Drs. Lall and Ivy are Assistant Professors of Radiology
at Louisiana State University Health Sciences Center at
Tuberous sclerosis (TS), or Bourneville's disease, is an
autosomal dominant disease with a prevalence of 1:10,000 to
showing variable penetrance. New mutations are responsible for a
large number of these cases.
The clinical triad includes epileptic seizures, mental retardation,
and cutaneous lesions that are thought to be diagnostic.
Multiple organ systems may be involved with this disease including
the skin, central nervous system (CNS), ocular system, kidneys,
heart, gastrointestinal tract, and skeletal system.
Osseous involvement in tuberous sclerosis
Cranial vault osseous abnormalities--
These include patchy areas of calvarial sclerosis related to
hyperostosis of the inner table, as well as prominence of the bony
trabeculae in the diploic spaces (figure 1). The inner and outer
tables may be thickened as well, with increased density seen on CT
scans. The frontal and parietal regions are commonly involved. A
common differential diagnosis for diploic thickening is long-term
Extracranial osseous abnormalities
Osseous lesions in tuberous sclerosis can involve both the axial
and appendicular skeleton and are fairly common in the disease.
Cortical lesions include subperiosteal new bone deposition
resulting in a thickened, irregular, often spiculated-appearing
cortical contour, most often seen in the short tubular bones of the
hands and feet but occasionally encountered in the long bones
(figures 2 and 3). Cortical pits and depressions have also been
Periungual fibromas of the skin often seen on the hands may lead to
adjacent bony erosion.
Varying size, round to oval cystic lesions with or without
associated periosteal reaction may be seen in the phalanges, most
commonly the distal phalanges (figure 4). Cystic areas may be
encountered in the metacarpals and metatarsals as well and
represent islands of fibrous tissue. Differential diagnosis
includes neurofibromatosis and sarcoidosis.
Medullary involvement in tuberous sclerosis presents as abnormal
areas of osteoblastic activity, the so-called "bone islands." The
lesions are usually oval or flame-shaped, and may be found in the
long bones, spine, or pelvis (figures 5, 6 and 7). These lesions
range from a few millimeters to several centimeters in size and may
enlarge slowly over several years, but characteristically do not
expand the bone.
Extraosseous multisystem involvement
Adenoma sebaceum occurs in 80% to 90% of cases but may not be
present till after puberty. Shagreen patches occur in 20% to 50% of
cases, characterized by dull red or tan firm plaques with a
wrinkled surface protruding slightly above the surrounding skin.
These lesions frequently are seen in the lumbar region and
occasionally are painful. Hypopigmented macules may be noted at
birth or in the neonatal period.
Central nervous system
The CNS lesions include subependymal hamartomas, small nodular
lesions in the subependymal region of the ventricles, a common CNS
finding. These lesions may calcify
and may be seen on plain skull radiographs. Subependymal nodules
with prominent contrast enhancement suggest the presence of a giant
cell astrocytoma, most commonly located at the foramen of Monro and
seen in 5% to 10% of affected individuals.
The most frequently encountered ocular finding is a retinal
hamartoma, located at the optic disc. These lesions are usually
multiple and may be detected with the opthalmoscope. Like
hamartomas of the brain, calcification may occur.
At birth, 52% of patients will have this lesion, making this the
most common abnormality detected at birth.
Approximately 55% of patients will develop a renal lesion including
cysts, angiomyolipomas, renal cell carcinomas, and aneurysms. At
least 50% of all renal angiomyolipomas occur in patients with TS.
On CT, detection of fat within these lesions is diagnostic.
Approximately 1% of patients with TS will develop pulmonary
symptoms. These usually occur late in the disease.
Radiographically, these lesions are identical to
lymphangioleiomyomatosis (LAM). Almost all of the affected patients
are female. A common complication is spontaneous pneumothorax. On
rare occasions, a patient may develop a chylothorax.
Rhabdomyoma is the most common cardiac tumor in infants and
children, and approximately 50% to 70% of these tumors are
associated with TS.
Osseous involvement in tuberous sclerosis can have a varied
radiographic appearance with involvement of both the axial and
appendicular skeleton. While many of the lesions have a
characteristic radiological appearance, some are unusual, and other
differential diagnoses need to be considered.