after ORGAN TRANSPLANTATION, allows the dormant
varicella-zoster VIRUSto emerge and cause shin-
gles. Injuries to the nerves, such as repetitious
motion and compression injuries, also become
more common with advancing age.
Antiviral medications, such as acyclovir or fam-
ciclovir, taken within 72 hours of the onset of her-
pes zoster symptoms may be effective in
preventing postherpetic neuralgia. Without antivi-
ral therapy, about 20 percent of people who
develop herpes zoster infection subsequently
develop postherpetic neuralgia. The extent to
which antiviral therapy for the herpes zoster
affects the likelihood of developing postherpetic
neuralgia remains unknown. Other preventive
measures include prompt treatment of NEURITIS
(INFLAMMATIONof a nerve), appropriate intake of
vitamin B 12 (which is vital for proper nerve func-
tion), and avoidance of toxins that can damage
the nerves.
See also AGING, NEUROLOGIC CHANGES THAT OCCUR
WITH; HEADACHE; HEAVY-METAL POISONING; NEURAL
BLOCKADE(NERVE BLOCK); NEUROPATHY.
neuritis INFLAMMATIONof a NERVE. Neuritis is usu-
ally an indication of an underlying injury or dis-
ease process such as irritation, compression, or
INFECTIONof the involved nerve. The most com-
mon symptom is PARESTHESIA (tingling) though
some people may experience PAIN(NEURALGIA) or
numbness. The diagnostic path is primarily clini-
cal, based on the person’s symptoms and a NEURO-
LOGIC EXAMINATION. PAPILLITIS and RETROBULBAR
NEURITIS, inflammations involving different parts of
the OPTIC NERVE, can result in vision loss. Retrobul-
bar neuritis can be an early sign of MULTIPLE SCLE-
ROSIS. Treatment targets the underlying cause and
may include anti-inflammatory medications or
ANTIBIOTIC MEDICATIONS; when the cause is compres-
sion due to an entrapment syndrome (such as
CARPAL TUNNEL SYNDROME), surgery may be neces-
sary to relieve the compression.
See also SCIATICA.
neurofibromatosis A genetic disorder in which
tumors (neurofibromas) form within the tissues
and structures of the NERVOUS SYSTEM. There are
two primary forms of neurofibromatosis, both of
which occur in an autosomal dominant INHERI-
TANCE PATTERN. The tumors, notably those that
involve the SKIN, are initially benign (noncancer-
ous) though have a high risk for turning cancer-
ous. Neurofibromatosis type 1 (NF-1) is the more
common form; it generates dozens of tiny tumors.
Neurofibromatosis type 2 (NF-2) primarily
involves the SPINAL CORDand eighth cranial NERVE
(vestibulocochlear nerve). Both forms of neurofi-
bromatosis may also involve the BONE, skin, MUS-
CLE, and connective tissue as well as the BRAINand
the visceral organs.
The earliest sign of neurofibromatosis is often
lightly colored patches of skin (café au lait mac-
ules). Many people who have NF-1 develop
numerous small growths that look like moles
(nevi). However, it is possible to press these tumors
below the surface of the skin as though turning
them into themselves (called a buttonhole effect),
whereas moles and similar growths are firm and
remain above the skin’s surface when pressed.
Tumors of NF-2 that arise in the spinal cord may
cause deformity of the spine and SCOLIOSIS.
Because the neurofibromas often develop
within the tissues of the brain, other symptoms
may include seizures, intellectual impairment, and
disturbances of motor function. Other symptoms
depend on the locations of the tumors. The diag-
nostic path includes a comprehensive FAMILY MED-
ICAL HISTORY; immediate family members who have
similar symptoms or a diagnosis of neurofibro-
matosis make the diagnosis fairly conclusive. A
NEUROLOGIC EXAMINATIONand imaging procedures
such as MAGNETIC RESONANCE IMAGING (MRI) and
COMPUTED TOMOGRAPHY(CT) SCANof the brain may
reveal tumors.
The preferred treatment is surgery to remove
the tumors whenever practical, and close monitor-
ing of tumors that the surgeon cannot remove to
assess any changes that could indicate developing
malignancies. Unfortunately the tumors tend to
recur. Left untreated, however, the tumors often
cause deformity of the tissues and structures in
which they are growing. As well, the risk for
malignancy is very high. Health experts strongly
recommend GENETIC COUNSELINGfor people diag-
nosed with neurofibromatosis.
See also ACOUSTIC NEUROMA; BRAIN TUMOR; CRA-
NIAL NERVES; GENETIC DISORDERS; MACULE; NEVUS;
PHEOCHROMOCYTOMA.neurofibromatosis 269