PEDIATRIC DEWTOLOGY
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CUTANEOUS SIGNS OF NEURAL
TUBE DYSRAPHISM
Beth A. Drolet, MD
The skin and the nervous system share a common ectodermal origin. Separation of the neural and cutaneous ectoderm occurs early in gestational life, at
about the same time that the neural tube is fusing. This embryologic association
may explain simultaneous malformations of the skin and the nervous system.
The term dysrapkia is defined as incomplete fusion of a raphe. This discussion is
limited to cutaneous markers of occult neural tube dysraphic conditions in the
cranial region (calvarial defects) and those along the spinal axis.
CRANIAL DYSRAPHISM
Cephaloceles
Cepkalocele is the general term for congenital herniation of intracranial structures through a scalp defect. Meningoceles are congenital lesions in which only
the meninges and cerebrospinal fluid herniate through a calvarial defect. Large
encephaloceles and meningoceles pose no diagnostic problem and are easily
diagnosed prenatally or at birth. Smaller or atretic encephaloceles and meningoceles may be mistaken for cutaneous lesions, such as hematomas, hemangiomas,
aplasia cutis, dermoid cysts, or inclusion cysts. All congenital, exophytic scalp
nodules should be evaluated thoroughly; 20%to 37% of congenital, nontraumatic
scalp nodules connect to the underlying CNS.=, 26 Cephaloceles occur in the
frontal, parietal, and occipital regions. They are usually midline, although they
also may be found 1 cm to 3 cm lateral to the midline. Small cephaloceles are
clinically heterogeneous, their appearance dictated by the cutaneous ectoderm
From the Departments of Dermatology and Pediatrics, Medical College of Wisconsin,
Milwaukee, Wisconsin
PEDIATRIC CLINICS OF NORTH AMERICA
VOLUME 47 NUMBER 4 * AUGUST 2000
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overlying the lesion. They may be covered with normal skin or have a blue,
translucent or glistening surface. A disruption of the surrounding and overlying
normal hair pattern is typically present. They are soft, compressible, round or
pedunculated nodules that grow when these infants cry or with a Valsalva
maneuver.
If a congenital nodule occurs in association with cutaneous abnormalities,
the diagnosis of cranial dysraphism is highly suspect. Cutaneous stigmata of
cranial dysraphism include hypertrichosis, or the "hair collar sign"; capillary
malformations; hemangiomas; and cutaneous dimples and sinuses." The hypertrichosis may overly the nodule, surround a small sinus, or encircle the nodule
(i.e., hair collar). A hair collar is a congenital ring of hair that is usually denser,
darker, and coarser than the normal scalp hair. When found encircling an
exophytic scalp nodule, it is highly suggestive of cranial dysraphism (Fig. l)?,
The hair collar sign may be found in association with encephaloceles, meningoceles, atretic encephaloceles, atretic meningoceles, and heterotopic brain tissue.
A hair collar may also be seen with some lesions of aplasia cutis, so this sign is
not entirely specific.'O Cranial neural tube defects also may be associated with
overlying red to pink, blanchable patches that represent capillary malformations.
The combination of hair collar sign and capillary malformation surrounding a
congenital scalp lesion is almost always indicative of a dysraphic condition.9
From a clinical standpoint, encephaloceles, meningoceles, atretic cephaloceles,
and heterotopic brain tissue are impossible to differentiate, and all should be
imaged and surgically corrected by a neurosurgeon as soon as possible to
prevent complications.
Nasal Gliomas
Gliomas are rests of ectopic neural tissue and differ from frontal encephaloceles in that they do not have a patent intracranial communication. The lesions
may be external, intranasal, or combined. Clinically, they are firm, noncompressi-
Figure 1. Encephafocele. Soft translucent, blue nodule 2 cm left of the vertex of the scalp.
There is a prominent ring of dark hair encircling the lesion (hair collar sign).
CUTANEOUS SIGNS OF NEURAL TUBE DYSRAPHISM
815
ble, nontender, skin-colored to red-purple nodules at the root of the nose. They
do not transilluminate. Gliomas may be covered with nasal mucosa or normal
skin often associated with telangiectasia and misdiagnosed as a hemangioma.
They may widen the nasal bone, giving the appearance of hypertelorism. They
are congenital and are not progressive, which helps to differentiate them from
hemangiomas. Immediate neurosurgical referral is required for surgical removal
and reconstruction.
Cranial Dermoid Cyst and Sinus
Dermoid cysts are congenital subcutaneous lesions that are distributed
along embryonic fusion lines. The cysts may occur within the fusion lines of the
facial processes or within the neural axis. Dermoid -cysts result from faulty
development and may include dermal and epidermal elements. Although they
are always congenital, they may not be noted until early childhood, when they
begin to enlarge. They can occur anywhere on the face, scalp, or spinal axis but
most commonly are seen overlying the anterior fontanel, at the bregma, the
upper lateral region of the forehead, and in the submental region.25,
27, 28 They are
nontender, noncompressible, nonpulsatile, cystic blue or skin-colored nodules
measuring 1 cm to 4 cm in diameter (Fig. 2). They do not transilluminate or
enlarge with a Valsalva maneuver. The overlying skin is normal, unless an
external connection exists in the form of a pit or a sinus (Fig. 3).
Midline or nasal dermoid cysts are of greater concern because 25% of these
have an intracranial ~ o n n e c t i o nNasal
. ~ ~ dermoid cysts may occur anywhere
from the glabella to the nasal tip; a nasal pit or sinus is present in approximately
half of cases (Fig. 3)J7 The pit often leads caudally to a dermal sinus and
eventuates in a cyst that may be external or within the nasal bones. If the
Figure 2. Nasal dermoid cyst. Firm blue nodule at the glabella giving the appearance of
hypertelorism.
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Figure 3. Nasal dermoid sinus. Asymptomatic 2 mm pit that led to a dermal sinus that
coursed the entire nose and ended in a small nasal derrnoid cyst with an intracranial
connection.
dermoid cyst connects to the CNS, cerebrospinal fluid may drain from the sinus.
As with nasal gliomas, these patients may have the appearance of hypertelorism
if a cyst has widened the nasal bones (see Fig. 2). Nasal dermoids aIways should
be excised because they enlarge over time and damage the nasal bones. Dermoid
cysts that are not midline also should be excised because they may develop
infection. Radiologic imaging and referral to a neurosurgeon are indicated only
for midline dermoid cysts.
Dermal sinuses are 1-mm to 5-mm tracts that connect a dermoid cyst to the
skin surface. These usually are midline, found on the nose, occipital scalp, and
anywhere along the spinal axis. They may become clinically apparent when they
become infected and drain purulent material (Fig. 4). A small tuft of hair is
often found protruding from the orifice. If the sinus or cyst directly communicates with the CNS, the patient is at risk for meningitis. The sinus serves as an
occult portal of entry for bacteria, often causing a recurrent meningitis that is
positive for skin flora. Staphylococcus uureus meningitis should be considered
secondary to a dermal sinus until proven otherwise. A thorough search for
cutaneous fistulas should be carried out and may necessitate shaving the scalp
hair.I9 All midline dermal sinuses should undergo radiology before surgical
excision. Probing these lesions is contraindicated, given the risk for meningitis.
SPINAL DYSRAPHISM
The term spinul dysrupkism encompasses many congenital anomalies of the
spine, including:
Meningocele
Myelomeningocele
Myeloschisis
CUTANEOUS SIGNS OF NEURAL TU3E DYSRAPHISM
817
Occult spina bifida
Diastematomyelia
Diplomyelia
Tethered conus
Intraspinal lipoma
Lipomyelomeningocele
Dermoid cyst
Dermal sinus
Larger defects are usually obvious at birth; however, small or occult malformations causing tethering of the spinal cord may be inapparent and asymptomatic at birth. Early diagnosis of a tethered spinal cord is imperative because
surgical correction can prevent irreversible neurologic damage. The spinal cord
and the spinal canal have the same length in early fetal life. Differential growth
leads to progressive ascent of the conus medullaris. At birth, the conus of a
healthy infant is at the L3 vertebra and reaches the adult level of Ll-L2 at 2 or
3 months of age. If the spinal cord is tethered or bound, it cannot ascend
normally and also loses its normal m~bility.~,
23, z9, 33, 38 Flexion of the normal spine
causes the cord to move upward; if the cord is fixed or tethered, traction injuries
occur and may lead to progressive damage of the lower cord and conus.38The
tethered cord syndrome is manifest by asymmetric muscle weakness of the
lower extremities, scoliosis, back pain, and sensory abnormalities with resultant
trophic changes. Approximately 20% of patients have neurogenic bladders and
present with repeated urinary tract infections or enuresis.23,38 When neurologic
symptoms and signs become apparent, most are irreversible, so physicians
must diagnose and surgically release the condition before the development of
neurologic abnormalities. Overlying cutaneous markers are found in 50% to 90%
Figure 4. Small atrophic patch just right of the midline with a 3 mm nonhealing, crusted
erosion. MR image of the spine was normal; however, surgical exploration found a small
dermal sinus.
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DROLET
of patients with occult tethered spinal cord. Cutaneous abnormalities may be
the only indication of tethered cord, especially in newborn infants.
The cutaneous lesions that should alert physicians to an underlying occult
spinal dysraphic state include:
High index of suspicion
Hypertrichosis
Dimples
Acrochordons, pseudotails, or true tails
Lipomas
Hemangiomas
Aplasia cutis or scar
Dermoid cyst or sinus
Low index of suspicion
Telangiectasia
Capillary malformation (port-wine stain)
Hyperpigmentation
Melanocytic nevi
Teratomas
Most of these lesions are found on or near the midline in the lumbosacral
region; however, similar markers in the cervical or thoracic regions also may be
indicative of an underlying malformation.
Lumbosacral cutaneous lesions have long been considered markers of spinal
dysraphism. The
5, 14, 16, *l, 34, 36 suggests that certain skin lesions are
more indicative than others are of an underlying malformation. Tavafoghi et a136
reviewed 200 cases of spinal dysraphsm and found that 102 had cutaneous
signs. Other studies have documented an even higher prevalence of cutaneous
malformations (71-100%).'*, 35 Unfortunately, no prospective studies have been
done to determine the percentage of children with cutaneous anomalies in the
spinal axis who have occult dysraphism. Interpretation of the literature is difficult because ambiguous terms, such as vascular nevus, telangiectasia, and pigmented macule or nevus, are used.
These cutaneous markers also should be evaluated in the context of a
complete history and physical examination, especially in older children. History
taking should include questions regarding additional congenital malformations,
family history of neural tube defects, weakness or pain in the lower extremities,
abnormal gait, scoliosis, difficulties with toilet training or incontinence, recurrent
urinary tract infections, and recurrent meningitis. The vertebrae should be palpated for any defects or abnormalities. Examination of the rectum and genitalia
is also indicated because associated congenital abnormalities of the urogenital
system are often present.13,17, 32 The gluteal cleft should be examined carefully
for small acrochordons or sinuses; it should be straight and the buttocks, symmetric. A gluteal cleft that deviates is suggestive of an underlying mass, such as
a lipoma or meningocele. Examination of the lower extremities is important in
older children because they may have trophic changes secondary to nerve damage.
Hypertrichosis
Localized lumbosacral hypertrichosis, or "hairy patch," is usually present
in these infants at birth. The hair may be dark or light. The texture of the hair
CUTANEOUS SIGNS OF NEURAL TUBE DYSRAPHISM
819
Figure 5. Hypertrichosis overlying a tethered cord.
also varies but is frequently described as silky (faun tail nevus).'4. 15, 36 The
hypertrichosis is often V-shaped and poorly circumscribed (Fig. 5). Prominent
hypertrichosis commonly is associated with other cutaneous stigmata of spinal
dysraphism and is highly indicative of a spinal defect. Hypertrichosis in the
lumbosacral region may be normal, especially in certain racial groups such as
African American, Asian, and Hispanic, and whether additional evaluation is
indicated is often difficult to discern. Referral to a neurosurgeon for a more
complete neurologic examination may be prudent in these cases.
Lipomas
Lipomas associated with spinal dysraphism are thought to be congenital
and are also highly indicative of an underlying defect. Lipomas may lie in the
dermis or spinal canal and often penetrate from the dermis through a vertebral
defect into the intraspinal space (i.e., lipomyelomeningocele). Intraspinal lipomas
are a common cause of the tethered cord. Appropriate radiologic investigation
of lumbosacral lipomas must be performed before surgical excision, and a
neurosurgeon should be involved because small intraspinal connections may be
missed, even with the most sensitive radiologic imaging.
Hemangiomas, Telangiectasia, and Capillary Malformations
Hemangiomas are proliferative vascular tumors that are present in 2.6%
of infants. In 1986, Goldberg et all3 described five children with large sacral
hemangiomas and several other associated abnormalities. Three of the five
children had lipomyelomeningoceles. In 1989, Albright et all reported seven
infants with lumbar hemangiomas and tethered spinal cords. Several subsequent
reports have supported this association. Hemangiomas associated with spinal
dysraphism are usually large (> 4 cm) and overlap the midline. A skin defect
or ulceration is often present within the hemangioma (Fig. 6).l The hemangiomas
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Figure 6. Ulcerated hemangioma overlying a lipornyelomeningocele. Surgety was complicated by wound infection, dehiscence, and cerebrospinal fluid leak.
may be associated with other cutaneous stigmata, such as lipoma, acrochordon,
or dermal sinus. These patients are difficult to manage because the hemangiomas
can ulcerate, and surgical repair of the tethered cord may have to be delayed
until the hemangioma partially regresses. Reports of "telangiectatic patches" are
probably describing nascent or partially regressed hemangiomas.
Enjolras et all1 reported two patients with cervical spinal dysraphism with
overlying capillary malformations (i.e., port-wine stain). Spinal dysraphism associated with a midline, lumbosacral capillary malformation without additional
clinical findings is probably uncommon. Two small studies19,24, 26 have shown a
small prevalence of spinal malformations associated with a solitary capillary
malformation of the lumbosacral region. Additional investigation is needed to
completely clarify the need for imaging in these infants. A neurosurgical consultation is probably warranted.
Dimples, Aplasia Cutis, and Congenital Scars
Lumbosacral dimples are common but can be a sign of spinal dysraphism.'*,
36 Most infants with sacral dimples that fall within the gluteal crease are
healthy. Dimples that are deep, large (> 0.5 cm), fall within the superior portion
15,
CUTANEOUS SIGNS OF NEURAL TUBE DYSRAPHISM
821
or above the gluteal crease (> 2.5 cm from the anal verge), or associated with
other cutaneous markers should be radiologically imaged.19Deep dimples may
be dermal sinuses communicating directly to the spinal canal. These lesions
should not be probed.
Aplasia cutis is a congenital absence of skin and occurs most commonly on
the scalp. Some forms of aplasia cutis are thought to be secondary to incomplete
closure of embryonic fusion lines.l0Aplasia cutis rarely has been reported in the
lumbosacral region and, in that site, may be associated with underlying spinal
dysraphism.16Scarlike defects also have been described in patients with spinal
dysraphism and may be a variant of aplasia cutis. The scarlike regions found in
lumbosacral hemangiomas may be a similar phenomenon.'
Acrochordons, Tails, and Pseudotails
Acrochordons are small, skin-covered, sessile or pedunculated papules or
nodules. Histologically they are composed of epidermis and a dermal stalk. A
true human tail (i.e., persistent vestigial tail) is rare and is differentiated from a
pseudotail and an acrochordon by the presence of a central core of mature fatty
tissue, small blood vessels, bundles of muscle fibers, and nerve fibers. A pseudotail is a stumplike structure and is considered a hamartoma composed of fatty
tissue and, often, cartilage. Clinically, these lesions are difficult to distinguish
clearly, and all have been associated with spinal dysraphism.* Radiologic investigation is indicated preoperatively in all cases.
DIAGNOSIS
Definitive diagnosis of neural tube dysraphism is made only at surgery.
Radiologic imaging is a sensitive screening method and should be undertaken
before surgical intervention. Three radiologic modalities are used for the preoperative diagnosis of dysraphism. The most sensitive study is magnetic resonance
imaging.4,h, 31, 32, 35, 37 Sonography is an excellent, noninvasive alternative in infants
less than 6 months of age.29,33 The vertebrae are not yet completely ossified in
29 If
these infants, and sonography is a relatively inexpensive screening
abnormalities are found, magnetic resonance imaging is required preoperatively.
CT scanning may delineate bony defects better and may also be necessary,
especially in the nasal region. Plain radiography was used extensively in the
past but is not sensitive and should not be used for screening. Magnetic resonance imaging has replaced myelograms, also used in the past. It is often
useful to speak to the radiologist before ordering the examination because the
technology is changing rapidly and varies by institution.
SUMMARY
Cutaneous markers have a crucial role in the detection and diagnosis of
occult neural tube dysraphism. Recognition of these stigmata and appropriate
radiologic imaging decrease the long-term morbidity of this condition.
*References 8, 13, 15, 17, 18, 22, 32, 34, and 36.
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References
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Address reprint requests to
Beth A. Drolet, MD
Pediatric Dermatology
Froedert West
9200 West Wisconsin Avenue
Milwaukee, WI 53226
e-mail: droletQmcw.edu