Biomedical Engineering Reference
In-Depth Information
Laser Treatment for Dermal Lesions
Nevus of Ota and Nevus of Ito
Nevus of Ota consists of bluish gray patches on the areas of
the face innervated by the fi rst and second divisions of the
trigeminal nerve. It is frequently associated with ipsilateral
ocular pigmentation and has been associated with glaucoma.
This nevus is most often found in Asians and people of African
ancestry and has a strong predilection for women. Incidence
in the Japanese population is estimated at 1-2%. Hori nevus is
a variant of nevus of Ota with a bilateral distribution. Nevus
of Ito has a similar clinical and histologic appearance like
nevus of Ota but is found in the areas innervated by the pos-
terior supraclavicular and lateral brachial cutaneous nerves.
The lesion is much rarer than nevus of Ota and the exact inci-
dence is unknown. The clinical appearance resembles a pow-
der blast, with poorly demarcated macules and patches
blending readily with the normal surrounding skin. Lesions
vary in color from brown to darker shades such as blue, gray,
and purple.
Histologic examination of both lesions shows long, slender
dermal melanocytes scattered largely in the upper half of the
dermis. The normal dermal collagen architecture is well pre-
served. Although the epidermis is generally normal, focal basal
hyperpigmentation may also be seen.
The lesions are usually benign, but rare cases of malignant
melanoma arising in a nevus of Ota have been reported,
and patients should be followed carefully. Development of
new subcutaneous nodules within the lesion is particularly
suggestive of malignant melanoma and the nodules should be
biopsied. Ophthalmologic evaluation for possible glaucoma or
ocular melanoma is necessary in patients with ocular involve-
ment. The optimized ability of the QS ruby (694 nm), alexan-
drite (755 nm), and Nd:YAG (1064 nm) lasers to target the
deeply situated melanocytes may be attributed to their longer
wavelengths. Lesions containing more superfi cially located
melanocytes may respond readily to treatment, whereas those
that are deeper will likely be more resistant. The pulse width of
the QS lasers is in the nanosecond range, thereby effectively
targeting melanocytes and minimizing thermal injury to the
surrounding collagen. Lesion clearance is generally noted
with fl uences ranging from 6 to 10 J/cm
2
, after one to seven
treatments (11). More resistant lesions generally continue to
demonstrate improvement with successive treatments, though
more slowly.
Confl icting reports of fl uences necessary for treatment, as
well as the necessary number of treatments and treatment
intervals, probably result from the variability in lesions and the
spot size used (61,62). Gradual clearing of lesions is noted
after multiple treatments over several months. The optimal
treatment interval between treatment sessions remains to be
elucidated, however the current recommendation is to wait
3 months between treatment sessions to allow for pigment
removal by melanophages and the resolution of all laser-
induced hyperpigmentation, which can be facilitated by the
use of zinc oxide sunblock and a hydroquinone preparation.
Fractional photothermolysis was also reported in a case report,
which resulted in the complete clearance of nevus of Ota with
a single treatment (63).
Case 10
Nevus of Ota
An 18-year-old man with a history of nevus of Ota presented for discussion of treatment options (Fig. 3.10A). He was treated
with QS Nd:YAG (1064 nm) laser using a 4-mm spot and 8.7 J/cm
2
fl uence over the area with a total of four treatment sessions
at 3-month intervals with signifi cant improvement (Fig. 3.10B).
(
A
)
(
B
)
Figure 3.10
Nevus of Ota. (
A
) Before and (
B
) after 4 treatment sessions (at 3-month intervals) with Q-switched Nd:YAG (1064 nm) laser.
