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King Edward Memorial Hospital Bombay, India
University of North Carolina School of Medicine Chapel Hill, NC
27599-7510
Intramedullary lipomas are rare, consisting of 2% of intramedullary tumors [1]. These lesions are common in patients with spinal dysraphism. Lipomas unassociated with spinal dysraphism is present in 1% of patients [2]. A 28-year-old woman presented with a 2-year history of a progressive weakness in all four limbs. The patient described a long-standing history of tingling and numbness in the extremities with nonradiating pain in the neck. Neurologic examination revealed mild, spastic quadriparesis (strength, 4/5) with brisk deep tendon reflexes. No sensory deficits existed. Conventional radiographs of the cervical and dorsolumbar spine were normal. MR imaging of the cervicodorsal spine revealed eccentric intramedullary mass lesions that had high signal intensity on unenhanced T1-weighted images (Fig. 1) and low signal intensity on T2-weighted sequences. The mass extended, in a noncontiguous fashion, from C3 to D7. There was no cord expansion or edema. Because the patient was symptomatic, surgical decompression was attempted. Subtotal resection of the lesion revealed intramedullary lipomas.
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The pathogenesis of intramedullary lipomas remains unclear. The location, age of onset, and close association with midline anomalies, are suggestive of a maldevelopment process. Some authors believe the cause to be an embryologic inclusion of misplaced cell types during neural tube closure. Ammerman et al. [3] consider it to be of hamartomatous origin. Histologically, intramedullary lipomas consist of mature fat cells with intervening collagen fibers, and admixed nerve bundles are often located at the periphery, suggestive of secondary entrapment of adjacent nerve roots [3].
Patients with intramedullary lipomas usually present with a slow, indolent, progressive deterioration of neurologic function. Ascending spastic paralysis of one or more limbs is the most frequent presenting symptom. Sensory disturbances in the form of nonradiating pain, urinary incontinence, ataxia, and signs of dorsal column impairment can be present and may exceed the motor symptoms [3]. Lipomas confined to the cervical region are known to have protracted symptoms as opposed to those lesions located more inferiorly within the cord [4].
CT may indicate cord lipomas; however, MR imaging is the technique of choice because of the characteristic MR appearance of fat and the significant delineation of the lesion facilitated by multiplanar imaging capability. The high proportion of fat confers a short T1 relaxation time; thus, lipomas are hyperintense on T1-weighted images. Benign lipomas have relaxation parameters similar to those of subcutaneous fat. Liposarcomas and other fat-related tumors have longer T1 relaxation times, rendering them less intense than subcutaneous fat on T1-weighted images. CT and MR imaging are characteristic and often obviate biopsy [1]. Cord lipomas commonly occur as single, well-defined loculi. Multiple, noncontiguous lipomas, as seen in our patient, are rare.
Treatment of intramedullary lipoma is controversial. Surgical decompression is indicated for symptomatic lipomas [1]. CO2 laser and sonographic aspiration are known to reduce intraoperative damage to the cord. With these techniques, early prophylactic intervention is proposed in select asymptomatic patients. Surgical intervention after onset of symptoms is unfavorable because of significant postoperative residual disability. Motor improvement is seen in 40% of symptomatic patients after surgery, and bladder control is achieved in only a minority of these patients [5].
In conclusion, multiple intramedullary lipomas are rare. Because of early compressive myelopathic changes, isolated intramedullary lipomas follow a more dismal clinical course than those associated with dysraphism. MR imaging is the technique of choice for diagnosis and follow-up of these cases.
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  S. K. Mukherji Author's Correction Am. J. Roentgenol., March 1, 2001; 176(3): 815 - 815. [Full Text] [PDF]
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