Spinal Lipomas

Jeffrey P. Blount, MD, and Scott Elton, MD, Division of Neurosurgery, University of Alabama at Birmingham, Children's Hospital of Alabama, Birmingham, Alabama

Neurosurg Focus. 2001;10(1) 

In This Article

Diagnosis of Lipoma of The Conus Medullaris

Signs and Symptoms

Subcutaneous Fat Mass. A palpable, nontender subcutaneous mass of fat (Figure 1) is present in greater than 90% of patients harboring a lipomyelomeningocele. In the incidence of fatty mass differs among large series of patients, but this likely reflects an age bias. In series such as those reported from Toronto and Chicago the authors report on younger patients (average age 6 months) when the finding of a large subcutaneous mass is likely to prompt referral and comprehensive evaluation.[10,20,27,38,40,73] In those series in which older children are reported this finding is observed less frequently.[33,55]

Figure 1

Photographs showing a palpable nontender soft mass of fat, the most common finding in lipomas of the conus medullaris. These can be distinguished from coccygeal teratomas by virtue of their somewhat higher position and soft contents. Teratomas will often have a mixed density of contents and will lie lower on the buttock. Digital rectal examination also allows palpation of the teratoma between the rectum and sacrum (see Oakes). Upper: A moderate-sized lumbosacral mass with an associated dermal sinus tract and cutaneous hemangioma. Lower: A somewhat smaller-sized mass, also associated with dermal sinus tract and asymmetrical gluteal cleft. Adapted with permission from Oakes.

Typically this lesion is fully skin covered, nontender, and extends in the midline off the spine. Slightly more than one third of such lesions will be asymmetrical with regard to midline.[49] There is a higher incidence of neurological deficit, usually greatest in the lower extremity ipsilateral to the side of the mass, in those patients with an asymmetrical mass. Normal neurological function at birth can be anticipated in the majority of infants with a symmetrical lipomyelomeningocele.[49]

The intergluteal crease is usually preserved in lipomyelomeningocele but may be obscured or distorted when a myelocystocele (cystic terminal dilation of the central canal into a meningocele) is present.[29]

Some lesions demonstrate considerable bulk, and the associated cosmetic defect is instrumental in prompting evaluation and care.

Skin Abnormalities. Abnormalities in the skin (Figure 1) are very common (50%) in patients harboring a lipomyelomeningocele. These anomalies may include an area of hypertrichosis, a capillary hemangioma, a dermal sinus tract, a dimple, or an additional appendage.[14,20] Many of these lesions occur in isolation and do not reflect underlying dysraphism.[46] When seen in combination with other cutaneous abnormality, the detection of a cutaneous anomaly should prompt a careful search for an underlying occult dysraphic lesion. Angiomas are particularly commonly associated with subcutaneous fatty masses of lipomyelomeningocele.[4] Truly isolated angiomas are, however, rarely indicative of an OSD.

The commonly seen coccygeal pit can be differentiated from a dysraphism-associated dermal sinus tract by virtue of its location within the gluteal cleft and the absence of other skin markers for dysraphism (including asymmetric cleft, fatty mass, hemangioma, and hypertrichosis).[49]

Extremity and Foot Changes. Morphological changes in the extremities and feet are present early in childhood in some children harboring lipomyelomeningoceles.[41] Such changes are often progressive and, as such, are most often detected later in childhood. Asymmetrical foot deformities (typically cavovarus but occasionally cavovalgus) arise from asymmetrical innervation of the feet (Figure 2). Foot-length and leg-length discrepancies, muscle mass discrepancies, and progressive joint deformities can be seen as well.[49]

Figure 2

Left: Progressive asymmetrical foot deformities are commonly seen in children harboring lipomas of the conus medullaris. Asymmetrical innervation of lower-extremity musculature may lead to cavovarus or carovalgus deformities and muscle wasting. Splaying of the toes or hammer toes may also be seen. Right: Asymmetry of the arch of the foot attests to asymmetrical innervation due to lipomyelomeningocele.

Neurological Changes

Sensory/Motor Changes. Although the majority of infants born with a symmetrical lipomyelomeningocele are neurologically intact, progressive neurological deterioration is common and represents the single most important reason why detection and appropriate treatment is important. The authors of many large series have demonstrated progressive neurological decline in patients with untreated lipomyelomeningocele.[8,40,41] Both upper- and lower-motor neuron deficits may be seen in the same extremity. Progressive asymmetrical weakness with patchy sensory loss in the lower extremities is a common finding in these patients.

Bladder/Sphincter Changes. Deterioration of urinary bladder function is common in patients harboring lipomyelomeningocele. The detection of bladder anomalies appears to correlate with the age at which a child is examined and the sensitivity of the means by which the patient is evaluated.[11] Using urodynamic studies Foster and colleagues [23] found abnormal bladder function in 15 of their 19 patients older than age 18 months. By contrast in five of 12 patients younger than age 18 months bladder dysfunction was demonstrated. In a series of 35 children with lipomyelomeningocele repair reported by Atala, et al.,[4] all six older children were shown to have bladder dysfunction. Recently Satar and associates [60] reviewed 21 older patients in whom OSD had been diagnosed; of these 19 underwent operative release. No improvement or worsening of symptoms in 16 of the 19 patients led the authors to conclude, "Older children and adults with occult spinal dysraphism are more likely to present with irreversible urological findings than younger children." By contrast, in a different report by the same group only seven of 28 ( 1 year of age) surgically treated patients with a lipomyelomeningocele were shown to have abnormal bladder function on preoperative urodynamic studies.[59]

By the time children reach 3 to 4 years of age, many are seen primarily for signs of neurogenic bladder.[49,73] This may be clinically manifest as repeated urinary tract infections, disordered or delayed voiding control, or frank incontinence.[60] By contrast rectal incontinence is unusual.

Pain. Low-back pain or tenderness of the subcutaneous mass is very unusual in infants and children but is seen in adolescents and adults. Generalized low-back pain, radicular leg pain, which may vary in distribution with time, and Lhermitte sign have all been described.[6,11,43,52] Often such pain is precipitated by physical exertion, traumatic injury, or direct contact, but spontaneous symptoms may occur as well.

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