Epidemiology of Lipoma
Lipoma of the Conus Medullaris (Lipomyelomeningocele)
A lipomyelomenigocele occurs in approximately one in 4000 births in the United States and females are at increased risk (prevalence female/male ratio 1.5:1).[27,51] The lesions are typically diagnosed in children because of the presence of a cutaneous marker or fatty mass; however, the diagnosis of underlying spinal dysraphism is all too often missed.[27,45] The proper association of a skin marker indicating an underlying problem is not made until adulthood when back pain or a progressive neurological deficit calls attention to the problem.[38,45,49]
Fatty Filum (Lipoma of the Terminal Filum)
The true incidence of fatty filum is unknown because the condition is truly occult. In the majority of patients there are no cutaneous anomalies or subcutaneous collections to indicate an underlying problem as is seen in cases of lipomyelomeningocele. Prior to the era of MR imaging there was little appreciation for this condition. In large series of lumbosacral lipomas the authors have reported that lipomas limited to the terminal filum represented 13 to 26% of lesions accounting for tethered cord.
The tight filum syndrome has been described as a cause of tethered spinal cord in which an abnormally enlarged terminal filum prevents normal ascent of the spinal cord within the lumbar spinal canal during normal development. Greater than 90% of cases in which this diagnosis is made demonstrate adipose cells in the filum.
An enlarged fat-filled filum is commonly seen in cases of caudal regression syndrome and other anomalies of the caudal cell mass.[51,61] These disorders are characteristically syndromic (vertebral, anal, tracheal, esophageal, and renal anomalies; Currarino triad) and involve cloacal and urogenital structures in addition to a tethered cord from an enlarged fat-infiltrated filum.[2,18,21,52,67]
The myelocystocele is a rare lesion characterized by cystic dilation of the distal end of the spinal cord. It is considered here because it is thought to arise via a disorder of secondary neurulation, which is currently the most widely supported hypothesis of the cause of the lipoma of the terminal filum. This lesion accounted for 5% of all spinal lipomas in the large series reported by Byrne, et al. In this lesion the central spinal canal demonstrates terminal cystic dilation into a meningocele.
Intradural Spinal Lipoma
These rare lesions affect males and females equally and represent only approximately 7% of spinal lipomas. In adults they are most commonly found in the thoracic region, whereas in children the cervical spine appears to be the most common site.
Neurosurg Focus. 2001;10(1) © 2001 American Association of Neurological Surgeons
Cite this: Spinal Lipomas - Medscape - Jan 01, 2001.