the nerves

and/or the central nervous system.

The best known of these neurocut-

aneous disorders is neurofibromatosis,

in which there are brown patches on the

skin and numerous fibrous nodules on

the skin and nerves. Another example is

tuberous sclerosis, which is character-

ized by small skin-coloured swellings

over the cheeks and nose, mental defic-

iency, and epilepsy.

neurodermatitisAn itchy, eczema-like

skin condition caused by repeated

scratching. (See also lichen simplex.)

NEURODERMATITIS

N

NEURAL TUBE DEFECT

Cerebrospinal fluid

Skin

Vertebra

Nerve root

Abnormal

spinal cord

Skin defect

Fluid-filled

sac

Abnormal

vertebra

NORMAL VERTEBRA

MYELOMENINGOCELE

NEURAPRAXIA

Spinal cord