d. Motor disturbances are exceptional, unless in the
case of tumours within the vertebral canal, which press on the spinal
medulla and cause paraplegia.

[Illustration: FIG. 86.--Diffuse enlargement of Nerves in generalised
Neuro-fibromatosis.

(After R. W. Smith.)]

Neuro-fibromatosis is frequently accompanied by _pigmentation of the
skin_ in the form of brown spots or patches scattered over the trunk.

The disease is often stationary for long periods. In progressive cases
the patient becomes exhausted, and usually dies of some intercurrent
affection, particularly phthisis. The treatment is restricted to
relieving symptoms and complications; removal of one of the tumours is
to be strongly deprecated.

In a considerable proportion of cases one of the multiple tumours takes
on the characters of a malignant growth ("secondary malignant neuroma,"
Garre). This malignant transformation may follow upon injury, or on an
unsuccessful attempt to remove the tumour. The features are those of a
rapidly growing sarcoma involving a nerve-trunk, with agonising pain
and muscular cramps, followed by paralysis from destruction of the
nerve fibres. The removal of the tumour is usually followed by
recurrence, so that high amputation is the only treatment to be
recommended. Metastasis to internal organs is exceptional.

[Illustration: FIG. 87.--Plexiform Neuroma of small Sciatic Nerve, from
a girl aet. 16.

(Mr. Annandale's case.)]

There are other types of neuro-fibromatosis which require brief mention.

_The plexiform neuroma_ (Fig. 87) is a fibromatosis confined to the
distribution of one or more contiguous nerves or of a plexus of nerves,
and it may occur either by itself or along with multiple tumours of the
nerve-trunks and with pigmentation of the skin. The clinical features
are those of an ill-defined swelling composed of a number of tortuous,
convoluted cords, lying in a loose areolar tissue and freely movable on
one another. It is rarely the seat of pain or tenderness. It most often
appears in the early years of life, sometimes in relation to a pigmented
or hairy mole. It is of slow growth, may remain stationary for long
periods, and has little or no tendency to become malignant. It is
usually subcutaneous, and is frequently situated on the head or neck in
the distribution of the trigeminal or superficial cervical nerves. There
is no necessity for its removal, but this may be indicated because of
disfigurement, especial